HR: 1340h
AN: GC43A-0944    [Abstracts]
TI: The Hadley circulation changes of the Atmosphere Ocean GCM under global warming
AU: * Gastineau, G
EM: gglmd@lmd.jussieu.fr
AF: Laboratoire de Météorologie Dynamique, 4 place Jussieu Tour 45-55, 3ét, BP99, PARIS, 75252, France
AU: Le Treut, H
EM: letreut@lmd.ens.fr
AF: Laboratoire de Météorologie Dynamique, 4 place Jussieu Tour 45-55, 3ét, BP99, PARIS, 75252, France
AU: Li, Z
EM: li@lmd.jussieu.fr
AF: Laboratoire de Météorologie Dynamique, 4 place Jussieu Tour 45-55, 3ét, BP99, PARIS, 75252, France
AB: The mean meridional tropical circulation of the Atmospheric Ocean coupled General Circulation Model (AOGCM) used in the Fourth IPCC assement (AR4) report is diagnosed, focusing on the CMIP3 simulation. In the conditions of a doubling in the carbon dioxide concentration, the AOGCMs show a gentle but significant weakening of the Hadley circulation for the winter cell in both hemispheres, accompanied by a poleward extension of the Hadley circulation area. The particular AOGCM IPSL-CM4 show similar changes for the austral winter but different for boreal winter. The northern hemisphere Hadley cell of the IPSL-CM4 AOGCM is stronger and show little changes in its extension, under global warming. The conditions explaining the modification of the Hadley circulation are analyzed using detailed outputs from the IPSL-CM4 AOGCM. At the first order, the changes of the Hadley circulation can be seen as a balance between the modification of the dry static stability, the latent and the radiative heating, and the eddy polaward transport, as a response of the SST changes. The changes of the southern hemisphere cell of the AOGCM IPSL-CM4 are due to the stronger increase of the dry static stability than the radiative cooling changes. For the northern hemisphere changes, an increase in the zonal component of the SST explain stronger convection and latent heating, which overcome the effects of the dry static increase.
DE: 0325 Evolution of the atmosphere (1610, 8125)
DE: 1610 Atmosphere (0315, 0325)
DE: 3319 General circulation (1223)
DE: 3337 Global climate models (1626, 4928)
DE: 3374 Tropical meteorology
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting