High Temperature Accelerates Onset Speed of the 2022 Unprecedented Flash Drought Over the Yangtze River Basin

Abstract

The Yangtze River Basin experienced one of the worst flash droughts on record during 2022 summer, but the relative contributions of precipitation deficit and high temperature to drought onset speed and intensity are difficult to separate due to the compounding feature of hot and dry extremes caused by persistent high-pressure anomalies. Based on high-resolution land surface model ensemble simulations with specified meteorological conditions that reproduce precipitation deficit and/or high temperature anomalies during 2022, we find the precipitation deficit is the dominant factor for triggering the flash drought. Meanwhile, high temperature further accelerates the decrease of soil moisture and intensifies drought condition by increasing evapotranspiration, which contributes 37% ± 14% (31% ± 15%) and 36% ± 11% (30% ± 15%) of the drought onset speed and intensity over upper reach (middle and lower reaches). Our study reveals the nontrivial role of high temperature in intensifying the 2022 Yangtze flash drought, which might be more significant in the warmer future.