Analysis of a dense haze event over North-eastern Pakistan using WRF-Chem model and remote sensing

Urban areas in Pakistan are experiencing escalation in haze episodes. Due to increase in economy, emissions of gaseous and aerosol components from automobiles, road constructions and industry is growing in Pakistan which has resulted in worsening air quality during winter and post-monsoon season. North Eastern (NE) Pakistan (71-74.5 degrees E, 28-34 degrees N) is experiencing haze and fog episodes because of the increase in aerosol pollution levels. In addition to anthropogenic emissions, winter pollution over NE Pakistan is associated with unfavourable meteorological conditions. Lahore, a metropolitan city in NE Pakistan experienced a dense haze event during the first week of November 2016. In this article, we examine the pollution levels before, during and after this heavily polluted episode in NE Pakistan based on model simulations and remote sensing data. In particular, the Weather Research Forecasting model coupled with chemistry (WRF-Chem) and pertinent satellite data from MODIS are utilized towards validation. Another goal of this study is to characterize sources and causes of this haze event especially over Lahore. Particulate matter concentrations, AOD, and concentration of gaseous components increased many folds than the usual levels. Additionally, Vertical Feature Mask (VFM) results are presented from measurements by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite revealing vertical layers of aerosol of thickness ranging from 2 to 5 km in the study region and period.