Effect of Land–Ocean–Atmosphere Interaction on Summer Heat Waves in North China

Based on statistical analysis and multiple sensitivity experiments using the Weather Research and Forecasting model, it is found that the relationship between preceding soil moisture anomalies and summer heat waves in North China is affected by the strength of the West Pacific Subtropical High (WPSH). When the WPSH is strong, the southerly winds on its west side carry a large amount of water vapor from the tropics to the southern parts of North China and increase the precipitation in the region, which is not conducive to maintain the preceding soil moisture dry anomaly, thereby restricting the contribution of the preceding soil moisture anomaly to the summer heat waves. In contrast, when the WPSH is weak, the soil moisture dry anomalies in North China can last for a longer duration and lead to heat waves. The WPSH intensity is associated with the Sea Surface Temperature (SST) in the tropical central−eastern Pacific. When the tropical Pacific SST exhibits positive anomaly in summer, the WPSH is relatively weak, and the precipitation in North China is low, which is conducive for maintaining dry soil conditions in North China. Under such scenarios, the preceding soil moisture anomaly can be employed as the prediction signal of heat waves in North China.