• The influence of local meteorology and convection on carbon monoxide distribution over Chennai

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      https://www.ias.ac.in/article/fulltext/jess/128/05/0119

    • Keywords

       

      Carbon monoxide; convection; India; simulation; troposphere; biomass burning.

    • Abstract

       

      The influence of local meteorology and convection activities on the vertical distribution of carbon monoxide (CO) over Chennai in southern India was investigated by analysing the measurements of ozone aboard airbus in-service aircraft observations during the years 2012–2013. The seasonal variation of CO in the free troposphere was observed to be different and less pronounced than that in the planetary boundary layer (PBL). The near surface mixing ratio of CO was the highest (190 $\pm$ 68 ppbv) during winter, while enhanced values (117 $\pm$ 11 ppbv) in the free troposphere were observed during post-monsoon. The mixing ratios were the lowest throughout the troposphere during the monsoon. In the PBL, the mixing ratios of CO showed a decline with an increase in wind speed and were the highest (>200 ppbv) under stagnant conditions (1-2 m s$^{-1}$) during winter. The higher CO in the lower free troposphere during the pre-monsoon period is attributed to the stronger biomass burning emissions. In the middle–upper troposphere, higher levels of CO during post-monsoon are due to the enhanced vertical mixing of regional emissions associated with weaker wind shears and frequent convection activities. Overall, the contrasting effects of stronger CO emissions can be observed in winter/pre-monsoon, while the efficient vertical mixing during the monsoon/post-monsoon season governs the observed seasonality of CO. The model for ozone and related chemical tracers, version 4 (MOZART-4) provides a reasonable representation of the convection effect on the CO mixing ratio. This study highlights a need to conduct more observations, especially of aircraft-borne instruments, to understand the effects of regional-scale emissions and dynamics in the middle–upper tropospheric chemistry over South Asia.

    • Author Affiliations

       

      Sahu L K1 Nidhi Tripathi1 2 Varun Sheel1 Ojha N1

      1. Physical Research Laboratory (PRL), Navrangpura, Ahmedabad 380 009, India.
      2. Indian Institute of Technology Gandhinagar, Palaj, Gandhinagar 382 355, India.
    • Dates

       
  • Journal of Earth System Science | News

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