Analysis of Summer Drought/flood in China and 50 hPa Mean Circulation over the Northern Hemisphere in 1997

Through analyzing the features of 50 hPa mean circulations over the Northern Hemisphere for three summer rainfall patterns in China, it is shown that the features of 50 hPa circulation for summer precipitation anomaly over China in 1997 are mainly expressed as the higher geopotential height of large area from winter to summer, and weaker polar vortex in winter and stronger in spring, and strengthening for the Pacific high anomaly in winter and spring.