Combining MODIS and AMSR-E observations to improve MCD43A3 short-time snow-covered Albedo estimation

Land surface albedo plays an important role in the radiation budget and global climate models. NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) provide 16-day albedo product with 500-m resolution every 8 days (MCD43A3). Some in-situ albedo measurements were used as the true surface albedo values to validate the MCD43A3 product. As the 16-day MODIS albedo retrievals do not include snow observations when there is ephemeral snow on the ground surface in a 16-day period, comparisons between MCD43A3 and 16 day averages of field data do not agree well. Another reason is that the MODIS cannot detect the snow when the area is covered by clouds. The Advanced Microwave Scanning Radiometer for EOS (AMSR-E) data are not affected by weather conditions and are a good supplement for optical remote sensing in cloudy weather. When the surface is covered by ephemeral snow, the AMSR-E data can be used as the additional information to retrieve the snow albedo. In this study, we developed an improved method by using the MODIS products and the AMSR-E snow water equivalent (SWE) product to improve the MCD43A3 short-time snow-covered albedo estimation. The MODIS daily snow products MOD10A1 and MYD10A1 both provide snow and cloud information from observations. In our study region, we updated the MODIS daily snow product by combining MOD10A1 and MYD10A1. Then, the product was combined with the AMSR-E SWE product to generate new daily snow-cover and SWE products at a spatial resolution of 500 m. New SWE datasets were integrated into the Noah Land Surface Model snow model to calculate the albedo above a snow surface, and these values were then utilized to improve the MODIS 16-day albedo product. After comparison of the results with in-situ albedo measurements, we found that the new corrected 16-day albedo can show the albedo changes during the short snowfall season. For example, from January 25 to March 14, 2007 at the BJ site, the albedo retrieved from snow-free observations does not indicate the albedo changes affected by snow; the improved albedo conforms well to the in-situ measurements. The correlation coefficient of the original MODIS albedo and the in-situ albedo is 0.42 during the ephemeral snow season, but the correlation coefficient of the improved MODIS albedo and the in-situ albedo is 0.64. It is concluded that the new method is capable of capturing the snow information from AMSR-E SWE to improve the short-time snow-covered albedo estimation. Copyright (c) 2012 John Wiley & Sons, Ltd.