近40a青藏高原冬季极端降雪的变化特征分析

Variation Characteristics of Extreme Snowfall in Winter over the Tibetan Plateau in Recent 40 Years

在全球变暖的背景下对青藏高原(简称高原)冬季极端降雪的时空变化特征进行研究,将对高原及周边地区政府部门在水资源的管控和利用方面有一定的参考意义。本文利用高原40个气象台站观测的1980~2019年冬季的逐日降水数据,运用百分位阈值法确定冬季极端降雪量阈值,进一步对极端降雪量、极端降雪频次、极端降雪强度以及极端降雪对降雪的贡献率(极端降雪量与总降雪量之比)的时空变化特征进行分析。结果表明:1) 高原冬季极端降雪量阈值、极端降雪量及极端降雪强度均呈现自东南向西北递减的空间分布特征,极端降雪频次主要在高原中东部存在大值区,其他地区较小,且极端降雪频次东南部大值区范围大于其他极端降雪指数;2) 1980~2019年高原冬季极端降雪量、极端降雪频次呈现显著增加的趋势,极端降雪强度增加趋势不显著。极端降雪量与极端降雪频次、强度的关系表明极端降雪的增加主要是与极端降雪频次的增加有关;3) 高原冬季极端降雪对总降雪的贡献率在空间上呈现自西南向东北递减的分布特征,时间上,贡献率呈现增加的趋势。总的来说,1980~2019年高原冬季极端降雪呈显著增加趋势,在总降雪中的占比也是增加的,这主要是与极端降雪事件的增多有关。

Under the background of global warming, studying the temporal and spatial variation characteristics of extreme snowfall in winter over the Tibetan Plateau (TP) will be of realistic reference to the management and utilization of water resources by government departments on the TP and its surrounding areas. In this paper, based on the daily precipitation data of 40 stations on the TP from 1980 to 2019, the percentile threshold method is used to determine the winter extreme snowfall threshold of each station, furthermore, the temporal and spatial variation characteristics of extreme snowfall, extreme snowfall frequency, extreme snowfall intensity and contribution rate of extreme snowfall to total snowfall (the ratio of extreme snowfall to total snowfall) are discussed. The results show that: 1) Extreme snowfall threshold, extreme snowfall and extreme snowfall intensity decreased from southeast to northwest of the TP, however, extreme snowfall frequency had larger value in the middle east of the TP, and with little value in other areas, and the range of large value of extreme snowfall frequency was larger than that of the other extreme snowfall indexes;2) Both extreme snowfall mount and frequency indicated significantly increasing trend in winter over the TP during 1980~2019, while extreme snowfall intensity had an insignificantly rising trend. The increase of extreme snowfall is mainly related to the increase of extreme snowfall frequency;3) The contribution rate of extreme snowfall to the total snowfall decreased from southern to northeast of the TP, and contribution rate presented an increasing trend during 1980~2019. Overall, both the extreme snowfall and contribution rate had an increasing trend during 1980~2019, which is mainly related to the increase of extreme snowfall events.