A GLOBAL HOURLY SOLAR RADIATION DATA SET USING SATELLITE AND REANALYSIS DATA

摘要

Datasets using images from geostationary satellites are extended widely used method to obtain hourly estimates of surface irradiance, but their coverage is limited to +/- 65° latitude, and even there they are not always freely available. Reanalysis products can be an alternative to generate a global hourly radiation dataset, but the quality of solar radiation data in the most common datasets (ERA-Interim and MERRA-2) is rather low. Looking for a product to complement satellite data, we evaluate the new ECMWF-ERA5 reanalysis (hourly, ～31 km) using 40 BSRN stations and two satellite products (SARAH and NSRDB). The results show a significant improvement obtained with the new ERA5. The yearly bias (6 W/m~2) is reduced around 50% compared to MERRA-2 and ERA-Interim, and it is comparable to SARAH and NSRDB for inland regions with homogeneous terrain. Still, the weaknesses of ERA5 are the spatial grid, which is too coarse for coasts or mountains, and a poor modeling of clouds, which causes a high variation of the bias with cloudiness and leads to larger absolute errors than satellite products. Hence, we recommend using satellite products when available, but taking into account its limitations, ERA5 is a reasonable alternative to complement the coverage of satellite datasets.