Seasonality and interannual variability of the Sri Lanka dome

Located in the southwest Bay of Bengal, the Sri Lanka Dome (SLD) is an upwelling tropical thermal dome that forms in a region of positive wind stress curl within the Southwest Monsoon Current (SMC) system. Here, we quantify variability in the SLD's sea surface slope, area, amplitude, and position using a 22-year record of absolute dynamic topography. We observe a seasonal cycle in the evolution of the SLD and its relationship to wind stress curl. The SLD typically forms in early June in a region of positive wind stress curl associated with the wind jet off Sri Lanka. For the first two months after formation, the magnitude of the SLD's sea surface slope strongly correlates with the strength of the wind stress curl. Later in the southwest monsoon, the SLD's position shifts northward moving out of the region of strong wind stress curl, before dissipating in typically September. The amplitude and area of the SLD vary together, and both are linked to the strength of the SMC on weekly timescales. Decadal variability in both the SLD and wind stress curl is reflected in the Dipole Mode Index, which reflects an integrated measure of regional forcing. These results suggest alignment between the SMC and the region of wind stress curl may play a pivotal role in controlling the strength of the SLD on seasonal and interannual timescales.