Abstract
Long-term global satellite and reanalysis soil moisture products have been available for several years. In this study, in situ soil moisture measurements from 2008 to 2012 over Southwest China are used to evaluate the accuracy of four satellite-based products and one reanalysis soil moisture product. These products are the Advanced Microwave Scanning Radiometer for the Earth observing system (AMSR-E), the Advanced Scatterometer (ASCAT), the Soil Moisture and Ocean Salinity (SMOS), the European Space Agency’s Climate Change Initiative soil moisture (CCI SM), and the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis (ERA-Interim). The evaluation of soil moisture absolute values and anomalies shows that all the products can capture the temporal dynamics of in situ soil moisture well. For AMSR-E and SMOS, larger errors occur, which are likely due to the severe effects of radio frequency interference (RFI) over the test region. In general, the ERA-Interim (R = 0.782, ubRMSD = 0.035 m3/m3) and CCI SM (R = 0.723, ubRMSD = 0.046 m3/m3) perform the best compared to the other products. The accuracy levels obtained are comparable to validation results from other regions. Therefore, local hydrological applications and water resource management will benefit from the long-term ERA-Interim and CCI SM soil moisture products.
Highlights
Soil moisture (SM) plays an important role in the interactions between the atmosphere and the land surface, and has been identified as an essential climate variable by the Global Climate Observing System (GCOS) [1]
From direct comparisons with in situ soil moisture, it is found that the AMSR-E X-band has better performance than the C-band with lower root mean square difference (RMSD) and unbiased RMSD (ubRMSD) values
Overpass times at night and in the early morning are more suitable for soil moisture retrieval from passive microwave satellites, because the isothermal conditions at night can minimize the errors associated with surface temperature [54]
Summary
Soil moisture (SM) plays an important role in the interactions between the atmosphere and the land surface, and has been identified as an essential climate variable by the Global Climate Observing System (GCOS) [1]. Soil moisture connects the energy and water fluxes due to its control on the partitioning of surface net energy into latent and sensible heat fluxes, as well as the partitioning of precipitation into infiltration and runoff [2,3]. The knowledge of soil moisture dynamics is important for climate change research, flood and drought monitoring, weather forecasting, as well as water resource management [4,5]. Several global satellite-based soil moisture products have been released. These products include the Advanced Microwave Scanning Radiometer E for the Earth observing system (AMSR-E) [9], the Advanced Scatterometer (ASCAT) [10,11], the Soil
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