Seasonal variation of atmospheric water circulation in the Antarctic region derived from objective analysis data

Abstract

Precipitable water, total moisture flux and its convergence are calculated based on the 6-year (1986-1991) twice-daily U.S. NMC data to investigate the atmospheric water circulation in the Antarctic region. The precipitable water becomes large in summer, but the zonal mean poleward moisture flux and its convergence, which corresponds to "precipitation minus evaporation", become large in winter and they also exhibit semi-annual variation. This is because the seasonal variation of moisture flux and its convergence is mainly controlled by the cyclonic activity in the Antarctic region. The westward moisture flux, which does not exist in the Arctic region, is seen poleward of 70° along the Antarctic continent and it is significant in summer. It is found that the atmospheric water circulation in the Antarctic region is very active compared with the global mean, especially in winter.