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首页> 外文期刊>Remote Sensing of Environment: An Interdisciplinary Journal >Monitoring snow cover variability in an agropastoral area in the Trans Himalayan region of Nepal using MODIS data with improved cloud removal methodology
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Monitoring snow cover variability in an agropastoral area in the Trans Himalayan region of Nepal using MODIS data with improved cloud removal methodology

机译：使用MODIS数据和改进的除云方法监测尼泊尔跨喜马拉雅地区农牧区的积雪变化

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摘要

Monitoring the extent and pattern of snow cover in the dry, high altitude, Trans Himalayan region (THR) is significant to understand the local and regional impact of ongoing climate change and variability. The freely available Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover images, with 500. m spatial and daily temporal resolution, can provide a basis for regional snow cover mapping, monitoring and hydrological modelling. However, high cloud obscuration remains the main limitation. In this study, we propose a five successive step approach - combining data from the Terra and Aqua satellites; adjacent temporal deduction; spatial filtering based on orthogonal neighbouring pixels; spatial filtering based on a zonal snowline approach; and temporal filtering based on zonal snow cycle - to remove cloud obscuration from MODIS daily snow products. This study also examines the spatial and temporal variability of snow cover in the THR of Nepal in the last decade. Since no ground stations measuring snow data are available in the region, the performance of the proposed methodology is evaluated by comparing the original MODIS snow cover data with least cloud cover against cloud-generated MODIS snow cover data, filled by clouds of another densely cloud-covered product. The analysis indicates that the proposed five-step method is efficient in cloud reduction (with average accuracy of > 91%). The results show very high interannual and intra-seasonal variability of average snow cover, maximum snow extent and snow cover duration over the last decade. The peak snow period has been delayed by about 6.7. days per year and the main agropastoral production areas of the region were found to experience a significant decline in snow cover duration during the last decade.
机译：监测喜马拉雅横贯干旱地区高海拔地区积雪的范围和模式对于了解持续的气候变化和多变性对当地和区域的影响非常重要。免费提供的中分辨率成像光谱仪（MODIS）的雪盖图像具有500. m的空间和每日时间分辨率，可为区域雪盖测绘，监测和水文建模提供基础。但是，高云遮盖仍然是主要限制。在这项研究中，我们提出了五个连续步骤的方法-结合Terra和Aqua卫星的数据;相邻时间推论基于正交相邻像素的空间滤波;基于区域雪线法的空间滤波;以及基于纬向雪周期的时间过滤-消除了MODIS日常积雪中的云雾。这项研究还研究了过去十年中尼泊尔THR中积雪的时空变化。由于该地区没有地面站可测量积雪数据，因此通过比较原始的MODIS积雪数据（云量最少）与由云生成的MODIS积雪数据（由另一个密云组成的云填充）比较了所提出方法的性能，涵盖产品。分析表明，提出的五步法可有效减少云（平均准确度> 91％）。结果表明，过去十年中平均积雪，最大积雪范围和积雪持续时间的年际和季节内变化很大。降雪高峰期已推迟了大约6.7。在过去十年中，发现该地区每年的平均天数和主要农牧产区的积雪持续时间明显减少。

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