资源环境科技发展态势分析平台

Twenty-three years of Archiving, Validation, and Interpretation of Satellite Oceanographic data absolute dynamic topography and HYbrid Coordinate Ocean Model sea surface height were analyzed with a focus on interannual variability of the Indian Southwest Monsoon in the southwest Arabian Sea. A new algorithm for identification and tracking of the Great Whirl (GW) is presented, which better accounts for the gyre's embedded environment than traditional mesoscale eddy tracking algorithms that use sea level observations. Based on this algorithm, the GW exhibits an average life span of 198 days, which is considerably longer than previous estimates, attributed primarily to a later termination date. A climatology of the GW evolution is created, peaking in early September. This study suggests a possible periodicity of the upper ocean structure during the mature phase of the GW and also highlights the sporadic nature of the decay phase.

Plain Language Summary The Great Whirl is an oceanic vortex that spins in a clockwise direction off the coast of east Africa. This feature is present for approximately half the year in coincidence with the Indian Southwest Monsoon. The Great Whirl is important because it can inhibit the flow of relatively fresh water into the salty Arabian Sea by recirculating the coastal current waters in a loop of intense currents. Here we evaluate a new algorithm specifically designed to track the Great Whirl. The algorithm is shown to provide increased accuracy in both satellite and model data over previous tracking methods and suggests a high-frequency periodicity in the size and strength of the Great Whirl, which has not yet been well documented. Additionally, interannual variability of the life cycle reveals a later termination date than previously thought.