Assessing Agrometeorological Drought in Iran’s Anthropocene

The present study aims to investigate Iran’s agrometeorological drought history and its properties using Multivariate Standardized Drought Index (MSDI). For this purpose precipitation and soil moisture recorded at 99 synoptic stations in Iran with more than 30 years observations were colected. Based on MSDI time series, drought properties including duration and severity were calculated and trend analysis was carried on using Trend Free Prewhitening Mann Kendall test. Also the standard normal homogeneity test (SNH-test) was applied to investigate chronological drought change-point detection (CPD). From agrometeorological perspective, results showed that longer and more severe droughts are more dominant in southern, southeastern, northeastern and some western regions of the country. Trend analysis revealed that most stations have rising frequency and significant drying trend especially in winter at central plateau and western regions. Also we recognized two main periods 1991–2000 and 2006–2010 that many stations experienced change-point in their MSDI time series, mainly because of climatic and anthropogenic causes. Drought properties assessment shows 6 stations with serious upward trend in drought duration and severity in northeast and western regions. The probability analysis revealed that most stations have a ratio around 2–5 times increase in drought occurrence probability after change point, leading to longer and more severe droughts in these stations. The paper indicates a serious situation related to agrometeorological drought occurrence, persistence and severity in Iran because of many climatic and anthropogenic factors over the last 30 years.