Spatial Characteristics of Surface Air Temperature–Land Surface Coupling Strength during Summer in China

Given the important role of land–atmosphere coupling (LAC) in extreme hot events, the multi-timescale characteristics of sensitivity-based coupling strength, which is between surface air temperature and land surface conditions in summer, were analyzed over China using the ERA5-Land reanalysis dataset. Results show that LAC strength varies remarkably with regions. In particular, the LAC hot spots where variations in land surface conditions considerably influence the surface air temperature through latent heat exchange are primarily located in Northwest China and Yangtze River basin. However, in terms of LAC defined by the sensitivity of surface air temperature to the land condition anomalies through sensible heat exchange, the hot spots are mainly located in the Hetao–Inner Mongolia areas, southwestern Xinjiang, and part of the south Yangtze River. This indicates that the differences in the spatial distribution of LAC indices can be largely explained by the dominant processes, in which land surface anomalies significantly affect the surface air temperature. Moreover, LAC strength varies considerably among different timescales, with monthly LAC strength being significantly weaker than that of shorter timescales (i.e., daily, pentad, and ten-day). As timescales increasing from one to ten days, the land–air temperature coupling strength based on latent heat flux gets weaker in majority parts of China, while that based on sensible heat flux gets stronger in the northern parts of China but remains a weakened state in other regions. Furthermore, in Northwest China, the coupling strength between the subsurface soil moisture and surface air temperature is weaker than that between the surface soil moisture and surface air temperature.