Assessment of daily MODIS snow cover products to monitor snow cover dynamics over the Moroccan Atlas mountain range
Assessment of daily MODIS snow cover products to monitor snow cover dynamics over the Moroccan Atlas mountain range
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DOI：
10.1016/j.rse.2015.01.002
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发表时间：
2015-04
影响因子：
13.5
通讯作者：
A. Marchane;L. Jarlan;L. Hanich;A. Boudhar;S. Gascoin;A. Tavernier;N. Filali;M. L. Page;O. Hagoll
中科院分区：
文献类型：
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作者：
A. Marchane;L. Jarlan;L. Hanich;A. Boudhar;S. Gascoin;A. Tavernier;N. Filali;M. L. Page;O. Hagoll
在半干旱的地中海地区，山上的积雪是许多下游居民的重要水源。这项研究评估了每天的MODIS分数积雪覆盖面积（FSC）产品超过7个集水区的混合雪雨水文制度，覆盖阿特拉斯链在摩洛哥。为此目的，超过4760每天的MODIS瓦片（MOD 10A 1版本5）从2000年9月至2013年6月进行了处理，基于时空滤波算法，旨在减少云覆盖和雪和云之间的歧视问题。识别为多云的像素数量减少了96%，从22.6%减少到0.8%。现场数据从五个雪站被用来调查的相对精度的MODIS雪产品。总体精度等于89%（0.1 m。雪的深度）。季节性降雪的时间也被正确地检测到，平均误差分别为11.4天和9.4天，发病和消融日期几乎没有偏差。FSC产品与马拉喀什附近Rheraya次盆地8米分辨率的一系列15张晴空FORMOSAT-2图像的比较表明，两个数据集具有良好的相关性（r = 0.97），负偏差为-27平方公里。最后，利用积雪消融期、积雪持续时间（SCD）和积雪最大覆盖范围（SCAmax）等季节性指标对FSC产品进行了分析：（1）积雪面积变化具有很强的年际信号，SCAmax的变异系数达到77%;（2）虽然研究结果表明，2000-2013年期间SCD在2 - 3月上升，4 - 5月下降，但没有证据表明统计上显著的长期趋势。该研究得出结论认为，尽管探测条件困难，但每天的中分辨率成像分光仪产品可用于绘制南地中海地区的雪盖图，具有合理的置信度。
In semi-arid Mediterranean areas, the snow in the mountains represents an important source of water supply for many people living downstream. This study assessed the daily MODIS fractional snow-covered area (FSC) products over seven catchments with a mixed snow–rain hydrological regime, covering the Atlas chain in Morocco. For this purpose, more than 4760 daily MODIS tiles (MOD10A1 version 5) from September 2000 to June 2013 were processed, based on a spatio-temporal filtering algorithm aiming at reducing cloud coverage and the problem of discrimination between snow and cloud. The number of pixels identified as cloudy was reduced by 96% from 22.6% to 0.8%. In situ data from five snow stations were used to investigate the relative accuracy of MODIS snow products. The overall accuracy is equal to 89% (with a 0.1 m. threshold for snow depth). The timing of the seasonal snow was also correctly detected with 11.4 days and 9.4 days of average errors with almost no bias for onset and ablation dates, respectively. The comparison of the FSC products to a series of 15 clear sky FORMOSAT-2 images at 8 m resolution in the Rheraya sub-basin near to Marrakech showed a good correlation of the two datasets (r = 0.97) and a reasonable negative bias of − 27 km2. Finally, the FSC products were analyzed through seasonal indicators including onset and melt-out dates, the Snow Cover Duration (SCD) and the maximum snow cover extent (SCAmax) at the catchment level: (1) the dynamic of the snow cover area is characterized by a very strong inter-annual signal with a variation coefficient of the SCAmax reaching 77%; (2) there is no evidence of a statistically significant long-term trend although results have pointed out that the SCD increased in February–March and, to a lesser extent, decreased in April–May for the 2000–2013 period. The study concludes that the daily MODIS product can be used with reasonable confidence to map snow cover in the South Mediterranean area despite difficult detection conditions.