WISHE and Its Effect on Waves in the Tropics

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WISHE and Its Effect on Waves in the Tropics

• A Review of Kerry Emanuels 1986 and 1993 Papers
  on WISHE

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WISHE (in hurricanes)

• Moist neutral troposphere
• Instability driven by wind induced fluxes
• Convective heating drives vorticity generation
• Subsidence in eyewall drops pressure
• Causes more surface convergence (i.e. enhances
  secondary circulation)
• Quantified by Carnot-like engine

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WISHE (pre-hurricanes)

• Emanuel (1986)
• This point leaves open the question of the
  question of whether the initial spin-up of the
  cyclone is due more to the organized release of
  ambient conditional instability or to anomalous
  sea surface fluxes.

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Convection Driven by WISHE

• Troposphere moist neutral
• Instability driven by air-sea fluxes of latent
  and sensible heat
• Boundary layer ?e balanced by the mean virtual
  temperature of the free atmosphere (keeps the
  atmosphere moist neutral)
• The convection excites different wave modes (n
  -1, 0, 1)

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Formulas

• See p.1764-5 for equations
• Eq.3 U-momentum
• Eq.4 V-momentum
• Eq.5 Incompressibility
• Eq.6 Thermodynamic
• Eq.7 W-momentum
• Eq.11 Introduces time lag between large scale
  forcing and convection Important!
• The rest solving the wave form equations

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Results (No time lag)
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Results (Kelvin Waves)

• t 0.025 ? 1 hour
• t 0.05 ? 2 hours

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Results (MRGs)
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Results (I-G waves)
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2D Kelvin Waves
Growth Rate
Phase Speed
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2D MRGs
Growth Rate
Phase Speed
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2D Kelvin Waves with Lag
Growth Rate
Phase Speed
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2D Kelvin Waves with Lag
Growth Rate
Phase Speed
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Summary

• MJO-like Planetary Kelvin Waves become
  convectively coupled, allowing them to sustain or
  intensify
• MRGs with wavelengths 2000-10,000 km with
  westward propagation and eastward phase velocity
• Poleward propagating synoptic scale waves (like
  easterly waves) that move with flow