Estimation of solar ultraviolet (UV-B) radiation using Aura satellite Ozone monitoring instrument (OMI) in Iran

Introduction
Part of the sun’s rays is made up of ultraviolet rays, which have short wavelengths and a lot of energy. Ultraviolet light in three ranges of long wavelength ultraviolet (UV-A) with a wavelength range of 0.390 - 0.315 μm, medium wavelength ultraviolet (UV-B) with a long range the wavelength is divided by 0.155 μm - 0.280 μm and short-wavelength ultraviolet (UV-C) with a wavelength less than 0.280 μm. UV-B light is the most harmful radiation on the skin and causes various side effects including sunburn, skin allergies and skin cancer. This radiation affects the DNA strand by altering the genetic material and increases the potential for intracellular carcinogenesis. Ultraviolet (UVI) index is a small (numerical) value that indicates the intensity of ultraviolet (UV) rays in the desired location and area. This index is a parameter for raising public awareness about the effects of UV radiation on health and how much skin protection is needed for different amounts. Based on the index provided by the World Health Organization, the concentration level or UV index is shown on a scale of 2 to +1. The higher the value of this index, the more destructive power it has on the skin and eyes.
 
Materials and Methods
In this study, the Level 3 product (OMUVBd-L3) of the solar ultraviolet (UV-B) index of the OMI sensor with a spatial resolution of 0.25 × 0.25 degree for the time series 2005 to 2020 was used. The required data was downloaded from the website http://aura.gsfc.nasa.gov in a daily time step and after the necessary processing; it was converted into monthly and seasonal values. The data used were converted into network data and information tables by applying the necessary algorithms, and the necessary outputs were extracted as a raster based on the geographical border of Iran. Finally, in order to better understand the temporal-spatial behavior of the UV index reaching the surface in Iran, the results were presented in the form of maps, graphs and graphs and the temporal-spatial estimation of solar UV radiation in Iran.
 
Results and Discussion
Spatially, there is a significant difference in the distribution of UV-B input radiation in Iran. According to the global index of solar ultraviolet radiation, more than 90% of Iran's area is exposed to high to very high radiation risk. The highest average of UV-B index is related to the summer season (11.29) and the lowest average is related to the winter season (3.53). In terms of spatial distribution, there are significant differences between the seasons.
The spatial distribution of the monthly UV index provides more information about the details of changes in solar UV radiation reaching the earth's surface throughout the year; So that it is possible to determine the minimum and maximum, months as well as the months with balanced UV radiation conditions. A comparison of the amount of UV-B radiation in different months clearly shows January as the least dangerous month and June as the most dangerous month of the year. Since the value of the solar UV index is a function of the total amount of incoming solar radiation. Therefore, factors such as the angle of radiation, the duration of radiation and the amount of UV control the UV-B solar ultraviolet index.
 
Conclusion
The results of the analysis and comparison of seasonal and monthly maps of solar UV index in Iran, indicate that in all months and seasons of the year from north to south, the intensity of solar UV radiation increases. In the northern part of Iran, due to higher latitude and less solar radiation reaching the earth's surface, the UV-B index is lower than other parts of Iran. On the other hand, in the more southern offerings, because both the angle of radiation is vertical and the sky is clearer, it provides the conditions for receiving the maximum amount of solar energy and consequently UV-B solar ultraviolet radiation. The prevalence of such conditions is established in all months and seasons of the year, so that the radiant regions (ultraviolet UV-B) are fully compliant with the mentioned conditions. Therefore, it can be said that in the warm period of the year (spring and summer), the highlands as well as the lower offerings have more solar UV radiation and therefore the risk of eye and skin vulnerability increases. Therefore, it is recommended to take protective measures against UV radiation if it is necessary to be present in areas exposed to direct sunlight.