Vertical profiles of carbon monoxide and ozone from MOZAIC aircraft over Delhi, India during 2003–2005

Abstract

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 (O3) 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. O3 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 O3 and CO concentrations are higher near surface, while during summer season, surface air masses enhance levels of H2O, 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 O3 profiles are compared with three chemistry-climate coupled models from the Coupled Model Inter-comparison Project Phase5 (CMIP5) with interactive O3 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.