Authors:

Abstract

During the southwest monsoon, a cold dome referred to as the Sri Lanka Dome (SLD) appears east of Sri Lanka in response to the cyclonic curl in the local wind field. In general, SLD forms around May/June and decays during September. However, satellite altimetry data revealed an anomalous propagation pattern of the SLD with a lifetime of more than six months in the southwestern region of the Bay of Bengal (BoB) during 2014. This study is carried out to explain the plausible forcing factors which produced this anomalous event using satellite altimetry, surface currents, and wind data. Previous studies have shown that in general, the SLD propagates westward and then northward from its initial centre. In 2014, the SLD first appeared east of Sri Lanka around 6.5–7.5° N, 83–84° E and propagated eastward/northeastward from its initial centre (7.1018° N, 83.7111° E) with forcing from wind-stress and the Summer Monsoon Current (SMC). During early August it started to propagate westward until mid- October with the support of westward geostrophic flow and upwelling Rossby waves, noted between 10-12° N latitudes. Then the western boundary currents (WBC) in the BoB further facilitated the trajectory of the SLD and guided it towards the Arabian Sea (AS), where it disappeared in late December 2014, south of India (4.5474° N, 78.0223° E). Thus, we show that the stronger winds and SMC existed during 2014 in the BoB, guided the SLD eastward/northeastward compared to its general trajectory, and that allowed the SLD to undergo the forcing from westward geostrophic flow, upwelling Rossby waves and WBC.

Keywords: Sri Lanka Dome, wind-stress, summer monsoon current, Rossby waves, western boundary currents