Atmospheric Fluctuations Which Lead to Trackable Radar Signals in the Marine Boundary Layer.

Abstract : A description and rough cataloguing of the dominant types of fluid dynamic features which may be expected to yield trackable radar targets in the atmospheric boundary layer is provided. Conditions favorable for target motion relative to the ambient wind velocity are discussed. One particularly interesting type of wave generated target is that involving Kelvin-Helmholtz wave breaking which occurs when a wave of sufficient amplitude passes through a slightly stable fluid shear layer. This type of wave breaking is examined numerically using A.R.A.P.'s second-order closure turbulence model. This normalized computation allows the evolution of the radar pattern for this particular type of event to be interpreted in terms of the temperature, humidity, and velocity across a particular shear zone, and the wave speed of the triggering internal wave.