SPATIO-TEMPORAL DISTRIBUTIONS AND TRENDS OF AEROSOL PARAMETERS OVER PAKISTAN USING REMOTE SENSING

Aerosols play a major role in atmospheric solar radiation budget, air quality degradation and climate change. In order to accurately evaluate aerosols effects, we require an in-depth knowledge of spatio-temporal distributions of their parameters. The focus of this paper is to analyze spatio-temporal distributions and trends of aerosol parameters over Pakistan. In present study, Terra-MODIS data have been used during April 2000-March 2014 to analyze AOD (550 nm), Angstrom exponent (470-660) (AE(470-660)), small mode fraction (SMF) and mass concentration (MC). Values of coefficient of determination (R-2) between Terra-AOD and AERONET-AOD are found to be 0.718 and 0.745 for Lahore and Karachi respectively. Terra-AOD has also been compared with other satellite-based observations obtained from Aqua, MISR and SeaWiFS. A notable spatial variability in mean annual Terra-AOD values (0.15-0.87) has been observed with high values (similar to 0.8) over northeastern and southern Pakistan. AE(470-660) ranges from 0.56 to 1.44 showing high values (greater than 0.8) over northern Pakistan and relatively low values (less than 0.8) over southern Pakistan. MC is found to be in the range from 7.6 mu g/cm(2) to 56.2 mu g/cm(2) with spatial distribution quite similar to AOD. Overall mean values of AOD, AE(470-660), SMF and MC are found to be 0.43 +/- 0.16, 0.68 +/- 0.06, 0.11 +/- 0.05 and 28.2 +/- 9.71 mu g/cm(2) respectively.