摘要:为了研究青藏高原低涡降水长期特征，利用1979~2015年高原低涡数据集、依照高原低涡降水范围，匹配高原各站逐日降水信息，对高原低涡降水特征进行统计分析。结果表明，青藏高原低涡降水量呈上升趋势，大值中心位于西藏那曲地区，呈向东南凸出递减分布，并以夏季低涡降水为主，全年和夏季高原低涡降水量与总降水量均存在明显的正相关关系。安多站高原低涡降水呈下降趋势，但对年降水的平均贡献率高达三成；那曲站与托托河站高原低涡降水在总体上却呈上升趋势，递增率分别为0.2 mm/a和0.7 mm/a，其中那曲低涡频数与低涡降水强度的正相关系数达0.66，而托托河低涡降水占总降水的百分比却呈下降趋势。高原低涡日降水量等级主要以小雨为主，但中雨却是低涡降水量的主要贡献者。趋势分析发现高原低涡降水递增中心位于青海北部，递增率达到0.9 mm/a，次中心在西藏西南部雅鲁藏布江沿线地区；同时，高原低涡引发小雨降水基本呈全区一致增加趋势，中心位于西藏东北部和青海西南部地区；中雨降水上升趋势主要集中在西藏西南部、青海地区以及四川西部，其中青海南部存在较为明显上升中心区，下降趋势主要分布在西藏北部和东部。
关键词:高原/
低涡降水/
时空分布/
降水量级
Abstract:In order to study long-term precipitation characteristics of the Tibetan Plateau vortex, statistical analysis of precipitation characteristics associated with the Tibetan Plateau vortex over the past 37 years has been conducted based on the dataset of the Tibetan Plateau vortex from 1979 to 2015. Precipitation areas as well as daily precipitation amount observed at weather stations in the Tibetan Plateau are also used. The results show that annual vortex precipitation exhibits an upward trend. The precipitation center is located at Naqu of the Tibetan Plateau, and decreases eastward. The precipitation is largely comprised of summer low vortex precipitation, while both summer precipitation and annual precipitation have a significant positive correlation with total precipitation. The vortex precipitation is declining at Anduo station, whereas its average contribution to annual total is as high as 33%. The vortex precipitation generally shows an upward trend at Naqu and Toto River stations with the increasing rates of 0.21 mm/a and 0.65 mm/a, respectively. The correlation coefficient between low vortex frequency and low vortex precipitation is 0.66 at Naqu area however, the percentage of precipitation accounted for by the vortex precipitation in the Toto River shows a decreasing trend. The low vortex precipitation in the Tibetan Plateau is dominated by light rainfall, while moderate rainfall is the main contributor to total vortex rainfall. The trend analysis shows that the largest increase center of the Tibetan Plateau vortex precipitation is located in northern Qinghai, where the increasing rate reaches 0.88 mm/a, and the second largest center is located along the Yarlung Zangbo River in southwestern Tibet. At the same time, light rainfall induced by the low vortex basically increases in the whole region with the center located in northeastern Tibet and southwestern Qinghai. The upward trend of moderate rainfall is mainly found in southwestern Tibet, Qinghai region and western Sichuan. An obvious rising center is located in southern Qinghai with an increasing rate of up to 0.67mm/a, and the downward trend is mainly distributed in northeastern Tibet.
Key words:Tibetan Plateau/
Vortex precipitation/
Temporal and spatial distribution/
Precipitation magnitude
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