Ocean feedback to tropical cyclones: climatology and processes - Archive ouverte HAL
Article Dans Une Revue Climate Dynamics Année : 2014

Ocean feedback to tropical cyclones: climatology and processes

Résumé

This study presents the first multidecadal and coupled regional simulation of cyclonic activity in the South Pacific. The long-term integration of state-of the art models provides reliable statistics, missing in usual event studies, of air-sea coupling processes controlling tropical cyclone (TC) intensity. The coupling effect is analyzed through comparison of the coupled model with a companion forced experiment. Cyclogenesis patterns in the coupled model are closer to observations with reduced cyclogenesis in the Coral Sea. This provides novel evidence of air-sea coupling impacting not only intensity but also spatial cyclogenesis distribution. Storm-induced cooling and consequent negative feedback is stronger for regions of shallow mixed layers and thin or absent barrier layers as in the Coral Sea. The statistical effect of oceanic mesoscale eddies on TC intensity (crossing over them 20 % of the time) is also evidenced. Anticyclonic eddies provide an insulating effect against storm-induced upwelling and mixing and appear to reduce sea surface temperature (SST) cooling. Cyclonic eddies on the contrary tend to promote strong cooling, particularly through storm-induced upwelling. Air-sea coupling is shown to have a significant role on the intensification process but the sensitivity of TCs to SST cooling is nonlinear and generally lower than predicted by thermodynamic theories: about 15 rather than over 30 hPa °C−1 and only for strong cooling. The reason is that the cooling effect is not instantaneous but accumulated over time within the TC inner-core. These results thus contradict the classical evaporation-wind feedback process as being essential to intensification and rather emphasize the role of macro-scale dynamics.
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Dates et versions

hal-01021621 , version 1 (09-07-2014)

Identifiants

Citer

Swen Jullien, Patrick Marchesiello, Christophe E. Menkès, Jérôme Lefèvre, Nicolas Jourdain, et al.. Ocean feedback to tropical cyclones: climatology and processes. Climate Dynamics, 2014, 43 (9-10), pp.2831-2854. ⟨10.1007/s00382-014-2096-6⟩. ⟨hal-01021621⟩
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