Document Type : Research Article
Authors
1 PhD Candidate in Agrometeorology, Bu-Ali Sina University, Hamedan, Iran
2 Professor in Meteorology, Bu-Ali Sina University, Hamedan, Iran
Abstract
Solar radiation that reaches the Earth's surface has a significant impact on human health, agricultural productivity, terrestrial, aquatic ecosystems, and air quality. The difficulties from shortage of experimental field data motivate the researchers to rely on other database such as satellites and reanalysis radiation data. In the present work, the integrated daily solar ultraviolet-visible radiation (total integral of ultraviolet-visible radiation from 200 to 440 nm) was extracted from the ERA5 reanalysis database during the historical period of 1979-2020. Moreover, Total Column Ozone (TCO), and the Percentage of Cloudiness (CF) were obtained from the same database. The study area was divided into eight clusters by Analytic Hierarchy Process (AHP) method and trend analysis was performed using Mann-Kendall test. Results indicated that mean annual integrated UV-VIS 200-440 radiation of north and northwest of the country has experienced a positive trend during the last four decades, but no significant trend was detected for other parts of the country. The study of the TCO also showed that in all eight clusters, the TCO trend during 1979 to 2000 has experienced a significant decreasing trend, but has increased from 2001 onward. The linear regression equations between UV-VIS200-440 with TCO and CF were also constructed for all time scales (monthly, seasonal, annual) and the corresponding coefficients of correlation were calculated accordingly. The maximum annual correlation (r) was found between UV-VIS200-440 and the cloudiness (0.81). However, the highest r between UV-VIS200-440 and the TCO was 0.25. This result highlights that the variation in cloudiness plays more important role on determination of surface UV radiation than the changes in ozone concentration. This study did not investigated the influence of aerosol optical depth on UV radiation. This issue demands further investigation for evaluating the impact of aerosols on incoming surface UV radiation reaching the ground.
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©2024 The author(s). This is an open access article distributed under Creative Commons Attribution 4.0 International License (CC BY 4.0)
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