An Empirical Model to Estimate UV index in Some Upper Egypt Regions

Abstract

Empirical models to estimate the ultraviolet index (UVI) for all sky conditions in ten locations in Upper Egypt have been developed. Multiple linear regression technique has been used for linking each of the UVI as a dependent variable, and all of the declination (δ), cosine solar zenith angle at noon (cosSZA<SUB>n</SUB>), total ozone column (TOC) in DU, reflectivity (reflc) in % and aerosol index (AI) as independent variables. A dataset corresponding to the period (1978-1999) was used to develop the models and an independent dataset (year 2000) was used for validation purposes. The data set for each location, including erythemal ultraviolet (EUV) at noon in mW/m<SUP>2 </SUP>, (TOC) in DU, reflectivity (reflc) in % and (AI), was retrieved from Total Ozone Mapping Spectrometer (TOMS) remote sensing instrument. For all locations, the empirical models explain more than 93% of UVI variability due to changes in all independent variables. In addition, one single model for all the locations has been constructed. Model performance was determined for each location by calculating the mean bias error (MBE %) and the root mean square error (RMSE %). In addition, mean absolute error (MAE %), modelling efficiency (ME), modelling index (d), and t-statistics have been computed. The empirical model provides reliable forecast UVI in order to inform the public about the possible harmful effects of UV radiation over-exposure.