noaa coare gas transfer parameterization: update using wave parameters c. w. fairall* noaa earth...
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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