A model analysis of the interactions between East Asian anthropogenic aerosols and North Pacific atmospheric transients in boreal winter

摘要

Perpetual winter simulations are conducted with the Community Earth System Model under conditions of normal and zero emission of East Asian anthropogenic aerosols. The inclusion of aerosol emission and subsequently the increase of aerosol concentrations over the North Pacific due to the downstream transport induce statistically robust changes to the structure of the time-mean atmospheric circulation across the basin. Specifically, the activity of atmospheric transient eddies significantly weakens in a zone extending from the east of Japan to the Bering Sea, Alaska, and slightly strengthens over the central North Pacific. Further partitioning in the frequency domain reveals that low-frequency eddies with a 10-30 days time scale dictates the overall transient eddy response to aerosols. The amplitude of synoptic-scale, high-frequency eddies (2-6 days), on the other hand, increases from the central North Pacific to the Gulf of Alaska and decreases at the entrance of the North Pacific storm track and near the west coast of North America. The changes in the synoptic eddy field leave a distinct and consistent signal in surface precipitation. An analysis of the local energy budget of transient eddies indicates that changes in baroclinic conversion, more specifically transient eddy heat flux, largely determines the simulated differences in the activity of atmospheric transients between conditions of normal and zero emission of East Asian anthropogenic aerosols.