Abstract
Surface net radiation plays an important role in land–atmosphere interactions. The net radiation can be retrieved from satellite radiative products, yet its accuracy needs comprehensive assessment. This study evaluates monthly surface net radiation generated from the Clouds and the Earth’s Radiant Energy System (CERES) and the Surface Radiation Budget project (SRB) products, respectively, with quality-controlled radiation data from 50 meteorological stations in China for the period from March 2000 to December 2007. Our results show that surface net radiation is generally overestimated for CERES (SRB), with a bias of 26.52 W/m2 (18.57 W/m2) and a root mean square error of 34.58 W/m2 (29.49 W/m2). Spatially, the satellite-retrieved monthly mean of surface net radiation has relatively small errors for both CERES and SRB at inland sites in south China. Substantial errors are found at northeastern sites for two datasets, in addition to coastal sites for CERES. Temporally, multi-year averaged monthly mean errors are large at sites in western China in spring and summer, and in northeastern China in spring and winter. The annual mean error fluctuates for SRB, but decreases for CERES between 2000 and 2007. For CERES, 56% of net radiation errors come from net shortwave (NSW) radiation and 44% from net longwave (NLW) radiation. The errors are attributable to environmental parameters including surface albedo, surface water vapor pressure, land surface temperature, normalized difference vegetation index (NDVI) of land surface proxy, and visibility for CERES. For SRB, 65% of the errors come from NSW and 35% from NLW radiation. The major influencing factors in a descending order are surface water vapor pressure, surface albedo, land surface temperature, NDVI, and visibility. Our findings offer an insight into error patterns in satellite-retrieved surface net radiation and should be valuable to improving retrieval accuracy of surface net radiation. Moreover, our study on radiation data of China provides a case example for worldwide validation.
Highlights
Surface net radiation is the net amount of radiative fluxes entering and leaving the Earth’s surface.It is composed of four components, including downward shortwave radiation (S↓), upward shortwave radiation (S↑), downward longwave radiation (L↓), and upward longwave radiation (L↑)
The errors are attributable to environmental parameters including surface albedo, surface water vapor pressure, land surface temperature, normalized difference vegetation index (NDVI) of land surface proxy, Remote Sens. 2015, 7 and visibility for Clouds and the Earth’s Radiant Energy System (CERES)
This study evaluates the accuracy of surface net radiation generated from the CERES and Surface Radiation Budget project (SRB)
Summary
Surface net radiation is the net amount of radiative fluxes entering and leaving the Earth’s surface. Kato et al [25] claimed that CRERS monthly S↓ (L↓) data compared to ground observations at 24 sites had a bias of −1.70 (−1.00 W/m2) with an RMSE of 7.80 (7.60 W/m2) over the global land area. This study uses nationwide surface observations of China’s meteorological sites to evaluate surface net radiation generated from the SRB and CERES products, respectively, and to identify main error sources in the net radiation for possible improvement. The observation sites represent a wide range of landscape, climatic, and hydrogeological conditions, and have been used to validate remote sensing radiation products such as insolation [29,30] and surface shortwave radiation [31].
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