Recent Climate Trends in the East Asia During the Baiu Season of 1979-2003

Recent climate trends in the East Asia during the Baiu season (June) of 1979-2003 are investigated. The precipitation is significantly decreasing around Philippines and the northeastern part of China, while increasing along the Baiu frontal zone (the southeastern part of China and Japan) and the western part of Siberia. The pressure trend that corresponds to the precipitation has barotropic structure in the midlatitudes and baroclinic structure in the subtropics. For the barotropic structure to be maintained, the Rossby wave propagation from the western part of Siberia and Tibetan Plateau seems to play an important role. On the other hand, the trend of diabatic heating around Philippines and Japan is important for the baroclinic structure. The pressure trend is investigated by a linearized primitive model. The results support the above idea that the effect of the Rossby wave propatation is important for the barotropic pressure trend in the midlatitudes and that the trend of apparent diabatic heating is an important factor for the baroclinic pressure trend in the subtropics. Interannual variability is also investigated. It is suggested that the trend of surface temperature around Mongolia and Philippines is related to the pressure trend.