NOAA COARE Gas Transfer parameterization:Update Using Wave Parameters

C. W. Fairall*NOAA Earth Science Research Laboratory, Boulder, CO, USA

Ludovic Bariteau and Jeffrey Hare**CIRES, University of Colorado, Boulder, CO, USA

Detlev Helmig

INSTAAR, University of Colorado, Boulder, CO, USA

Wade McGillisLDEO

• Concept: Change from windspeed-driven parameterizations to scaling models based on physics of the processes

Background On Flux – Transfer Velocity Relationships

• The flux, Fx, of trace gases between

the atmosphere and ocean:

• Xw=concentration in the water, Xa=concentration in air

• r subscript reference height/depth zr

• s subscript at interface

• kx=transfer velocity for X

• More general form of k includes water-side and air-side transfer processes expressed as RESISTANCES, R

• Gases reactive in water

– ‘Chemical enhancement factor β

– If enhancement is large, transfer velocity usually called deposition velocity

)/('' arxwrxxx XXkxwF

aswsx XX /

x

ardxxa

arx XV

R

XF

1][ xaxxwx RRk

Do You Feel Lucky? k=cu2

Basic Budget Equation For Gas Concentration XIn One Fluid

z xx dzzQS )(

xxx Sz

XzKDF

)]([

z

XzKxw

)(''

z

SzXDxwQ

z

zXDxwXUtX xx

sourcex

]/''[]/''[/

Source term in flux form

Near the surface we can use an eddy diffusion representation of turbulent flux

Total Flux=Sum of transport and reaction/source effects

In dynamic equilibrium Fx is independent of z

If Sx=0, we can relate the flux to the change in X from the surface, s, to some reference height/depth in the fluid, z=zr

xxx

x

xxrrs RF

V

F

zKD

dxFzXXX

)(

)(

x

x

DzK

F

z

X

)(

COARE MODEL HISTORY• 1996 Bulk Meteorological fluxes (ku=u*Cd)

– Update 2003 (8000 eddy covariance obs)– Oceanic cool skin module – molecular sublayer

• 2000 CO2• 2004 DMS• 2006 Ozone

Air-Sea transfer coefficients as a function of wind speed: latent heat flux (upper panel) and momentum flux (lower panel). The red line is the COARE algorithm version 3.0; the circles are the average of direct flux measurements from 12 ETL cruises (1990-1999); the dashed line the original NCEP model.

NOAA COARE Gas Transfer Algorithm:COARE Turbulent-Molecular Physics and Woolf Bubble Physics

))]2/(ln(5[ 2/12/1* cadcaaaxa SCShRu

)]/ln([/ 2/1* uwwrcwwawwxa zShRu

111 ])[( axxbwxx RkRk

nncwxxb

ob SeW

B

Vk ])(1[ /12/11

Ahw

3.13

Bubbles enhance transfer on ocean side

Atmos Resistance

Ocean Resistance

A is adjustable constant, phi a buoyancy function

Woolf bubble xfer velocity

B is adjustable constant

Wb is whitecap fraction

U*a*a from COARE3.0 bulk flux algorithm: from COARE3.0 bulk flux algorithm:

Windspeed or wave-based uWindspeed or wave-based u** relationships relationships

4.3610*8.3 UWb

GASEX-I, GASEX-II, and DMS Field Programs:Difference in CO2 and DMS from Solubility-Bubble Effect

THIS IS THE DATA

Whitecap - Fetch Effects

Energy Of Wave Breaking

• Wave Model

– p computed from wave spectral model

• Energy flux from atmosphere

• Both u*w and Wb coupled to p

)()0( 0 wavetotalwavewavew UCE

wavewavew CEp

ijijija

ja

SUuuUP

E

21

Uz

UwuWwPzE aaw )()()( 2

5.3*2.3 aaup

Coupled atmosphere-wave model

Fan et al. 2007

Whitecap Parameterizations:Wind Speed, Wave parameters, Wave Breaking

4.3610*8.3 UWb

96.0

*710*4

Hu

W ab

0.3710*6 UWa

wa pW /

Monahan

Mellville

Woolf

100

101

102

10-4

10-3

10-2

10-1

100

101

Whitecap Functions: Hurricane Wave Model Results

Wh

iteca

p F

ract

ion

Wind Speed (m/s)

10*Wp

Mon

Woolf

10*Mellvile

URI and UM Wave Models

Spread of Energy at Fixed Wind Speed

Present Plans

• NOAA COARE GAS: CO2, DMS, and Ozone

• Produce new version for use with wave parameters

• Tune it to wind-speed version

• Observations? Ozone cruises, SOLAS, GASEX III