MONTHLY AVERAGE SPATIAL INTERPOLATION FOR AIR POLLUTANTS IN EGYPTSARA OSAMA AHMED1, REDA MAZLOUM AND HALA ABOU-ALIAbstract This paper analyzes the monthly averages of air pollutants in Egypt for the year 2015. Two air pollutants are utilized, namely Nitrogen Dioxide (NO2) and Sulfur Dioxide (SO2), measured by the monitoring stations network. A log transformation is applied to achieve normality. Two interpolation techniques are performed. First, the ordinary kriging for each month separately and second the ordinary cokriging where the previous three months are treated as the co-variables. Then, cross validation is executed between the two methods in order to determine the best methodology using Root Mean Squares. The estimation procedure starts with exploratory spatial data analysis carried out on the air pollutant; followed by plotting and modeling the experimental semi-variograms. The results indicate that cokriging gives better results especially when the months are correlated. Therefore, using ArcGIS, surface maps with the corresponding standard errors are generated by performing spatial interpolation using the ordinary cokriging model. This helps in determining the highly polluted regions besides the highly polluted months taking into consideration the effect of previous situations.
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