Observation-Based Estimates of Surface Cooling Inhibition by Heavy Rainfall under Tropical Cyclones
Observation-Based Estimates of Surface Cooling Inhibition by Heavy Rainfall under Tropical Cyclones
Tropical cyclones drive intense ocean vertical mixing that explains most of the surface cooling observed in their wake (the “cold wake”). In this paper, the authors investigate the influence of cyclonic rainfall on the cold wake at a global scale over the 2002–09 period. For each cyclone, the cold wake intensity and accumulated rainfall are obtained from satellite data and precyclone oceanic stratification from the Global Eddy-Permitting Ocean Reanalysis (GLORYS2). The impact of precipitation on the cold wake is estimated by assuming that cooling is entirely due to vertical mixing and that an extra amount of energy (corresponding to the energy used to mix the rain layer into the ocean) would be available for mixing the ocean column in the hypothetical case with no rain. The positive buoyancy flux of rainfall reduces the mixed layer depth after the cyclone passage, hence reducing cold water entrainment. The resulting reduction in cold wake amplitude is generally small (median of 0.07 K for a median 1 K cold wake) but not negligible (>19% for 10% of the cases). Despite similar cyclonic rainfall, the effect of rain on the cold wake is strongest in the Arabian Sea and weak in the Bay of Bengal. An analytical approach with a linearly stratified ocean allows attributing this difference to the presence of barrier layers in the Bay of Bengal. The authors also show that the cold wake is generally a “salty wake” because entrainment of subsurface saltier water overwhelms the dilution effect of rainfall. Finally, rainfall temperature has a negligible influence on the cold wake.
205-221
Jourdain, Nicolas C.
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Lengaigne, Matthieu
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Vialard, Jérome
797ded89-e453-48df-a587-e8d8b86c3088
Madec, Gurvan
ffb28deb-4bbd-4a4c-914f-492f813e4864
Menkes, Christophe E.
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Vincent, Emmanuel M.
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Jullien, Swen
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Barnier, Bernard
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January 2013
Jourdain, Nicolas C.
768842f8-f66e-4ab0-bfd7-74dd4dbec93d
Lengaigne, Matthieu
3f78eafe-bcd2-41c4-9e0e-3b8bb3c55aa4
Vialard, Jérome
797ded89-e453-48df-a587-e8d8b86c3088
Madec, Gurvan
ffb28deb-4bbd-4a4c-914f-492f813e4864
Menkes, Christophe E.
6c3b7f35-ac87-42e0-bbd2-862657d9c5df
Vincent, Emmanuel M.
06aa233c-bb5e-438e-8672-7a53b826e014
Jullien, Swen
7df84684-a8bc-4d92-929a-b4664238fa67
Barnier, Bernard
af67a33e-f7c3-4681-b37b-1fbebf74983a
Jourdain, Nicolas C., Lengaigne, Matthieu, Vialard, Jérome, Madec, Gurvan, Menkes, Christophe E., Vincent, Emmanuel M., Jullien, Swen and Barnier, Bernard
(2013)
Observation-Based Estimates of Surface Cooling Inhibition by Heavy Rainfall under Tropical Cyclones.
Journal of Physical Oceanography, 43 (1), .
(doi:10.1175/JPO-D-12-085.1).
Abstract
Tropical cyclones drive intense ocean vertical mixing that explains most of the surface cooling observed in their wake (the “cold wake”). In this paper, the authors investigate the influence of cyclonic rainfall on the cold wake at a global scale over the 2002–09 period. For each cyclone, the cold wake intensity and accumulated rainfall are obtained from satellite data and precyclone oceanic stratification from the Global Eddy-Permitting Ocean Reanalysis (GLORYS2). The impact of precipitation on the cold wake is estimated by assuming that cooling is entirely due to vertical mixing and that an extra amount of energy (corresponding to the energy used to mix the rain layer into the ocean) would be available for mixing the ocean column in the hypothetical case with no rain. The positive buoyancy flux of rainfall reduces the mixed layer depth after the cyclone passage, hence reducing cold water entrainment. The resulting reduction in cold wake amplitude is generally small (median of 0.07 K for a median 1 K cold wake) but not negligible (>19% for 10% of the cases). Despite similar cyclonic rainfall, the effect of rain on the cold wake is strongest in the Arabian Sea and weak in the Bay of Bengal. An analytical approach with a linearly stratified ocean allows attributing this difference to the presence of barrier layers in the Bay of Bengal. The authors also show that the cold wake is generally a “salty wake” because entrainment of subsurface saltier water overwhelms the dilution effect of rainfall. Finally, rainfall temperature has a negligible influence on the cold wake.
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Published date: January 2013
Organisations:
Marine Systems Modelling
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Local EPrints ID: 362972
URI: http://eprints.soton.ac.uk/id/eprint/362972
ISSN: 0022-3670
PURE UUID: 453e3956-3c26-464b-82b5-14aecff359bd
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Date deposited: 10 Mar 2014 14:59
Last modified: 14 Mar 2024 16:16
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Author:
Nicolas C. Jourdain
Author:
Matthieu Lengaigne
Author:
Jérome Vialard
Author:
Gurvan Madec
Author:
Christophe E. Menkes
Author:
Emmanuel M. Vincent
Author:
Swen Jullien
Author:
Bernard Barnier
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