Mixed layer cooling in mesoscale oceanic eddies during Hurricanes Katrina and Rita

Benjamin Jaimes, Lynn K Shay

Research output: Contribution to journalArticle

84 Citations (Scopus)

Abstract

During favorable atmospheric conditions, Hurricanes Katrina and Rita deepened to category 5 over the Loop Current's (LC) bulge associated with an amplifying warm core eddy. Both hurricanes subsequently weakened to category 3 after passing over a cold core eddy (CCE) prior to making landfall. Reduced (increased) oceanic mixed layer (OML) cooling of;1°C (4.5°C) was observed over the LC (CCE) where the storms rapidly deepened (weakened). Data acquired during and subsequent to the passage of both hurricanes indicate that the modulated velocity response in these geostrophic features was responsible for the contrasts in the upper-ocean cooling levels. For similar wind forcing, the OML velocity response was about 2 times larger inside the CCE that interacted with Katrina than in the LC region affected by Rita, depending on the prestorm OML thickness. Hurricane-induced upwelling and vertical mixing were increased (reduced) in the CCE (LC). Less wind-driven kinetic energy was available to increase vertical shears for entrainment cooling in the LC, as the OML current response was weaker and energy was largely radiated into the thermocline. Estimates of downward vertical radiation of near-inertial wave energies were significantly stronger in the LC (12.1 × 10-2 W m-2) than in the CCE (1.8 × 10-2 W m-2). Katrina and Rita winds provided O(1010)Wto the global internal wave power. The vertical mixing induced by both storms was confined to the surface water mass. From a broader perspective, models must capture oceanic features to reproduce the differentiated hurricane-induced OML cooling to improve hurricane intensity forecasting.

Original languageEnglish (US)
Pages (from-to)4188-4207
Number of pages20
JournalMonthly Weather Review
Volume137
Issue number12
DOIs
StatePublished - Dec 2009

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hurricane
mixed layer
eddy
cooling
vertical mixing
wave power
wind forcing
upper ocean
internal wave
wave energy
thermocline
entrainment
water mass
kinetic energy
upwelling
cold
surface water
energy

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

Mixed layer cooling in mesoscale oceanic eddies during Hurricanes Katrina and Rita. / Jaimes, Benjamin; Shay, Lynn K.

In: Monthly Weather Review, Vol. 137, No. 12, 12.2009, p. 4188-4207.

Research output: Contribution to journalArticle

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