Fourth Study Conference on BALTEX Scala Cinema Gudhjem

Figure 2: Velocity profile for different stratification:
neutral case (bold line), summer case (dotted line) and
winter case (dashed line). (Material constants: density of sea
water ρ sea = 1025 kg / m 3 and of air ρ air = 1.203 kg / m 3 ,
viscosity of sea water νsea = 1.05 10 -6 m 2 / s and of air ν air =
1.41 10 -5 m 2 / s,)
Figure 3: Temperature profile (Further material constants:
heat conductivity of air κair = 2.12 10 -5 m 2 / s and of sea
water κsea = 1.45 10 -7 m 2 / s, heat capacity of air c p.air = 2 10 3
J / ( kg K ) and of sea water c p.sea = 4 10 3 J / ( kg K ) ).
Figure 4: Carbon dioxide concentration profile for a flux
of J CO2 = -1 10 -12 kg / ( m 2 s ) (Further material constants:
diffusion coefficient for CO2 in air D CO2,air = 1.39 10 -5 m 2 / s
and in sea water D CO2,sea = 1.58 10 -9 m 2 / s, Henry
constant for CO2 H CO2 = 1.23).
While the flux resistance for momentum is mainly in the
bulk of the air, it is for carbon dioxide in the skin of the sea.
This demonstrates the capability of the theory to deal with
any material, in particular to take care of effects of small
- 152 -
diffusion coefficients and high Henry constants. Another
aspect is the sensitivity of the profiles to stratification
effects. Note, that the total heat flux in summer is
downwards due to stable stratification, while it is directed
downwards in wintertime due to convection. Although the
effect is small for the chosen parameter set, there occur
more extreme situations for example strong heating over
the day or night-time convection.
4. Summary
The present theory has been applied to Baltic Sea
conditions in calm winter / summer weather. It describes
the transfer resistance for different material in either the
skin or bulk of air or sea.
The theory in the present form is limited to calm situations
according to the assumption of an aerodynamically
smooth interface. Problems occur when wind increases
and microscale wave breaking takes place. Further
increase of the wind requires the proper treatment of
bubbles and spray. Also, the differential heating by solar
radiation has been neglected so far. This is subject of
future work.
The implementation of the present theory into circulation
models would require as input air-side and sea-side
measurements of the relevant quantities and it would put
out the corresponding surface values and fluxes. We are
looking forward for an intercomparison with direct
measurements of turbulent fluxes of physical and chemical
quantities, which establishes also a challenge for sea-going
oceanographers.
References
Jähne, B. & H. Haußecker, Air-water gas exchange.
Annual Review of Fluid Mechanics, 30, 443 – 468,
1998.
Monin, A.S. & A.M. Yaglom, Statistical Fluid
Mechanics: Mechanics of Turbulence. Vol. 1. MIT
Press, Cambridge, 1971
Reichardt, H., Der Einfluss der wandnahen Strömung auf
den turbulenten Wärmeübergang. Mitteilungen des
Max-Planck-Instituts für Strömungs-Forschung Nr. 3
(in German), 1950.
Taylor, P.K. (Ed.), Intercomparison and validation of
ocean-atmosphere energy flux fields. Report of the
SCOR-WG "Air-Sea Fluxes" WCRP-112 (WMO/TD-
No. 1036, November, 2000)
http://www.soc.soton.ac.uk/JRD/MET/WGASF/Repor
t.pdf, 2000
Zülicke, Ch., Air-sea fluxes including the effect of the
molecular skin layer, Deep-Sea Research II,
submitted, 2004.