Findlater Jet Induced Summer Monsoon Memory in the Arabian Sea
Vikas Kumar KUSHWAHA, University of Hyderabad, India
S Prasanna KUMAR, University of Hyderabad, India
Feba FRANCIS, University of Hyderabad, India
Ashok KARUMURI , University of Hyderabad, India
A cross-equatorial low-level wind, known as Findlater Jet (FJ), modulates the thermocline in the Arabian Sea (AS) during the summer monsoon. By analyzing ocean and atmospheric data, we show that the FJ signal gets ‘trapped’ in the AS in the form of tropical cyclone heat potential till the following winter monsoon months. This memory is the consequence of the FJ-induced wind stress curl and the annual downwelling Rossby waves in the AS. During the summer monsoon months, the strong low-level westerly winds cause a negative wind stress curl in the south of the FJ core over the central AS, resulting in a deeper thermocline. In winter monsoon months, though the winds are weaker, and spread over a larger area, causing a positive wind stress curl over the entire AS, the signal remains in the subsurface. This is due to the presence of downwelling Rossby waves radiated from the eastern AS, which further depresses the thermocline, resulting in a thicker mixed layer. During the following spring, the Rossby waves collapse. This leads to the mixing of underlying waters with surface waters and the resurfacing of the signal. The resurfacing signal makes the AS a memory bank of the FJ winds.
Mots clés : Arabian Sea|Findlater Jet|Wind stress curl|Tropical cyclone heat potential|Rossby wave
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