Convective Coupling and Interannual and Intraseasonal Coupled Variabilities in the Tropics
IR@C-MMACS: CSIR-Centre for Mathematical Modelling and Computer Simulation, Bangalore
View Archive Info| Field | Value | |
| Title |
Convective Coupling and Interannual and Intraseasonal Coupled
Variabilities in the Tropics
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| Creator |
Goswami, P
K, Rameshan |
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| Subject |
Climate Modelling
Meteorology and Climatology |
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| Description |
Recent analyses point at close structural similarities and intimate dynamical connections among the members
of a wide spectrum of variabilities in the global Tropics. This suggests that these oscillations with widely different
timescales may have a common dynamical origin, although diverse dynamical evolution. The present work
explores such a dynamical framework for the genesis of tropical variabilities. The highlight of the dynamical
framework is a parameterization of air–sea interaction, which the authors call convective coupling. In the proposed
parameterization the effect of sea surface temperature (SST) on the atmosphere is only through the modulation
of the column precipitation. The changed convective heating modifies the low-level flow, which in turn changes
the oceanic variables, thus closing the cycle. Thus the forcing due to convective coupling behaves like a (second
order) threshold process, with (SST modulated) convection acting like a switch.
Since many of the observed variabilities exhibit a primarily Kelvin wave structure, the implications of convective
coupling are investigated for the dynamics of Kelvin waves. To account for the different mean conditions
over which the variabilities of different scales occur, two scenarios, characterized by the strengths of certain
physical parameters, are considered to represent the interannual and intraseasonal (mean) conditions. Oscillations
of appropriate periods appear for each scenario. Two different representations of dynamics of SST are also
considered to explore coupled variabilities in ocean basins with different SST dynamics. It is also shown that
the convective coupling can support interannual variability in ocean basins with small zonal scale.
The dynamical scenario that emerges from this study is that the genesis of a wide spectrum of tropical
variabilities is caused by a selective excitation of a convectively coupled Kelvin wave embedded in the timemean
state of the corresponding timescale of oscillation. The postgenesis evolution and structure of each oscillation
is then influenced by local spatiotemporal characteristics. The results provide both insight for modeling
air–sea interaction in the Tropics and constraints for model diagnostics and evaluation.
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| Publisher |
American Meteorological Society
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| Date |
2000-08-01
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| Type |
Article
PeerReviewed |
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| Format |
application/pdf
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| Identifier |
http://cir.cmmacs.ernet.in/245/1/J%20Atm%20Sc_2000.pdf
Goswami, P and K, Rameshan (2000) Convective Coupling and Interannual and Intraseasonal Coupled Variabilities in the Tropics. J of Atmospheric Science, 57 ( 15). pp. 2445-2462. ISSN Online ISSN: 1520-0469 Print ISSN: 0022-4928 |
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| Relation |
http://journals.ametsoc.org/toc/atsc/current
http://cir.cmmacs.ernet.in/245/ |
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