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The paper presents the temporal variations of surface ozone (O) and its precursors (oxides of nitrogen (NO), carbon monoxide (CO), methane (CH) and non-methane hydrocarbons (NMHCs)) along with particulate matter (PM and PM) and their relationship with meteorology during January 2012 to December 2014 at an urban site of Delhi, India. The mean mixing ratio of surface O, NO, CO, CH and NMHCs were 29.5 ± 7.3 ppb, 34.7 ± 11.2 ppb, 1.82 ± 0.52 ppm, 3.07 ± 0.37 ppm and 0.53 ± 0.17 ppm, respectively. This study also comprises an analysis of the relation between UV irradiance and surface O. A relationship between the total oxidant concentrations (OX) and NO has been used to identify the regional background O values and the local levels of primary pollution. An attempt has been made to identify the existence of NO or NMHC sensitive regime by charting out relationships between O, NO and NMHCs. The respective high pollution periods of surface O and PM differ on a seasonal timescale. Linear regression analysis has been used to quantify the negative influence of the chemical constituents of PM (elemental carbon, NO , SO ) on O values. Statistical validation using bivariate correlation analysis, multiple linear regression (MLR) analysis and principal component analysis (PCA) strongly describes the intricate relationships among the aforesaid variables and meteorology. Potential Source Contribution Function (PSCF) and Concentration Weighted Trajectory (CWT) analysis indicated upper Indo-Gangetic Plain (IGP) as a significant source region of O precursor gases contributing for O values at the study site. [ABSTRACT FROM AUTHOR]

The Indo-Gangetic Plains is one of the most densely populated regions in the world and associated with large anthropogenic pollutants. Aircraft measurements of two such pollutants, ozone (O) and carbon monoxide (CO) over Delhi, an urban location are analyzed to study monthly and seasonal variations. Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) vertical profile data during 2003-2005 are used in the present study. O over Delhi exhibits a lower tropospheric (surface to 850 mb) high value during post-monsoon (October and November) and winter (December-February) seasons, upper tropospheric (above 400 mb) enhancement during pre-monsoon and a zone of high values in the mid-troposphere (700-400 mb) during monsoon. The anthropogenic emissions show high CO concentrations below 800 mb during winter and pre-monsoon seasons in addition to transported CO in the upper atmosphere during pre-monsoon. During winter season, convective activities are suppressed as a result O and CO concentrations are higher near surface, while during summer season, surface air masses enhance levels of HO, CO and other trace gases are lifted and subsequently mixed into the large scale circulation that enhance mixing ratios of many trace gases in the upper level anticyclones. MOZAIC observed vertical O profiles are compared with three chemistry-climate coupled models from the Coupled Model Inter-comparison Project Phase5 (CMIP5) with interactive O chemistry. All the models show good agreement with MOZAIC during pre-monsoon, with large biases during winter and monsoon seasons. Finally, monthly variations of MOZAIC observed CO show a good comparison with AIRS and MOPITT satellite data. [ABSTRACT FROM AUTHOR]