Feedback of Land–Sea Thermal Contrast and Impact on Regional Warming

Abstract:

This study investigated the feedback of land–sea thermal contrast and impact on regional climate. A land–sea index (LSI) wasdefined to measure asymmetric zonal thermal forcing, which determined that it has changed from a negative to positive anomaly since the 1980s. In the positive phase of the LSI, the 500-hpageopotential height decreased in polar regions and increased in the mid-latitudes. The tropospheric planetary wave activity also became stronger and exerted an easterly wind forcing on the westerly wind.These circulation changes were favorable for westerly wind acceleration and the decrease in blocking. In turn, the response of the westerly and blocks could further enhance continental warming, which would strengthen the “cold ocean and warm land (COWL)” pattern. This positive feedback could amplify regional warming in the context of overall global warming.