Abstract:
In this study, the spatial and temporal distributions of tropospheric NO2 Vertical
Column Densities (VCDs) over Pakistan are presented. The data products from
three satellite instruments SCIAMACHY, OMI and GOME-2 are used. This study
provides first database of NO2 concentration over Pakistan useful for various
stakeholders concerned with air quality and its regulations. The spatial, seasonal
and overall trend of NO2 column densities over Pakistan were determined from
2002 – 2012. Identification of sources for increased NO2 column densities is also
discussed. The results show a large NO2 growth over the major cities of Pakistan
particularly the areas with rapid urbanization and economic growth. Overall
temporal increase of 58% was observed over Pakistan. Different seasonal cycles
were observed in the eastern and western sides of Pakistan. In the east and south of
Pakistan, NO2 maximum is found in winters while low in summer and vice versa
trend was observed in the west. On the eastern side, the increase can be attributed
to the anthropogenic emissions as these are the areas with high population density
and industrial activities. While on the western side, natural emissions such as from
soil and lightning dominate. The vehicle population showed a positive correlation
with NO2 column densities in the major provinces of Punjab, Sindh and KPK with
exception of Balochistan. Similarly, the areas with major industrial activity showed
high amount of NO2 concentration. The data of three satellite instruments compare
well with each other. Auto correlation function (ACF) and regression analysis was
also performed to test the statistical significance of the data used in this study.
