ENVIRONMENTAL CHEMISTRY, POLLUTION & WASTE MANAGEMENT | RESEARCH ARTICLE Ventilation coefficient and boundary layer height impact on urban air quality

3 Abstract: In the present study, ventilation coefficient (VC) was estimated in order to understand the concentration of pollutants over the urban region of Hyderabad during 2009-2011. Nocturnal boundary layer height (BLH) was calculated using the accurate (0.2% for Refractivity Profiles) high vertical resolution global positioning system radio occultation (GPSRO), Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC)-derived one-dimensional variational (1-DVAR) refractivity profiles, and observations of boundary layer LIDAR (BLL). The statisti- cal results revealed that the coefficient of determination (R 2 ) between LIDAR- and GPSRO-estimated BLH is 0.51, whereas that for VC is 0.68. The maximum BLH observed during the study period was maximum in the summer season and the minimum was observed in monsoon season, whereas the maximum VC was observed during summer and the minimum in winter. When the BLH and VC are low, the pollutant concentration of black carbon (BC) is higher and vice versa. This means that the dispersion of pollutants in the lower atmosphere is due to convective mixing. It was found that high VC values could dilute air pollutants whereas low values leads to more pollution.