Spatiotemporal Distribution of Precipitation Microphysical Characteristics over the Tianshan Mountains Based on GPM/DPR Observations

Spatiotemporal Distribution of Precipitation Microphysical Characteristics over the Tianshan Mountains Based on GPM/DPR Observations | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Spatiotemporal Distribution of Precipitation Microphysical Characteristics over the Tianshan Mountains Based on GPM/DPR Observations Xue Mei, Lianmei Yang, Abuduwaili Abulikemu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8720683/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract Using monthly mean Level-3 GPM/DPR products from March 2014 to February 2023, this study systematically investigates the spatial distribution, vertical structure, and microphysical characteristics of stratiform and convective precipitation over the Tianshan Mountains. The results indicate that stratiform precipitation is generally weak but widespread, with maximum precipitation rates mostly below 4 mm h⁻¹ and maximum radar reflectivity mainly ranging from 20 to 29 dBZ. It contributes more than 60% of total precipitation annually, increasing to over 90% in winter. In contrast, convective precipitation exhibits much higher intensity and pronounced extremes, with maximum precipitation rates commonly exceeding 4 mm h⁻¹ and radar reflectivity typically between 29 and 38 dBZ, locally surpassing 41 dBZ, and is primarily concentrated in summer over the western Tianshan and windward slopes. Storm-top height generally ranges from 4 to 7 km, while convective precipitation frequently exceeds 8 km, showing a clear west-to-east decreasing pattern controlled by topography. Vertically integrated liquid, ice, and total hydrometeor contents associated with convective precipitation are substantially higher than those of stratiform precipitation, with summer total water content reaching 350–400 g m⁻². These findings provide satellite-based evidence for improving the understanding of precipitation processes and microphysical mechanisms in complex mountainous regions. Earth and environmental sciences/Climate sciences Earth and environmental sciences/Environmental sciences Earth and environmental sciences/Hydrology Earth and environmental sciences/Natural hazards Tianshan Mountains GPM/DPR stratiform and convective precipitation microphysical structure topographic effects Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1 Introduction The Tianshan Mountains serve as the most vital “water tower” in Central Asia, playing a critical role in regional socioeconomic development and ecological security. With the rapid advancement of satellite remote sensing technology, satellite-based precipitation observation and analysis have become increasingly sophisticated. The tropical rainfall measuring mission (TRMM) provided invaluable precipitation data for tropical and subtropical regions, significantly advancing research on convective-stratiform precipitation classification and precipitation microphysical parameter retrieval (Kummerow et al., 2000 ; Hou et al., 2014 ). As TRMM’s successor, the global precipitation measurement (GPM) mission utilizes the dual-frequency precipitation radar (DPR) alongside multi-sensor combined retrievals, markedly enhancing precipitation detection in mid- to high-latitude areas and complex terrains (Seto and Iguchi, 2015 ; Grecu et al., 2016 ). Unlike TRMM, which primarily focused on mesoscale precipitation systems within tropical and subtropical zones, GPM’s key advancement lies in its improved ability to observe clouds, light rainfall (< 0.5 mm h − 1 ), solid precipitation, and detailed precipitation microphysical structures. These precipitation types are especially significant in mid- to high-latitude arid and semi-arid regions such as Xinjiang, making GPM observations particularly valuable for precipitation studies over the Tianshan Mountains (Lu et al., 2024 ; Lu and Wei, 2017 ). Previous studies have highlighted the advantages of GPM products in mountainous regions. Jin et al. ( 2016 ) assessed the performance of CMORPH, TRMM, and GPM IMERG precipitation products over the Tianshan Mountains and found that GPM demonstrated the best overall accuracy, particularly in detecting light precipitation, exhibiting higher detection probabilities and lower false-alarm rates. Spatially, larger errors were concentrated in areas with complex terrain and heavy precipitation, whereas estimates over mid-elevation zones (1250–2800 m) were the most accurate. This pattern likely reflects the limitations of dual-frequency radar in detecting snowfall and the influence of terrain effects. Zhang et al. ( 2020 ) divided the Tianshan Mountains into four subregions and further confirmed that GPM significantly outperforms TRMM in daily precipitation detection, especially in the northwestern and southwestern parts of the range. Beyond quantifying precipitation amounts, GPM has been extensively utilized to investigate precipitation structures and microphysical properties. Liu and Zipser ( 2015 ) mapped the global distribution of the largest, deepest, and most intense precipitation systems using GPM Ku-band radar observations. Yamaji and Takahashi ( 2023 ) demonstrated that variations in mass-weighted mean diameter are influenced not only by precipitation intensity but also by changes in precipitation characteristics. Ma et al. ( 2023 ) analyzed plateau vortex precipitation, revealing distinct spatial patterns differentiating deep weak convection from shallow precipitation. Zhang et al. ( 2025 ) highlighted the strong connection between convective system occurrence and topography, emphasizing that precipitation intensity is jointly governed by particle size and concentration. Li et al. ( 2024 ) found that both convective and stratiform precipitation over plains are, on average, approximately 20% stronger than those over mountainous regions, while the higher frequency of weak convective precipitation in mountains largely explains the increased precipitation occurrence there. By integrating GPM DPR observations with ERA5 reanalysis data, Wang et al. ( 2024 ) demonstrated that precipitation vertical structures are modulated by microphysical processes at various atmospheric levels as well as by environmental conditions. Long-term precipitation variability in Xinjiang and the broader Tianshan region has also been extensively studied using gauge-based and reanalysis datasets. Guan et al. (2021) analyzed GPCC precipitation data from 1950 to 2016, revealing the spatiotemporal evolution of annual and seasonal precipitation through ensemble empirical mode decomposition and Mann-Kendall tests. Li et al. ( 2024 ) conducted a systematic investigation of the spatiotemporal distribution and vertical structures of stratiform and convective precipitation over Xinjiang, showing that convective precipitation is most active during summer, when radar reflectivity and storm-top heights (STHs) reach their annual peaks and are significantly greater over mountainous areas compared to basins. Zheng et al. ( 2019 ) examined total precipitable water vapor across Xinjiang, identifying a clear gradient of decreasing moisture from major basins toward surrounding mountain ranges, along with a pronounced seasonal cycle peaking in summer. Despite these advances, most existing studies using GPM observations in the Tianshan region have primarily concentrated on the spatiotemporal variability of precipitation amounts. While some research has explored differences between convective and stratiform precipitation, systematic seasonal comparisons of their microphysical characteristics in complex terrain remain limited. Therefore, this study aims to investigate the seasonal evolution and regional variations of the microphysical properties of convective and stratiform precipitation over the Tianshan Mountains using GPM DPR observations, with the objective of advancing the understanding of precipitation structures and processes in mountainous environments. 2 Study Area and Data Sources 2.1 Overview of the Study Area The Tianshan Mountains are situated between the arid regions of Central Asia and the mid-latitude monsoon-arid transition zone, lying at the core of a large-scale climate regime dominated by the westerlies, known as the westerly-dominated climate region (Jin et al., 2024 ). As the largest and longest east-west-oriented mountain system in Central Asia, the Tianshan Mountains not only form the structural backbone of the topographic framework in northwestern China but also serve as a key driver of regional climate variability and hydrological cycle evolution. Shaped by multiple phases of tectonic activity, the Tianshan range comprises several nearly zonal mountain ranges separated by intermontane basins, creating a distinctive stepwise geomorphological pattern that establishes complex dynamical and thermodynamical conditions conducive to precipitation formation and redistribution. Under the combined influence of westerly circulation and orographic forcing, the Tianshan region functions as a “wet island” within the predominantly arid and semi-arid areas of northwestern China, with mean annual precipitation exceeding 400 mm (Kong and Pang, 2016 ; Wang et al., 2019 ; Zhu et al., 2023 ). Precipitation displays a pronounced spatial gradient, with the highest annual totals occurring in the western Tianshan, often surpassing 700 mm, while the eastern region receives the lowest amounts, sometimes less than 50 mm (Chen et al., 2025 ; Wang et al., 2016 ). Moisture primarily arrives from westerly airflows originating over the Atlantic and Arctic Oceans. Due to its considerable elevation, distinctive geometry, being wider in the central section and narrower at both ends, and unique orientation, substantial regional disparities in precipitation distribution are observed across the Tianshan Mountains (Zhao et al., 2011 ). The study area encompasses the section of the Tianshan Mountains within China, spanning Xinjiang (73.5°-95.0°E, 39.5°-45.5°N). This region is marked by significant topographic relief, with elevations generally exceeding 1500 m, and the main ridge along with high-mountain zones commonly rising above 3000 m. These high-elevation terrains serve as the primary orographic drivers of regional precipitation formation and distribution (Fig. 1 ). Extending predominantly east-west, the Tianshan Mountains separate Xinjiang into the Junggar Basin to the north and the Tarim Basin to the south, creating a characteristic “mountain-basin” geomorphological pattern typical of arid regions. Orographic uplift and barrier effects associated with the mountain system strongly influence moisture transport pathways and vertical motion structures, thereby shaping the pronounced spatial heterogeneity and seasonal variability of precipitation. 2.2 Data Sources and Methodology The data used in this study were obtained from the DPR onboard the GPM Core Observatory, a joint mission operated by the national aeronautics and space administration and the Japan aerospace exploration agency. We utilized GPM Level-3 products covering the period from March 2014 to February 2023. Specifically, the GPM DPR Level-3 Version 07 (GPM_3DPR_07) dataset was employed, which provides globally gridded statistics derived from Level-2 instantaneous orbital observations of the Ku- and Ka-band DPR. These products deliver temporally consistent daily and monthly climatological records of precipitation and radar-related parameters. The Level-3 products are provided on latitude-longitude grids with spatial resolutions of 0.5° (G1) and 0.25° (G2), covering latitudes from − 70° to 70° and longitudes from − 180° to 180°. Based on the scanning mode, DPR products are classified into three categories: (1) Full swath (FS), which offers the widest spatial coverage; (2) Matched swath (MS), where Ku- and Ka-band observations are spatially collocated, allowing dual-frequency retrievals with the highest accuracy; and (3) High-sensitivity swath (HS), designed to enhance sensitivity to weak and solid precipitation, particularly snowfall. Both FS and MS modes include single-frequency and dual-frequency retrievals from the Ku and Ka bands, whereas the HS mode contains only Ka-band high-sensitivity single-channel data. In this study, monthly mean MS/G2 products with a spatial resolution of 0.25° × 0.25° were selected. The key parameters analyzed include precipitation rate (PreR), radar reflectivity factor (PRF), storm top height (STH), vertically integrated precipitation liquid water content (PWI), and vertically integrated precipitation ice water content (PII). These variables were used to systematically investigate the spatial distribution, topographic influences, and seasonal variations of major precipitation microphysical characteristics over the Tianshan Mountains, providing a solid data foundation for understanding the spatiotemporal variability of precipitation in this complex mountainous region. 3 Results and Discussion 3.1 Spatial distribution of precipitation microphysical characteristics Figure 2 illustrates the seasonal spatial distributions of the near-surface maximum precipitation rate (Max-PreR, mm h − 1 ) for both stratiform and convective precipitation, while Fig. 3 presents the corresponding seasonal variations of near-surface maximum radar reflectivity (Max-PRF, dBZ). Pronounced differences are evident between stratiform and convective precipitation in terms of intensity and spatial coverage. Stratiform Max-PreR values are generally low, typically below 4 mm h − 1 , with corresponding Max-PRF mainly concentrated between 20 and 29 dBZ. During summer, localized enhancements in stratiform precipitation occur, with Max-PreR reaching approximately 6 mm h − 1 and Max-PRF exceeding 35 dBZ. In contrast, convective precipitation commonly exhibits Max-PreR values exceeding 4 mm h − 1 , with Max-PRF predominantly ranging from 29 to 38 dBZ and locally surpassing 41 dBZ. The spatial distribution of convective precipitation is more concentrated and marked by pronounced extrema, reflecting vigorous convective development and strong localized uplift. From a seasonal perspective, stratiform precipitation in spring is relatively weak, with Max-PreR generally ranging from 0 to 2 mm h − 1 and Max-PRF approximately between 17 and 26 dBZ. In contrast, convective precipitation already exhibits localized high-intensity centers during spring, with Max-PreR exceeding 8 mm h − 1 and Max-PRF above 35 dBZ, indicating that orographic and thermodynamic lifting can initiate localized convective activity even in early spring. In summer, precipitation intensity increases markedly, with convective precipitation reaching its annual maximum, Max-PreR surpassing 9 mm h − 1 and Max-PRF generally above 35 dBZ, forming continuous bands of strong precipitation along the central and western Tianshan and northern slopes. Stratiform precipitation also intensifies relative to spring, with Max-PreR ranging from about 2 to 6 mm h − 1 and reflectivity increasing to 23–32 dBZ. During autumn, precipitation gradually weakens: stratiform Max-PreR decreases to 1–3 mm h − 1 and Max-PRF to 20–32 dBZ, while convective precipitation maintains localized strong centers (> 7 mm h − 1 and > 35 dBZ) but with substantially reduced spatial extent, reflecting the seasonal transition. In winter, stable atmospheric stratification predominates, and precipitation mainly occurs as persistent weak stratiform events, with Max-PreR generally below 1 mm h − 1 and Max-PRF around 14–20 dBZ. Overall, the spatial patterns of precipitation intensity and reflectivity exhibit strong consistency between stratiform and convective precipitation, with topography playing a significant role in regulating both types. Orographic lifting associated with the Tianshan Mountains not only enhances the efficiency of stratiform precipitation formation but also creates favorable conditions for triggering deep convection. Compared to other regions, summer Max-PRF values over the Tianshan Mountains are stronger than those observed over plateau regions (15–40 dBZ) but weaker than those over non-plateau areas such as Anhui, the western Pacific, and the eastern Pacific (15–50 dBZ). In contrast, Max-PRF over the Tibetan Plateau predominantly remains below 26 dBZ, whereas strong convective precipitation with higher Max-PRF is more widespread across the Tianshan during summer, exhibiting an opposite distribution pattern to that of the plateau regions (Fu et al., 2022). Figure 4 presents the spatial distributions of the fractional contributions of stratiform and convective precipitation. Overall, stratiform precipitation covers a much broader area across the Tianshan region. Its occurrence is closely linked to large-scale circulation and moisture advection, spanning most low- and mid-elevation zones and generally following topographic contours. The mean contribution of stratiform precipitation exceeds 60%, reaching over 80% in regions below 1500 m elevation. In contrast, convective precipitation typically contributes less than 30%. High fractions of convective precipitation are distributed in banded patterns along elevation contours and windward mountain slopes, with the “funnel-shaped” region of the western Tianshan identified as a convection-prone zone, where convective contributions can reach up to 70%. The relative contributions of stratiform and convective precipitation vary markedly with season. Convective precipitation increases substantially during summer, while stratiform precipitation dominates in winter, with an average contribution exceeding 90%. These findings indicate that stratiform precipitation governs the primary precipitation processes over the Tianshan region, whereas convective precipitation, though contributing less overall, can be locally enhanced under specific topographic and seasonal conditions. It should be noted that the complex terrain features, such as elevation, slope, and other mesoscale topographic-meteorological factors, pose significant challenges for satellite-based precipitation estimation in this region. In particular, the pronounced topographic variability in the “funnel-shaped” area of the western Tianshan limits the detection capability of satellite products, resulting in large relative biases (PB > 55%) (Jin et al., 2016 ). Fu et al. (2022) further reported that most precipitation profiles identified by the DPR algorithm are classified as stratiform, with only a few strong-reflectivity profiles categorized as convective. Moreover, some profiles exhibiting convective characteristics are still classified as stratiform, underscoring limitations and potential misclassification issues in the DPR algorithm. 3.2 STH and precipitation rate distribution characteristics The STH of precipitation over the Tianshan Mountains shows a pronounced dependence on topography. Spatially, high STH values for both stratiform and convective precipitation are primarily concentrated along the western mountainous regions (approximately 74–84°E, 40–44°N) and the windward slopes, while lower STH values are found mainly on the leeward southern slopes, the central mountainous region (approximately 84–92°E, 41–44°N), and adjacent plains. This distribution underscores the strong influence of orographic forcing on the vertical structure of precipitation. Additionally, STH exhibits a clear seasonal cycle, with lower values in winter and higher values in summer, typically ranging between 4000 and 7000 m. Convective STH is generally higher than stratiform STH, reaching up to approximately 8000 m, with maximum differences of up to 5000 m, reflecting stronger vertical development and greater spatial heterogeneity. In spring, stratiform STH predominantly ranges between 4000 and 6000 m, with high-value centers located over the western Tianshan and the western part of the central Tianshan (west of 88°E) on both northern and southern slopes, where peak values exceed 7000 m. During the same season, convective STH typically spans 5000 to 8000 m, with localized maxima surpassing 8000 m. Summer marks the period with the highest STH values throughout the year. Stratiform STH generally rises to 5000–7000 m, locally exceeding 8000 m, while convective STH exhibits its strongest vertical development. During this season, STH commonly exceeds 6000 m over the Tianshan west of 84°E and its northern slopes, as well as the southern slopes of the eastern Tianshan (88–94°E), with some intense convective cores penetrating above 9000 m. Simultaneously, a distinct northeast-southwest-oriented belt of relatively low STH emerges, reflecting a typical signature of terrain-forced circulation. In autumn, stratiform STH decreases to 4000–6000 m, with localized values above 6000 m, whereas convective STH is mainly concentrated between 5000 and 7000 m; although the spatial extent of high STH values diminishes, localized maxima persist. In winter, stratiform precipitation is strongly limited, and STH generally remains below 5000 m. Compared to other regions in China, the STH of both stratiform and convective precipitation over the Tianshan Mountains is lower than in eastern China, where echo-top heights of stratiform precipitation reach 8–10 km and convective precipitation can extend up to approximately 14 km (Zhang et al., 2025 ). However, STH over the Tianshan is slightly higher than that observed over the Tibetan Plateau (Fu, 2023 ). In South China, echo-top heights generally average around 6 km, rising to about 9 km in summer and decreasing to approximately 3 km in winter (Du et al., 2020 ). These values are overall somewhat higher than those over the Tianshan, with a broader spatial distribution of high-value regions. To better characterize the vertical distribution of precipitation rate, the study area was divided into three subregions based on the spatial pattern of STH (Fig. 1 ). Region A (74.0-84.2°E, 39.5–45.0°N), located in the western Tianshan, includes the Ili Valley and the windward northern slopes of the range. This region is strongly influenced by moisture transport associated with the midlatitude westerlies, resulting in abundant moisture availability and pronounced orographic lifting. Consequently, precipitation systems here exhibit deep vertical development and frequent convective activity, making Region A the primary deep-convection zone characterized by intense precipitation and high STH over the Tianshan. Region B (84.2–91.5°E, 42.0–44.0°N) corresponds to the central Tianshan mountainous area. Although topographic relief remains pronounced, moisture supply is reduced relative to Region A due to downstream effects on westerly moisture transport. Additionally, the combined influence of basin thermal circulations and orographic blocking limits thermodynamic uplift, thereby constraining the vertical growth of precipitation systems. Region C (91.5–95.5°E, 43.0–44.0°N), located in the eastern Tianshan, represents a low-STH area. Moisture intrusion into this region is strongly impeded by surrounding high-elevation mountain ranges, leading to relatively low precipitation amounts, particularly in winter (Liu and Han, 1992; Guan et al., 2022 ). Figure 6 illustrates the vertical distributions of precipitation rate for stratiform and convective precipitation across the western (Region A), central (Region B), and eastern (Region C) Tianshan in different seasons. Overall, stratiform precipitation intensity exhibits a clear west-to-east decreasing gradient across the Tianshan. In Regions A and B, stratiform precipitation is consistently present, displaying a typical vertical structure characterized by weaker intensities aloft and stronger intensities near the surface, with mean precipitation rates generally below 1 mm h − 1 . In contrast, the vertical extent of precipitation in Region C is significantly constrained by elevation and moisture availability. Convective precipitation shows pronounced seasonal and regional contrasts, along with distinct differences in peak intensity and vertical distribution. In Region A (Figs. 6 a-d), convective precipitation in spring exhibits two pronounced maxima, exceeding approximately 7 mm h − 1 at midlevels around 3.5 km and about 4 mm h − 1 near the surface. During summer, no distinct peak is evident, with precipitation rates generally around 2 mm h − 1 below 6 km. In autumn, convective systems deepen under the influence of cold-warm air interactions, with a peak precipitation rate of roughly 4.3 mm h − 1 near 6.5 km, representing the annual maximum. Winter precipitation is dominated by weak ice-phase stratiform events, with rates remaining below 1 mm h − 1 throughout the column. In Region B (Figs. 6 e-h), convective precipitation during spring and summer displays a multi-peak vertical structure below 5 km, with peak values near 2 mm h − 1 . In spring, these peaks occur mainly in the lower and middle layers, whereas in summer convection deepens, and a secondary peak of about 1.5 mm h − 1 appears at higher altitudes around 8.5 km. In autumn, the vertical precipitation pattern shows a “midlevel maximum with weaker upper and lower levels,” peaking at approximately 4.7 mm h − 1 near 5 km, with rates of 1–3 mm h − 1 at both lower and upper layers. In winter, near-surface precipitation rates reach about 1 mm h − 1 , higher than in Region A, but decrease rapidly above approximately 1 km. In Region C (Figs. 6 i-l), stratiform precipitation in summer can extend up to roughly 8 km, exhibiting large variability below 5 km and a steady decrease with height above this level. Spring and autumn precipitation are suppressed, with vertical extent limited to below 5 km and stratiform peaks near 0.8 mm h − 1 occurring at different heights, around 2–3 km in spring and below 1 km in autumn. Winter precipitation is even more constrained, with vertical development limited to less than 3 km. Convective precipitation in Region C shows a multi-peak structure with considerable vertical variability. In spring, a peak of about 2.8 mm h − 1 occurs near 2 km; in autumn, a peak of approximately 1.8 mm h − 1 appears near 1 km. During summer, convection reaches higher altitudes, but peak precipitation rates concentrate below 5 km, with maxima near 0.5 km and 3 km exceeding 2 mm h − 1 . From a microphysical perspective, the vertical variations in precipitation rate for convective and stratiform precipitation reflect distinct processes of moisture condensation, hydrometeor growth, and sedimentation. In convective regions, the precipitation rate increases markedly within the 2–6 km layer, maintains relatively high values between 6 and 10 km, and gradually decreases at higher altitudes. Summer maxima reach approximately 1.8–2.0 mm h⁻¹ in this layer. This vertical structure corresponds to microphysical mechanisms driven by strong updrafts, which transport abundant moisture upward and sustain continuous ice‑particle and raindrop growth within ascending air. Vigorous vertical motions enhance particle aggregation, collision, and coalescence, allowing elevated precipitation rates to persist even at higher levels. In contrast, stratiform precipitation is sustained by weaker vertical motions, with microphysics dominated by ice‑crystal formation and aggregation aloft, followed by gravitational settling and melting. Hydrometeors undergo phase changes and rapid growth near the 0°C level (approximately 4–6 km), while precipitation rates decline noticeably above this layer due to reduced ice‑crystal concentrations or enhanced evaporation. Below the melting layer, collision‑coalescence and sedimentation processes prevail, yielding a modest increase in precipitation rate toward the surface. 3.3 Vertically integrated hydrometeor content characteristics Figures 7 – 9 demonstrate that vertically integrated precipitation water content (PWI), ice water content (PII), and total water content (PTI) all exhibit pronounced topographic dependence and seasonal variability. Overall, hydrometeor contents associated with convective precipitation are significantly higher than those of stratiform precipitation. High-value centers are primarily located over the western Tianshan (west of 83°E) and along the windward northern slopes of the central Tianshan (83–87°E, 44–45°N). These areas are closely linked to moisture transport and orographic lifting. This region serves as a convergence zone between the midlatitude westerly jet and terrain-forced local airflow, where moisture accumulation and forced ascent promote strong condensation and phase-change processes, resulting in a distinct topographic influence on the spatial distribution of hydrometeor contents. PWI values are generally low and decrease gradually from west to east along the mountain range. Stratiform PWI mostly remains below 90 g m⁻², with local enhancements during summer and significant reductions in spring and autumn, indicating a strong dependence on terrain-induced moisture uplift. In contrast, convective PWI is more concentrated over the windward slopes of the western Tianshan and exhibits substantially higher magnitudes, with local summer maxima exceeding 150 g m⁻². This reflects intense liquid-water condensation and efficient growth of small- to medium-sized droplets. In the eastern Tianshan, limited moisture supply leads to generally low PWI values and scattered high-value areas, consistent with the progressive weakening of zonal moisture flux. The spatial pattern of PII broadly resembles that of PWI but with systematically larger magnitudes, underscoring the significant contribution of ice-phase particles to precipitation over the Tianshan. For both precipitation types, high PII values form banded structures along the northwestern slopes of the main Tianshan ridge and increase with elevation. In summer, stratiform PII can locally reach 120–150 g m⁻², whereas convective PII is more concentrated and exhibits greater variability, with peak values up to approximately 270 g m⁻². This indicates active production of ice crystals, graupel, and snow particles in the mid- and upper troposphere. Notably, convective PII tends to decrease at higher elevations, possibly due to downward particle transport, melting processes, or enhanced turbulence induced by terrain blocking, highlighting a strong orographic influence on ice-phase microphysical processes. As the sum of PWI and PII, PTI reflects the combined characteristics of both components in its spatial and seasonal variability. High-value regions of stratiform PTI largely overlap with those of PWI and PII, exhibiting peak values around 200–250 g m⁻². In contrast, convective PTI is strongly concentrated over the windward slopes of the western and central Tianshan, with summer maxima reaching 350–400 g m⁻², nearly twice those of stratiform precipitation. This indicates that efficient condensation, freezing, and aggregation processes associated with strong summer convection play a dominant role in enhancing PTI, an effect further amplified by terrain-induced moisture convergence. Seasonal comparisons reveal that PTI variability in spring, autumn, and winter is mainly controlled by PII, suggesting that ice-phase growth dominates hydrometeor content under weaker instability conditions, whereas in summer, enhanced PWI highlights the primary role of intense condensation in increasing liquid water content. 4 Conclusions Using monthly mean Level-3 GPM/DPR products from 2014 to 2023, this study systematically investigated the spatiotemporal distribution, vertical structure, and microphysical characteristics of stratiform and convective precipitation over the Tianshan Mountains. Three representative subregions were identified to deepen understanding of precipitation formation mechanisms in complex mountainous terrain. The main conclusions are summarized as follows: (1) Stratiform and convective precipitation over the Tianshan Mountains exhibit pronounced differences in spatial distribution and seasonal variability. Stratiform precipitation is generally weak, with maximum precipitation rates (Max-PreR) mostly below 4 mm h − 1 and maximum radar reflectivity (Max-PRF) primarily between 20 and 29 dBZ, but it covers a broad area. Local enhancements occur in summer, with Max-PreR reaching approximately 6 mm h − 1 and Max-PRF exceeding 35 dBZ, while winter precipitation is dominated by weak stratiform rain (< 1 mm h − 1 , 14–20 dBZ). In contrast, convective precipitation is much stronger, with Max-PreR commonly exceeding 4 mm h − 1 and Max-PRF mainly between 29 and 38 dBZ, locally surpassing 41 dBZ. Convective precipitation also exhibits a more concentrated spatial distribution and higher extremes. (2) Stratiform precipitation is the dominant precipitation type throughout the year, with mean contributions generally exceeding 60% and increasing to over 90% in winter. Below 1500 m elevation, its contribution can exceed 80%, indicating widespread spatial coverage and a relatively stable structure. Convective precipitation typically accounts for less than 30% overall but locally reaches up to 70% in the western Tianshan “funnel-shaped” region and on windward slopes, where it plays a critical role in high-intensity precipitation events. (3) STH exhibits a strong dependence on topography. High STH values are primarily distributed over the western mountainous areas and windward slopes, while low values are found on leeward slopes, central mountains, and adjacent plains. STH displays a clear seasonal pattern, with lower values in winter and higher values in summer, generally ranging from 4000 to 7000 m. Convective STH consistently exceeds stratiform STH, frequently surpassing 8000 m, indicating stronger vertical development. In the western Tianshan, STH is relatively high in spring, peaks in summer with a pronounced banded distribution, contracts in autumn, and reaches its minimum extent in winter. (4) Stratiform precipitation generally follows a west-to-east decreasing pattern. In Regions A and B, precipitation rate profiles show weaker values aloft and stronger values near the surface, with mean rates generally below 1 mm h − 1 . In Region C, vertical precipitation extent is clearly constrained by elevation and limited moisture supply. Convective precipitation exhibits more pronounced seasonal and regional variability. In Region A, convective activity is strongest in spring and autumn, with distinct peaks near 3.5 km and 6.5 km, respectively, weaker in summer, and largely absent in winter except for weak stratiform precipitation. In Region B, convective precipitation displays a multi-peak vertical structure during spring and summer, extending to higher altitudes in summer, while the strongest peak occurs near 5 km in autumn. Region C shows the weakest vertical development, with convective heights generally below 5 km in spring and autumn; although vertical extension increases in summer, peak intensities remain confined to lower levels. (5) Overall, convective precipitation exhibits substantially higher precipitation water content integral (PWI) than stratiform precipitation. High PWI values are concentrated mainly over the western Tianshan and the northern windward slopes of the central Tianshan, with PWI decreasing from west to east along the mountain range. Stratiform PWI is mostly below 90 g m⁻², with local summer enhancements, whereas convective PWI peaks over the western windward slopes and can exceed 150 g m⁻² in summer. The spatial pattern of precipitation ice water content integral (PII) is similar to that of PWI but with higher magnitudes, highlighting the significant role of ice-phase processes; summer convective PII peaks can reach approximately 270 g m⁻². Total precipitation water content integral (PTI), which combines liquid and ice phases, reflects features of both variables. Convective PTI attains its highest values over windward slopes in summer, reaching 350–400 g m⁻², significantly exceeding stratiform values. This indicates that strong summer convection, combined with topographic lifting, plays a dominant role in enhancing integrated precipitation water content. This study supplements existing research by providing a comparative analysis of the seasonal variability of precipitation microphysical parameters over the Tianshan Mountains, offering satellite-based evidence useful for cloud water resource assessment, numerical model parameterization improvement, and regional climate change studies in the “Central Asian water tower” region. However, the dual-frequency radar system of GPM has limited capability in detecting snowfall over high-elevation areas and tends to substantially underestimate winter precipitation (Jin et al., 2016 ). Similar to the single-frequency precipitation radar onboard TRMM, GPM/DPR faces uncertainties in bright-band identification over complex high-mountain terrain (Fu, 2023 ). Future work should integrate ground-based radar and radiosonde observations for multi-source validation to further improve precipitation estimation accuracy in cold, high-altitude mountainous regions. Declarations This work was supported by Key Research and Development Program of Xinjiang Uygur Autonomous Region (2023B03019-1) and Tianshan Talent Training Program Project (2022TSYCLJ0003). The authors have no relevant financial or non-financial interests to disclose. All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Xue Mei, Lianmei Yang and Abuduwaili Abulikemu. The first draft of the manuscript was written by Xue Mei and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. The data used in this study are available from the official GPM website and the data generated and analyzed during the study period are available from the corresponding author upon reasonable request. Funding Xinjiang Uygur Autonomous Region Key R&D Program (2023B03019-1); Tianshan Talent Training Program (2022TSYCLJ0003). Author Contribution All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Xue Mei, Lianmei Yang and Abuduwaili Abulikemu. The first draft of the manuscript was written by Xue Mei and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Data Availability The data used in this study are available from the official GPM website and the data generated and analyzed during the study period are available from the corresponding author upon reasonable request. References Chen, C., Hu, Y., Fan, M., et al., 2025. Investigation on the linkage between precipitation trends and atmospheric circulation factors in the Tianshan Mountains. Water , 17(5), 726. https://doi.org/10.3390/w17050726. Chen, Y., Li, Z., Fang, G., et al., 2017. Impact of climate change on water resources in the Tianshan Mountains, Central Asia. Acta Geographica Sinica , 72(1), 18–26. (in Chinese) Du, S., Wang, D. H., Li, G. P., et al., 2020. Vertical structure characteristics of precipitation over South China based on GPM dual-frequency spaceborne precipitation radar data. Journal of Tropical Meteorology , 36(1), 115–130. (in Chinese) Fu, Y. F., 2023. Investigation of summer cloud, precipitation, and radiation over the Tibetan Plateau using spaceborne observations. PhD dissertation, University of Science and Technology of China, Hefei, China. (in Chinese) Fu, Y., Yang, L., Wu, Z., et al., 2024. A new algorithm of rain type classification for GPM dual-frequency precipitation radar in summer Tibetan Plateau. 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Kong, Y., Pang, Z., 2016. A positive altitude gradient of isotopes in precipitation over the Tianshan Mountains: Effects of moisture recycling and sub-cloud evaporation. Journal of Hydrology , 542, 222–230. https://doi.org/10.1016/j.jhydrol.2016.09.036. Kummerow, C., Simpson, J., Thiele, O., et al., 2000. The status of the Tropical Rainfall Measuring Mission (TRMM) after two years in orbit. Journal of Applied Meteorology , 39(12), 1965–1982. https://doi.org/10.1175/1520-0450(2000)0392.0.CO;2. Jin, C., Wang, B., Cheng, T. F., et al., 2024. How much do we know about precipitation climatology over the Tianshan Mountains—the Central Asian water tower? npj Climate and Atmospheric Science , 7(1), 21. https://doi.org/10.1038/s41612-024-00521-5. Jin, X. L., Shao, H., Zhang, C., et al., 2016. Applicability analysis of GPM satellite precipitation data over the Tianshan mountainous region. Journal of Natural Resources , 31(12), 2074–2085. (in Chinese) Li, C., Han, T., 1992. Relation between recent glacier variations and climate in the Tien Shan Mountains, Central Asia. Annals of Glaciology , 16, 11–16. https://doi.org/10.3189/S0260305500014263 Liu, C., Zipser, E. J., 2015. The global distribution of the largest, deepest, and most intense precipitation systems. Geophysical Research Letters , 42(9), 3591–3595. https://doi.org/10.1002/2015GL063576 Li, D., Qi, Y., Li, H., 2024. Vertical structures and microphysical characteristics of summer precipitation in North China detected by GPM-DPR. Science of the Total Environment , 933, 173129. https://doi.org/10.1016/j.scitotenv.2024.173129 Li, X., Yang, L., Tong, Z., et al., 2024. Analysis of convective and stratiform precipitation characteristics in Xinjiang, China based on GPM dual-frequency precipitation radar. Advances in Meteorology , 2024, 8043060. https://doi.org/10.1155/2024/8043060 Lu, M. Q., Wei, M., 2017. Application of GPM data in analyzing the vertical structure of precipitation associated with Typhoon Rainbow. Remote Sensing Technology and Application , 32(5), 904–912. (in Chinese) Lu, X., Wang, X., Li, C., et al., 2024. Validation of drop size distributions from GPM DPR with ground-based disdrometers over the Tianshan region, China. Remote Sensing , 17(1), 79. https://doi.org/10.3390/rs17010079 Ma, B. X., Feng, X. Y., Li, Y., et al., 2023. Structural characteristics of summer plateau vortex precipitation detected by the GPM satellite. Plateau and Mountain Meteorology Research , 43(1), 8–16. (in Chinese) Seto, S., Iguchi, T., 2015. Intercomparison of attenuation correction methods for the GPM dual-frequency precipitation radar. Journal of Atmospheric and Oceanic Technology , 32(5), 915–926. https://doi.org/10.1175/JTECH-D-14-00252.1 Sorg, A., Bolch, T., Stoffel, M., et al., 2012. Climate change impacts on glaciers and runoff in Tien Shan (Central Asia). Nature Climate Change , 2(10), 725–731. https://doi.org/10.1038/nclimate1592 Wang, R., Tian, W., Chen, F., et al., 2021. Analysis of convective and stratiform precipitation characteristics during summers of 2014–2019 over Northwest China based on GPM observations. Atmospheric Research , 262, 105762. https://doi.org/10.1016/j.atmosres.2021.105762 Wang, S., Du, M., Zhang, M., et al., 2019. Precipitation isotopes associated with the duration and distance of moisture trajectories in a westerly-dominant setting. Water , 11(12), 2434. https://doi.org/10.3390/w11122434 Wang, S., Zhang, M., Hughes, C. E., et al., 2016. Factors controlling stable isotope composition of precipitation under arid conditions: An observation network in the Tianshan Mountains, Central Asia. Tellus B , 68(1), 26206. https://doi.org/10.3402/tellusb.v68.26206 Wang, Z., Hu, X., Ai, W., et al., 2024. Microphysical characteristics of monsoon precipitation over the Yangtze–Huai River Basin and South China: A comparative study based on GPM DPR observations. Remote Sensing , 16(18), 3433. https://doi.org/10.3390/rs16183433 Yamaji, M., Takahashi, H. G., 2023. Seasonal differences in precipitation and microphysical characteristics over the Asian monsoon region using spaceborne dual-frequency precipitation radar. Journal of the Atmospheric Sciences , 80(8), 2115–2128. https://doi.org/10.1175/JAS-D-22-0205.1 Yang, Y., Shen, L., Wang, B., 2022. Vertical distribution of precipitation in arid mountainous regions of Northwest China. Journal of Geographical Sciences , 32(2), 241–258. https://doi.org/10.1007/s11442-022-1941-6 Zhang, L., Duan, J., Xu, C., et al., 2025. Macro- and microphysical structural characteristics of mesoscale convective systems over East China based on GPM data. Plateau Meteorology , XX(XX), 1–17. (in Chinese) Zhang, Y., Hanati, G., Danierhan, S., et al., 2020. Evaluation and comparison of daily GPM and TRMM precipitation products over the Tianshan Mountains, China. Water , 12(11), 3088. https://doi.org/10.3390/w12113088 Zhao, C. C., Ding, Y. J., Ye, B. S., et al., 2011. Spatial distribution of precipitation and its estimation methods in the Tianshan Mountains. Advances in Water Science , 22(3), 315–322. (in Chinese) Zheng, N., Liu, Q., Huang, G., et al., 2019. Spatiotemporal distribution characteristics of precipitable water vapor over the three major mountainous regions of Xinjiang. Arid Land Geography , 42(1), 77–84. (in Chinese) Zhu, H., Zhu, L., Luo, L., et al., 2023. Seasonal variations of modern precipitation stable isotopes over the northern Tibetan Plateau and their influencing factors. Water , 16(1), 150. https://doi.org/10.3390/w16010150 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 16 Mar, 2026 Reviews received at journal 24 Feb, 2026 Reviews received at journal 20 Feb, 2026 Reviewers agreed at journal 20 Feb, 2026 Reviewers agreed at journal 13 Feb, 2026 Reviewers invited by journal 10 Feb, 2026 Editor invited by journal 05 Feb, 2026 Editor assigned by journal 02 Feb, 2026 Submission checks completed at journal 02 Feb, 2026 First submitted to journal 28 Jan, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8720683","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":591022506,"identity":"727a5253-b912-48e2-917f-170b4d22f272","order_by":0,"name":"Xue Mei","email":"","orcid":"","institution":"Xinjiang University","correspondingAuthor":false,"prefix":"","firstName":"Xue","middleName":"","lastName":"Mei","suffix":""},{"id":591022507,"identity":"eacadaa7-54f3-43ed-a1bc-d663a8c37f61","order_by":1,"name":"Lianmei Yang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAApElEQVRIiWNgGAWjYLCCBww2PAwHSNKSwJBGupbDDMRrMTh+9vCLxJzzMnzXDjB+LiBKy5m8NIvEbbd5JG8nMEvPIErLgRwzA5AWg9sJbMw8RGk5/wak5RwpWm7kGD9I3HaABC2SN96YMSRuSwb6JbFZmigtfOdzjD983GZnz3c7+eBnorQoHGBgk4AwGRuI0cDAIN/AwPyBOKWjYBSMglEwYgEAez40zt065QkAAAAASUVORK5CYII=","orcid":"","institution":"China Meteorological Administration","correspondingAuthor":true,"prefix":"","firstName":"Lianmei","middleName":"","lastName":"Yang","suffix":""},{"id":591022508,"identity":"d1dce997-a1ad-4643-af44-b7d604480e87","order_by":2,"name":"Abuduwaili Abulikemu","email":"","orcid":"","institution":"Xinjiang University","correspondingAuthor":false,"prefix":"","firstName":"Abuduwaili","middleName":"","lastName":"Abulikemu","suffix":""}],"badges":[],"createdAt":"2026-01-28 12:24:37","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8720683/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8720683/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102789278,"identity":"69753105-fbbf-449b-9bc7-d7bb5db42a35","added_by":"auto","created_at":"2026-02-16 16:52:26","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":236752,"visible":true,"origin":"","legend":"\u003cp\u003eOverview of the subregional divisions of the study area\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8720683/v1/cb547e4d92b4ae2b3044b4ad.png"},{"id":103049271,"identity":"06df86db-5efb-404e-ba8d-ff08554d6f7f","added_by":"auto","created_at":"2026-02-20 07:39:24","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":492737,"visible":true,"origin":"","legend":"\u003cp\u003eSpatial distribution of Max-PreR for stratiform (a spring, c summer, e autumn, g winter) and convective (b spring, d summer, f autumn) precipitation. The black lines denote the 1500 m and 2500 m elevation contours.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8720683/v1/1aa45894a6c84e1221d643ff.png"},{"id":102789279,"identity":"e03deefb-0051-4ee9-80e2-3bcc6d2cc2cd","added_by":"auto","created_at":"2026-02-16 16:52:26","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":541322,"visible":true,"origin":"","legend":"\u003cp\u003eSame as Fig. 2, but for the spatial distribution of Max-PRF.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8720683/v1/0cbf2796fe37e6f39d799933.png"},{"id":102789281,"identity":"8fce6226-4fb1-47db-b600-eedf1391a4af","added_by":"auto","created_at":"2026-02-16 16:52:26","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":583679,"visible":true,"origin":"","legend":"\u003cp\u003eSame as Fig. 2, but for the spatial distribution of precipitation-type fractions.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8720683/v1/4bed17b54c296fa626ef6cf7.png"},{"id":102962510,"identity":"92d366d5-ddcf-428a-97fd-e46fd1fb06e8","added_by":"auto","created_at":"2026-02-19 04:09:32","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":569627,"visible":true,"origin":"","legend":"\u003cp\u003eSame as Fig. 2, but for the spatial distribution of STH.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8720683/v1/3aa0a35cc8a09fece2c8ad68.png"},{"id":102963097,"identity":"82b99ff2-5059-4559-9f9b-30ed9c26745b","added_by":"auto","created_at":"2026-02-19 04:13:29","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":964408,"visible":true,"origin":"","legend":"\u003cp\u003eVertical profiles of layer-averaged precipitation rate for Region A (a spring, b summer, c autumn, d winter), Region B (e spring, f summer, g autumn, h winter), and Region C (i spring, j summer, k autumn, l winter). Dashed lines denote convective precipitation and solid lines denote stratiform precipitation. The vertical axis represents relative height, defined as the altitude after subtracting the underlying terrain elevation.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-8720683/v1/253c3cc702edf241d24f806d.png"},{"id":102962540,"identity":"ad524ea4-49fa-4f97-91b3-ff7db58414ab","added_by":"auto","created_at":"2026-02-19 04:09:44","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":395336,"visible":true,"origin":"","legend":"\u003cp\u003eSame as Fig. 2, but for the spatial distribution of PWI.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-8720683/v1/9056706d835423eb8a9693e1.png"},{"id":102962591,"identity":"26960a03-134f-438f-b4e8-3c5096311fb7","added_by":"auto","created_at":"2026-02-19 04:09:59","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":422716,"visible":true,"origin":"","legend":"\u003cp\u003eSame as Fig. 2, but for the spatial distribution of PII.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-8720683/v1/f2efeea5787af9cbb80ae848.png"},{"id":102789282,"identity":"947d2d75-b4f8-4f62-8567-94615a808336","added_by":"auto","created_at":"2026-02-16 16:52:26","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":430877,"visible":true,"origin":"","legend":"\u003cp\u003eSame as Fig. 2, but for the spatial distribution of PTI.\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-8720683/v1/368121973a1c60ee51934652.png"},{"id":104834864,"identity":"762727ce-81db-4584-96d5-fe840992db6a","added_by":"auto","created_at":"2026-03-17 17:33:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5202477,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8720683/v1/c793596e-c0da-45b3-aeb1-e33aba6c4462.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Spatiotemporal Distribution of Precipitation Microphysical Characteristics over the Tianshan Mountains Based on GPM/DPR Observations","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eThe Tianshan Mountains serve as the most vital \u0026ldquo;water tower\u0026rdquo; in Central Asia, playing a critical role in regional socioeconomic development and ecological security. With the rapid advancement of satellite remote sensing technology, satellite-based precipitation observation and analysis have become increasingly sophisticated. The tropical rainfall measuring mission (TRMM) provided invaluable precipitation data for tropical and subtropical regions, significantly advancing research on convective-stratiform precipitation classification and precipitation microphysical parameter retrieval (Kummerow et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Hou et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). As TRMM\u0026rsquo;s successor, the global precipitation measurement (GPM) mission utilizes the dual-frequency precipitation radar (DPR) alongside multi-sensor combined retrievals, markedly enhancing precipitation detection in mid- to high-latitude areas and complex terrains (Seto and Iguchi, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Grecu et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Unlike TRMM, which primarily focused on mesoscale precipitation systems within tropical and subtropical zones, GPM\u0026rsquo;s key advancement lies in its improved ability to observe clouds, light rainfall (\u0026lt;\u0026thinsp;0.5 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), solid precipitation, and detailed precipitation microphysical structures. These precipitation types are especially significant in mid- to high-latitude arid and semi-arid regions such as Xinjiang, making GPM observations particularly valuable for precipitation studies over the Tianshan Mountains (Lu et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Lu and Wei, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003ePrevious studies have highlighted the advantages of GPM products in mountainous regions. Jin et al. (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) assessed the performance of CMORPH, TRMM, and GPM IMERG precipitation products over the Tianshan Mountains and found that GPM demonstrated the best overall accuracy, particularly in detecting light precipitation, exhibiting higher detection probabilities and lower false-alarm rates. Spatially, larger errors were concentrated in areas with complex terrain and heavy precipitation, whereas estimates over mid-elevation zones (1250\u0026ndash;2800 m) were the most accurate. This pattern likely reflects the limitations of dual-frequency radar in detecting snowfall and the influence of terrain effects. Zhang et al. (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) divided the Tianshan Mountains into four subregions and further confirmed that GPM significantly outperforms TRMM in daily precipitation detection, especially in the northwestern and southwestern parts of the range.\u003c/p\u003e \u003cp\u003eBeyond quantifying precipitation amounts, GPM has been extensively utilized to investigate precipitation structures and microphysical properties. Liu and Zipser (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) mapped the global distribution of the largest, deepest, and most intense precipitation systems using GPM Ku-band radar observations. Yamaji and Takahashi (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) demonstrated that variations in mass-weighted mean diameter are influenced not only by precipitation intensity but also by changes in precipitation characteristics. Ma et al. (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) analyzed plateau vortex precipitation, revealing distinct spatial patterns differentiating deep weak convection from shallow precipitation. Zhang et al. (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2025\u003c/span\u003e) highlighted the strong connection between convective system occurrence and topography, emphasizing that precipitation intensity is jointly governed by particle size and concentration. Li et al. (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) found that both convective and stratiform precipitation over plains are, on average, approximately 20% stronger than those over mountainous regions, while the higher frequency of weak convective precipitation in mountains largely explains the increased precipitation occurrence there. By integrating GPM DPR observations with ERA5 reanalysis data, Wang et al. (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) demonstrated that precipitation vertical structures are modulated by microphysical processes at various atmospheric levels as well as by environmental conditions.\u003c/p\u003e \u003cp\u003eLong-term precipitation variability in Xinjiang and the broader Tianshan region has also been extensively studied using gauge-based and reanalysis datasets. Guan et al. (2021) analyzed GPCC precipitation data from 1950 to 2016, revealing the spatiotemporal evolution of annual and seasonal precipitation through ensemble empirical mode decomposition and Mann-Kendall tests. Li et al. (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) conducted a systematic investigation of the spatiotemporal distribution and vertical structures of stratiform and convective precipitation over Xinjiang, showing that convective precipitation is most active during summer, when radar reflectivity and storm-top heights (STHs) reach their annual peaks and are significantly greater over mountainous areas compared to basins. Zheng et al. (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) examined total precipitable water vapor across Xinjiang, identifying a clear gradient of decreasing moisture from major basins toward surrounding mountain ranges, along with a pronounced seasonal cycle peaking in summer.\u003c/p\u003e \u003cp\u003eDespite these advances, most existing studies using GPM observations in the Tianshan region have primarily concentrated on the spatiotemporal variability of precipitation amounts. While some research has explored differences between convective and stratiform precipitation, systematic seasonal comparisons of their microphysical characteristics in complex terrain remain limited. Therefore, this study aims to investigate the seasonal evolution and regional variations of the microphysical properties of convective and stratiform precipitation over the Tianshan Mountains using GPM DPR observations, with the objective of advancing the understanding of precipitation structures and processes in mountainous environments.\u003c/p\u003e"},{"header":"2 Study Area and Data Sources","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Overview of the Study Area\u003c/h2\u003e \u003cp\u003eThe Tianshan Mountains are situated between the arid regions of Central Asia and the mid-latitude monsoon-arid transition zone, lying at the core of a large-scale climate regime dominated by the westerlies, known as the westerly-dominated climate region (Jin et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). As the largest and longest east-west-oriented mountain system in Central Asia, the Tianshan Mountains not only form the structural backbone of the topographic framework in northwestern China but also serve as a key driver of regional climate variability and hydrological cycle evolution. Shaped by multiple phases of tectonic activity, the Tianshan range comprises several nearly zonal mountain ranges separated by intermontane basins, creating a distinctive stepwise geomorphological pattern that establishes complex dynamical and thermodynamical conditions conducive to precipitation formation and redistribution.\u003c/p\u003e \u003cp\u003eUnder the combined influence of westerly circulation and orographic forcing, the Tianshan region functions as a \u0026ldquo;wet island\u0026rdquo; within the predominantly arid and semi-arid areas of northwestern China, with mean annual precipitation exceeding 400 mm (Kong and Pang, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Zhu et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Precipitation displays a pronounced spatial gradient, with the highest annual totals occurring in the western Tianshan, often surpassing 700 mm, while the eastern region receives the lowest amounts, sometimes less than 50 mm (Chen et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Moisture primarily arrives from westerly airflows originating over the Atlantic and Arctic Oceans. Due to its considerable elevation, distinctive geometry, being wider in the central section and narrower at both ends, and unique orientation, substantial regional disparities in precipitation distribution are observed across the Tianshan Mountains (Zhao et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe study area encompasses the section of the Tianshan Mountains within China, spanning Xinjiang (73.5\u0026deg;-95.0\u0026deg;E, 39.5\u0026deg;-45.5\u0026deg;N). This region is marked by significant topographic relief, with elevations generally exceeding 1500 m, and the main ridge along with high-mountain zones commonly rising above 3000 m. These high-elevation terrains serve as the primary orographic drivers of regional precipitation formation and distribution (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Extending predominantly east-west, the Tianshan Mountains separate Xinjiang into the Junggar Basin to the north and the Tarim Basin to the south, creating a characteristic \u0026ldquo;mountain-basin\u0026rdquo; geomorphological pattern typical of arid regions. Orographic uplift and barrier effects associated with the mountain system strongly influence moisture transport pathways and vertical motion structures, thereby shaping the pronounced spatial heterogeneity and seasonal variability of precipitation.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Data Sources and Methodology\u003c/h2\u003e \u003cp\u003eThe data used in this study were obtained from the DPR onboard the GPM Core Observatory, a joint mission operated by the national aeronautics and space administration and the Japan aerospace exploration agency. We utilized GPM Level-3 products covering the period from March 2014 to February 2023. Specifically, the GPM DPR Level-3 Version 07 (GPM_3DPR_07) dataset was employed, which provides globally gridded statistics derived from Level-2 instantaneous orbital observations of the Ku- and Ka-band DPR. These products deliver temporally consistent daily and monthly climatological records of precipitation and radar-related parameters.\u003c/p\u003e \u003cp\u003eThe Level-3 products are provided on latitude-longitude grids with spatial resolutions of 0.5\u0026deg; (G1) and 0.25\u0026deg; (G2), covering latitudes from \u0026minus;\u0026thinsp;70\u0026deg; to 70\u0026deg; and longitudes from \u0026minus;\u0026thinsp;180\u0026deg; to 180\u0026deg;. Based on the scanning mode, DPR products are classified into three categories: (1) Full swath (FS), which offers the widest spatial coverage; (2) Matched swath (MS), where Ku- and Ka-band observations are spatially collocated, allowing dual-frequency retrievals with the highest accuracy; and (3) High-sensitivity swath (HS), designed to enhance sensitivity to weak and solid precipitation, particularly snowfall. Both FS and MS modes include single-frequency and dual-frequency retrievals from the Ku and Ka bands, whereas the HS mode contains only Ka-band high-sensitivity single-channel data.\u003c/p\u003e \u003cp\u003eIn this study, monthly mean MS/G2 products with a spatial resolution of 0.25\u0026deg; \u0026times; 0.25\u0026deg; were selected. The key parameters analyzed include precipitation rate (PreR), radar reflectivity factor (PRF), storm top height (STH), vertically integrated precipitation liquid water content (PWI), and vertically integrated precipitation ice water content (PII). These variables were used to systematically investigate the spatial distribution, topographic influences, and seasonal variations of major precipitation microphysical characteristics over the Tianshan Mountains, providing a solid data foundation for understanding the spatiotemporal variability of precipitation in this complex mountainous region.\u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results and Discussion","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Spatial distribution of precipitation microphysical characteristics\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e illustrates the seasonal spatial distributions of the near-surface maximum precipitation rate (Max-PreR, mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) for both stratiform and convective precipitation, while Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e presents the corresponding seasonal variations of near-surface maximum radar reflectivity (Max-PRF, dBZ). Pronounced differences are evident between stratiform and convective precipitation in terms of intensity and spatial coverage. Stratiform Max-PreR values are generally low, typically below 4 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, with corresponding Max-PRF mainly concentrated between 20 and 29 dBZ. During summer, localized enhancements in stratiform precipitation occur, with Max-PreR reaching approximately 6 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and Max-PRF exceeding 35 dBZ. In contrast, convective precipitation commonly exhibits Max-PreR values exceeding 4 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, with Max-PRF predominantly ranging from 29 to 38 dBZ and locally surpassing 41 dBZ. The spatial distribution of convective precipitation is more concentrated and marked by pronounced extrema, reflecting vigorous convective development and strong localized uplift.\u003c/p\u003e \u003cp\u003eFrom a seasonal perspective, stratiform precipitation in spring is relatively weak, with Max-PreR generally ranging from 0 to 2 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and Max-PRF approximately between 17 and 26 dBZ. In contrast, convective precipitation already exhibits localized high-intensity centers during spring, with Max-PreR exceeding 8 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and Max-PRF above 35 dBZ, indicating that orographic and thermodynamic lifting can initiate localized convective activity even in early spring. In summer, precipitation intensity increases markedly, with convective precipitation reaching its annual maximum, Max-PreR surpassing 9 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and Max-PRF generally above 35 dBZ, forming continuous bands of strong precipitation along the central and western Tianshan and northern slopes. Stratiform precipitation also intensifies relative to spring, with Max-PreR ranging from about 2 to 6 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and reflectivity increasing to 23\u0026ndash;32 dBZ. During autumn, precipitation gradually weakens: stratiform Max-PreR decreases to 1\u0026ndash;3 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and Max-PRF to 20\u0026ndash;32 dBZ, while convective precipitation maintains localized strong centers (\u0026gt;\u0026thinsp;7 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and \u0026gt;\u0026thinsp;35 dBZ) but with substantially reduced spatial extent, reflecting the seasonal transition. In winter, stable atmospheric stratification predominates, and precipitation mainly occurs as persistent weak stratiform events, with Max-PreR generally below 1 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and Max-PRF around 14\u0026ndash;20 dBZ.\u003c/p\u003e \u003cp\u003eOverall, the spatial patterns of precipitation intensity and reflectivity exhibit strong consistency between stratiform and convective precipitation, with topography playing a significant role in regulating both types. Orographic lifting associated with the Tianshan Mountains not only enhances the efficiency of stratiform precipitation formation but also creates favorable conditions for triggering deep convection. Compared to other regions, summer Max-PRF values over the Tianshan Mountains are stronger than those observed over plateau regions (15\u0026ndash;40 dBZ) but weaker than those over non-plateau areas such as Anhui, the western Pacific, and the eastern Pacific (15\u0026ndash;50 dBZ). In contrast, Max-PRF over the Tibetan Plateau predominantly remains below 26 dBZ, whereas strong convective precipitation with higher Max-PRF is more widespread across the Tianshan during summer, exhibiting an opposite distribution pattern to that of the plateau regions (Fu et al., 2022).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e presents the spatial distributions of the fractional contributions of stratiform and convective precipitation. Overall, stratiform precipitation covers a much broader area across the Tianshan region. Its occurrence is closely linked to large-scale circulation and moisture advection, spanning most low- and mid-elevation zones and generally following topographic contours. The mean contribution of stratiform precipitation exceeds 60%, reaching over 80% in regions below 1500 m elevation. In contrast, convective precipitation typically contributes less than 30%. High fractions of convective precipitation are distributed in banded patterns along elevation contours and windward mountain slopes, with the \u0026ldquo;funnel-shaped\u0026rdquo; region of the western Tianshan identified as a convection-prone zone, where convective contributions can reach up to 70%.\u003c/p\u003e \u003cp\u003eThe relative contributions of stratiform and convective precipitation vary markedly with season. Convective precipitation increases substantially during summer, while stratiform precipitation dominates in winter, with an average contribution exceeding 90%. These findings indicate that stratiform precipitation governs the primary precipitation processes over the Tianshan region, whereas convective precipitation, though contributing less overall, can be locally enhanced under specific topographic and seasonal conditions.\u003c/p\u003e \u003cp\u003eIt should be noted that the complex terrain features, such as elevation, slope, and other mesoscale topographic-meteorological factors, pose significant challenges for satellite-based precipitation estimation in this region. In particular, the pronounced topographic variability in the \u0026ldquo;funnel-shaped\u0026rdquo; area of the western Tianshan limits the detection capability of satellite products, resulting in large relative biases (PB\u0026thinsp;\u0026gt;\u0026thinsp;55%) (Jin et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Fu et al. (2022) further reported that most precipitation profiles identified by the DPR algorithm are classified as stratiform, with only a few strong-reflectivity profiles categorized as convective. Moreover, some profiles exhibiting convective characteristics are still classified as stratiform, underscoring limitations and potential misclassification issues in the DPR algorithm.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.2 STH and precipitation rate distribution characteristics\u003c/h2\u003e \u003cp\u003eThe STH of precipitation over the Tianshan Mountains shows a pronounced dependence on topography. Spatially, high STH values for both stratiform and convective precipitation are primarily concentrated along the western mountainous regions (approximately 74\u0026ndash;84\u0026deg;E, 40\u0026ndash;44\u0026deg;N) and the windward slopes, while lower STH values are found mainly on the leeward southern slopes, the central mountainous region (approximately 84\u0026ndash;92\u0026deg;E, 41\u0026ndash;44\u0026deg;N), and adjacent plains. This distribution underscores the strong influence of orographic forcing on the vertical structure of precipitation. Additionally, STH exhibits a clear seasonal cycle, with lower values in winter and higher values in summer, typically ranging between 4000 and 7000 m. Convective STH is generally higher than stratiform STH, reaching up to approximately 8000 m, with maximum differences of up to 5000 m, reflecting stronger vertical development and greater spatial heterogeneity.\u003c/p\u003e \u003cp\u003eIn spring, stratiform STH predominantly ranges between 4000 and 6000 m, with high-value centers located over the western Tianshan and the western part of the central Tianshan (west of 88\u0026deg;E) on both northern and southern slopes, where peak values exceed 7000 m. During the same season, convective STH typically spans 5000 to 8000 m, with localized maxima surpassing 8000 m. Summer marks the period with the highest STH values throughout the year. Stratiform STH generally rises to 5000\u0026ndash;7000 m, locally exceeding 8000 m, while convective STH exhibits its strongest vertical development. During this season, STH commonly exceeds 6000 m over the Tianshan west of 84\u0026deg;E and its northern slopes, as well as the southern slopes of the eastern Tianshan (88\u0026ndash;94\u0026deg;E), with some intense convective cores penetrating above 9000 m. Simultaneously, a distinct northeast-southwest-oriented belt of relatively low STH emerges, reflecting a typical signature of terrain-forced circulation. In autumn, stratiform STH decreases to 4000\u0026ndash;6000 m, with localized values above 6000 m, whereas convective STH is mainly concentrated between 5000 and 7000 m; although the spatial extent of high STH values diminishes, localized maxima persist. In winter, stratiform precipitation is strongly limited, and STH generally remains below 5000 m.\u003c/p\u003e \u003cp\u003eCompared to other regions in China, the STH of both stratiform and convective precipitation over the Tianshan Mountains is lower than in eastern China, where echo-top heights of stratiform precipitation reach 8\u0026ndash;10 km and convective precipitation can extend up to approximately 14 km (Zhang et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). However, STH over the Tianshan is slightly higher than that observed over the Tibetan Plateau (Fu, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In South China, echo-top heights generally average around 6 km, rising to about 9 km in summer and decreasing to approximately 3 km in winter (Du et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). These values are overall somewhat higher than those over the Tianshan, with a broader spatial distribution of high-value regions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo better characterize the vertical distribution of precipitation rate, the study area was divided into three subregions based on the spatial pattern of STH (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Region A (74.0-84.2\u0026deg;E, 39.5\u0026ndash;45.0\u0026deg;N), located in the western Tianshan, includes the Ili Valley and the windward northern slopes of the range. This region is strongly influenced by moisture transport associated with the midlatitude westerlies, resulting in abundant moisture availability and pronounced orographic lifting. Consequently, precipitation systems here exhibit deep vertical development and frequent convective activity, making Region A the primary deep-convection zone characterized by intense precipitation and high STH over the Tianshan. Region B (84.2\u0026ndash;91.5\u0026deg;E, 42.0\u0026ndash;44.0\u0026deg;N) corresponds to the central Tianshan mountainous area. Although topographic relief remains pronounced, moisture supply is reduced relative to Region A due to downstream effects on westerly moisture transport. Additionally, the combined influence of basin thermal circulations and orographic blocking limits thermodynamic uplift, thereby constraining the vertical growth of precipitation systems. Region C (91.5\u0026ndash;95.5\u0026deg;E, 43.0\u0026ndash;44.0\u0026deg;N), located in the eastern Tianshan, represents a low-STH area. Moisture intrusion into this region is strongly impeded by surrounding high-elevation mountain ranges, leading to relatively low precipitation amounts, particularly in winter (Liu and Han, 1992; Guan et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e illustrates the vertical distributions of precipitation rate for stratiform and convective precipitation across the western (Region A), central (Region B), and eastern (Region C) Tianshan in different seasons. Overall, stratiform precipitation intensity exhibits a clear west-to-east decreasing gradient across the Tianshan. In Regions A and B, stratiform precipitation is consistently present, displaying a typical vertical structure characterized by weaker intensities aloft and stronger intensities near the surface, with mean precipitation rates generally below 1 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. In contrast, the vertical extent of precipitation in Region C is significantly constrained by elevation and moisture availability. Convective precipitation shows pronounced seasonal and regional contrasts, along with distinct differences in peak intensity and vertical distribution.\u003c/p\u003e \u003cp\u003eIn Region A (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea-d), convective precipitation in spring exhibits two pronounced maxima, exceeding approximately 7 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at midlevels around 3.5 km and about 4 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e near the surface. During summer, no distinct peak is evident, with precipitation rates generally around 2 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e below 6 km. In autumn, convective systems deepen under the influence of cold-warm air interactions, with a peak precipitation rate of roughly 4.3 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e near 6.5 km, representing the annual maximum. Winter precipitation is dominated by weak ice-phase stratiform events, with rates remaining below 1 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e throughout the column. In Region B (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ee-h), convective precipitation during spring and summer displays a multi-peak vertical structure below 5 km, with peak values near 2 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. In spring, these peaks occur mainly in the lower and middle layers, whereas in summer convection deepens, and a secondary peak of about 1.5 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e appears at higher altitudes around 8.5 km. In autumn, the vertical precipitation pattern shows a \u0026ldquo;midlevel maximum with weaker upper and lower levels,\u0026rdquo; peaking at approximately 4.7 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e near 5 km, with rates of 1\u0026ndash;3 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at both lower and upper layers. In winter, near-surface precipitation rates reach about 1 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, higher than in Region A, but decrease rapidly above approximately 1 km. In Region C (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ei-l), stratiform precipitation in summer can extend up to roughly 8 km, exhibiting large variability below 5 km and a steady decrease with height above this level. Spring and autumn precipitation are suppressed, with vertical extent limited to below 5 km and stratiform peaks near 0.8 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e occurring at different heights, around 2\u0026ndash;3 km in spring and below 1 km in autumn. Winter precipitation is even more constrained, with vertical development limited to less than 3 km. Convective precipitation in Region C shows a multi-peak structure with considerable vertical variability. In spring, a peak of about 2.8 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e occurs near 2 km; in autumn, a peak of approximately 1.8 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e appears near 1 km. During summer, convection reaches higher altitudes, but peak precipitation rates concentrate below 5 km, with maxima near 0.5 km and 3 km exceeding 2 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eFrom a microphysical perspective, the vertical variations in precipitation rate for convective and stratiform precipitation reflect distinct processes of moisture condensation, hydrometeor growth, and sedimentation. In convective regions, the precipitation rate increases markedly within the 2\u0026ndash;6 km layer, maintains relatively high values between 6 and 10 km, and gradually decreases at higher altitudes. Summer maxima reach approximately 1.8\u0026ndash;2.0 mm h⁻\u0026sup1; in this layer. This vertical structure corresponds to microphysical mechanisms driven by strong updrafts, which transport abundant moisture upward and sustain continuous ice‑particle and raindrop growth within ascending air. Vigorous vertical motions enhance particle aggregation, collision, and coalescence, allowing elevated precipitation rates to persist even at higher levels. In contrast, stratiform precipitation is sustained by weaker vertical motions, with microphysics dominated by ice‑crystal formation and aggregation aloft, followed by gravitational settling and melting. Hydrometeors undergo phase changes and rapid growth near the 0\u0026deg;C level (approximately 4\u0026ndash;6 km), while precipitation rates decline noticeably above this layer due to reduced ice‑crystal concentrations or enhanced evaporation. Below the melting layer, collision‑coalescence and sedimentation processes prevail, yielding a modest increase in precipitation rate toward the surface.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Vertically integrated hydrometeor content characteristics\u003c/h2\u003e \u003cp\u003eFigures \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e demonstrate that vertically integrated precipitation water content (PWI), ice water content (PII), and total water content (PTI) all exhibit pronounced topographic dependence and seasonal variability. Overall, hydrometeor contents associated with convective precipitation are significantly higher than those of stratiform precipitation. High-value centers are primarily located over the western Tianshan (west of 83\u0026deg;E) and along the windward northern slopes of the central Tianshan (83\u0026ndash;87\u0026deg;E, 44\u0026ndash;45\u0026deg;N). These areas are closely linked to moisture transport and orographic lifting. This region serves as a convergence zone between the midlatitude westerly jet and terrain-forced local airflow, where moisture accumulation and forced ascent promote strong condensation and phase-change processes, resulting in a distinct topographic influence on the spatial distribution of hydrometeor contents.\u003c/p\u003e \u003cp\u003ePWI values are generally low and decrease gradually from west to east along the mountain range. Stratiform PWI mostly remains below 90 g m⁻\u0026sup2;, with local enhancements during summer and significant reductions in spring and autumn, indicating a strong dependence on terrain-induced moisture uplift. In contrast, convective PWI is more concentrated over the windward slopes of the western Tianshan and exhibits substantially higher magnitudes, with local summer maxima exceeding 150 g m⁻\u0026sup2;. This reflects intense liquid-water condensation and efficient growth of small- to medium-sized droplets. In the eastern Tianshan, limited moisture supply leads to generally low PWI values and scattered high-value areas, consistent with the progressive weakening of zonal moisture flux.\u003c/p\u003e \u003cp\u003eThe spatial pattern of PII broadly resembles that of PWI but with systematically larger magnitudes, underscoring the significant contribution of ice-phase particles to precipitation over the Tianshan. For both precipitation types, high PII values form banded structures along the northwestern slopes of the main Tianshan ridge and increase with elevation. In summer, stratiform PII can locally reach 120\u0026ndash;150 g m⁻\u0026sup2;, whereas convective PII is more concentrated and exhibits greater variability, with peak values up to approximately 270 g m⁻\u0026sup2;. This indicates active production of ice crystals, graupel, and snow particles in the mid- and upper troposphere. Notably, convective PII tends to decrease at higher elevations, possibly due to downward particle transport, melting processes, or enhanced turbulence induced by terrain blocking, highlighting a strong orographic influence on ice-phase microphysical processes.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs the sum of PWI and PII, PTI reflects the combined characteristics of both components in its spatial and seasonal variability. High-value regions of stratiform PTI largely overlap with those of PWI and PII, exhibiting peak values around 200\u0026ndash;250 g m⁻\u0026sup2;. In contrast, convective PTI is strongly concentrated over the windward slopes of the western and central Tianshan, with summer maxima reaching 350\u0026ndash;400 g m⁻\u0026sup2;, nearly twice those of stratiform precipitation. This indicates that efficient condensation, freezing, and aggregation processes associated with strong summer convection play a dominant role in enhancing PTI, an effect further amplified by terrain-induced moisture convergence. Seasonal comparisons reveal that PTI variability in spring, autumn, and winter is mainly controlled by PII, suggesting that ice-phase growth dominates hydrometeor content under weaker instability conditions, whereas in summer, enhanced PWI highlights the primary role of intense condensation in increasing liquid water content.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4 Conclusions","content":"\u003cp\u003eUsing monthly mean Level-3 GPM/DPR products from 2014 to 2023, this study systematically investigated the spatiotemporal distribution, vertical structure, and microphysical characteristics of stratiform and convective precipitation over the Tianshan Mountains. Three representative subregions were identified to deepen understanding of precipitation formation mechanisms in complex mountainous terrain. The main conclusions are summarized as follows:\u003c/p\u003e \u003cp\u003e(1) Stratiform and convective precipitation over the Tianshan Mountains exhibit pronounced differences in spatial distribution and seasonal variability. Stratiform precipitation is generally weak, with maximum precipitation rates (Max-PreR) mostly below 4 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and maximum radar reflectivity (Max-PRF) primarily between 20 and 29 dBZ, but it covers a broad area. Local enhancements occur in summer, with Max-PreR reaching approximately 6 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and Max-PRF exceeding 35 dBZ, while winter precipitation is dominated by weak stratiform rain (\u0026lt;\u0026thinsp;1 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 14\u0026ndash;20 dBZ). In contrast, convective precipitation is much stronger, with Max-PreR commonly exceeding 4 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and Max-PRF mainly between 29 and 38 dBZ, locally surpassing 41 dBZ. Convective precipitation also exhibits a more concentrated spatial distribution and higher extremes.\u003c/p\u003e \u003cp\u003e(2) Stratiform precipitation is the dominant precipitation type throughout the year, with mean contributions generally exceeding 60% and increasing to over 90% in winter. Below 1500 m elevation, its contribution can exceed 80%, indicating widespread spatial coverage and a relatively stable structure. Convective precipitation typically accounts for less than 30% overall but locally reaches up to 70% in the western Tianshan \u0026ldquo;funnel-shaped\u0026rdquo; region and on windward slopes, where it plays a critical role in high-intensity precipitation events.\u003c/p\u003e \u003cp\u003e(3) STH exhibits a strong dependence on topography. High STH values are primarily distributed over the western mountainous areas and windward slopes, while low values are found on leeward slopes, central mountains, and adjacent plains. STH displays a clear seasonal pattern, with lower values in winter and higher values in summer, generally ranging from 4000 to 7000 m. Convective STH consistently exceeds stratiform STH, frequently surpassing 8000 m, indicating stronger vertical development. In the western Tianshan, STH is relatively high in spring, peaks in summer with a pronounced banded distribution, contracts in autumn, and reaches its minimum extent in winter.\u003c/p\u003e \u003cp\u003e(4) Stratiform precipitation generally follows a west-to-east decreasing pattern. In Regions A and B, precipitation rate profiles show weaker values aloft and stronger values near the surface, with mean rates generally below 1 mm h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. In Region C, vertical precipitation extent is clearly constrained by elevation and limited moisture supply. Convective precipitation exhibits more pronounced seasonal and regional variability. In Region A, convective activity is strongest in spring and autumn, with distinct peaks near 3.5 km and 6.5 km, respectively, weaker in summer, and largely absent in winter except for weak stratiform precipitation. In Region B, convective precipitation displays a multi-peak vertical structure during spring and summer, extending to higher altitudes in summer, while the strongest peak occurs near 5 km in autumn. Region C shows the weakest vertical development, with convective heights generally below 5 km in spring and autumn; although vertical extension increases in summer, peak intensities remain confined to lower levels.\u003c/p\u003e \u003cp\u003e(5) Overall, convective precipitation exhibits substantially higher precipitation water content integral (PWI) than stratiform precipitation. High PWI values are concentrated mainly over the western Tianshan and the northern windward slopes of the central Tianshan, with PWI decreasing from west to east along the mountain range. Stratiform PWI is mostly below 90 g m⁻\u0026sup2;, with local summer enhancements, whereas convective PWI peaks over the western windward slopes and can exceed 150 g m⁻\u0026sup2; in summer. The spatial pattern of precipitation ice water content integral (PII) is similar to that of PWI but with higher magnitudes, highlighting the significant role of ice-phase processes; summer convective PII peaks can reach approximately 270 g m⁻\u0026sup2;. Total precipitation water content integral (PTI), which combines liquid and ice phases, reflects features of both variables. Convective PTI attains its highest values over windward slopes in summer, reaching 350\u0026ndash;400 g m⁻\u0026sup2;, significantly exceeding stratiform values. This indicates that strong summer convection, combined with topographic lifting, plays a dominant role in enhancing integrated precipitation water content.\u003c/p\u003e \u003cp\u003eThis study supplements existing research by providing a comparative analysis of the seasonal variability of precipitation microphysical parameters over the Tianshan Mountains, offering satellite-based evidence useful for cloud water resource assessment, numerical model parameterization improvement, and regional climate change studies in the \u0026ldquo;Central Asian water tower\u0026rdquo; region. However, the dual-frequency radar system of GPM has limited capability in detecting snowfall over high-elevation areas and tends to substantially underestimate winter precipitation (Jin et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Similar to the single-frequency precipitation radar onboard TRMM, GPM/DPR faces uncertainties in bright-band identification over complex high-mountain terrain (Fu, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Future work should integrate ground-based radar and radiosonde observations for multi-source validation to further improve precipitation estimation accuracy in cold, high-altitude mountainous regions.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eThis work was supported by Key Research and Development Program of Xinjiang Uygur Autonomous Region (2023B03019-1) and Tianshan Talent Training Program Project (2022TSYCLJ0003).\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Xue Mei, Lianmei Yang and Abuduwaili Abulikemu. The first draft of the manuscript was written by Xue Mei and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003eThe data used in this study are available from the official GPM website and the data generated and analyzed during the study period are available from the corresponding author upon reasonable request.\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eXinjiang Uygur Autonomous Region Key R\u0026amp;D Program (2023B03019-1);\u003c/p\u003e \u003cp\u003eTianshan Talent Training Program (2022TSYCLJ0003).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAll authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Xue Mei, Lianmei Yang and Abuduwaili Abulikemu. The first draft of the manuscript was written by Xue Mei and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data used in this study are available from the official GPM website and the data generated and analyzed during the study period are available from the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eChen, C., Hu, Y., Fan, M., et al., 2025. Investigation on the linkage between precipitation trends and atmospheric circulation factors in the Tianshan Mountains. \u003cem\u003eWater\u003c/em\u003e, 17(5), 726. https://doi.org/10.3390/w17050726.\u003c/li\u003e\n \u003cli\u003eChen, Y., Li, Z., Fang, G., et al., 2017. 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Spatiotemporal distribution characteristics of precipitable water vapor over the three major mountainous regions of Xinjiang. \u003cem\u003eArid Land Geography\u003c/em\u003e, 42(1), 77\u0026ndash;84.\u0026nbsp;(in Chinese)\u003c/li\u003e\n \u003cli\u003eZhu, H., Zhu, L., Luo, L., et al., 2023. Seasonal variations of modern precipitation stable isotopes over the northern Tibetan Plateau and their influencing factors. \u003cem\u003eWater\u003c/em\u003e, 16(1), 150. https://doi.org/10.3390/w16010150\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Tianshan Mountains, GPM/DPR, stratiform and convective precipitation, microphysical structure, topographic effects","lastPublishedDoi":"10.21203/rs.3.rs-8720683/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8720683/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eUsing monthly mean Level-3 GPM/DPR products from March 2014 to February 2023, this study systematically investigates the spatial distribution, vertical structure, and microphysical characteristics of stratiform and convective precipitation over the Tianshan Mountains. The results indicate that stratiform precipitation is generally weak but widespread, with maximum precipitation rates mostly below 4 mm h⁻\u0026sup1; and maximum radar reflectivity mainly ranging from 20 to 29 dBZ. It contributes more than 60% of total precipitation annually, increasing to over 90% in winter. In contrast, convective precipitation exhibits much higher intensity and pronounced extremes, with maximum precipitation rates commonly exceeding 4 mm h⁻\u0026sup1; and radar reflectivity typically between 29 and 38 dBZ, locally surpassing 41 dBZ, and is primarily concentrated in summer over the western Tianshan and windward slopes. Storm-top height generally ranges from 4 to 7 km, while convective precipitation frequently exceeds 8 km, showing a clear west-to-east decreasing pattern controlled by topography. Vertically integrated liquid, ice, and total hydrometeor contents associated with convective precipitation are substantially higher than those of stratiform precipitation, with summer total water content reaching 350\u0026ndash;400 g m⁻\u0026sup2;. These findings provide satellite-based evidence for improving the understanding of precipitation processes and microphysical mechanisms in complex mountainous regions.\u003c/p\u003e","manuscriptTitle":"Spatiotemporal Distribution of Precipitation Microphysical Characteristics over the Tianshan Mountains Based on GPM/DPR Observations","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-16 16:52:21","doi":"10.21203/rs.3.rs-8720683/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-16T09:48:06+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-24T21:43:24+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-21T02:29:24+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"204929472698242221750557175275190843468","date":"2026-02-21T01:59:49+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"41016250643230762799960830121457537922","date":"2026-02-13T14:25:07+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-02-10T18:57:10+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-02-05T18:42:10+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-03T01:50:44+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-03T01:50:19+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2026-01-28T11:03:42+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"903c2b2b-bc0f-4981-9889-9ec292bd9338","owner":[],"postedDate":"February 16th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":62898543,"name":"Earth and environmental sciences/Climate sciences"},{"id":62898544,"name":"Earth and environmental sciences/Environmental sciences"},{"id":62898545,"name":"Earth and environmental sciences/Hydrology"},{"id":62898546,"name":"Earth and environmental sciences/Natural hazards"}],"tags":[],"updatedAt":"2026-03-26T20:38:20+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-16 16:52:21","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8720683","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8720683","identity":"rs-8720683","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}