Impact of Air Pollutants on Atmospheric Visibility in Delhi

The air pollution problem has been serious in Delhi due to the rapidly expanding economic, industrial and vehicular developments. It has significant influences on atmospheric visibility, whose degradation dominates in urban areas. Increased air pollution in urban area may lead to the atmospheric reactions, resulting into the formation of secondary pollutants similar to cloud the condensation processes. Northern regions of India experience severe visibility degradation conditions during the peak of winter season (December-January) each year. In this study, air pollutants concentration, meteorological parameters and atmospheric visibility in Delhi during 2006-2011 peak winter season of the years have been studied. In order to study the impact of air pollutants on visibility at IGI airport of Delhi during the winter season (December and January), the daily data of visibility and meteorological parameters like dry bulb temperature , humidity , wind speed , Dew point temperature have been collected and a study is carried out to correlate these parameters and air quality in terms of the concentration of CO , NOx , SO2 and O3 with the observed visibility. The analysis is carried out in two different ways to find the impact of air pollutants as well as other meteorological parameters on visibility. At first stage the normalized values of daily observed concentration of air pollutants and averaged values of daily visibilities along with other meteorological parameters are studied. Secondly, the analysis of hourly normalized data of the 7440 observations of hourly visibility and daily averaged visibility in the above said period is found to be 1636.9 meters and 1625.1 meters respectively. The regression analysis of daily averaged visibility using empirical model demonstrates that higher the concentration of air pollutants (CO, NOx, SO2, O3), lower the visibility. Because air pollutants have a significant impact on atmospheric visibility, it is also observed that a targeted reduction of air pollutants in Delhi would improve the visual range.