Convection-permitting regional climate simulation on soil moisture-heatwaves relationship over eastern China

Through soil moisture-temperature feedback, soil moisture significantly impacts heatwaves, which have detrimental effects on ecosystems, society, and human health. This study analyzed the spatiotemporal features of heatwave indices, including heatwave magnitude (HWM) and frequency (HWF) over eastern China during 1998-2010, and their relationships with antecedent soil moisture based on both observations and model simulations. To reasonably capture the land-atmosphere feedback, the convection-permitting (4 km grid spacing) Weather Research and Forecast model (WRF_CPM) was adopted for the investigation. Results show that WRF_CPM can reasonably simulate the observed spatial and temporal features of heatwave indices over most of the six chosen subregions of eastern China, except HWM in Jiangnan Hills (JNH). As a good indicator of soil moisture anomaly (SMA), the standardized precipitation evapotranspiration index (SPEI) was applied to illustrate the soil moisture-heatwave relationship. SPEI is negatively correlated with both HWF and HWM over JNH, Yangtze-Huai River basin (YHR), Sichuan Basin (SCB), and North China Plain (NCP). Such negative correlations are well reproduced by WRF_CPM, except for HWM in southeast China and HWF in NCP. It is indicated that increased soil moisture suppresses HWM in most areas, especially for the high quantiles, and such relationship is pronounced in YHR, JNH, NCP, Loess Plateau (LP), and SCB. Similarly, HWF was more dependent on SPEI for the higher quantiles, especially in YHR, JNH, SCB, and NCP. WRF can well capture the heterogeneous responses of heatwave indices to antecedent SPEI over most subregions except for underestimate the high-quantile HWF responses in NCP, and slightly overestimate HWF responses in JNH, respectively. The relationship between SPEI and soil moisture is consistent with the theoretical considerations. Additionally, the results illustrate the advantages of a high-resolution (4 km) convection-permitting model in simulating the impacts of antecedent soil moisture on heatwaves in China, which are also important implications for land-atmosphere coupling research as well as heatwave monitoring and forecasting.