Impulse propagation in the nocturnal boundary layer: Experimental observations outdoors with a vertical array

Abstract

As observed experimentally by Chunchuzov et al. [J. Acoust. Soc. Am. 88, 455 (1990)], impulsive signals propagating in the downward refracting atmospheres typical of the nocturnal boundary layer have a canonical long-range form: they consist of multiple arrivals followed by a low frequency tail. Theoretical arguments that such behavior is canonical and an identification of the low frequency tail with the ground-coupled surface mode have been recently presented [J. Acoust. Soc. Am. 117, 2532 (2005)]. In November 2006, pulse propagation experiments were performed at night on farmland in the Mississippi River Delta. The source used was a propane cannon and the receiver was a 10 meter tower with 16 equally spaced microphones microphones located 1.6 km downwind from the source. Meteorological data was collected from three sensor stations mounted on the tower, six attached to a tethersonde line and a sodar device. Results from these experiments will be presented and discussed.