The Inhomogeneous Tropospheric Warming as the driver of Tropical Sea Level Pressure and Walker Circulation Changes.

Bayr, Tobias and Dommenget, Dietmar (2013) The Inhomogeneous Tropospheric Warming as the driver of Tropical Sea Level Pressure and Walker Circulation Changes. [Talk] In: EGU General Assembly 2013. , 07.-12.04.2013, Vienna, Austria .

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Abstract

In this presentation we follow the idea to split up the global warming signal in a spatial homogeneous warming and in a spatial inhomogeneous warming. In Bayr and Dommenget (2012) the changes of the tropical sea level pressure (SLP) due to inhomo-geneous tropospheric warming in climate change, which is mostly the land-sea warming contrast, was investigated in a multi model ensemble. The amplitude of the inhomogeneous tropospheric warming is roughly 10 times smaller than the total warming of the tropical troposphere, but it can explain on average two third of the tropical SLP changes in different climate models. The explained SLP changes are of hydrostatical nature.
As the zonal temperature differences are the main driver of the zonal circulation cells like the Walker Circulation, the inhomogeneous tropospheric warming also chang-es the zonal circulations. This response is simulated with Atmospheric General Circula-tion Model and compared with the effect of the homogenous warming on the zonal cir-culations. The results show that the effect of the inhomogeneous warming can be nearly contrary to the effect of the homogeneous warming, so strengthening of the zonal tropical circulations in the inhomogeneous warming case and a weakening as proposed by Vecchi and Soden (2007) in the homogeneous warming case. As the ratio between the homogeneous and inhomogeneous warming is model dependent, this can partly explain the spread in the response of the zonal circulations of the individual climate models.

References
Bayr, T., and D. Dommenget, 2012: The Tropospheric Land-Sea Warming Contrast as the Driver of Tropical Sea Level Pressure Changes. Journal of Climate, doi:10.1175/JCLI-D-11-00731.1.

Vecchi, G. A., and B. J. Soden, 2007: Global Warming and the Weakening of the Tropical Circulation. Journal of Climate, 20, 4316–4340, doi:10.1175/JCLI4258.1.

Document Type: Conference or Workshop Item (Talk)
Keywords: Global warming, tropical circulation, sea level pressure, walker circulation
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-ME Maritime Meteorology
Open Access Journal?: Yes
Projects: DFG DO1038/5-1
Date Deposited: 04 Nov 2013 13:52
Last Modified: 04 Nov 2013 13:52
URI: http://oceanrep.geomar.de/id/eprint/22332

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