Clear-Sky Shortwave Downward Flux at the Earth's Surface: Ground-Based Data vs. Satellite-Based Data

Abstract

The radiative flux data and other meteorological data in the BSRN archive start from 1992, but the RadFlux data, the clearsky radiative fluxes at the BSRN sites derived through regression analyses of actually observed clearsky fluxes, did not come into existence until the early 2000s, and at first, they were limited to the 7 NOAA SURFRAD and 4 DOE ARM sites, a subset of the BSRN sites. Recently, the RadFlux algorithm was applied more extensively to the BSRN sites for the production of clearsky groundbased fluxes. At the time of this writing, there are 7119 site-months of clearsky fluxes at 42 BSRN sites spanning the time from 1992 to late 2017. These data provide an unprecedented opportunity to validate the satellite based clearsky fluxes. In this paper, the GEWEX SRB GSW(V3.0) shortwave downward fluxes spanning 24.5 years from 198307 to 200712, the CERES SYN1deg(Ed4A) and EBAF(Ed4.0) shortwave fluxes spanning 200003 to mid2017 are compared with their RadFlux counterparts on the hourly, 3hourly, daily and monthly time scales. All the three datasets show reasonable agreement with their groundbased counterparts. Comparison of the satellitebased surface shortwave clearsky radiative fluxes to the BSRN RadFlux analysis shows negative biases. Further analysis shows that the satellitebased atmosphere contains greater aerosol optical paths as well as more precipitable water than RadFlux analysis estimates