西藏贡嘎沙尘天气气候及环流特征

利用1978-2012年西藏贡嘎的浮尘、扬沙和沙尘暴资料,分析了贡嘎沙尘天气的气候特征。结果表明:贡嘎沙尘天气冬、春季最多,秋季较少,夏季很少发生;扬沙和沙尘暴主要发生在午后,浮尘则全天均可发生;近35年来,扬沙和沙尘暴呈波动减少趋势,减少幅度分别约为7 d-10a和2.2 d-10a,浮尘约以0.5 d/10a的幅度呈不显著增加趋势;基于2005-2012年沙尘天气同期红外差值沙尘指数(IDDI)空间分布图和地面流场、沙地分布图,定性得出贡嘎、尼木、南木林、日喀则、拉孜区域的雅鲁藏布江沿岸沙地是贡嘎沙尘天气的沙尘来源。利用沙尘暴天气个例分析了贡嘎沙尘天气的地面气象要素和高空环流特征,发现相对湿度小、风速大、连续多日无降水是沙尘天气的地面气象要素特征,高空环流形势可分为阻塞型(占40%)、干南支槽型(占17%)、西北气流型(占26%)和热低压型(占17%)等4类。

Climate and Circulation Characteristics of Dust Weather in Gonggar,Tibet, China

Using dust weather data including flowing dust, blowing sand and sandstorm in Gonggar of Tibet Autonomous Region of China from 1978 to 2012, the dust weather climate and circulation characteristics in Gonggar was analyzed. The result shows that dust weather most occurred in winter and spring, less in autumn, rarely in summer; blowing sand and sandstorm mainly occurred in the afternoon, and the flowing dust occurred throughout the day; blowing sand and sandstorm showed a fluctuating decreasing trend at the rate of approximately 7 d-10a and 2.2 d-10a, respectively, flowing dust increased insignificantly with 0.5 d/10a trend in the recent 35 years. Qualitative analysis showed sand/dust source areas of dust weather in Gonggar included Gonggar, Nimu, Namling, Shigatse, and Lhatse by using infrared difference dust index (IDDI) spatial distribution data and ground wind field data, and sandy land distribution data from 2005 to 2012. Small relative humidity, high wind speed, and long consecutive days without precipitation caused dust weather, and atmospheric circulation pattern can be divided into 4 categories: blocking pattern (40%), dry southern branch trough pattern (17%), northwest flow pattern (26%) and thermal low pressure pattern (17%).