基于HJ-1数据的木孜塔格峰地区雪深时空变化

The temporal and spatial changes of snow depth in Ulugh Muztagh area derived from HJ-1 satellite data

以木孜塔格峰地区为研究区,从不同坡度、坡向的样方内测量雪深和采集光谱,通过分析归一化差分雪盖指数(Normalized Difference Snow Index,NDSI)、反照率、HJ-1卫星的红外波段反射率与雪深的相关关系,建立了适用于HJ-1星的积雪深度反演模型,估算出2012年4月14日-25日木孜塔格峰地区的雪深时空变化,并结合实测数据进行验证。结果表明:反照率反演模型的复相关系数为0.992;通过NDSI阈值区分混合雪盖像元和积雪像元,雪深估测精度可达92.78%。冰川区的反照率、NDSI与海拔的相关系数分别为0.626和0.733,且高海拔带反照率值明显高于低海拔带的反照率值。受西风带降雪的影响,非冰川区的北坡雪深值较大;西坡、南坡次之;东坡最小,且雪深最大值出现在坡度约等于10°处。雪深估测的相对误差随着样地的坡度增大而增加,坡度为15°时相对误差较大。

The paper analyzes the relationship among the NDSI （Normalized Difference Snow Index） albedo, the H J-1 satellite infrared band reflectance and snow depth in the vicinity of Ulugh Muztagh. At the same time, snow depth and reflectance spectrum are measured in different slopes and aspects on April 14 to 26, 2012. In order to estimate spatial and temporal changes in snow depth, snow depth inversion model was established by their correlation among measured snow depth data, infrared band reflectance and albedo; furthermore, it accuracy is verified by the measured snow depth and spectral data. The results show the multiple correlation coefficient of albedo inversion model is 0.992, and the significance level is less than 0.05. Through setting distinguishing between mixed and pure snow coverage pixel by NDSI threshold, its estimated accuracy is up to 92.78%. The correlation coefficients between albedo of the glacier area, NDSI value and altitude data are 0.626 and 0.733, respectively, and the significance level is less than 0.01. Moreover, albedo value in high altitude zone is significantly higher than that of the low altitude zone. The snow depth value of northern aspect in non-glacier area is larger, followed by the southern and western aspects; while the snow depth in southern aspect reaches the minimum value, under influence of the westerlies snowfall. When the slope is about 10~, there is the maximum snow depth. The relative error with snow depth estimated increases as the increase of the plot slope, and when the slope is 15°, the relative error is the largest.