A novel efficient broadband model to derive daily surface solar Ultraviolet radiation (0.280-0.400 μm).

The climatic characteristics of solar Ultraviolet radiation (UV) are of vital important for the climate change and photochemical reactions. High-quality records of solar UV radiation are the premise for solar UV researches and applications, but solar UV radiation observations are sparse around the world. Among all wavelength of UV radiations, only UVA (0.315-0.400 nm) and UVB (0.280-0.315 nm) could reach the earth surface. This study attempted to develop a novel efficient physically broadband parameterization (hereafter, FASTUV) for estimating surface solar UV radiation (0.280-0.400 μm) in all-sky conditions based on Leckner's spectral model for calculating shortwave solar radiation, using MERRA_2 reanalysis data. The Quadratic polynomial formula and artificial neural networks were used to calculate the cloud transmittance for UV, using sunshine durations measurements at 2474 CMA stations. The surface solar UV radiation measurements at 29 CERN (The Chinese Ecosystem Research Network) stations were used for validating the estimated UV values. The result showed the FASTUV model could be used for estimating UV values with high accuracy, strong robustness and fast speed. Then, the spatial and temporal variation of surface solar UV radiation in China were revealed. The result indicated that the Qinghai Tibetan Plateau and the Palmier Plateau has always been the areas with highest UV values, while the Northeastern China is the area with the lowest UV values. Meanwhile, the FASTUV model have been packaged into a software namely 'FASTUV_V1.0'. We provide the executable file of FASTUV model in publicly available repository: https://doi.org/10.6084/m9.figshare.11409666.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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