Wintertime Modulation of the Local Cloud and Diagnostic Fields by the Hadley Cell Subsiding Boundary Over the Western North Pacific

摘要

The responses of cloud and diagnostic fields to the poleward shift of the local Hadley cell subsiding edge are examined using observational and reanalysis data from December 1982 to February 2016. Over the western North Pacific, the interannual variability of the local Hadley cell subsiding edge is marked by an anomalous rising motion, decreased large-scale static stability, and corresponding increases of the midlevel cloud fraction over the climatological sinking zone around 35 degrees N. The most sensitive cloud type is identified to be cumulus congestus, with cloud top pressures in the range of 440-680 hPa and optical thicknesses in the range of 23-60. This kind of cloud is estimated to be the main contributor to the net negative top-of-atmosphere radiation anomaly and to constrain the distribution of the anomalous precipitation associated with the local HC expansion.