Suitability of assimilated data-based standardized soil moisture index for agricultural drought monitoring

Drought is a recurring extreme climate event. Frequent droughts have serious impacts on agriculture and threaten food security. The Huang-Huai-Hai(HHH) Plain is one of the most important food-producing areas in China, and agricultural drought is one of the main factors leading to the decline of grain production in this region. Therefore, accurate and effective agricultural drought monitoring is of great significance to develop disaster mitigation strategies and reduce disaster losses. The standardized soil moisture index(SSMI) is an agricultural drought index based on historical soil moisture time series. Currently, the suitability of SSMI for monitoring agricultural drought is scarce. In previous studies, an agricultural drought index was mainly evaluated by comparisons with other commonly used drought indices or meteorological elements. Only a few studies considered the drought disaster records and the impact of drought on crop yield. In this study, the SSMI was established by using the assimilated root zone soil moisture to monitor agricultural drought in the HHH Plain. The SSMI-based results showed that several drought events occurred between 2002 and 2010. Of these droughts, the moderate or extreme droughts occurred in 2002, 2004, and 2006, matching well with the reality. Subsequently, the suitability of the SSMI was evaluated by comparing with the standardized precipitation-evapotranspiration index(SPEI), agricultural drought records, and winter wheat yield. The results showed that the average correlation coefficient between the SSMI and SPEI was 0.52, indicating a significant correlation(P