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Tobias Bayr and Dietmar Dommenget The Inhomogeneous Tropospheric Warming as the Driver of Tropical Sea Level Pressure and Walker Circulation Changes
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Tobias Bayr and Dietmar Dommenget. The Inhomogeneous Tropospheric Warming as the Driver of Tropical Sea Level Pressure and Walker Circulation Changes . Tobias Bayr and Dietmar Dommenget. Tropical Circulation Changes . Overview. Motivation. Tropical SLP changes. - PowerPoint PPT Presentation

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EGU 2012

Tobias Bayr and Dietmar DommengetThe Inhomogeneous Tropospheric Warming as the Driver of Tropical Sea Level Pressure and Walker Circulation Changes Tobias Bayr and Dietmar DommengetTropical Circulation Changes Overview

Motivation

Tropical SLP changes

Tropical Circulation changes3Overview

Motivation

Tropical SLP changes

Tropical Circulation changes4

SLP trend in CMIP3 multi model ensemble (A1B Scenario)MotivationVecchi and Soden (2007)What drives the Tropical SLP Changes in Global Warming?5Weakening of the tropical circulations?Held and Soden (2006), Vecchi and Soden (2007):specific humidity +7 % per K warming [ClausiusClapeyron]precipitation increases only by 2 % per K warming vertical transport -5 % per K warming weakening of the tropical circulationsComparable with a widening of a water pipe in a circulationMotivation

TodayFuture

SLP trend in Vecchi and Soden (2007)What drives the Tropical SLP Changes in Global Warming?

SLP trend in Bayr and Dommenget (2013)MotivationHomogeneous and inhomogeneous surface warmingTotal surface warmingHomogeneous warmingInhomogeneous warming

Overview

Motivation

Tropical SLP changes

Tropical Circulation changes9

Relative Trends of Tropospheric TemperatureBayr and Dommenget (2013)surface1000 850 hPa

850 500 hPa

500 300 hPa

300 100 hPa

Relative warming overOceans LandLand-Sea Warming Contrast

Inhomogeneous surface warming

Bayr and Dommenget (2013)Bayr and Dommenget (2013)Tropospheric Temperature and SLP Trends

pattern correlation = -0.90Ttropos relative warming

SLP changeMechanism: Bjerknes circulationBayr and Dommenget (2013) T1 = T2p1 = p2warmingcoolingp1 = p2 T1 > T2p1 < p2 T1 > T2mass flowIn fnf Schritten aufbauen13Tropospheric Temperature and SLP Trends

Bayr and Dommenget (2013)Overview

Motivation

Tropical SLP changes

Tropical Circulation Changes15

Zonal Stream function in CMIP5 multi model ensembleMean state in 20C16Zonal Stream function in CMIP5 multi model ensemble

Difference 21C-20C (contours: mean state)patterncorrelation = -0.48

Weakening of the zonal circulation cells?ECHAM5 AGM Experiments:Homogeneous vs Inhomogeneous warmingTotal surface warmingHomogeneous warmingInhomogeneous warming

InhomogeneousHomogeneousDiff in Total warming run

Homogenous + Inhomogeneous

ECHAM5 AGM Experiments:Homogeneous vs Inhomogeneous warmingConclusionsTropical SLP change = inhomogeneous Ttropos change (direct Bjerknes Circulation)

Land-Sea Contrast dominates inhomogeneous Ttropos change

Homogeneous and In-homogeneous warming have contrary effects on the Zonal Circulation Cells Thank you for your attention!Bayr and Dommenget:The Tropospheric Land-Sea Warming Contrast as the Driver of Tropical Sea Level Pressure Changes.Journal of Climate, 2013, 26, (4), pp. 1387-1402.