<title>Near-surface scintillation in a coastal ocean region</title>

Abstract

Infrared scintillation measurements were obtained along a 7 km path over San Diego Bay concurrently with meteorological measurements obtained from a buoy at the midpoint of the path. Bulk estimates of the refractive index structure parameter Cn2, were computed from the buoy data and compared with scintillation-derived Cn2 values. The bulk Cn2 estimates agreed well with the scintillation measurements in unstable conditions. In stable conditions the bulk Cn2 estimates were higher than the scintillation data, by up to an order of magnitude on average. This disagreement may be due to the effects of ocean waves in decreasing the vertical temperature and humidity gradients in stable conditions from the assumed Monin-Obukhov similarity theory forms, resulting in bulk Cn2 values that are too high. The bulk Cn2 estimates decrease rapidly when the absolute air-sea temperature difference approaches small positive values. These predicted decreases in Cn2 were not observed in the path-averaged scintillation measurements or in single-point turbulence measurements, demonstrating that bulk models which estimate structure parameters based on mean air-sea differences are not valid when the mean air-sea difference approaches zero. It is believed that obtaining a better understanding of surface wave modification of near- surface atmospheric gradients represents the most promising means toward improving the bulk model.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.