The impact of soil moisture-surface temperature coupling on the compound heat wave event in the middle and lower reaches of the Yangtze River in August 2022
The compound heat wave in the middle and lower reaches of the Yangtze River during August 2022 caused serious impacts on various aspects,including social economy,human health,agricultural production and natural environment.This study utilizes data such as daily maximum and minimum temperatures from June-August 1979 to 2022 provided by the National Information Center and soil moisture from the European Centre for Medium-Range Weather Forecasts reanalysis datasets.We define an intensity index for compound heat wave event and a corresponding soil moisture-surface temperature coupling index.Various methods,including segmented linear fitting,are employed to investigate the characteristics of compound heat wave event and the impacts of soil moisture-surface temperature coupling.The results show that,(1)the intensity of the compound heat wave event in the middle and lower reaches of the Yangtze River in August 2022 is the strongest since 1979,accompanied by the most intense soil moisture-surface temperature coupling.The spatial distribution shows that intense heat wave occurs in eastern Sichuan,western Chongqing,Hunan and other areas,where the soil moisture is seriously dry and evaporation is restricted.The net radiation received by the surface is primarily transported to the upward as sensible heat flux,resulting in a strong positive feedback process between soil moisture and surface temperature,playing a crucial role in sustainability of heat wave.(2)The effect of soil moisture-surface temperature coupling in the compound heat wave differs in physical forcing and processes between daytime and nighttime heat wave.During the daytime,the enhanced downward shortwave radiation at the surface forces strong soil moisture-surface temperature coupling,leading to a daytime heatwave.At night,the heat accumulated in the soil during the daytime slows down the decrease of surface temperature by reducing the divergence of atmospheric heat flux,forming a nighttime heat wave.This differs from previous studies on the process of nighttime heat wave,which are considered to be accompanied by the moist conditions in the atmospheric column with increases in atmospheric inverse radiation.
Compound heat waveSoil moisture-surface temperature couplingThe middle and lower reaches of the Yangtze River region
NETL
NSTL
万方数据
