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2012 GeoSci EXPO Presentation Stratosphere- tropopshere Coupling and Rossby Wave Breaking

2012 GeoSci EXPO Presentation Stratosphere- tropopshere Coupling and Rossby Wave Breaking. By Clare Huang (Supervisor: Noboru Nakamura). Stratosphere- tropopshere coupling. Little moisture, almost no weather Above the troposphere Less dense Larger amplitude of fluctuation / wave).

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2012 GeoSci EXPO Presentation Stratosphere- tropopshere Coupling and Rossby Wave Breaking

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  1. 2012 GeoSci EXPO PresentationStratosphere-tropopshere CouplingandRossby Wave Breaking By Clare Huang (Supervisor: Noboru Nakamura)

  2. Stratosphere-tropopshere coupling • Little moisture, almost no weather • Above the troposphere • Less dense • Larger amplitude of fluctuation / wave) Stratosphere ?? Atmospheric wave propagate upward • Rich in weather • Closer to the land / mountains • Denser • Smaller amplitude of fluctuation / wave) Troposphere

  3. Stratosphere-tropopshere coupling Stratosphere Troposphere What drives this? Vertically propagating Rossby Waves

  4. However, waves break unpredictably… Large amplitude Irreversible mixing Turbulent kinetic energy

  5. Wave breaking in the Northern Hemisphere What determines the onset of wave breaking?

  6. Onset of wave breaking • Fyfe and Held (1990): • An attempt in a quasi-linear framework with WKB approximation and non-acceleration theorem

  7. Onset of wave breaking *Quasi-linear barotropicRossby wave in a shear flow* Linear = small amplitude wave WKB approximation = approximate dispersion relationship for the disturbance Non-acceleration theorem = partition of zonal mean wind speed and wave field (wave activity ) Singularity arises when *Critical Layer* emerges.

  8. Results by Fyfe and Held(1990) Non-acceleration theorem + WKB + Quasi-linear formalism… (Zonal Mean Wind) Wave breaks when is decelerated to Critical Layer Wave breaks Total Vorticity Q / Material Contour (Time)

  9. Results by Fyfe and Held(1990) However, for fully non-linear integration… Wave can break before encountering a critical layer. Wave breaks before critical layer is formed.

  10. Conclusion • Baldwin and Dunkerton (2001): Large stratospheric anomalies precede tropospheric mean-flow anomalies. • Long term tropospheric weather forecast can be possible if the onset of wave breaking in stratosphere is understood. • Fyfe and Held (1990): Wave can break before encountering a critical layer.

  11. Future Research Direction… • Extension of wave breaking theory beyond • The WKB approximation • small amplitude approximation  finite amplitude • New definition of critical layer / line

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