Uncertainty Characterization of Ground‐Based, Satellite, and Reanalysis Snow Depth Products Using Extended Triple Collocation
Dejing Qiao, Zhen Li, Jiangyuan Zeng, Shuang Liang, Kaighin A. McColl, Haiyun Bi, Jianmin Zhou, Ping Zhang
Abstract
Abstract The optimal use of hemispheric‐scale snow depth (SD) products for various hydrometeorological applications requires a comprehensive assessment of their quality. Most previous validation studies of SD products adopted in situ observations as the ground truth, which may cause representativeness errors due to spatial scale mismatch between point‐based ground SD measurements and grid‐based SD products. The extended triple collocation (ETC) technique is a powerful tool to estimate the uncertainty of three independent data sets without assuming any one data source is an error‐free “truth” reference. This study first used the ETC to assess the uncertainty of three types of hemispheric‐scale SD products, including the ground‐based analysis Canadian Meteorological Centre (CMC), the satellite‐based Advanced Microwave Scanning Radiometer 2 (AMSR2), and the model‐based Global Land Data Assimilation System (GLDAS) SD products. Furthermore, the uncertainties of each SD product were analyzed using ETC metrics, that is, the correlation coefficient ( R ) and error standard deviations (STDs), with respect to several environmental and perturbing factors. Overall, the CMC outperforms the AMSR2 and GLDAS, with a higher R and a smaller STD. Considering multiple environmental and perturbing factors, the poorest performance of the three SD products is mainly found in densely vegetated regions, and they are strongly related to the forest cover fraction and surface roughness. Despite the above factors, the best performance for all three SD products is found over temperate climate regions. The results demonstrate the usefulness of the ETC approach to quantify the uncertainty of SD products particularly in remote regions with sparse in situ measurements.