Measurements of eddy-fluxes over the sea from an off-shore oil rig
✍ Scribed by B. B. Hicks; A. J. Dyer
- Publisher
- John Wiley and Sons
- Year
- 1970
- Tongue
- English
- Weight
- 366 KB
- Volume
- 96
- Category
- Article
- ISSN
- 0035-9009
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✦ Synopsis
Abstract
Two eddy correlation instruments (Fluxatrons) and associated anemometers were installed on the Marlin natural gas platform, which stands in Bass Strait about 60 m deep and 40 km off the Victorian coast (lat. 38° 14′S, long. 148° 13′E). The sensing heads were mounted 5 m above the sea surface on a boom extending from the rig. At this height the rig did not appear to affect the wind flow.
The measured Reynolds stresses give an average value of 0.0011 ± 0.0001 for the drag coefficient referred to the 10 m wind speed (31 half hour observations over the wind speed range 2–10 m s^−1^). Below about 5 m s^−1^ the drag coefficient is not significantly different from that of an aerodynamically smooth surface. Above this speed, it increases with velocity, reaching about 0.0015 at 10 m s^−1.^
The measured sensible heat‐fluxes are small, showing that evaporation dominates sensible heat in the sea‐air energy budget. There is no reason to dispute the bulk aerodynamic approach, in which the heat‐flux is written as H = p c~p~ d u~a~ Δθ~a.~ The data do not allow an accurate estimate of the transfer coefficient, d, which is found here to be 0.0014 (±25 per cent), insignificantly different from the value found for the case of evaporation from inland lakes.
Heat budget considerations imply that about 60 per cent of the day‐time net radiation was used to heat the water body.
The success of the experiment suggests the feasibility of using oil rigs as platforms for further air‐sea interaction studies. The stability of such platforms, even at very high wind speeds, is particularly attractive.