横断山区近代气候变化的研究

横断山地处我国西南的藏东、川西和滇西北一带,境内地形复杂,平均海拔在3000米以上。长期以来,由于资料短缺,对该地区历史时期气候变化研究甚少。经实地考察,作者获取若干树木年轮标本,辅以其它类型资料,对该地区最近数百年来的温度、降水变化及气候类型演替,予以初步分析。并论及气候变化的振幅与周期性。

A PRELIMINARY STUDY OF THE MODERN CLIMATIC CHANGE IN HENGDUAN MOUNTAINS

The Hengduan Mountain area Lies in Southwest China, including Parts of East Tibet, West Sichuan and Northwest Yunnan, and has a varied topogra-phy.The average altitude of it is over 3,000m a.s.l, The climatic change during Historical Time in this area has not been studied because of the lack of data.By field investigation, the authors have got a large quantity of tree ring specimens in the area. After preliminary dating and necessary dendrochro-nological processing, twelve standardized deadrochronologies have been built Baaed on these chronologies, two curves including the fluctuations of the air temperature and the annual precipitation during the last hundreds of years in the mountain area were drawn,Some significant cold/warm and dry/wet periods could be divided also.A combined analysis between dendrochronologies and historical literature data which have five classes could help us to understand the successive variations of each climatic pattern since 1600 A.D. In addition the amplitude and periodicity of climatic change in the area have been calculated in this paper.It is obvious that the chief characteristies oi the modern climatic change in Kengduan Mountains might be concluded as follows.1)The temperature fluctuation during the last four hundred years in the area is similar to that in Tibetan Plateau, and the coldest period occurred in the first half of the 17th century.2)The long-term oscillation of precipitation is more obvious than that of air temperature.3) The statistical feature in the present century is, on the average ,lower temperature and lower precipitation, but the climate pattern with high temperature and low precipitation has been increasing since 1950's,4)The amplitude of climatic variation in the area is smaller than tha t in Tibet or in the plain area located on the east of Tibet Plateau.5)By carrying out analysis on various series, some periodicities have been found, such as 'quasi two year pulse' , s. 6 years, 35 years and so on.