The Land-Sea Warming Contrast as the Driver of Tropical Sea Level Pressure Changes.

Bayr, Tobias and Dommenget, Dietmar (2012) The Land-Sea Warming Contrast as the Driver of Tropical Sea Level Pressure Changes. [Poster] In: EGU General Assembly 2012. , 22.-27.04.2012, Vienna, Austria .

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Abstract

In this presentation we address the causes of the large-scale tropical sea level pressure (SLP) changes during climate change. The analysis we present is based on climate change model simulations, observed trends and the seasonal cycle. In all three cases the regional changes of tropospheric temperature (Ttropos) and SLP are strongly related to each other. This relationship basically follows the Bjerknes Circulation Theorem, with relative low regional SLP where we have relative high Ttropos and vice versa. A simple physical model suggests a tropical SLP response to horizontally inhomogeneous warming in the tropical Ttropos, with a regression coefficient of about -1.7 hPa/K. This relationship explains a large fraction of observed and predicted changes in the tropical SLP.
It is shown that in climate change model simulations the tropical land-sea warm-ing contrast, is the most significant structure in the regional Ttropos changes relative to the tropical mean changes. Since the land-sea warming contrast exist in the absent of any atmospheric circulation changes it can be argued that the large-scale response of tropical SLP changes is to first order a response to the tropical land-sea warming con-trast, with decreasing SLP over the sector of strongest warming (South America to Afri-ca) and increasing SLP elsewhere, which is roughly the Indo-Pacific warm pool region. A model intercomparison reveals that climate models with a strong land-sea contrast in surface temperature tend to have also a strong land-sea contrast in Ttropos and SLP. In an idealized land-sea contrast experiment a similar response of the SLP and Ttropos as in the climate change experiments can be found. As SLP changes and changes in atmospheric circulation go hand in hand, these results suggest an increase in the potential for deep convection conditions over the Atlantic Sector and a decrease over the Indo-Pacific warm pool region in the future.

Document Type: Conference or Workshop Item (Poster)
Keywords: Global warming, sea level pressure, tropical circulation
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-ME Maritime Meteorology
Date Deposited: 04 Nov 2013 13:45
Last Modified: 04 Nov 2013 13:45
URI: http://oceanrep.geomar.de/id/eprint/22335

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