Study of Ground-Based and CERES-Retrieved Solar UVA and UVB Radiations Over Different Stations in India

Abstract

This study presents a comprehensive comparative analysis of ground-based and satellite based clouds and the earth’s radiant energy system (CERES) retrieved Solar UVA (315–400 nm) and UVB (280–315 nm) radiations across eight diverse stations in India. Utilizing data from ground-based instruments set-up by India Meteorological Department and satellite platform CERES providing the larger spatial coverage, the research aims to assess the consistency and reliability of solar radiation measurements. The selected stations represent varied geographical and climatic conditions, allowing for a thorough evaluation of the UVA and UVB radiation levels over the regions. We have also studied the CERES-retrieved aerosol optical depth at 550 nm (AOD) to see the impact of columnar aerosols on the UV radiation. The observed data for UVA and UVB fluxes were compared with CERES-derived data over the period of one year at all the stations and corrected using linear offset bias correction method. The comparisons show significant correlation values (~ 0.72–0.97) over all the stations. The Mean Bias Deviation (MBD in %) lies in range 0 to − 2.48% for UVA and 0 to -3.03% for UVB suggesting that the observed data was slightly underestimated by the satellite data. The Root Mean Square Deviation (RMSD in %) varies from 8 to 22% for UVA flux and 9–26% for UVB flux. We have also studied the impact of AOD which shows the inverse-linear relation with UVA/B radiations, with unit increase in AOD leading to a decrease of 1.29–19.07 Wm⁻² for UVA flux and 0.01–0.47 Wm⁻² for UVB flux across all the stations. Further, we have also studied the diurnal, monthly and seasonal variation of UVA and UVB along with AOD across all the stations. The 10-years trend analysis for UVA shows the negative linear trend in the range of 0.014–0.048 Wm⁻² years⁻¹ whereas a negligible trend of 0.0001–0.001 Wm⁻² years⁻¹ is observed in UVB, at all the stations except at Srinagar, where both UVA and UVB fluxes has shown the positive trend of 0.055 Wm⁻² years⁻¹ and 0.002 Wm⁻² years⁻¹, respectively. The AOD shows a positive trend ranging from 0.001 years⁻¹ to 0.016 years⁻¹across all sites, except at Srinagar it shows a negative trend with 0.002 years⁻¹. The results indicate the inverse relation between UV flux and AOD.