古尔班通古特沙漠积雪覆盖、沙尘天气特征及其相互关系

Characteristics of Snow Cover and Sand-dust Events and Their Correlation in Gurbantunggut Desert

利用TERRA/MODIS MOD10A2雪盖产品数据和地面观测积雪日数、冻土深度和沙尘天气日数等数据,从不同时间尺度分析古尔班通古特沙漠地表积雪覆盖与沙尘天气的特征及其相互关系。结果表明:①沙尘天气主要发生在4—10月,春季(4—5月)沙尘天气最多,夏秋季逐渐减少。从年际变化看,20世纪80年代前,沙尘天气发生日数呈逐年增加趋势,而积雪日数增减波动较大,二者间关系不明显,80年代后,沙尘天气逐年减少,积雪日数呈波动增加趋势。②冬春季积雪覆盖率、≥1cm积雪日数、≥5cm积雪日数、≥10cm积雪日数与翌年春季沙尘天气发生均呈显著负相关关系,冬春季≥1cm积雪日数每超过常年平均积雪日数1d,翌年春季沙尘天气日数则减少4.3d,而平均冻土深度与沙尘天气呈显著正相关关系。③积雪覆盖使沙漠地表形成冷源性下垫面和近地层逆温层结,增加了大气稳定度,同时春季积雪消融增加了土壤湿度,为荒漠植被生长提供充足的水分,使表层土壤为强风提供沙尘的可能性降低,从而对沙尘天气的发生起到阻碍、消弱作用。

The temporal characteristics of snow cover and sand-dust events and their correlation in Gurbantunggut desert were analyzed based on snow cover data of TERRA/MODIS MOD10A2, observation data of snow cover days, depth of frozen soil and sand-dust days from meteorological stations. The main results are as follows： （1） Sand-dust events happened mainly from April to October with the most in spring. The relationship between the sand-dust events and the number of snow-cover days isn＇ t obvious before 1980s because the sand-dust events increased year after year while number of snow-cover days fluctuated significantly. The sand-dust events decreased year after year after 1980s, while the number of snow-cover days increased. （2） There was a negative relationship between sand-dust events in next spring and snow-cover ratio in winter and next spring, ≥1 cm snow-cover days, ≥5 cm snow-cover days, ≥10 cm snow-cover days in winter and next spring. The sand-dust days in next spring decreased by 4.3 days according to statistics when the ≥1 cm snow-cover days in winter and next spring exceeded the annual mean number by 1 days. The sand-dust events in next spring is positively correlated with mean depth of frozen soil in winter. （3） Snow cover reduces the sand-dust events because snow cover leads to not only the formation of a cold underlying surface and temperature inversion, but also the improvement of soil moisture and vegetation cover.