长江黄河源区积雪空间分布与年代际变化

应用长江黄河源区及其周边地区16个气象站逐日积雪资料,分析了长江黄河源区积雪的空间分布和年代际变化特征.结果表明:以巴颜喀拉山主峰为中心的黄河源头和长江源东南部地区是年积雪深度高值中心,黄河源头以西和五道梁以东的长江源东北部和黄河源西北部广大地区是低值中心.冬春累积积雪深度占年累积积雪深度的比例>71.0%,夏半年(6~9月)对其的贡献小,但夏半年的积雪日数占年积雪日数的1/3.曲麻莱达日一线以南地区积雪主要发生在1月份,以北地区一年有两个高值期:前冬10~11月和春季3~5月.长江源和黄河源头地区积雪建立早,积雪季节长,结束晚,消退过程缓慢;而黄河源东部地区,积雪建立稍晚,积雪发展比较缓慢,消退过程迅速.近40 a来长江黄河源区积雪呈确定的增长态势,长江源区冬春积雪增长了62.11%,黄河源区增长了60.18%.但二者积雪变化位相基本相反,变化幅度长江源大起大落,而黄河源比较平缓,多雪年份出现也不一致.整个源区20世纪60年代至70年代初为积雪偏少期,70年代中期至90年代是积雪偏多期.从20世纪70年代中至80年代末,积雪明显增加,90年代积雪增加速度有所放慢,近40 a江河源区平均冬春累积积雪深度增加了60.95%.长江源区对整个源区积雪变化起主导作用,源区平均冬春累积积雪深度变化主要表现长江源的特征.

Distribution of Snow Cover and Its Inter-decadal Variation in the Source Regions of the Yangtze and Yellow Rivers

The spatial distribution and inter-decadal variations of snow cover are analyzed with the use of snow data of 16 meteorological stations in the source regions of the Yangtze and Yellow Rivers and their periphery.The results show that there are a maximal center and a minimal center of the snow depth in the study regions.The maximal center of snow depth is between the headwaters of the Yellow River and the southeastern source regions of the Yangtze River around the main peak of Bayan Har Mountains.The minimal center of snow depth is between northeastern source regions of the Yangtze River and northwestern source regions of the Yellow River.Annual snow depth is mainly determined by snow depth from October to May of the following year(v period).The ratio of cumulative snow depth in the v period to annual cumulative snow depth is more than 71.0%.There is less contribution of snow depth from June to August to annual snow depth.But number of snow cover days from June to August is not negligible.It accounts for 1/3 of the annual number of snow cover days.The annual variation of snow is not fully consistent in different areas of the source regions of the Yangtze and Yellow Rivers.The snow falls mainly in January in the south of the line from Qumarl b to Darlag.Snow has two high value periods in the north of the line.One is the period from October to November.The other is March to May.Snow cover starts early,duration of snow is long,snow finishes lately and snow melting process are slow in the headwaters of the Yellow River and the source regions of the Yangtze River.However,snow cover starts lately,snow cover develops slowly and snow melting process is quick in the eastern source regions of the Yellow River.The snow cover in the study regions increases definitely over the past 40 years. Snow cover in the v period increases by 62.11% in the source regions of the Yangtze River and by 60.18% in the source regions of the Yellow River.However, there is marked difference in snow variation in the two source regions.The snow was less from the 1960s to the initial stage of the 1970s,rich from the middle stage of the 1970s to the 1990s in the whole source regions.The snow obviously increased from the middle stage of 1970s to the end of 1980s,and decreased in the 1990s.Snow cover in the v period increases by 60.95% in the whole source regions.Snow variation in the source regions of the Yangtze River dominates that in the whole source regions.