This paper is based on aerosol data level-2 as obtained from Moderate Resolution Imaging Spectroradiometer (MODES) onboard Aqua and Terra satellites and cloud data of Automatic Picture Transmission (APT) onboard NOAA (12.15,16) satellites. These data were obtained at different lat/long over Pakistan for the period 2000-2003. Aerosol Optical Thickness (AOT) was studied for area covering 22-36ºN, 60-68ºE. The maximum value is in the range 0.2-0.6 at 22ºN60-68ºE over the Arabian Sea during the months of Apr-June. The reason is, during the northern hemisphere summer, pressure becomes low over Asia, where there is intense surface heating but remains quite high over the cool seas to the south. The moist equatorial air moves north under this pressure gradient, which decreases the optical thickness. As the air moves north, away from the equator the Coriolis force has more and more effect, so the winds are south and southwesterly over Pakistan. Similarly aerosol optical thickness at 31ºN, 60-80º E (in land over Pakistan) shows that it is in the range of 0.2-0 8. Like aerosols, clouds were also affect the weather, therefore, the APT cloud data for the period 2000-2003 were used to study over well distributed places of Pakistan, which implied that during this period the northern areas of Pakistan remained mast cloudy and the southern part of the country remained least cloudy in the winter and post monsoon seasons.
Seasonal study of aerosol shows that in monsoon season (June-Aug value o f AOT over the areas covering 22-31ºN 60-72ºE. is in the range 0.3-0.6 while in dry post monsoon (Sep-Nov) and cold winter season (Dec-Feb) it is mostly in the range U 7-0.8. The study of AOT at 36ºN, 60~75ºE (northern mountainous region; shows that most of the time it is in the range 0.2-0.4 in the mentioned seasons implying that the atmosphere was not perfectly transparent. Since aerosols act as Cloud Condensation Nuclei(CCN) so upper region of Pakistan remained mostly cloudy in the same period. |
Abstracts 
