Surf produced aerosol

Abstract

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.