塔城地区沙尘天气变化特征

 根据1961-2005年塔城地区9个气象站地面实测资料，用线性趋势分析、Mann-Kendall、相关分析和合成分析等方法对塔城地区沙尘天气的时空分布及变化特征进行了分析，并对其机理进行了讨论。结果表明：1) 沙尘天气高发区位于沙湾、乌苏一带，次高值中心位于额敏，沙尘日数与大风日数、降水量空间分布呈反向分布的特点；2) 年均沙尘暴日数为3.8 d，主要发生在4-9月；3) 沙尘日数呈减少的趋势，其中沙尘暴日数以1.0 d/10a的速率显著减少，大风日数以10.5 d/10a的速率显著减少；4) 沙尘暴、扬沙、浮尘日数分别在1993、1992、1973年发生了显著减少的突变；5) 近半个世纪来新疆的冷空气活动强度和频率有所减弱(小)，而大风日数的显著减少是沙尘日数减少的主要原因。

Analysis on the Variation Characteristics of Dust Weather in Tacheng RegionLi

Based on the surface meteorological observation data from 9 stations in Tacheng region from 1961 to 2005, using the linear trend analysis, Mann-Kendall test, correlation analysis, and composite analysis, the temporal and spatial distributions and change characteristics of sand-dust weather were analyzed; and physical mechanisms for changes in sandstorms and blowing-sand weather were discussed. The results show as follows: 1) The high frequency area of sand-dust weather lies in the Wusu-Shawan area, the second high frequency area lies near Emin station. Distribution of day numbers of sand-dust (south-more-north-less) showed an opposite spatial pattern to both high wind days and precipitation(north-more-south-less). 2) The average annual sandstorm days over Tacheng region was 3.8 days, mainly in the period from April to September. 3) Sandstorm and blowing-sand days were decreasing in the period 1961-2005; sandstorm and high wind days obviously decreased at a rate of 1.0 d/10a and 10.5 d/10a, respectively. 4) An abrupt reduction in regional sandstorms, blowing-sand, and floating dust occurred in 1993, 1992, and 1973, respectively. 5) In the period 1961-2005, the northern hemispheric polar vortex showed a weakening trend in strength, and a shrinking trend in area, which was responsible for reduced intensity and frequency of the cold air activities in Xinjiang. Weakened cold air activities directly resulted in the reduction in annual mean strong winds, which was the primary reason for reduction in the day number of sandstorms.