An evaluation of the Arabian Sea Mini Warm Pool's advancement during its mature phase using a coupled atmosphere-ocean numerical model

Abstract. A coupled atmosphere-ocean numerical model has been used to examine the relative contributions of atmospheric and oceanic processes in developing the Arabian Sea Mini Warm Pool (MWP). The model simulations were performed for three independent years, 2013, 2016, and 2018, through April–June, and the results were compared against observations. The model simulated sea surface temperature (SST) and salinity bias were less than 1.75 ^oC and 1 psu, respectively; this bias was minimal in the MWP region. Moreover, the model simulated results effectively represented the presence of the MWP across the three years. The mixed layer heat budget analysis indicates that the net heat flux raised the mixed layer temperature tendency of the MWP by a maximum of 0.1 °C/day during its development phase. The vertical processes, thereafter, exerted a cooling impact of −0.08 ^oC/day in the temperature tendency, causing it to dissipate. Further, four sensitivity numerical experiments were performed to investigate the comparative consequences of the ocean and atmosphere on the advancement of the MWP. The sensitivity experiments indicated that pre-April ocean conditions in years with a strong MWP result in a 136 % increase in MWP intensity in years when  MWP SST was close to climatology, which shows the primary role of oceanic preconditioning in determining MWP strength during strong MWP years rather than the atmospheric forcing. However, once the oceanic preconditions are met, the atmospheric conditions of weak MWP years lead to an 82 % reduction in MWP intensity relative to normal years, highlighting the detrimental impact of atmospheric forcing under such circumstances. Additionally, atmospheric conditions, particularly wind, are critical in influencing the spatial evolution and dissipation of MWP in the SEAS by modulating vertical processes. A wind shadow zone, characterized by less turbulent kinetic energy that does not exist during weak MWP years, facilitates the spatial expansion of MWP in SEAS during moderate to strong MWP years.