Constructing High-Resolution (10 km) Daily Diffuse Solar Radiation Dataset across China during 1982–2020 through Ensemble Model

Abstract

Diffuse solar radiation is an essential component of surface solar radiation that contributes to carbon sequestration, photovoltaic power generation, and renewable energy production in terrestrial ecosystems. We constructed a 39-year (1982–2020) daily diffuse solar radiation dataset (CHSSDR), using ERA5 and MERRA_2 reanalysis data, with a spatial resolution of 10 km through a developed ensemble model (generalized additive models, GAM). The validation results, with ground-based measurements, showed that GAM had a high and stable performance with the correlation coefficient (R), root-mean-square error (RMSE), and mean absolute error (MAE) for the sample-based cross-validations of 0.88, 19.54 Wm−2, and 14.87 Wm−2, respectively. CHSSDR had the highest consistency with ground-based measurements among the four diffuse solar radiation products (CERES, ERA5, JiEA, and CHSSDR), with the least deviation (MAE = 15.06 Wm−2 and RMSE = 20.22 Wm−2) and highest R value (0.87). The diffuse solar radiation values in China range from 59.13 to 104.65 Wm−2, with a multi-year average value of 79.39 Wm−2 from 1982 to 2020. Generally, low latitude and low altitude regions have larger diffuse solar radiation than high latitude and high altitude regions, and eastern China has less diffuse solar radiation than western China. This dataset would be valuable for analyzing regional climate change, photovoltaic applications, and solar energy resources. The dataset is freely available from figshare.

Evaluation and Bias Correction of the ERA5 Reanalysis over the United States for Wind and Solar Energy Applications

“…Similar underestimates of the DHI irradiances and overestimates of the DIRhor irradiances are found for all of the SURFRAD, SOLRAD, and ARM-SGP sites. We note that Wu et al [17], Jiang et al [18], and Li et al [19] also found similar opposing diffuse and direct beam biases in the ERA5 in China, demonstrating the consistency of these errors across diverse geographic regions.…”

“…Fewer studies have evaluated the solar direct and diffuse components of downward solar irradiance, which are required for calculating solar power on tilted panels. Using a network of 17 stations in China, Wu et al [17] found that the ERA5 underestimates the diffuse irradiance, while Jiang et al [18], using an observation network of 39 stations in China, found that the ERA5 underestimates diffuse radiation by 43 Wm −2 , but overestimates the direct radiation by 74 Wm −2 . Using observations from 14 stations, Li et al [19] also found a negative ERA5 bias for diffuse irradiance, and a positive bias for the direct beam, and concluded that, in addition to cloud effects, at least part of these biases can be attributed to aerosols.…”