Seasonal Variability of aerosol over various cities of Pakistan

This study simulates seasonal and temporal variations in aerosol optical depth (AOD) over various regions of Pakistan using Moderate Resolution Imaging Spectroradiometer (MODIS) data during the period (2001-2011). The obtained result indicated seasonal variation in AOD with high value of 2.3, in summer and low values of 0.2, in winter for the costal part of the region. Angstrom exponent has been found to be high (> 0.61) during winter season, indicating higher abundance of fine particles. The maximum mean AOD value of 2.3 with the corresponding value of 0.4 was found for Karachi, while the minimum mean AOD value < 0.7 with the corresponding value of > 0.15 was recorded for the northern region of the country during summer season. A Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used for trajectory analysis in order to investigate the origins of air masses and understand the spatio-temporal variability of aerosol concentrations. The HYSPLIT model revealed that air masses reached Pakistan from Afghanistan, Iran, Thar desert, Saudi Arabia and Sahara deserts, and subsequently passed over the various locations in Pakistan.

Keywords:

Aerosol , AOD , Angstrom Exponent , HYSPLIT , Pakistan