Daily drought index based on evapotranspiration can characterize the spatiotemporal evolution of regional droughts

With climate warming, frequent drought events have occurred in recent decades, causing huge losses to industrial and agricultural production, and affecting people's daily lives. The monitoring and forecasting of drought events has drawn increasing attention. However, compared to the various monthly drought indices and their wide application in drought research, daily drought indices, which would be much more suitable for drought monitoring and forecasting, are still scarce. The development of a daily drought index would improve the accuracy of drought monitoring and forecasting, and facilitate the evaluation of existing indices.

A recent study is led by Dr. Xia Zhang and Dr. Yawen Duan, under the guidance of Prof. Jianping Duan, members of Key Laboratory of Regional Climate-Environment Research for Temperate East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences. In this study, they constructed a new daily drought index, the daily evapotranspiration deficit index (DEDI), based on actual and potential evapotranspiration data from the high-resolution ERA5 reanalysis dataset of the European Center for Medium-Range Weather Forecasts.

This new index was applied to analyze the spatial and temporal evolution characteristics of four drought events that occurred in southwest, north, northeast, and eastern northwest China in the spring and summer of 2019. Comparisons with the operationally used Meteorological Drought Composite Index and another commonly used index, the Standardized Precipitation Evapotranspiration Index, indicated that DEDI characterized the spatiotemporal evolution of the four drought events reasonably well and was superior in depicting the onset and cessation of the drought events, as well as multiple drought intensity peaks.

Additionally, DEDI considers land surface conditions, such as vegetation coverage, which enables its potential application not only for meteorological purposes but also for agricultural drought warning and monitoring. Their previous study have shown that the evapotranspiration-based drought index can more sensitively capture the biological changes of ecosystems in response to the dynamics of drought intensity, compared with the indices of precipitation and temperature.

The drought index is easy to calculate, and ERA5 provides near-real-time data of actual and potential evapotranspiration, which can satisfy the needs of rapidly obtaining drought information in people's daily lives and industrial and agricultural production.

This research was published in Advances in Atmospheric Sciences and Science China Earth Sciences.