The Reliability Study Of SMOS And SMAP Data

SMOS(Soil Moisture and Ocean Salinity)is the L-band passive soil moisture detection satellite launched by the European Space Agency(ESA)in 2009,SMAP(Soil Moisture Active/Passive)is the L-band active-passive soil moisture detection satellite launched by the National Aeronautics and Space Administration(NASA)in 2015,due to their similarity in algorithm mechanism and data system,how to fully and effectively compare SMOS and SMAP soil moisture data has become a research focus in the past two years with the fundamental goal of establishing a consistent global soil data set.In this paper,we used high observation frequency and large space scale in-situ data to compare and verify SMOS and SMAP L2 soil moisture data from 2016 to 2017 in the USA.The main research achievements of this paper are as follows:(1)The validation of SMOS and SMAP soil moisture products.The results showed that: both of SMAP and SMOS could well capture the dynamic changes of soil moisture and presented a good fitting with the measured data,SMAP was better than SMOS in general;In some regions,the soil moisture value of SMOS L2 fluctuates violently compared with the measured soil moisture value,while the SMAP data is relatively stable in the whole research area with little fluctuation;The descending soil moisture data is wetter than the ascending data.On the whole,the retrieval has a certain "dry bias".(2)The verification of SMOS and SMAP soil moisture under different vegetation covers.The results show that SMOS inversion accuracy is greatly affected by cover species.When the study area is mainly coniferous forest,broad-leaved forest or mixed forest,SMOS inversion accuracy of soil moisture is the lowest,while SMAP inversion accuracy is not only affected by cover species,but also related to the degree of surface complexity.(3)Influence factor analysis of SMOS and SMAP comparison verification results: During SMOS and SMAP transit time,surface soil moisture variation has no influence on the verification errors of both;when the observed brightness temperature is lower than the fixed value,SMOS and SMAP bright temperature data differ greatly,which may have an impact on the soil moisture product comparison results of the two;scale difference does not affect the contrast results of SMOS and SMAP inversion accuracy.