Paper Title
Impact of Air Pollution on Visibility Over New Delhi, India: A Case Study of Winter Fog

The winter season over northern part of India is prone to poor atmospheric visibility & high aerosol contents. Atmospheric visibility is produced by suspended Hydrometeors and Litho meteors. Fog (visibility < 1000 m), mist, are linked with hydrometeors, whereas haze & smoke are associated with Litho meteors. The visibility phenomenon is considerably influenced by the mass of aerosols. Mass distribution (μg/m3) from 0.3 to 20 μm of particulate matter (PM) were measured simultaneously along with the meteorological parameters in New Delhi during the month of January 2014 & 2015 to get an appreciation of their role in the atmospheric obscurity. A statistical model is developed for fog forecasting based on meteorological elements and mass concentrations of PM. The average visibility during 07:00 to 13:00 hrs on Republic Day is found to be 2000 m  1400 m. The daily mean concentrations of PM10 and PM2.5 during 22 to 27th January in the year 2014 and 2015 were found to be 1.23 to 5.20 times and 1.22 to 4.80 times higher than the Indian national ambient air quality standards. The correlation coefficient (r) and coefficient of determination (r2) values of 0.88 and 0.77 respectively suggest that visibility < 1000 m can be predicted satisfactorily using multiple regression model based on various meteorological elements and atmospheric pollutants. This study provides a knowledge and guidance to aviation meteorologists and aviators on visibility pattern during the Republic Day ceremony. It will also enhance the accuracy of visibility forecast and contribute towards flight safety. Keywords- Fog, thermal inversion, particulate matter, depression temperature, wind speed