Merging ground-based sunshine duration observations with satellite cloud and aerosol retrievals to produce high-resolution long-term surface solar radiation over China

Abstract

Although great progress has been made in estimating surface solar radiation from meteorological observations, satellite retrieval, and reanalysis, getting best-estimated long-term variations in span classCombining double low line inline-formula iR are sorely needed for climate studies. It has been shown that span classCombining double low line inline-formula iR data derived from sunshine duration (SunDu) can provide reliable long-term variability, but such data are available at sparsely distributed weather stations. Here, we merge SunDu-derived span classCombining double low line inline-formula iR with satellite-derived cloud fraction and aerosol optical depth (AOD) to generate high-spatial-resolution (0.1 span classCombining double low line inline-formula ) span classCombining double low line inline-formula iR over China from 2000 to 2017. The geographically weighted regression (GWR) and ordinary least-squares regression (OLS) merging methods are compared, and GWR is found to perform better. Based on the SunDu-derived span classCombining double low line inline-formula iR from 97 meteorological observation stations, which are co-located with those that direct span classCombining double low line inline-formula iR measurement sites, the GWR incorporated with satellite cloud fraction and AOD data produces monthly span classCombining double low line inline-formula iR with span classCombining double low line inline-formula iR /i2Combining double low line0.97 and standard deviation span classCombining double low line inline-formula Combining double low line11.14 span classCombining double low line inline-formula W m-2 , while GWR driven by only cloud fraction produces similar results with span classCombining double low line inline-formula iR /i2Combining double low line0.97 and standard deviation span classCombining double low line inline-formula Combining double low line11.41 span classCombining double low line inline-formula W m-2 . This similarity is because SunDu-derived span classCombining double low line inline-formula iR has included the impact of aerosols. This finding can help to build long-term span classCombining double low line inline-formula iR variations based on cloud data, such as Advanced Very High Resolution Radiometer (AVHRR) cloud retrievals, especially before 2000, when satellite AOD retrievals are not unavailable. The merged span classCombining double low line inline-formula iR product at a spatial resolution of 0.1 span classCombining double low line inline-formula in this study can be downloaded at a hrefCombining double low line.