Effect of Wave Boundary Layer on Sea-to-Air Dimethylsulfide (DMS) - - PowerPoint PPT Presentation

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Effect of Wave Boundary Layer on Sea-to-Air Dimethylsulfide (DMS) - - PowerPoint PPT Presentation

Oct 29, 2023 280 likes •511 views

UNCLASSI FI ED Effect of Wave Boundary Layer on Sea-to-Air Dimethylsulfide (DMS) Transfer Velocity during Typhoon Passage Peter C Chu, and Kuofeng Cheng Naval Ocean-Atmospheric Prediction Laboratory Department of Oceanography Naval

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UNCLASSI FI ED UNCLASSI FI ED

Effect of Wave Boundary Layer on Sea-to-Air Dimethylsulfide (DMS) Transfer Velocity during Typhoon Passage

Peter C Chu, and Kuofeng Cheng

Naval Ocean-Atmospheric Prediction Laboratory Department of Oceanography Naval Postgraduate School Monterey, California, USA pcchu@nps.edu http://www.oc.nps.navy.mil/~chu

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References

  • Chu, P.C., and K.F. Cheng, 2006: Effect of wave

boundary layer on the sea-to-air dimethylsulfide transfer velocity during typhoon passage. Journal

  • f Marine Systems, in press.
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The dominant natural source of sulfur to the atmosphere is the

  • ceanic DMS

(Bates et al., 1992; Gondwe et al., 2003).

DMS changes the radiation budget in the atmosphere and in turn changes the climate.

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Flux Parameterization Issues (Fairall el al. 2005)

  • Representation in GCM
  • Most observations are point time averages
  • Concept of gustiness sufficient?
  • Mesoscale variable? Precip, convective mass flux, …
  • Strong winds
  • General question of turbulent fluxes, flow separation, wave momentum

input

  • Sea spray influence
  • Waves
  • Stress vector vs wind vector (2-D wave spectrum)
  • zo vs wave age & wave height
  • Breaking waves
  • Gas and particle fluxes
  • Distribution of stress and TKE in ocean mixed layer
  • Gas fluxes
  • Bubbles
  • Surfactants (physical vs chemical effects)
  • Extend models to chemical reactions
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What is the effect of the wave boundary layer (WBL) on the sea-to-air DMS transfer?

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Waves

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Drag Coefficient and Roughness Length Nondimensional Roughness Length zr = 10 m

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Effect of WBL

  • n Momentum Transfer
  • Without WBL: Charnock

(1955) parameter

  • With WBL: Chalikov (1995)

parameterization Cp is the peak phase speed.

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WBL Effects

  • Waves →

z0 → CD → ka

  • Waves →

z0 → (Re, Sc) → kw

  • WaveWatch-3 for the South China Sea as an

example

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NOAA WaveWatch-3 Third Generation Wave Model (Tolman 1999) σ θ θ λ λ θ φ φ φ S N N k k N N t N

g

= ∂ ∂ + ∂ ∂ + ∂ ∂ + ∂ ∂ + ∂ ∂

  • cos

cos 1

in nl ds bot

S S S S S = + + +

cos R U cg

φ

θ φ + =

  • ,

φ θ λ

φ

cos sin R U cg + =

  • ,

R cg

g

θ φ θ θ cos tan − =

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WaveWatch-3 was evaluated using T/P (a) crossover points and (b) tracks in the SCS (Chu et al., 2003, JTECH)

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South China Sea

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UNCLASSI FI ED UNCLASSI FI ED Typhoon 23W (Wukong) Sept 5-11, 2000

Maximum Sustained Wind: 38 m/s

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Effect of WBL on z0*

Nondimensional Peak Wave Frequency

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Effect of WBL on CD

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Relative Difference of CD

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Sea-to-Air DMS Flux (McGillis et al., 2000)

  • Air transfer velocity ka
  • Water transfer velocity kw
  • DMS concentrations at

airside (Ca)

  • DMS concentrations at

waterside (Cw)

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Waterside DMS Transfer Velocity (Jahne et al., 1987; McGillis et al., 2000)

  • Waterside transfer

velocity (n = 0.58)

  • Schmidt Number = 720

(DMS at 300 K)

  • DMS Diffusion coefficient

(Saltzman et al., 1993) Roughness Reynolds Number

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WBL Effects

  • Waves →

z0 → CD → ka

  • Waves →

z0 → (Re, Sc) → kw

  • WaveWatch-3 for the South China Sea as an

example

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Effect of WBL on kw

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Relative Difference of kw

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Conclusions

  • (1) WBL increases CD and in turn enhances the

momentum flux.

  • (2) WBL decreases kw and in turn weakens the sea-to-air

DMS transfer.

  • (3) Such opposite WBL effects are evident for minor

typhoon (Wukong, max wind ~ 38 m/s)

  • (4) Such opposite WBL effects on the climate should be

further investigated.