A modelling approach to ascertain the memory induced by Findlater Jet in the Arabian Sea

Abstract The formation of Findlater Jet (FJ) in the lower atmosphere over the Arabian Sea (AS) is an integral part of the Indian summer monsoon (ISM, June–September). Based on observations, our earlier study indicated that the FJ-induced heat signal during the ISM is potentially preserved in the upper ocean in the form of heat content in the southern AS until the following winter season. Through various sensitivity experiments with an ocean model, we could demonstrate the above and identify the processes that lead to the observed memory. We further demonstrate that the simulated mixed layer depth and the upper ocean heat content are higher in the southern AS during a flood monsoon year compared to a drought year. This is attributed to a relatively stronger FJ-induced wind stress curl during the flood summer monsoon, which deepens the thermocline and results in higher heat retention in the southern AS during the subsequent winter and spring seasons. The accumulated heat enhances pre-monsoon rainfall over the west Indian coastal region and, in turn, influences the ensuing monsoon rainfall.