Influence of Mesoscale Ocean Wind Variability on Tropical Atmospheric Convection

Abstract:

The atmosphere and ocean are tightly coupled elements of the climate system, yet many of their interactions remain poorly understood. In particular, our knowledge of the relationship between precipitation and synoptic/mesoscale sea surface wind patterns suffers due to the lack of observations over the ocean. Satellite-based scatterometer wind retrievals, with their ability to observe surface winds near rainfall, coupled with atmospheric reanalysis enable the investigation of the relationships between flows and surface atmosphere exchanges of water and energy near precipitation. In this study, we examine the interactions between surface wind features and the oceanic state, and the kinematic and thermodynamic environment surrounding heavy rain producing oceanic tropical convective systems (excluding tropical cyclones). Three-hourly rainfall data from the TRMM product 3B42 are used to identify extreme precipitation events, and composites of surrounding meteorological fields are examined to understand the forcing and maintenance of these systems. Atmosphere-ocean surface heat and moisture fluxes are analyzed with corresponding meteorological fields provided by MERRA reanalyses, as well as bulk aerodynamic formulae using scatterometer data. In addition, QuikSCAT, ASCAT, and RapidSCAT are used to represent surface wind data surrounding the precipitation systems in question, and differences between MERRA and scatterometer near surface winds are investigated. The goal of this research is to understand the co-evolution of surface wind kinematic features and heavy precipitation, and their water and energy budgets in intense oceanic tropical rainfall.