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Tobias Bayr and Dietmar Dommenget

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.

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Tobias Bayr and Dietmar Dommenget

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  1. Tobias Bayrand Dietmar Dommenget The Inhomogeneous Tropospheric Warming as the Driver of Tropical Sea Level Pressure and Walker Circulation Changes

  2. Tobias Bayrand Dietmar Dommenget Tropical Circulation Changes

  3. Overview Motivation Tropical SLP changes Tropical Circulation changes

  4. Overview Motivation Tropical SLP changes Tropical Circulation changes

  5. Motivation What drives the Tropical SLP Changes in Global Warming? SLP trend in CMIP3 multi model ensemble (A1B Scenario) Vecchi and Soden (2007)

  6. Motivation Weakening of the tropical circulations? Today Future Comparable with a widening of a water pipe in a circulation Held and Soden (2006), Vecchi and Soden (2007): • specific humidity +7 % per K warming [Clausius–Clapeyron] • precipitation increases only by 2 % per K warming • vertical transport -5 % per K warming • weakening of the tropical circulations

  7. Motivation What drives the Tropical SLP Changes in Global Warming? SLP trend in Vecchi and Soden (2007) SLP trend in Bayr and Dommenget (2013)

  8. Homogeneous and inhomogeneous surface warming Total surface warming Homogeneous warming Inhomogeneous warming

  9. Overview Motivation Tropical SLP changes Tropical Circulation changes

  10. Relative Trends of Tropospheric Temperature 300 – 100 hPa 500 – 300 hPa 850 – 500 hPa 1000 – 850 hPa surface Bayr and Dommenget (2013)

  11. Land-Sea Warming Contrast Relative warming overOceans Land Inhomogeneous surface warming Bayr and Dommenget (2013)

  12. Tropospheric Temperature and SLP Trends Ttropos relative warming SLP change pattern correlation = -0.90 Bayr and Dommenget (2013)

  13. Mechanism: Bjerknes circulation mass flow T1 > T2 T1 = T2 T1 > T2 p1 = p2 p1 = p2 p1<p2 warming cooling Bayr and Dommenget (2013)

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

  15. Overview Tropical Circulation Changes Motivation Tropical SLP changes

  16. Zonal Stream function in CMIP5 multi model ensemble Mean state in 20C

  17. Zonal Stream function in CMIP5 multi model ensemble Difference 21C-20C (contours: mean state) patterncorrelation = -0.48

  18. Weakening of the zonal circulation cells?

  19. ECHAM5 AGM Experiments: Homogeneous vs Inhomogeneous warming Total surface warming Homogeneous warming Inhomogeneous warming

  20. ECHAM5 AGM Experiments: Homogeneous vs Inhomogeneous warming Diff in Total warming run Homogeneous Inhomogeneous Homogenous + Inhomogeneous

  21. Conclusions • Tropical SLP change = inhomogeneous Ttropos change • (direct Bjerknes Circulation) • Land-Sea Contrast dominates inhomogeneous Ttroposchange • Homogeneous and In-homogeneous warming have contrary effects on the Zonal Circulation Cells

  22. 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.

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