| 06 Oct 2025
First High-Resolution Surface Spectral Clear-Sky Ultraviolet Radiation Dataset across China (1981–2023): Development, Validation, and Variability
Abstract. Solar ultraviolet radiation (UV) plays a fundamental role in the Earth’s energy balance, influencing a wide range of processes, including material degradation, biophysical reactions, ecological dynamics, or public health. In this context, the first high-resolution (10×10 km) hourly dataset of surface solar UV under clear-sky conditions over mainland China from 1981 to 2023 is introduced, derived from ERA5 and MERRA2 reanalysis data and a reconstruction based on the SMARTS (Simple Model of the Atmospheric Radiative Transfer of Sunshine) spectral model. Leveraging the SMARTS model’s accuracy and capabilities, this dataset provides UV data at 0.5 nm intervals between 280 nm and 400 nm, offering enhanced granularity for wavelength-specific analysis, thus filling a key gap in high-resolution hourly UV data for China. Validation of the UV dataset against ground observations at 37 stations of the Chinese Ecosystem Research Network (CERN) demonstrates strong performance, with a correlation coefficient (R), root mean square error (RMSE), and mean bias error (MBE) of 0.919, 5.07 W m-2 and −0.07 W m-2, respectively. Compared with the Earth’s Radiant Energy System (CERES) UV product, this dataset offers higher spatial and temporal resolution as well as higher accuracy in comparison with observations, thus enhancing data quality for a wide range of applications. The spatial and temporal distribution of clear-sky UV radiation exhibits distinct regional and seasonal variations, with higher values in the west and south, and lower values in the east and north. Over the past 43 years, the annual mean clear-sky broadband UV radiation averaged over China was 20.05 W m⁻², showing a slightly increasing trend (+0.0237 W m⁻²yr⁻¹). This dataset is now available at https://cjgeodata.cug.edu.cn/#/pageDetail?id=110 or https://doi.org/10.6084/m9.figshare.28234298, offering a valuable resource for addressing regional challenges related to UV radiation.
Competing interests: Martin Wild is a member of the editorial board of Earth System Science Data.
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The authors present a high-spectral-resolution clear-sky ultraviolet radiation dataset for China, which features unprecedented 0.5 nm spectral sampling across the 280-400 nm range. The integration of reanalysis data with physical radiative transfer model (SMARTS) represents a robust approach. Its credibility is further strengthened by comprehensive validation against ground-based CERN stations and CERES satellite products. The dataset appears to be a valuable resource, particularly given its spectral resolution and spatial coverage over China. The manuscript merits publication after addressing the following minor reversion.
Abstract: Please correct "Earth’s Radiant Energy System" to the full name "Clouds and the Earth's Radiant Energy System".
Section 2.2: The sun-earth distance correction factor have two different letters, “S” and “s”; standardise the format.
Section 2.3: Phrase “concentration and distribution” is redundant, as the distribution characteristics of errors already encompass the concept of central tendency.
Figure 3: Part of the site name is obscured in Figure 3.
Table 1: How are the variables presented in Table 1 incorporated into the SMARTS model?
Figure 4: The unites of solar radiation in Figure 4 are inconsistently represented, with both “Wm-2” and “W m-2” being used.
Figure 5: The same issue as in Figure 4.
Line 263: “The normally strong aggrement ...” is an inaccurate statement.
Section 4.2: The conclusion could be enhanced by providing additional analytical insights regarding the distinctive features and relative performance of the two products, which would help users make informed selections.
Line 315: “-50.06% to -40.90% per AOD unit” change in UV irradiance require clarification.
Section 4.4.1: Replace the imprecise term “near 400 nm” with the scientifically accurate designation of either “UV-A range (315-400 nm)” or “long-wave interval (380-400 nm)”.
Section 4.4.2: The comparative analysis of the three regions would be strengthened by establishing a unified reference baseline, such as expressing their UV radiation levels as deviations from the national average value.
Figure 12: Please briefly quantify the radiation differences between transitional seasons (Spring/autumn).
Line 389: “considerable altitude” is not appropriate.
Line 431: “coinciding with” inappropriate wording.