Sensitivity of tropical Pacific SST annual cycle to Tokioka parameter

Despite the semiannual cycle in the solar radiation on the equator, the annual cycle in SST in the eastern tropical Pacific is dominant mainly due to ocean-atmosphere interactions. Here, we investigate the sensitivity of the equatorial Pacific SST annual cycle to the cumulus convective scheme to describe the dynamical interactions among the climate elements within feedback mechanisms using a GAIA coupled GCM, which is developed based on the Geophysical Fluid Dynamics Laboratory (GFDL) coupled model version 2.1 (CM2.1). In which, we change the strength of the moist convective trigger by controlling a critical entrainment rate called 'Tokioka parameter'. Change in Tokioka parameter alters the mean state of the equatorial Pacific basin. The larger Tokioka parameter suppresses the deep convection, which results in decrease of the east-west temperature gradient across the equatorial Pacific. The smaller temperature gradient weakens the wind field and upwelling in the eastern Pacific. As a result deepened mixed layer causes ocean response to atmosphere to be less sensitive. Furthermore, we attempt to propose dynamical relationship between convection, SST, and ITCZ to explain how change in deep convection leads to change in the amplitude of SST annual cycle and the ITCZ location.