An experimental campaign, aiming to investigate the perturbation effects induced by fixed obstacles on turbulence measurements in airflows at the air-sea interface, was carried out at the marine platform of the Italian Navy, located in the harbour of La Spezia (North Ligurian Sea, Italy), near Lerici, on 28th, 29th, and 30th June 1994. This study was prompted by the ever-growing interest in more reliable estimates of energy, mass, and momentum exchanges between water surfaces and atmosphere, whose measurements are severely limited by the geometrical constraints of floating or fixed platforms where they are installed. Two types of meteorological instruments have been used: fast response (20 and 21 Hz) ultrasonic anemometers and fluxmeters to measure turbulent momentum, sensible, and latent heat fluxes and slow-response sensors (less than 4 Hz and sampled at a rate of 1022 Hz) to measure average wind and temperature vertical profiles in the perturbed boundary layer. Both fast- and slow-response instruments have been located a few meters apart from each other, along horizontal and vertical directions, so as to establish also an upper limit to the reliability of horizontal and vertical divergences and gradients of average and turbulent quantities in the obstacle wake. It has been observed that, in the airflow perturbed by the marine platform and its fixed structures, the fast-response instruments of the same type and made by the same manufacturers gave results that compared well with each other, even if they were located at different positions and heights (except for the vertical component of turbulent wind speed), while the comparison among different types of fast instruments gave more uncertain results. On the contrary, as far as mean values of the physical quantities were concerned, the measurements of slow-response
instruments in the perturbed airflow were always in good agreement with the averaged data of fast instruments, irrespective of their factory or construction features.
[1]
M. G. Morselli,et al.
A study of the assessment of air temperature, and sensible-and latent-heat fluxes from sonic-anemometer observations
,
1995
.
[2]
R. McMillen,et al.
An eddy correlation technique with extended applicability to non-simple terrain
,
1988
.
[3]
T. Blanc.
Variation of Bulk-Derived Surface Flux, Stability, and Roughness Results Due to the Use of Different Transfer Coefficient Schemes
,
1985
.
[4]
Pearn P. Niiler,et al.
Upper Ocean Heat Budget During the Hawaii-to-Tahiti Shuttle Experiment
,
1983
.
[5]
Mark A. Cane,et al.
On Equatorial Dynamics, Mixed Layer Physics and Sea Surface Temperature
,
1983
.
[6]
P. Lamb,et al.
On the Heat Budget of Hydrosphere and Atmosphere in the Indian Ocean
,
1980
.
[7]
S. P. S. Arya,et al.
Introduction to micrometeorology
,
1988
.