【摘要】 <正>西藏高原及其周围地区是否存在季风?若存在,是东南季风还是西南季风? 或是高原本身自成一季风体系?这些问题一直为我国气候学者所注视。早在五十年代叶笃正等就指出,夏季高原低层的风是围绕高原作气旋性旋转的;杨鉴初等利用单站资料讨更多还原

【Abstract】 Studies on the mean pressure, wind and precipitation data over the Xizang Plateau and its neighbourhood reveal their climatic characteristics as follows:1.The Plateau has its own permanent pressure systems in the lower and middle troposphere, i.e., the cold high in winter (Nov.- March) and the heat low in summer (June-Sept.).2.In summer, the Xizang heat low is separated from the Indian monsoon depression by a so-called Southern Plateau high belt, its axis is almost paralleled to the Ximalaya range.On the northern slope of the Plateau, there is a high belt too, its axis with a slope about 1/200 dips toward the plateau proper.3.In winter, the Xizang cold high is separated from the Indian high by a Southern Plateau low belt, its position has shifting northward from the summer southern Plateau high belt and with a slope about 1/100 dipping toward the Plateau proper.4.The vertical distribution of the prevailing winds over the Xizang Plateau is distributed into three layers: the lower is the mountain-valley wind layer, with a thickness about 1 km; the middle is the plateau monsoon layer, with a thickness about 2? km over the margins of the Plateau and about 1 km over the Plateau proper; the upper is the plenetary circulation, under the control of the global atmospheric circulation.5.The plateau monsoon, is not a part of the Indian monsoon, there exist a distinguishable anticyclone belt in summer and a cyclone belt in winter between these two monsoon systems.The plateau monsoon is caused by the seasonal variation of the thermal effect on the Xizang Plateau.更多还原