In highly stratified atmospheric and oceanic environments, a large fraction of energy input by various sources can be manifest as internal waves (IWs). The propagating nature of IWs results in the distribution of the energy over a large fraction of the air/water column. Wakes of translating bodies are one source of input energy that has been of continued interest. To further the understanding of wakes in strongly stratified environments, and particularly the near-field regime where strong coupling to the internal wavefield is evident, an extensive series of experiments on the internal wavefield generated by a towed sphere was performed, wherein the internal wavefield was measured over a Froude number range 0.1 Fr 5 (where Fr = U/ND, U is the tow speed, D the sphere diameter and N the Brunt-Väisälä (BV) frequency). In a second series of experiments, the temporal wavefield evolution was studied over two BV periods. These measurements show that the body generation (lee wave) mechanism dominates at Fr 1, while the random eddies in the turbulent wake become the dominant source at Fr 1. In the low-Fr regime, Fr 1, there is a resonant peak in the coupling of the input wake energy to the internal wavefield at a Froude number of ∼0.5, and at its maximum 70 % of the input energy is coupled into IW potential energy. In this regime it was also found that the spreading angle of the evolving wavefield was considerably broader than predicted by the classical point-source models for the wavefield further downstream, owing to the existence in the near field of a significant energy content in the higher-IW modes that deteriorate at later times. In the low-Fr regime, it was found that, while the IW potential energy increases ∝ Fr 2 , the fraction of the total energy input is a weak function of Fr, varying as Fr 1/2 .

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Near surface clear air radio frequency (RF) propagation in the coastal area is the result of air/sea/land interactions influenced primarily by the characteristics of the surface of the land and sea. Synoptic influences by large scale (approximately 300km) meteorological features such as cold fronts and high-pressure ridges control wind direction and sources of water vapor. Mesoscale meteorological influences (approximately 50km) such as sea breeze and convective precipitation may rapidly change the propagation environment. Microscale meteorological structures (approximately lkm) such as the atmospheric boundary layer react to the larger synoptic and mesoscale features to create spatiotemporal refractivity fields. This paper will present the results of a three-year research effort that identifies the larger scale meteorological processes that impose non-standard propagation structures in the coastal marine atmospheric boundary layer. Highly resolved propagation and thermodynamic data from Wallops Island, Virginia, the California coast, and the Persian Gulf are combined with archived meteorological data in order to relate anomalous clear air propagation to universal weather map features.

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