1030 Impact of the Ocean–Atmosphere Background State in the Tropical Cyclones Cold Wake Magnitude Variability

Wednesday, 15 January 2020
Hall B (Boston Convention and Exhibition Center)
Mauricio Zapata, Sistema de Alerta Temprana del Valle de Aburrá (SIATA), Medellín, Colombia; Universidad Nacional de Colombia, Medellín, Medellín, Colombia; and C. D. Hoyos and Y. Cardona

The reduction of sea surface temperature (SST) as a response of a Tropical Cyclone (TC) passage is often referred to as a TC cold wake. Several authors have studied the ocean-atmosphere response to a tropical cyclone passage since 1950. This SST anomaly is typically assessed as a function of TC intensity, analyzing the life cycle of a single TC, without considering the background state of the ocean-atmosphere system, the dynamical and geographical differences among the ocean basins and the kinetic energy involved in the cooling process. The goal of this study is to find climatological evidence of the cold wake magnitude as a function of the variables modulating the ocean-atmosphere interaction. In particular, we assess the evolution of the cold wake inside of the outermost closed isobar radius (ROCI) as a function of SST, TC intensity and lifecycle, thermocline depth, surface momentum transfer (integrated surface TC kinetic energy), Ekman pumping potential, and surface fluxes, for all TCs on record, using data from moored buoys, satellite retrievals, atmospheric (ERA5) and ocean (ORAS5) reanalysis products, and TC tracks from The International Best Track Archive (IBTrACS). We find a strong link between the cold wake magnitude and the coupled ocean-atmosphere background state, with a strong influence of the depth of the thermocline, modulating the Ekman pumping efficiency to reduce the SSTs. We further explore the role of the thermocline depth and the basic state of the coupled system in a regional numerical coupled ocean-atmosphere modeling experiment using WRF-ROMS-OASIS to evaluate the cold wake magnitude under idealized scenarios varying the depth of the thermocline and other relevant variables, and finally, we evaluate the effect of the TC cold wake on the TC magnitude and evolution.
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