Abstract:
The analysis of land–atmosphere interactions and their impact on summer high temperature events in eastern China reveals significant regional differences. Using the “two-legged coupling index” using ERA5-Land/GLDAS-NOAH reanalysis data, we examined how these interactions influence high-temperature events. The results show a strong negative correlation between extreme high-temperature events and soil moisture. In the northeast region and the middle and lower reaches of the Yangtze River, the impact is most significant. Here, extreme high temperature events and abnormal soil moisture changes show a dipole pattern, with reverse phase changes occurring between the north and south. Further analysis reveals obvious spatial differences in land–atmosphere coupling, along with significant differences in how soil moisture influences high-temperature events. In Northeast China, these events are largely affected by increased sensible heat owing to soil drying. When soil is dry, evapotranspiration decreases, reducing latent heat flux and increasing sensible heat flux, which contributes to surface warming. At the same time, the development of blocking high-pressure systems and abnormal land surface heating eventually leads to frequent high-temperature events in Northeast China. In the middle and lower reaches of the Yangtze River, high-temperature events are mainly affected by changes in surface energy and atmospheric circulation. During these events, the West Pacific subtropical high extends westward, reducing cloud cover and increasing short-wave radiation. This leads to abnormal surface warming owing to adiabatic heating from subsidence, causing the surface temperature to rise. As a result, evapotranspiration increases, and soil moisture decreases. This creates a positive feedback loop that maintains surface warming and supports favorable conditions for high-temperature events in this region.