Satellite Retrieval of Aerosol Optical Thickness over Arid Region: Case Study over Makkah, Mina and Arafah, Saudi Arabia

In this study, we presents the potentiality of retrieving Aerosol Optical Thickness (AOT) in the atmosphere which combined Landsat 7 ETM+ satellite and ground based closures enable the determination of required aerosol characteristics over moderate bright surfaces area of Makkah, Mina and Arafah. A multispectral algorithm was developed by assuming that surface condition of study area was lambertian and homogeneous. In-situ AOT data was calculated using Beer Lambert law from transmittance of atmospheric measured using the FieldSpec handheld spectroradiometer and their locations were determined by a handheld Global Positioning System (GPS). The Digital Number (DN) recorded by satellite imageries were converted to top of the atmosphere (TOA) reflectance which is the sum of the ground reflectance and atmospheric reflectance. Then, the atmospheric correction (ATCOR2) method was used to retrieve the surface reflectance. The reflectance measured from the satellite at the top of the atmosphere (TOA) was subtracted from the amount given by the surface reflectance to obtain the atmospheric reflectance. Measured PM10 and AOT were correlated with atmospheric reflectance value using regression technique. Various types of regression algorithms were then examined by comparing the correlation coefficient (R) values and the Root-Mean-Square Error (RMSE) values. The three band model of algorithm was selected based on the highest R value and the lowest RMSE value. The proposed algorithm added evidence on the correlation found between aerosol optical thickness derived from Landsat 7 ETM+ satellite using multispectral algorithm with Terra Multiangle Imaging SpectroRadiometer (MISR) AOT product.