Stationary Eddies and the Zonal Asymmetry of Net Precipitation and Ocean Freshwater Forcing

摘要: Transport of water vapor in the atmosphere generates substantial spatial variability net precipitation (precipitation minus evaporation). Over half total annual-mean precipitation is accounted for by deviations from zonal mean. land, these regional differences determine in surface availability. oceans, they account, example, Pacific–Atlantic difference sea surface salinity, with implications deep overturning circulation. This study analyzes atmospheric-water budget reanalyses ERA-Interim and MERRA, to investigate which physical balances lead zonal variation precipitation. It is found that leading-order contribution variation stationary-eddy vertical motion. Transient eddies modify pattern zonally anomalous moving moisture from subtropical tropical oceans onto land poleward across Northern Hemisphere storm tracks. Zonal specific humidity stationary-eddy horizontal advection play a secondary role. The dynamics leading via vertical motion stationary can be understood lower-tropospheric vorticity budget. large-scale variations are primarily described Sverdrup balance Ekman pumping, some modification transient eddies. These results suggest it important to understand changes their influence on eddy fluxes, order They highlight relative importance of different atmospheric mechanisms freshwater forcing North Pacific Atlantic.