Effect of wind shear on atmospheric wave instabilities revealed by FM/CW radar observations |
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| Authors: | E E Gossard J H Richter D R Jensen |
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| Institution: | (1) Wave Propagation Laboratory, NOAA Environmental Research Laboratories, 80302 Boulder, Colo., USA;(2) Propagation Technology Division, Naval Electronics Laboratory Center, 92152 San Diego, Calif., USA |
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| Abstract: | An FM/CW radar sounding system designed and built by one of us (Richter, 1969) reveals atmospheric wave structure in unparalleled detail.The most outstanding features evident in the record are; internal gravity waves; features resembling Kelvin/Helmholtz instability structures; and multiple layering, often with lamina only a few meters thick.This paper shows a variety of atmospheric structural patterns and compares them with several hypothetical models of internal waves to obtain more insight into the atmospheric processes at work. Special attention is given to the distribution of the Richardson number in trapped and untrapped gravity waves. It is proposed that the multiple layers result from untrapped internal gravity waves whose propagation vector is directed nearly vertically within very stable height regions. It is argued that the layers are caused by dynamic instability resulting from reduction in the Richardson number due to wave induced shear and to some background wind shear when the amplitude-to-wavelength ratio grows during propagation into thermally stable height regions of the atmosphere. |
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