Atmospheric turbulence above coastal waters: determination of stability classes and a simple model for offshore flow including advection and dissipation

Abstract

Atmospheric turbulence intensities and timescales have been measured for one year and modeled in a shoreline environment. Measurements were carried out at two sites, on both sides of the shoreline, about 10 km from the beach. The frequency distribution of Pasquill stability classes [determined using the COPS (calculation of Pasquill stability) method by analyzing wind fluctuations] was compared with similar observations at the land site. A shift to the more stable classes is observed. Moreover, a large shift to the stable classes was shown at a overwater site for the COPS method in comparison to the Hanna et al. and Hsu method, which is based upon z/L values, originating from sea-air temperature differences. It is concluded that atmospheric turbulence intensity above sea in the vicinity of the shoreline is strongly influenced by horizontal gradients and cannot be described successfully only in terms of local parameterization. -from Authors