Abstract Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover maps have been successfully applied in regional snow cover mapping and hydrological modelling in many regions. The new MODIS products (i.e. Collection 6) provide information about the Normalized Difference Snow Index (NDSI) instead of simple binary information about snow cover of the former products. The objective of this study is to investigate the sensitivity and accuracy of different NDSI thresholds used for snow cover mapping and to compare the results with former snow cover classification based on a fixed NDSI threshold (NDSI=0.4). The accuracy is tested for both Aqua (MYD10A1) and Terra (MOD10A1) daily snow cover products by using daily snow depth observations at 665 climate stations in Austria in the period 2002 - 2014. The results show the overall classification accuracy over 665 climate stations to be larger than 97% (97.4% for Terra and 97.6% for Aqua) in Austria. The best NDSI thresholds fitted to individual stations can differ from a fixed threshold (NDSI=0.4) and are sensitive to the snow depth threshold indicating snow cover at the ground. The thresholds vary seasonally, decrease with increasing elevation and are lower in forested than open land cover settings. We found that the thresholds fitted to different elevation and land cover classes improve regional snow cover mapping by 3-10% in forested regions above 900m a.s.l. in January to March.

中文翻译：

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从奥地利的每日收藏 6 MODIS 产品中绘制积雪覆盖图

摘要 中分辨率成像光谱仪（MODIS）积雪图已成功应用于多个地区的区域积雪制图和水文建模。新的 MODIS 产品（即集合 6）提供有关归一化差异雪指数 (NDSI) 的信息，而不是有关以前产品的雪盖的简单二进制信息。本研究的目的是调查用于积雪映射的不同 NDSI 阈值的敏感性和准确性，并将结果与​​以前基于固定 NDSI 阈值 (NDSI=0.4) 的积雪分类进行比较。通过使用 2002 年至 2014 年期间奥地利 665 个气候站的每日积雪深度观测，对 Aqua (MYD10A1) 和 Terra (MOD10A1) 每日积雪产品的准确性进行了测试。结果显示，奥地利 665 个气候站的总体分类准确度大于 97%（Terra 为 97.4%，Aqua 为 97.6%）。适合各个站点的最佳 NDSI 阈值可能不同于固定阈值 (NDSI=0.4)，并且对指示地面积雪的雪深阈值敏感。阈值随季节变化，随海拔升高而降低，并且在森林覆盖环境中低于开放土地覆盖环境。我们发现，在 1 月至 3 月，适合不同海拔和土地覆盖类别的阈值将 900m 以上的森林地区的区域积雪映射提高了 3-10%。4) 并且对指示地面积雪的雪深阈值敏感。阈值随季节变化，随海拔升高而降低，并且在森林覆盖环境中低于开放土地覆盖环境。我们发现，在 1 月至 3 月，适合不同海拔和土地覆盖类别的阈值将 900m 以上的森林地区的区域积雪映射提高了 3-10%。4) 并且对指示地面积雪的雪深阈值敏感。阈值随季节变化，随海拔升高而降低，并且在森林覆盖环境中低于开放土地覆盖环境。我们发现，在 1 月至 3 月，适合不同海拔和土地覆盖类别的阈值将 900m 以上的森林地区的区域积雪映射提高了 3-10%。