利用MODIS和AMSR-E进行积雪制图的比较分析

MODIS和被动微波辐射计AMSR-E提供了识别积雪的不同方法.MODIS首先计算反映积雪在1.6μm强吸收特性的归一化差值积雪指数NDSI,在剔除卷云的影响后,得到MODIS积雪分布.AMSR-E则根据积雪在微波波段的差异性散射特性识别积雪.通过案例分析比较了MODIS和AMSR-E积雪分布,发现由于云的遮蔽使MODIS积雪分布面积会比实际小,但由于MODIS的空间分辨率很高,得到的积雪边界线轮廓清晰.而微波由于不受云的影响,得到的AMSR-E积雪分布比较符合实际,但积雪的边界线较粗.

A Comparison of MODIS and Passive Microwave Snow Mappings

MODIS and Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) supplies different methods of snow detection. MODIS detects snow according to a Normalized Difference Snow Index (NDSI), which utilizes the low reflectance of snow in 1.6 mm infrared band. AMSR-E detects snow according to different scattering characteristics of snow in microwave channels. Aiming to overcome the weakness of 1.6 mm infrared band of AQUA-MODIS, this paper presents an alternative method of MODIS snow detection, Modified Normalized Difference Snow Index (MNDSI), derived form MODIS band 7(2.105~2.135 μm) with an accuracy similar to NDSI in snow mapping.Several cases of snow mapping indicate that AMSR-E 89 GHz channel with high resolution is better than 37 GHz channel for snow cover monitoring. 89 GHz snow mapping has a boundary and a snow area similar to that of MODIS snow mapping.MODIS and AMSR-E snow mappings have different merits. Due to its better spatial resolution, MODIS snow cover has a clear boundary and AMSR-E snow mapping is rough. However, MODIS snow cover occupies less area than true snow cover when cloud distributes with a large area. Conversely, AMSR-E snow cover is stable with a sure accuracy, because of its capacity to penetrate cloud, despite the effects of cloud and night. MODIS and AMSR-E located on the same satellite, Aqua offers a potential of snow mapping with a high accuracy even on a daily basis.