Abstract:

Drought is one of the most catastrophic natural hazards which have severe impacts on human society and yet it is the least understood hazard. Monitoring drought in a reliable way plays a critical role in the early warning as well as the mitigation of drought hazard. Generally, the integrated agro-meteorological drought monitoring is one of the most popular drought monitoring methods and it is the key step to mitigate droughts effectively. However, the originally developed integrated drought monitoring index included nothing about evapotranspiration, and it does perform not well in reflecting impacts of evapotranspiration on occurrence of droughts. In this case, this study attempted to propose an improved version of the multivariate standardized drought index (MSDI) using standardized precipitation evapotranspiration index (SPEI) and standardized soil moisture index (SSI), i.e. modified multivariate standardized drought index (MMSDI). Based on the statistical records of drought-affected crop area in 7 geographical zones across China, this study tests the applicability of MMSDI in drought monitoring across China in 3-month and 6-month time scales, with comparison to the meteorological drought monitored by SPEI, agricultural drought monitored by SSI and integrated agro-meteorological drought monitored by MSDI. The result indicates that MMSDI can monitor meteorological drought and agricultural drought simultaneously. Furthermore, MMSDI has greater superiority than SPEI, SSI and MSDI in the veracity of drought monitoring. Besides, MMSDI can monitor droughts in bad conditions where meteorological drought and agricultural drought monitoring technique cannot be applied. Moreover, MSDI tends to overestimate the drought intensity and the size of drought-affected regions across China. In sum, MMSDI proposed in this study can be used to monitor and detect drought conditions in a more accurate way from perspectives of meteorological drought and agricultural drought. Meanwhile, drought conditions monitored by MMSDI are very close to in-situ observations and to the real-world observations of droughts in terms of drought-affected regions and related losses. In this sense, this study provides a theoretical foundation for large-scale drought monitoring across China, and provides practical regional case studies for related research in other regions of the world.

Key words: drought monitoring, integrated agro-meteorological drought, soil moisture, downscaling, nonparametric drought monitoring method