12th Conference on Interactions of the Sea and Atmosphere


Infrared Propagation in the Marine Atmospheric Surface Layer: Extinction and Refraction

Dimitri Tsintikidis, SPAWAR Systems Center, San Diego, CA; and S. M. Doss-Hammel, P. A. Frederickson, and K. L. Davidson

An infrared (IR) or optical signal propagating along a ‘line-of-sight’ horizontal or slant path within the marine surface layer can encounter substantial perturbations. These perturbations include signal extinction due to molecules or aerosol particles; refractive modulations that can amplify or reduce a signal; and scintillation, which is a higher frequency fluctuation in signal intensity. The sea roughness and its influence on aerosol production directly influence these refractive distortions.

In an effort to elucidate these issues an infrared transmission link was included in the Rough Evaporation Duct (RED) field test at Oahu, Hawaii, during August-September 2001. The optical and infrared portion of the RED experiment was conducted on a transmission path approximately 10 km long connecting an IR broadbeam transmitter onboard R/V FLIP (13 m above waterline) and an IR telescope receiver at Malaekahana (3 m above ground) on the northeast coast of Oahu. The broadbeam source accommodated the pitch, roll, yaw, and translation of FLIP. In addition, a meteorological station was mounted on top of a 30-ft mast outside the receiver station at Malaekahana.

Detailed meteorological measurements were made on FLIP, and on the Naval Postgraduate School flux meteorological buoy that was located at the mid-point of the propagation path. The buoy measured near-surface meteorological quantities, flux quantities, optical turbulence (CT2), and wave spectra. This data is used as input information for models that predict the received IR signal intensity. The focus of this paper is a comparison of these prediction models with the collected data.

Initial examination of the transmissometer data set reveals an unexpectedly weak transmission signal. The data analysis effort will include the influence of geometrical considerations (including the large 54 degree pointing excursions of the source on FLIP); extinction (absorption and scattering by aerosols and molecules); and refractive effects induced by the long near-surface propagation path.

extended abstract  Extended Abstract (396K)

Session 9, RED SEAS Experiments
Thursday, 13 February 2003, 8:30 AM-2:15 PM

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