Statistical characteristics of remotely sensed daily ultraviolet index (UVI) over Riyadh Province, Saudi Arabia: an OMI/AURA data-based assessment
摘要
The spatial and temporal characteristics of the daily ultraviolet index (UVI) in the Riyadh province of the Kingdom of Saudi Arabia (KSA) were examined in this study. A dataset covering a period of 19 years (2004–2023) was utilized, with measurements of Ultraviolet-B (UV-B) irradiance obtained from the Ozone Monitoring Instrument (OMI) on board the AURA satellite. Various statistical analyses were conducted, including an assessment of daily and seasonal UVI, a long-term trend analysis using the Mann Kendall (MK) statistical test, and an evaluation of the rate of change of daily UVI using Theil-Sen’s slope test. Additionally, the correlation between UVI and solar zenith angle (SZA), cloud optical thickness (COT) as well as total column ozone (TCO) were examined using Spearman’s correlation test. The results of the analysis revealed significant variability in the measured daily UVI, with more than 78% of the data falling into the category of very high and above values. Furthermore, the UVI exhibited seasonal variation in the region. A strong negative correlation was identified between daily UVI and SZA, while a weaker and less significant negative correlation was noted between daily UVI and COT. Conversely, a moderate positive correlation was observed between UVI and TCO in the study area. The trend analysis using the MK test showed varying trend (MK Z statistics i.e. MKz) characteristics in the study area. Some regions exhibited a significantly increasing trend, while others showed a non-significantly decreasing trend. The values ranged from 4.02 to -0.71, indicating the magnitude and direction of the trends. Specifically, the urbanized and densely populated northern region experienced a notable upward trend in UVI, while the southern part of the area demonstrated a decline in trends. The rate of change of UVI, estimated using Theil-Sen’s slope method, further supported these findings. It showed an increase in UVI in the northern part of the study area and a decrease in the southern portion. The values ranged from − 9.54 × 10− 6 day− 1 in the south to 8.60 × 10− 3 day− 1 in the north, indicating the magnitude of the changes. Based on these results, it is recommended that precautionary measures be implemented in the northern portion of the region to mitigate the risks associated with UVR exposure. This recommendation applies to both humans and animals, as they are both susceptible to the harmful effects of UVR. Furthermore, it is very important to organize frequent awareness initiatives in order to educate and enhance the understanding of the general public regarding the possible hazards associated with direct and prolonged contact with UV irradiation to mitigate the risks associated with such exposure.