TITLE:
Long-Term Variability and Empirical Estimation of Daily UVB Doses in Riyadh: Insights from a Decade of Ground-Based Measurements
AUTHORS:
Abdullrahman Maghrabi, Latifah Shaber, Abdulah Aldosari, Mohammed Altlasi, Ghada Khouqeer
KEYWORDS:
Daily UVB Dose, Clear Sky Residual Analysis, Arid Desert Climate, Aerosol Modulation, Empirical Modeling
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.16 No.4,
October
16,
2026
ABSTRACT: This study presents a decadal climatology of daily UVB doses at a single ground-based station in Riyadh, central Saudi Arabia, based on ten years (2015-2025) of half-hourly ground-based measurements. Temporal variability, sky-condition influences, and atmospheric controls on surface UVB radiation were examined using empirical modelling and clear-sky residual analysis. Results reveal a pronounced seasonal cycle driven primarily by solar geometry, with summer maxima of ~85 kJ∙m−2∙day−1 and winter minima of 35 - 38 kJ∙m−2∙day−1. Annual mean daily UVB doses ranged from 43.84 to 68.11 kJ∙m−2∙day−1 and were largely attributable to variations in clear-sky frequency (~85% of days) and aerosol loading. Overcast conditions suppressed daily UVB doses by ~70% relative to clear skies. Simple linear empirical models based solely on global horizontal irradiance (G) and the cosine of the solar zenith angle (cos SZA) explained 74% - 75% of day-to-day variability with near-zero bias and outperformed more complex artificial neural network approaches. Residual analysis after removing the dominant effects of G and SZA demonstrated that secondary factors, particularly PM10 and total column ozone, continue to exert measurable influence on clear-sky UVB doses. These findings address an important observational gap in the Arabian Peninsula and provide transparent, physically interpretable tools for estimating daily UVB doses in high-insolation, aerosol-variable desert environments. The models have potential applications in public-health policy, solar-energy assessments, and climate-impact studies.