Propagation characteristics and mechanism from meteorological to agricultural drought in various seasons

Agricultural drought poses a serious threat to national food security, and the investigation on the propagation from meteorological to agricultural drought plays an important role in drought mitigation and social stability. Nevertheless, the seasonal dynamic propagation from meteorological to agricultural drought and its dominant influence factors in a changing environment remain unresolved. To this end, the meteorological drought and agricultural drought are characterized by the Standardized Precipitation Index (SPI) and Standardized Soil Moisture Index (SSMI), respectively. The propagation time from meteorological to agricultural drought is determined by selecting the maximum conditional probability value between SPI with various timescales and SSMI with time scale of 1 month (SSMI-1). Furthermore, the seasonal dynamic propagation patterns are obtained based on the moving window and Mann-Kendall trend test. Subsequently, the influence factors are explored based on the diverse hydro-meteorological factors and irrigation water consumption. The Wei River Basin (WRB), a typical arid and semi-arid as well as an important agricultural production area in China, is taken as the research object. Results manifest that: (1) it is more suitable to determine the drought propagation time by conditional probability method considering linear and nonlinear relations simultaneously; (2) the seasonal propagation time of the whole basin is getting shorter as a whole, especially in the main stream basin; (3) the increasing temperature and decreasing soil moisture and precipitation have strong effects on the propagation dynamics while irrigation water consumption has a little influence, and teleconnection factors may indirectly affect drought propagation by influencing hydro-meteorological factors. Overall, it is of great significance to study the propagation of meteorological drought to agricultural drought for drought prevention, drought resistance and food security.