Role of Thermal Condition over Asia in the Weakening Asian Summer Monsoon under Global Warming Background

The large-scale Asian summer monsoon circulation has experienced a weakening tendency in recent decades. Using observed data and output from model experiments with the atmospheric component of the NCEP Climate Forecast System, the authors show that a relatively smaller warming in Asia compared to the surrounding regions may be a plausible reason for this change in the monsoon. Although the surface temperature over Asia has increased, the landmass has become a relative "heat sink" because of the larger warming in other regions of the world. Indeed, over Asia, the vertically integrated tropospheric temperature in the most recent decades is colder than that in the earlier decades, a feature different from the characteristics outside Asia.