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Proceedings Paper

Measurements of mixing layer height variability during the Ligurian air-sea interaction experiment (LASIE '07)
Author(s): J. Förster
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Paper Abstract

Air-sea interaction processes play a dominant role with respect to detection ranges of shipborne radar and infrared sensor systems. Especially in the littoral most often temperature and humidity gradients affect propagation paths and are the reason for abnormal phenomena such as ducting or mirage. Besides refractivity, spray and aerosols ejected from the sea surface can further degrade the quality of shipborne surveillance systems. Thus environmental effects might seriously hamper ship self defense. During the Ligurian Air-Sea Interaction Experiment (LASIE '07 - 16.06.-26.06.2007) the Federal Armed Forces Underwater Acoustics and Marine Geophysics Research Institute (FWG) carried out simultaneous in-situ measurements of meteorological and oceanographic parameters to study air-sea interaction processes with respect to littoral boundary layer variability. The characterization of the environment included both, in-situ measurements of atmospheric and sea surface parameters. Investigations were carried out on board RV PLANET, RV URANIA and at the ODAS-Italy1 buoy of the Italian National Council of Research (CNR). On board RV PLANET the sea surface and meteorological conditions were analyzed by two multi-sensor buoys, ship sensors and radiosondes. Emphasis was given to the vertical structure of the Marine Boundary Layer (MBL) and its variability. It was analyzed by a one lense lidar ceilometer CL31, a tethersonde system TT12 and radiosondes RS92 (Vaisala). The latter were launched every three hours. The TT12 consisted of three radiosondes, which could be adapted to separate altitudes of special interest. The experiment was characterized by changing meteorological conditions resulting in offshore and onshore blowing winds. In the first case the air temperature TAir was higher than the sea surface temperature TWater leading to a very stable surface layer. This situation was associated with a strong temperature inversion and a very clear atmosphere with a visibility of about 70 km. The second case (TAir<TWater) was dominated by convection processes and a pronounced aerosol production. Good correlation was found for the Mixing Layer Height (MLH) by the lidar ceilometer and the radio soundings.

Paper Details

Date Published: 30 September 2009
PDF: 12 pages
Proc. SPIE 7476, Optics in Atmospheric Propagation and Adaptive Systems XII, 747603 (30 September 2009); doi: 10.1117/12.830384
Show Author Affiliations
J. Förster, Bundeswehr Technical Ctr. for Ships and Naval Weapons (Germany)

Published in SPIE Proceedings Vol. 7476:
Optics in Atmospheric Propagation and Adaptive Systems XII
Anton Kohnle; Karin Stein; John D. Gonglewski, Editor(s)

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