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Abrupt Climate Change on Titan

Abrupt Climate Change on Titan. Jeff Portwood B.S. Geophysics and Space Physics, UCLA CSI Intern. Outline. Brief survey of Titan Motivation Model Radiation Scheme Effects of Methane on Equilibrium Temperature Future adjustments of Model. Titan. Saturn’s largest moon Thick atmosphere

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Abrupt Climate Change on Titan

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  1. Abrupt Climate Change on Titan Jeff Portwood B.S. Geophysics and Space Physics, UCLA CSI Intern

  2. Outline • Brief survey of Titan • Motivation • Model • Radiation Scheme • Effects of Methane on Equilibrium Temperature • Future adjustments of Model

  3. Titan • Saturn’s largest moon • Thick atmosphere • 95.1% N2 • 4.9% CH4 • Hydrocarbon lakes near poles • Fluvial erosion features across the surface • Methane rain • “Wet” versus “dry” climate

  4. Motivation • Mitchell [2008] showed a possibility of multiple climate equilibria following abrupt climate change on Titan • I will further explore the effect that various levels of methane concentrationshave on the dynamics of the atmosphere using a simpler one-dimensional mode • Model Hierarchy: step up for realism, step down for understanding Mitchell [2008]

  5. Model • One-dimensional radiative-convective model • Useful for modeling planetary heat budget • Lacks horizontal heat transport and latitudinal redistribution of methane • Highlights the importance of the thermodynamics of methane evaporation and condensation

  6. Energy Balance 55% 100% 45% S 30% 15% T SW absorption 10% 113% 120% 2% 1%

  7. Dry Convection vs. Moist Convection Observed Dry Adiabat Moist Adiabat Pressure [mbar] ~90 ~94 Temperature [K]

  8. Abrupt Climate Transition Addition/Removal of surface methane produces a transition in surface equilibrium temperature

  9. Wet and Dry Temperature Profiles Ts (dry) ~ 93 K Ts (wet) ~ 91 K

  10. Future goals • Many parameters to be looked at in more detail • Diffusion • Boundary Layer • Huygens fluxes • McKay et al. 1991 in good agreement with Huygen’s landing site • Increasing the speed of the model • Each run takes ~7 hours • Build simplified two-dimensional model • Allow for horizontal heat transport

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