Comparative Analysis Of GLASS Albedos Over The Tibetan Plateau Based On Multi-source Data

The land surface albedo is one of the important parameters influencing the surface energy balance, the medium and long term numerical weather prediction, and the research of global change. The huge thermodynamic forcing and land-surface interactions on the Tibetan Plateau (TP) have great impact on the severe weather of eastern and southern China, as well as Asia, and even the global climate change. The Chinese GLASS (Global Land Surface Satellite) albedo product is a unique self-developed product in China with high accuracy and perfect spatial resolution and long-term temporal continuousness, and it is also the longest time series albedo product of the international global land surface albedo product. A comprehensive assessment on the GLASS albedo product over the Tibetan Plateau has great potential to be used in the study of the land surface radiation energy budget and land-atmosphere interaction over the TP.The main work of this paper includes:(1) Validating the accuracy of GLASS albedo product over the TP using ground measurements. Using upword and downword total solar shortwave radiation measured by seven automatic weather stations, preliminary evaluation of the accuracy of GLASS albedo product was made. The results show that:the overall change trends of GLASS albedo products are consistent with ground measurements, which could indicate the state of surface fair well. Cloud cover might result in higher results of GLASS albedo products than ground measurements, while snow cover might result in lower results of GLASS albedo products than ground measurements. The biases and rmses between GLASS albedo products and ground measurements fell evidently under the condition of snow-free, the minimum value of which are 0.0184 and 0.0124 respectively.(2) Validating the accuracy of GLASS albedo product over the TP using satellite remote sensing inversion albedo products. Using MODIS (MODerate-resolution Imaging Spectroradiometer) albedo product and GlobAlbedo product, further evaluation of the accuracy of GLASS albedo product over the TP was made. The results show that:GLASS albedo products are in good consistency with MCD43B3 generally. The mimimun biases and rmses between them are 0.0089 and 0.0086, the maximum R2 are 0.9722. While GLASS albedo products are in bad consistency with GlobAlbedo, the mimimun biases and rmses between them are 0.0189 and 0.0210, the maximum R2 are 0.8636. The retrieval efficiency of GLASS is higher than that of MODIS and GlobAlbedo. The proportion of GLASS high quality data number is higher than that of MODIS, which is concentrated in more than 80% and almost no annual and interannual variations. The distribution range of GLASS high quality inversion results are larger than MODIS albedo product throughout the whole TP. However, both the proportion of GLASS and MODIS high quality data number over southeastern TP are less than other areas over the TP. The spatial distribution of the proportion of biases that less than 0.05 between GLASS and MODIS and GlobAlbedo is large over the TP, concentrated in between 80% and 100% mostly.(3) Evaluating the accuracy of GLASS albedo product over the TP. Using long-time series GLASS albedo products from 2002-2012, systematic evaluation of the accuracy of GLASS albedo product over the TP was made. The results show that: The retrieval efficiency are higher than 99.95% and the maximum proportion of high quality inversion results are higher than 98% from 2002-2012. In addition, distortion results exist in the inversion result of GLASS albedo products over the TP.