RESPONSE OF TIBETAN SNOW COVER TO GLOBAL WARMING
青藏高原积雪对全球变暖的响应

A study is presented of trend testing of Tibetan snow cover variation by using daily snow depth records at 60 primary climatic stations covering the period from 1957 to 1992.A statistical model consisting of a trend plus serialy correlated noice is fitted to the areal and point time series data to test for trends in snow cover variation.The results of three trend estimates based on difference of average.least squares fitting.and slope AR(1) process imply that the increase in annual snow depth is a systematic development as evidenced by the presence of a deterministic trend.The increase of snow depth is almost omnipresent over the Tibetan plateau.However noable exceptions are the Yarlung Zangbo valley to the west of Lhasa,and along highway between Da Qaidam and Beilu Heyan.further examination of year-to-year fluctuation of snow cover over the Tibetan plateau and surface air temperature in wintertime over the northern Hemisphere during the period between 1957 and 1992.reveals a positive relationship between the two.This association tends to contrast sharply with reduced extent of snow cover in extratropical Lands in late 1980s,but coincides with the recent increases in Antarctic and Greenland snow accumulation.