Uncertainty of snow water equivalent retrieved from AMSR-E brightness temperature in northeast Asia

Accurate estimation of snow water equivalent (SWE) has been significantly recognized to improve management and analyses of water resource in specific regions. Although several studies have focused on developing SWE values based on remotely sensed brightness temperatures obtained by microwave sensor systems, it is known that there are still a number of uncertainties in SWE values retrieved from microwave radiometers. Therefore, further research for improving remotely sensed SWE values including global validation should be conducted in unexplored regions such as Northeast Asia. In this regard, we evaluated SWE through comparison of values produced by the Advanced Microwave Scanning Radiometer Earth Observing System (AMSR-E) from December 2002 to February 2011 with in situ SWE values converted from snow-depth observation data from four regions in the South Korea. The results from three areas showed similarities which indicated that the AMSR-E SWE values were overestimated when compared with in situ SWE values, and their Mean Absolute Errors (MAE) by month were relatively small (1.1 to 6.5mm). Contrariwise, the AMSR-E SWE values of one area were significantly underestimated when compared with in situ SWE values and the MAE were much greater (4.9 to 35.2mm). These results were closely related to AMSR-E algorithm-related error sources, which we analyzed with respect to topographic characteristics and snow properties. In particular, we found that snow density data used in the AMSR-E SWE algorithm should be based on reliable in situ data as the current AMSR-E SWE algorithm cannot reflect the spatio-temporal variability of snow density values. Additionally, we derived better results considering saturation effect of AMSR-E SWE. Despite the demise of AMSR-E, this study's analysis is significant for providing a baseline for the new sensor and suggests parameters important for obtaining more reliable SWE. Copyright (c) 2013 John Wiley & Sons, Ltd.