Interpolation for Aerosol Optical Depth at Four Wavelengths over Ilorin from Observed Aeronet Data

Abstract

The Aerosol Optical Depth (AOD), which is the integral part of the atmospheric extinction coefficient from the surface to the top of the atmosphere, is an important parameter for observation of visibility degradation due to atmospheric pollution, solar radiation extinction and other climate effects. The wavelength dependence of Aerosol Optical Depth (AOD) varies between different aerosol types because of their different physical and chemical characteristic. This paper presents new data points using interpolation for Aerosol Optical Depth (AOD) at four spectral wavelengths (440-870nm. The data used consist of measurements collected at Ilorin AERONET site (8°32’N, 4°34’E) for AOD and Angstrom exponent at the four wavelengths (α440-870). Angstrom empirical formula was used to compute new data points by interpolation. A Regression analysis was then used to estimate the relationship between the interpolated AOD and the observed AOD at the different wavelengths of 440nm, 500nm, 670nm and 870nm. The coefficients of determination were found to be 0.978, 0.980, 0.999 and 0.997 respectively, indicating that the interpolated data agrees well with the measured data.