Long Term Spatio-Temporal Trends In Aerosol Optical Depth And Its Relationship With Enhanced Vegetation Index And Meteorological Parameters Over South Asia

Abstract Satellite-based Aerosol optical depth (AOD) is columnar light extinction by aerosol absorption and scattering and has become the most important variable for the assessment of the spatiotemporal distribution of aerosols at a regional and global level. In this paper, we have used AOD observations from multi-angle imaging spectroradiometer (MISR), moderate resolution imaging spectroradiometer (MODIS) and sea viewing wide field-of-view Sensor (SeaWiFS). We have observed the association of AOD with enhanced vegetation index (EVI) and meteorological variables (temperature (TEMP), WS and relative humidity (RH)). The findings show that AOD in eastern Pakistan is higher than in the western Pakistan due to increase in population density and biomass burning. Mean annual peak AOD (˃0.7) has been observed over the IGB region because of the significant increase in economical, industrial and agricultural activities. The highest seasonal mean AOD (0.8) has been seen over Bihar, India during the winter season. However, the mean AOD over eastern Pakistan is maximum in both monsoon and post-monsoon season but relatively low in pre-monsoon and winter. The higher mean AOD anomaly value is found to be 0.2 over eastern Pakistan and western India. In northeastern Pakistan and central India, AOD and RH are positively correlated (R ˃0.54) while negatively correlated over southwestern Pakistan. AOD is negatively correlated (R= ~-0.3) with EVI over northeastern and southeastern Pakistan. The correlation coefficient (R) obtained among Aqua and Terra AOD is 0.97 over south Asia. The satellite observations of Aqua-AOD was also compared with SeaWiFS and MISR AOD.