The Local and Remote Impacts of Asian Aerosol Forcings on the East Asian Winter Monsoon and ENSO

The East Asian winter monsoon (EAWM) is a prominent feature of the northern hemisphere atmospheric circulation during boreal winter, which has a large influence on the weather and climate of the Asian-Pacific region. At interannual time scales, the strength of the EAWM is strongly influenced by the El Niño-Southern Oscillation (ENSO). With the increasing influence of human activities, the greenhouse gas-driven changes in the climate mean state and the interannual variability of the EAWM received widespread attention. However, the impact of anthropogenic aerosols has been considered only in a few studies, which may accelerate or counteract greenhouse gas-driven climatic changes over different regions. Using fixed sea surface temperature and atmosphere–ocean coupled simulations from the Precipitation Driver Response Model Intercomparison Project (PDRMIP), the local and remote impacts of Asian aerosol forcings on the broad East Asian-Pacific region are examined. Results indicate that increased sulfate concentrations over Asia by a factor of 10 strengthen the EAWM through the regional aerosol‐induced cooling first, then extend the EAWM circulation southeastward through the broader cooling over the Maritime Continent and the North Pacific. Remotely, the cooler Northern Hemisphere shifts the Intertropical Convergence Zone (ITCZ) toward the south, and the warmer sea surface temperature (SST) over the equatorial eastern Pacific leads to western-central equatorial Pacific westerly wind anomalies. These changes contribute to the increase in the ENSO’s amplitude, mainly through strengthening the Bjerknes or zonal wind feedback. Furthermore, in response to the increase in extreme El Niño and La Niña frequency, the interannual variability of the EAWM increases, with more extreme strong and weak EAWM years.