Modeling the formation of rain layers in the East Indian Ocean

Abstract:

Surface freshening through precipitation can act to stably stratify the upper ocean, forming a rain layer. Rain layers inhibit subsurface ocean mixing, consequently altering sea surface temperature (SST), sea surface salinity (SSS), and surface fluxes. For this study, we focus on the evolution of rain layer frequency, intensity and duration in the East Indian Ocean throughout the Madden-Julian Oscillation (MJO) lifecycle.

The General Ocean Turbulence Model (GOTM) is used to simulate rain layers in the East Indian Ocean. GOTM is initialized and calibrated using observations of the upper ocean collected during the Dynamics of the Madden-Julian Oscillation (DYNAMO) field campaign. Our results indicate that the impact of rain layers on upper ocean temperature and salinity profiles can be effectively captured by a 1-D ocean model. We will estimate the climatology of tropical rain layers and their regulation by the MJO by forcing GOTM with observations from surface moorings. Future steps focus on investigation of ocean feedback to atmospheric convection through implementation of a coupled ocean-atmosphere model; specifically, interaction between rain layers and atmospheric convection during the suppressed-to-active transition of the MJO.