Global-scale assessment and combination of SMAP with ASCAT (active) and AMSR2 (passive) soil moisture products

摘要

AbstractGlobal-scale surface soil moisture (SSM) products retrieved from active and passive microwave remote sensing provide an effective method for monitoring near-real-time SSM content with nearly daily temporal resolution. In the present study, we first inter-compared global-scale error patterns and combined the Soil Moisture Active Passive (SMAP), Advanced Scatterometer (ASCAT), and Advanced Microwave Scanning Radiometer 2 (AMSR2) SSM products using a triple collocation (TC) analysis and the maximized Pearson correlation coefficient (R) method from April 2015 to December 2016. The Global Land Data Assimilation System (GLDAS) and globalin situobservations were utilized to investigate and to compare the quality of satellite-based SSM products.The average R-values of SMAP, ASCAT, and AMSR2 were 0.74, 0.64, and 0.65 when they compared within situnetworks, respectively. The ubRMSD values were (0.0411, 0.0625, and 0.0708) m3m?3; and the bias values were (?0.0460, 0.0010, and 0.0418) m3m?3for SMAP, ASCAT, and AMSR2, respectively. The highest average R-values from SMAP against thein situresults are very encouraging; only SMAP showed higher R-values than GLDAS in severalin situnetworks with low ubRMSD (0.0438m3m?3). Overall, SMAP showed a dry bias (?0.0460m3m?3) and AMSR2 had a wet bias (0.0418m3