Hadley circulation changes under global warming conditions indicated by coupled climate models

International audienceWe use the mean meridional tropical circulation of the Atmospheric Ocean Coupled General Circulation Models(AOGCM) to diagnose and quantify the modifications of the mean meridional circulation of the atmosphere underglobal warming conditions. The AOGCMs generally show a weakening of the Hadley circulation for the winter cellin both hemispheres, accompanied by a poleward extension of the Hadley circulation area. The conditions explainingthese modifications are analysed using detailed outputs from IPSL-CM4. The AOGCM IPSL-CM4 shows changes,under CO2 doubling, that are in accordance with the other models, for austral winter. On the other hand, for borealwinter, the winter cell shows little change in intensity and in extension. The poleward shift of the Southern Hemispherewinter Hadley cell corresponds to changes in the transient eddies, whereas the increase of the dry static stability ismainly responsible for the mean weakening of the cell. For boreal winter, a strong shrinking of the ascending brancharea, and an increase of the latent heating, is found to cancel the weakening of the circulation due to dry static stabilityincrease