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The BD circulation and wave forcing Influence on the QBO period

The BD circulation and wave forcing Influence on the QBO period. Le Kuai. The wave-induced zonal force per unit mass. A: the vertical momentum flux at z0=16 km (z): the thermal damping rate N: the Brunt-Vaisala frequency K: the zonal wavenumber C: phase speed.

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The BD circulation and wave forcing Influence on the QBO period

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  1. The BD circulation and wave forcing Influence on the QBO period Le Kuai

  2. The wave-induced zonal force per unit mass A: the vertical momentum flux at z0=16 km (z): the thermal damping rate N: the Brunt-Vaisala frequency K: the zonal wavenumber C: phase speed

  3. QBO period variation caused by: • Planetary wave induced equatorial heating rate • QBO induced circulation • Descent rate of critical line (westerly regular and faster than easterly ) • Year-to-year variability in the amplitude of wave forcing • SAO above 30 km (Gray and Pyle, 1989)

  4. Case without PW: regular downward propagation of easterly and westerly phase regimes.Period:~20 month Case with PW:leads to a stalling of more than one year in the easterly wind downwelling Shear zone ~ 50 hPa

  5. 197

  6. 148:+20/-30193:+20/-20194:+25/-30195:+23/-30

  7. 196, 1.1 westerly forcing 197, 1.2 westerly forcing

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