Process‑based evaluation indicators of grape drought and risk characteristics in Bohai Rim Region (BRR), China

Drought stress is one of the major environmental limiting factors for grape growth in the Bohai Rim Region (BRR) in China. Investigation of process-based meteorological evaluation indicators is of particular interest to precisely understand the spatiotemporal characteristics of grape drought processes, providing substantial support for grape drought monitoring, prevention, and mitigation. In this study, a daily index grape drought index (GDI) was constructed based on the rolling calculation of water profit and deficit. Characteristics of GDI in historical drought disaster samples were analyzed, and drought evaluation level indicators were constructed, facilitating the assessment of process-based grape drought risk. The results showed that duration days with GDI<-0.4 identified can be used as drought level indicators, and the threshold of grape drought in germination-new shoot (P1), flowering-fruit setting (P2), fruit expansion (P3), and coloring-mature (P4) were 14, 13, 12, and 13 days with GDI<-0.4, respectively. Identification results calculated by grape drought indicators were basically consistent with historic occurrence levels of grape drought, with 76.9% of historical records completely consistent with the grape level assessment, and 15.4% within one level. The process-based grape drought risk gradually decreased with the advancement of grape growth process, with grape drought risk in the order of P1 > P2 > P3 > P4. Beijing, Tianjin, Hebei and west of Liaoning were detected with the higher drought risk.