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The NOW regional coupled model: Application to the tropical Indian Ocean climate and tropical cyclone activity

The NOW regional coupled model: Application to the tropical Indian Ocean climate and tropical cyclone activity
The NOW regional coupled model: Application to the tropical Indian Ocean climate and tropical cyclone activity
This paper presents the NOW regional coupled ocean-atmosphere model built from the NEMO ocean and WRF atmospheric numerical models. This model is applied to the tropical Indian Ocean, with the oceanic and atmospheric components sharing a common ¼° horizontal grid. Long experiments are performed over the 1990–2009 period using the Betts-Miller-Janjic (BMJ) and Kain-Fritsch (KF) cumulus parameterizations. Both simulations produce a realistic distribution of seasonal rainfall and a realistic northward seasonal migration of monsoon rainfall over the Indian subcontinent. At subseasonal time scales, the model reasonably reproduces summer monsoon active and break phases, although with underestimated rainfall and surface wind signals. Its relatively high resolution results in realistic spatial and seasonal distributions of tropical cyclones, but it fails to reproduce the strongest observed cyclone categories. At interannual time scales, the model reproduces the observed variability associated with the Indian Ocean Dipole (IOD) and the delayed basin-wide warming/cooling induced by the El Niño Southern Oscillation (ENSO). The timing of IOD occurrence in the model generally matches that of the observed events, confirming the influence of ENSO on the IOD development (through the effect of lateral boundary conditions in our simulations). Although the KF and BMJ simulations share a lot in common, KF strongly overestimates rainfall at all time scales. KF also overestimates the number of simulated cyclones by a factor two, while simulating stronger events (up to 55 m s-1) compared to BMJ (up to 40 m s-1). These results could be related to an overly active cumulus parameterization in KF.
Indian Ocean climate, regional climate modeling, atmospheric convection, IOD, tropical cyclone
1942-2466
700-722
Samson, G.
784950ca-14c8-4dec-b5b7-5feed8f131b1
Masson, S.
facf31ca-bea1-4286-9fd2-61ff721f2165
Lengaigne, M.
64572929-e2cd-4234-83a5-0a6281c3ff97
Keerthi, M.G.
d9b9eb36-41ab-4d22-93ed-afb2bda21c92
Vialard, J.
fb000633-202c-4606-b203-0fb9bac9db0e
Pous, S.
e84f9d22-3ca8-44a9-8052-1332a4d1a9ae
Madec, G.
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Jourdain, N.C.
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Jullien, S.
5a582cd3-2737-4c1f-8e9e-89a7a3739fd8
Menkes, C.
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Marchesiello, P.
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Samson, G.
784950ca-14c8-4dec-b5b7-5feed8f131b1
Masson, S.
facf31ca-bea1-4286-9fd2-61ff721f2165
Lengaigne, M.
64572929-e2cd-4234-83a5-0a6281c3ff97
Keerthi, M.G.
d9b9eb36-41ab-4d22-93ed-afb2bda21c92
Vialard, J.
fb000633-202c-4606-b203-0fb9bac9db0e
Pous, S.
e84f9d22-3ca8-44a9-8052-1332a4d1a9ae
Madec, G.
7e2ec04b-896a-4861-b2d0-b74f39d748c2
Jourdain, N.C.
44c62af3-48d0-47a1-864e-9d4c53a1426e
Jullien, S.
5a582cd3-2737-4c1f-8e9e-89a7a3739fd8
Menkes, C.
7a30ebbe-4117-4039-a912-c94e6a40cb3e
Marchesiello, P.
6c809642-5d60-4d1b-912a-2234827a50c5

Samson, G., Masson, S., Lengaigne, M., Keerthi, M.G., Vialard, J., Pous, S., Madec, G., Jourdain, N.C., Jullien, S., Menkes, C. and Marchesiello, P. (2014) The NOW regional coupled model: Application to the tropical Indian Ocean climate and tropical cyclone activity. Journal of Advances in Modeling Earth Systems, 6 (3), 700-722. (doi:10.1002/2014MS000324).

Record type: Article

Abstract

This paper presents the NOW regional coupled ocean-atmosphere model built from the NEMO ocean and WRF atmospheric numerical models. This model is applied to the tropical Indian Ocean, with the oceanic and atmospheric components sharing a common ¼° horizontal grid. Long experiments are performed over the 1990–2009 period using the Betts-Miller-Janjic (BMJ) and Kain-Fritsch (KF) cumulus parameterizations. Both simulations produce a realistic distribution of seasonal rainfall and a realistic northward seasonal migration of monsoon rainfall over the Indian subcontinent. At subseasonal time scales, the model reasonably reproduces summer monsoon active and break phases, although with underestimated rainfall and surface wind signals. Its relatively high resolution results in realistic spatial and seasonal distributions of tropical cyclones, but it fails to reproduce the strongest observed cyclone categories. At interannual time scales, the model reproduces the observed variability associated with the Indian Ocean Dipole (IOD) and the delayed basin-wide warming/cooling induced by the El Niño Southern Oscillation (ENSO). The timing of IOD occurrence in the model generally matches that of the observed events, confirming the influence of ENSO on the IOD development (through the effect of lateral boundary conditions in our simulations). Although the KF and BMJ simulations share a lot in common, KF strongly overestimates rainfall at all time scales. KF also overestimates the number of simulated cyclones by a factor two, while simulating stronger events (up to 55 m s-1) compared to BMJ (up to 40 m s-1). These results could be related to an overly active cumulus parameterization in KF.

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More information

Published date: September 2014
Keywords: Indian Ocean climate, regional climate modeling, atmospheric convection, IOD, tropical cyclone
Organisations: Marine Systems Modelling

Identifiers

Local EPrints ID: 370751
URI: http://eprints.soton.ac.uk/id/eprint/370751
ISSN: 1942-2466
PURE UUID: fd5d8506-78d2-499a-8622-f3031154b20e

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Date deposited: 05 Nov 2014 16:36
Last modified: 14 Mar 2024 18:21

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Contributors

Author: G. Samson
Author: S. Masson
Author: M. Lengaigne
Author: M.G. Keerthi
Author: J. Vialard
Author: S. Pous
Author: G. Madec
Author: N.C. Jourdain
Author: S. Jullien
Author: C. Menkes
Author: P. Marchesiello

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