IUGG 2003 Abstract

JSP09 Physical Aspects of Air-Sea Interaction (IAPSO, IAMAS)  Friday, July 11 PM Location: Site B, Room 20 Presiding Chairs:L. Shay, P. Black

TIME [ 1515 ] [ JSP09/11P/B20-005 ]

EFFECTS OF OCEANIC MIXED LAYER ENTRAINMENT CLOSURE ON THE AIR-SEA FLUXES DURING A TROPICAL CYCLONE PASSAGE

S. Daniel JACOB(GEST, NASA GSFC/ UMBC)

Chester J. KOBLINSKY(NASA GSFC, Greenbelt, MD 20771, USA) Lynn Keith SHAY ( RSMAS, University of Miami, Miami, FL 33149, USA ) George R. HALLIWELL ( RSMAS, University of Miami, Miami, FL 33149, USA )

Upper ocean heat content is an important factor in the rapid intensficationof tropical cyclones. During storm passage, a large fraction of upper oceancooling and reduction in heat content is due to entrainment of cooler lessturbulent water from below the oceanic mixed layer. Analysis ofhigh-resolution measurements acquired during the passage of hurricaneGilbert (1988) in the western Gulf of Mexico revealed that the heat and massbudgets strongly depended upon the entrainment scheme used. In this paper,the time evolution of mixed layer quantities for different entrainmentclosure schemes during Gilbert is investigated using a high resolutionnumerical model with realistic forcing fields and the results are comparedto observations. The main objective is to understand the upper ocean heatand mass budget variability due to the various entrainment closure schemes. The HYbrid Coordinate Ocean Model (HYCOM) initialized with observational data and realistic forcing is used in this study. This model is configured with fourentrainment mixing schemes. Results indicate qualitatively similar pattern of oceanic mixed layer temperature and depth changes, but the entrainment rates differ for these schemes confirming observational findings. Simulated fields are compared to observations to identify a scheme that performs well. This is crucial for the upper ocean and coupled response studies and the resulting air-sea fluxes during storm passage.