Transport effects on the vertical distribution of tropospheric ozone over the tropical marine regions surrounding India

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.