Trace Gases over the Marine Regions
Extensive measurements of trace gases have been made over the Arabian Sea, the Bay of Bengal, and the Indian Ocean using ORV Sagar Kanya and other ships (Fig. 8). These measurements of ozone, CO, NOx, NMHCs, and SO2 revealed large variability over these marine regions (Lal et al. 1998; Chand et al. 2003; Naja et al. 2004; David and Nair 2011; Mallik et al. 2013). Estimated south to north latitudinal gradients in O3 (3.95 ppbv/°) and CO (16.56 ppbv/°) were significantly higher than those observed during earlier campaigns. Principle component analysis indicated contributions of ship emissions to NOx levels over the BoB. Influences of fire from the Myanmar and Thailand regions are shown to be the potential contributor to enhanced CO levels (>250 ppbv) over the BoB during 14-15 November 2010 (Mallik et al. 2013). Diurnal variations in surface O3 revealed effects of advection, entrainment, and photochemistry.
Fig. 8 Variations in surface ozone over the Arabian Sea, Bay of Bengal, Indian Ocean, and coastal region