Calibration of the ESA CCI-Combined Soil Moisture Products on the Qinghai-Tibet Plateau

Soil moisture (SM) retrieved from satellite and spaceborn sensors provides useful parameters for earth system models (ESMs). The Climate Change Initiative (CCI) SM products released by the European Space Agency have been widely used in many humid/semi-humid climatic regions due to their relatively long-term record. However, performance of these cold arid regions, such as Qinghai-Tibetan Plateau (QTP), is largely unknown, necessitating urgent evaluation calibration areas. In this work, we evaluated reliability improved accuracy active-passive combined CCI (CCI-C) using in-situ measured contents (SMC) under different underlying surface conditions. First, some conventional were investigate relationship between CCI-C observed SMC, yielding similar fitting performances. Next, random forest method multiple linear regression contrast calibrate validate product based on was found highest accuracy. data with best-performed spatial zonation methods, e.g., climate, topography, land cover, vegetation, resulted distinct patterns SM. Compared a widely-used product, namely Moisture Active Passive (SMAP) dataset, calibrated vegetation larger but had patterns. This study also points value support studies QTP.