Abstract
Circulation patterns linked to the East Asian winter monsoon (EAWM)
affect precipitation, surface temperature, and air quality extremes over
East Asia. These circulation patterns can in turn be influenced by
aerosol radiative and microphysical effects through diabatic heating and
its impacts on atmospheric vorticity. Using global model simulations, we
investigate the effects of anthropogenic aerosol emissions and
concentration changes on the intensity and variability of the EAWM.
Comparison with reanalysis products indicates that the model captures
the mean state of the EAWM well. The experiments indicate that
anthropogenic aerosol emissions strengthen the Siberian High but weaken
the East Asian jet stream, making the land areas of East Asia colder,
drier, and snowier. Aerosols reduce mean surface air temperatures by
approximately 1.5°C, comparable to about half of the difference between
strong and weak EAWM episodes in the control simulation. The mechanisms
behind these changes are evaluated by analyzing differences in the
potential vorticity budget. Anthropogenic aerosol effects on diabatic
heating strengthen anomalous subsidence over southern East Asia,
establishing an anticyclonic circulation anomaly that suppresses deep
convection and precipitation. Aerosol effects on cloud cover and cloud
longwave radiative heating weaken stability over the eastern flank of
the Tibetan Plateau, intensifying upslope flow along the western side of
the anticyclone. Both circulation anomalies contribute to reducing
surface air temperatures through regional impacts on thermal advection
and the atmospheric radiative balance.