新疆积雪对气候变暖的响应
RESPONSE OF XINJIANG SNOW COVER TO CLIMATE CHANGE
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摘要: 积雪对全球变暖的响应是当前正在争论的问题.文中通过地面气象台站和SMMR微波卫星遥感两种积雪资料所建立的两个独立的积雪序列的一致性,证明前者在表现新疆积雪长期变化能力方面具有可靠性.阐明了积雪年际变化特征及其与冬季气温和降水量年际波动的关系,检验了积雪长期变化趋势.研究表明,虽然近50a来新疆冬季变暖十分显著,尤其20世纪90年代为最温暖的时期,但是积雪并未出现持续减少的现象;积雪长期变化表现为显著的年际波动过程叠加在长期缓慢的增加趋势之上.积雪年际波动是冬季降水量和气温两者年际波动共同作用的结果;冬季气温和降雪量变化受不同的欧亚环流振荡所控制;积雪增加趋势与降雪量趋势相一致,这可能是由于全球变暖导致海洋蒸发量增加,以及在寒冷干燥气候下积雪对降雪量变化更为敏感的缘故.Abstract: How snow cover will react to global warming is presently a controversial issur.Here two homogeneous time series of Xinjiang snow cover were created separately from a 46-selected synoptical station network and by using revised passive microwave satellite data derived from SMMR.They compared favorably with each other that confirms the ability of the station data to accurately represent the ground truth of the snow cover variability.Then a multiple linear regression analysis was conducted to show the association between the snow cover and wintertime temperature as well as precipitation during the period between 1951 and 1997.Further,a statistical model consisting of a possible trend plus noise are fitted to the snow and climate time series to testing for their long-term trends.Results indicate that Xinjiang did not experience any continuant decrease in snow cover during its recent greatest warming period from 1977 to 1997,as well as in the warmest 1990′s,It is of interist to note that no any correlation was identified between the cool season temperature and precipitation in the study area.How ever snow cover responds to both of precipitation (snowfall) and temperature.A bout one-half to two-third of the total snow cover variance are able to be explained by the linear variations of corresponding precipitation and temperature.The long-term variability of Xinjiang snow cover is characterized by a large interannual fluctuation superimposed on a smal positive trand.It displays fluctuation on multiple timescales around the mean,and the anomalies did not appear to be outside the range of natural variation.No persistent and dominant frequencies were found.It represents simply a stochastic variability.The snow cover fluctuation is largely controled by at mospheric circulation oscillation.While positive snow fall and negative temperature relationships were found in year-to-year fluctuation,the longterm trend exhibits a gradual increase that is more closely linked to the snow fall trend.This suggest that snow cover in continental climate region is more sensitive to snow falthan to temperature.The snow cover positive trend is a consequence of CO2-induced global warming which causes an increase in ocean evaporation and more intense hydrological cycle with more frepuent heavy snowfall events.