Electro-Optical Propagation Assessment Research Articles

An Empirical Analysis of Bulk Cn2 Models over Water

AbstractThis article examines some of the difficulties associated with the determination of C2n over water in a coastal region using a bulk model. The analysis shows the need to supplement bulk models with elements that do not belong to traditional Monin–Obukhov surface-layer theory. A reexamination of the scintillation measurements collected during the Electro-Optical Propagation Assessment in a Coastal Environment (EOPACE) campaign leads the authors to include 1) the nonuniformity of sensible heat and humidity fluxes and 2) a deficit of the scintillation that seems to depend only on the characteristic virtual potential temperature. It is suggested that the anomalous scintillation deficit represents an alteration of a characteristic length related to the optical turbulence, likely caused by the interaction of the surface layer with the sea surface. The new parameters are estimated using Bayesian regression methods applied to the EOPACE data. Predictions obtained with this new model are then compared with scintillation measurements obtained during the recent Validation Measurement for Propagation in the Infrared and Radar (VAMPIRA) campaign. Better agreement is obtained with the new model than with a conventional bulk model. The implications of the modifications made to the calculation of C2n are discussed.

Studies of Aerosols in The Marine Boundary Layer in the Coastal Area During The EOPACE’99 Campaign

Results are presented based on measurements taken using an FLS-12 lidar system and laser particle counters only on the Atlantic coast of the U.S.A. during a campaign within the scope of the international EOPACE experiment. The objectives of the EOPACE (Electro-optical Propagation Assessment in Coastal Environments) effort, which was conducted in Duck, N.C. (U.S.A.) between 25 February and 11 March 1999, involved investigating, developing and evaluating ocean and coastal aerosol models and their effects on visibility; integrating and developing simple, realistic models for infrared propagation near the ocean surface and developing a consistent chemical/optical model for aerosol particles suitable for inclusion in navy meteorological models.

Electro-optical propagation assessment in coastal environments (EOPACE): summary and accomplishments

EOPACE (electro-optical propagation assessment in coastal environments) was a 5-yr multinational and interdisciplinary effort to improve the performance assessment for electro-optical (EO) systems operating in coastal environments. The initial results of the EOPACE program include: (1) the parameterization of the surf-zone generated aerosol-size distribution as a function of swell height; (2) the characterization of aerosol plume structures and the transport of surf generated aerosols; (3) the development of a quantitative surf aerosol source function; (4) the description of the contribution and impact of surf-zone generated aerosols on coastal infrared (IR) transmission; (5) the measurement and modeling of the near surface transmission effects (aerosol and molecular extinction, refraction, scintillation, and wave shadowing); (6) an analysis of the contribution of anthropogenic and land derived aerosols to the air mass characteristics in the coastal zone; (7) the application of direct and remote sensing techniques to develop the scaling parameters for aerosols in the prevailing air mass; (8) an analysis of near ocean surface bulk meteorological scaling which works well for unstable conditions but is less reliable for neutral and stable conditions; and (9) the incorporation of the improved sea radiance models into TAWS (target acquisition weather software) which improved the error analysis by a factor of 3. These initial accomplishments are described in this overview of the EOPACE effort. ©

EOPACE (Electrooptical Propagation Assessment in Coastal Environments) overview and initial accomplishments

EOPACE (Electrooptical Propagation Assessment in Coastal Environments) overview and initial accomplishments

Surf produced aerosol

A unique source of aerosol found in the coastal environment is the action of the breaking waves near the shore. This process is unique among wave generated aerosol processes because these aerosol are produced even when there is no wind at the site of the aerosol production. The major cause of this phenomenon is distant oceanic storms which produce long wavelength oceanic swell which then propagate for long distances and break on various types of shore lines. These shore lines can be gently sloping rocky or sand beaches, cliffs, or off shore reefs. Surf produced aerosol have usually been considered negligible because of the narrow width of the generating area when the effects of marine aerosol are discussed. They nevertheless exist and their effects can be of local importance. On days of heavy surf, a long narrow cloud stretching along the coastline can be seen when conditions are right, and the deposition of salt nuclei from surf produced aerosol are common near a heavy surf line during on shore winds.This paper utilizes the data recently obtained from a series of experiments from the Electro Optical Propagation Assessment in Coastal Environments, (EOPACE) effort, which has as one of its objectives the determination of the impact of surf produced aerosols in the propagation in infrared radiation. These experiments were carried out in both San Diego and in Monterey Bay, California.The experiments discussed here use several techniques to detect and measure the physical aspects of surf produced aerosol. The primary sources of information were obtained from: 1.Aerosol size distribution spectrometers, condensation nuclei counters, particle volume meters, visibility meters and meteorological instruments mounted at various positions and elevations along a pier, on a beach, and on a small boat.2.The photographic results of the scattering of surf aerosol by a visible laser beam spread vertically into a 45 degree sector of a circle but of very thin thickness.3.The infrared transmission along a low altitude 3.5 micron transmissometer path which includes a surf zone.The initial analysis of the EOPACE data indicates that indeed, the surf produced aerosol cloud is not uniform although it might appear so from looking at it from the outside. Videos and still photographs of the surf zone illuminated by the thin wafer of green laser light at night probe into the interior of this cloud and show a dynamic aerosol production process involving upward projecting streams of aerosol and the gravitational separating of various sizes of these aerosol.