Obstacle-induced perturbations on turbulent quantities measured in airflows over the sea

Ferrarese, S. and Bacci, P. and Bertoni, D. and Cassardo, C. and Forza, R. and Giraud, C. and Longhetto, A. and Morselli, M. G. and Pangia, M. and Purini, R. (1998) Obstacle-induced perturbations on turbulent quantities measured in airflows over the sea. Il nuovo cimento C, 21 C (4). pp. 357-392. ISSN 1826-9885

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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.

Item Type: Article
Uncontrolled Keywords: Convection, turbulence, and diffusion; sea-air energy exchange processes; Boundary layer structure and processes
Subjects: 500 Scienze naturali e Matematica > 550 Scienze della Terra > 551 Geologia, Idrologia, Meteorologia
Depositing User: Marina Spanti
Date Deposited: 28 May 2018 10:11
Last Modified: 28 May 2018 10:11
URI: http://eprints.bice.rm.cnr.it/id/eprint/12790

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