Boundary Layer Oscillations from Thunderstorms at Sydney Airport

Richard Manasseh School of Mathematics, University of New South Wales, Sydney, New South Wales, Australia

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Jason H. Middleton School of Mathematics, University of New South Wales, Sydney, New South Wales, Australia

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Abstract

Analyses of wind velocity and air pressure data, acquired by a set of low-level anemometers at Sydney Airport, Australia, indicate the passage of a set of three remarkably smooth atmospheric boundary layer oscillations that traveled ahead of a thunderstorm on 27 December 1991. The oscillations were probably generated by a nearby thunderstorm outflow, propagating into a stably stratified atmospheric layer. It is likely that the phenomenon was initiated by the degenerating of an outflow gravity current into a family of amplitude-ordered solitary waves. Although reasonable agreement can be obtained on the propagation speed using a linear theory, the weakness of the trapping mechanism for this solution and an overestimation of the weakly nonlinear wave half-width leads to a conclusion that the waves fully nonlinear.

Abstract

Analyses of wind velocity and air pressure data, acquired by a set of low-level anemometers at Sydney Airport, Australia, indicate the passage of a set of three remarkably smooth atmospheric boundary layer oscillations that traveled ahead of a thunderstorm on 27 December 1991. The oscillations were probably generated by a nearby thunderstorm outflow, propagating into a stably stratified atmospheric layer. It is likely that the phenomenon was initiated by the degenerating of an outflow gravity current into a family of amplitude-ordered solitary waves. Although reasonable agreement can be obtained on the propagation speed using a linear theory, the weakness of the trapping mechanism for this solution and an overestimation of the weakly nonlinear wave half-width leads to a conclusion that the waves fully nonlinear.

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