Abstract:
The measurements of vertical distribution of ozone have been made over the Bay of
Bengal and the Arabian Sea in spring 2006 during a cruise campaign, namely, the Integrated
Campaign for Aerosol, Gases and Radiation Budget. The average tropospheric columnar
ozone (TCO) values are found to be 36.1± 6.9 Dobson unit (DU) and 41.7± 5.0 DU over the
Bay of Bengal and the Arabian Sea, respectively. In contrast to TCO, ozone mixing ratios are
higher by about 10 ppbv in the lower 3 km over the Bay of Bengal due to Indo Gangetic
outflow above the marine atmospheric boundary layer. Major contribution in the higher TCO
value over the Arabian Sea is, possibly, by stratospheric intrusion when ozone in the upper
troposphere is higher by about 20 ppbv. The lowest columnar ozone content of 22.4 DU was
observed on 30 March in the central Bay of Bengal due to convective activity resulting into
lower ozone throughout the troposphere, except between 6 and 10 km altitude. These near
simultaneous ozone observations over the Bay of Bengal and the Arabian Sea in spring season
have revealed the role of regional and long-range transport and local dynamics on the vertical
distribution of ozone over these tropical marine regions.
