2000—2006年中国天山山区积雪时空分布特征研究

Study of the Temporal and Spatial Distribute of the Snow Cover in the Tianshan Mountains,China

以中国境内天山山区为研究区,基于2000—2006年的遥感积雪产品积雪分布时间序列趋势和空间分布特征,对积雪分布的年际变化趋势、积雪分布随海拔的变化趋势、积雪频率以及积雪雪线高度的年变化进行了分析.结果表明:1)积雪经历从秋季开始累积到春季开始消融的过程,1—2月积雪面积达到最大,7—8月面积最小.冬季积雪所占比例最大,超过50%;2)2000—2006年积雪面积年际变化略呈上升趋势,冬季上升趋势较明显,春、秋和夏季变化趋势不明显.冬季积雪面积在海拔<4000m呈上升趋势,≥4000m呈下降趋势.在海拔2000m积雪的上升趋势达到最高点;3)从积雪频率来看,存在5个高值区,覆盖频率高达70%左右.从空间分布来看,天山中段积雪最多,东段次之,西段最少.在海拔3000m以下积雪次数较少,海拔3000m以上积雪次数显著增加.月积雪次数随海拔的变化表现为:海拔4000m以上各月的积雪次数都很多,12月至翌年2月在各高程带的积雪次数都较大;10—11月和3—4月积雪以海拔2500m为界,之下次数较少,以上次数增加显著;5—9月的积雪次数在海拔3000m以下非常少,在海拔3000m以上次数逐渐增加;4)以覆盖率≥40%相对应的海拔作为各个月份的雪线高度,天山山区平均雪线海拔在2875m.夏季雪线海拔在4000m以上;冬季雪线海拔在1500m.

Based on the remote sensing snow cover data from 2000 to 2006 over the Tianshan Mountains in China, the annual change of snow distribution, the snow distribution change with elevation, the snow cover frequency and snow line altitude change are studied. The result shows that： 1） the snow cover accumulates from autumn and melts in spring, the snow cove extent of January and February is the maximum, but in July and August is the minimum, the proportion of the winter snow cover extent exceeds by 50%; 2） the snow cover extent has a little increasing tendency. Seasonally, the snow cover extent is increasing in winter, however, in spring, summer and autumn the snow cover extent does not show obviously change trend. The snow cover extent changes with elevation, it increases with elevation below 4 000 m and decreases with elevation above 4 000 m. At the altitude of 2 000 m the increasing trend reaches the maximum; 3） there are five large snow cover areas, with the maximum snow cover ratio over 70%. Spatially, in the middle of Tiansban Mountains snow cover is the most, followed by that in the east of Tianshan Mountains. Below 3 000 m, there is less snow cover frequency, but above 3 000 m the frequency increases obviously. Monthly snow cover frequency is very often above 4 000 m, especially in December, January and February; above 2 500 m, the snow cover frequency is more than that below 2 500 m in October, November March and April; the snow cover frequency is more above 3 000 m than that below 3 000 m in May, June, July, August and September; 4）taken the elevation where the snow cover ratio is 40G as the snow line altitude, the average snow line altitude is about 2 875 m, and snow line altitude in summer is above 4 000 m but in winter it is about 1 500 m.