Abstract:
Spatial and temporal distributions of tropospheric NO2 vertical column densities over Pakistan during the time period of 2002 – 2014 are discussed. Data products from three satellite instruments SCIAMACHY, OMI and GOME-2 are used. Further force was made on inter-satellite comparison for NO2 observations over Pakistan. Minor differences are observed among the satellite instruments mainly attributed to difference in spatial resolution and overpass time. This study first time provides a database of tropospheric NO2 column densities over Pakistan and useful for various stakeholders concerned with air quality and regulations. Temporal evolution of tropospheric NO2 column densities over Pakistan is determined. Identification of different type of plausible NO2 sources is also discussed. The results show a large NO2 growth over the major cities of Pakistan, particularly the areas with rapid urbanization. The increase can be attributed to the anthropogenic emissions as these are the areas with high population, traffic density and industrial activities. Source identification revealed that use of fossil fuels for power generation, vehicular emissions and agriculture fires are significant source of tropospheric NO2 in Pakistan.
