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Geophysical Fluid Dynamics Laboratory Review

Explore the impact of warming on the tropical climate system through numerical modeling, theory, and observations. Investigate changes in tropical circulation, precipitation patterns, and the expansion of dry zones. Understand the implications for El Niño and Atlantic hurricane activity.

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Geophysical Fluid Dynamics Laboratory Review

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  1. Geophysical Fluid Dynamics LaboratoryReview June 30 - July 2, 2009

  2. Response of the Tropical Climate System to Warming Presented by Gabriel Vecchi

  3. Response of the Tropical Climate System to Warming GOALS: Use numerical modeling, theory and observations to understand the controls on tropical climate change. Build predictive understanding of the global and regional impacts of tropical climate change. EXAMPLES Weakening of tropical circulation from increased CO2. Controls to subtropical precipitation changes.

  4. IPCC-AR4 model projections: warm, moist and more rainfall, but reduced atmospheric circulation SRESA1B Temp.Increases MoistureIncreases Circulationdecreases Precip.Increases Held and Soden (2006, J. Clim.) Vecchi and Soden (2007, J. Clim.)

  5. CM2.1 used to attribute historical weakening of Walker Circulation to anthropogenic forcing 1861-1992 Trends 2007 OAR Outstanding Paper Vecchi, Soden, Wittenberg, Held, Leetmaa and Harrison (2006, Nature)

  6. Models project changes in wind shear connected to a weakened Walker Circulation. Atlantic wind shear increases connected to reduced Atlantic hurricane frequency(e.g., Knutson et al 2008, Nature Geosci.; Garner et al 2009, J. Climate; Zhao et al. 2009, J. Climate). Adapted from Vecchi and Soden (2007, GRL), CCSP 3.3 (2008)

  7. Wet-get-wetter, Dry-get-drier Thermodynamic Control: Warming (increase qsat) -> increase atmospheric moisture. -> increase moisture flux divergence/convergence. Adapted from Held and Soden (2006, J. Clim.) Figure by N. Naik., LDEO/Columbia Adapted from Held and Soden (2006, J. Clim.) Adapted from Held and Soden (2006, J. Clim.)

  8. Wider Tropics: Wider Dry Zones Poleward shift of descending branch of Hadley Circulation is associated with a poleward shift of dry zones. Northern Hemisphere Southern Hemisphere Lu, Vecchi and Reichler (2007, GRL)

  9. U.S. Southwest Projected to Get Drier 21st Century Projected % Change in Runoff “Dry-get-drier” and expansion of dry zones contribute to drying. Change in SW US Precip. minus Evap. Multi-model Milly et al (2008, Science) GFDL-CM2.1 Seager et al (2007, Science)

  10. Response of the Tropical Climate System to Warming • Weakening of tropical circulation, largely Walker Circulation • Detection/attribution studies on Walker Circulation • Sets stage for changes in El Niño • Associated with Atlantic wind shear changes (hurricane-relevant) • Wet-get-wetter, dry-get-drier • Poleward expansion of Hadley Circulation • Dynamical and thermodynamic constraints on rainfall • Associated with subtropical drying (including SW-U.S.)

  11. Geophysical Fluid Dynamics LaboratoryReview June 30 - July 2, 2009

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