NUMERICAL MODELING OF THE INFLUENCE OF EURASIAN OROGRAPHY ON THE ATMOSPHERIC CIRCULATION IN DIFFERENT SEASONS

Two experiments based on the spectral atmospheric component “SAMIL” of the Climate Model “F-GOALS” are presented: one is with full orography and the other is without Eurasian orography. The influences of Eurasian orography on the atmospheric circulation in difference seasons are obtained by analyzing the differences between the two experiments of geopotential height, streamline function, precipitation and temperature. Results show that such influences are seasonal dependant. The features can be classified into winter pattern (November-next year April), summer pattern (June-September) and transition pattern (May and October), with an equivalent barotropic vertical structure appearing over the high and middle latitudes. For the height difference, the winter pattern is characterized by the north-south and west-east seesaws along 35°N and 100°E, with high to the west and low to the east in north, and low to the west and high to the east in south. The summer pattern is featured as high in the north and low in the south over Western Pacific, and upper layer positive and lower layer negative over the continent. As to the streamline difference at 850 hPa, the winter type is characterized as cyclonic/anticyclonic circulations over the northern/southern Western Pacific, and a “TP dipole pattern” over the continent. Whereas the summer patter in the subtropics is featured by a cyclonic circulation surrounding the TP and an anticyclonic circulation over west Pacific. The orography forced “TP dipole pattern” enhances the winter cold break from Siberia and forms the spring persistant precipitation over the south of Yangtze River and the premonsoon precipitation over South China. The orography forced summer pattern forms the strong difference of precipitation from the Bay of Bengal to the central and eastern TP, enables the rain band to extend northward, and redistributes the precipitation over Asia.