Trace gases over marine regions around India

Abstract

Measurements of O3, CO, CH4, NO and SF6 were made during four ship cruises in January, February and March months of years 1996, 1997, 1998, and 1999 over the Arabian Sea and the Indian Ocean. Measurements were also made over the Bay of Bengal in February and March of the year 2001. All the measured trace gases show systematic gradient with decrease in their mixing ratios from the Coastal India to the South Indian Ocean. Transport of these gases also takes place from the surrounding countries over the marine regions. Ozone and CO show higher values over the Bay of Bengal than over the Arabian Sea, indicating stronger transport of polluted air-masses from northeast India and south Asia. Dramatic increase in ozone levels in the marine boundary layer (MBL) while showing no signature of in-situ photochemical production indicates the role of dynamical processes. The diurnal patterns in ozone are very different over the marine environments when compared with continental site, which is due to the nature and levels of pollutants transported from the continental regions and emissions of certain gases over the marine regions. Estimate shows that ozone production over India is less efficient, when compared to mid latitude.