偏西風帯の定在ロスビー波と夏季アジアモンスーンとの関係について-ケーススタディー-

Abstract

The relationships between the stationary Rossby wave with intraseasonal time scales along the subtropical westerly and the Tibetan high in 1983 summer are investigated. The Tibetan high is one of the intrinsic elements of Asian summer monsoon circulation system.The time changes of the activity of the stationary Rossby wave and the temperature around the Tibetan high are well correlated with each other. That is, the stationary Rossby wave becomes active about 10 days after the temperature maximum of the Tibetan high. While the Rossby wave has no zonal phase propagation, it has eastward group velocity at about 25 m/s. As the Rossby wave packet propagates eastward, the high temperature area around the Tibetan high moves eastward with approximately same speed as the group velocity of the Rossby wave.These relationships can be evidently seen for all three major 'warming events' of the Tibetan high (early July, late July and late August) in 1983. It is also shown that the maximum windspeeds of the Indian monsoon westerly occur about 10 days earlier than the maximum temperature events around the Tibetan high.The vertical structure of the potential temperature of the Tibetan high shows that the 'warming events' of the Tibetan high are established by the accumalation of the high potential temperature air mass. This process may be caused mainly by the latent heat release and maintained by the air mass enclosure by strong anticyclonic circulation.