Two systems for remote measurements of the air-sea fluxes of momentum, sensible heat and moisture during moderate to strong winds are described. One employs the dissipation method and the other the Reynolds flux or eddy correlation method. A modified Gill propeller-vane anemometer is the velocity sensor and a method of resolving the vertical velocity component, that accounts for the propeller's non-cosine behavior and avoids its non-linear operating region, is derived. The dynamic responses of the sensors are found from measurements in the actual turbulent conditions of the flux measurements.
The results of an experiment on the Bedford tower, a stable platform moored in 59m of water 10 km offshore, are presented. Spectra, cospectra, turbulence statistics and transfer coefficients are calculated from the Reynolds flux velocity and temperature data and found to be comparable to previously reported values. Simultaneous dissipation and Reynolds flux estimates of both the momentum and sensible heat fluxes in up to 20 m/s winds are shown to be in excellent agreement.
Also presented are the results of a second experiment where the systems were deployed on the weathership CCGS Quadra. A comparison of ship and tower drag coefficients from the dissipation system, demonstrates that the Bedford tower is essentially an open ocean site. The neutral drag coefficient, CDN, is found, on average, to be nearly constant at 1.14x10⁻³ for winds between 4 and 10 m/s and to increase almost linearly to about 2.18x10⁻³ at 26 m/s. No variation with either fetch
(greater than 10 km) or stability is observed. Dissipation estimates of the sensible heat flux from a wide range of conditions are presented. The neutral transfer coefficient, CTN, is found, on average, to vary from about 0.69x10⁻³ in stable stratification to 1.08x10⁻³ in the unstable case. An increase in CTN with increasing wind speed is suggested by only some of the data.
Time series of the fluxes are used to investigate additional sources of variation in the transfer coefficients. Their statistical variability about a running mean is seen to be about 10%. Evidence is presented that indicates that persistent departures from average values are related to sea surface conditions. CDN is observed to be significantly smaller, on average, during rising winds than during falling winds or after a change in wind direction. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/22196 |
| Date | January 1979 |
| Creators | Large, William George |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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