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K. Matcheva, P. Drossart, E. Raynaud, B. Sicardy (LESIA, Paris Observatory-Meudon)
The vertical temperature profile of a planetary atmosphere obtained via in situ or remote sensing techniques typically exhibits small scale fluctuations, which are usually interpreted as signatures of propagating atmospheric waves. By studying the observed wave amplitude and phase behavior, and the altitude variations of the vertical wavelength of individual wave modes one can acquire valuable information about the dominant dissipative processes in the atmosphere as well as detect the presence of vertical gradients in the background horizontal wind.
The method is based on the use of the Continuous Wavelet Transform of the temperature profile for identifying and subsequently reconstructing the dominant wave modes present in the atmosphere. Model generated waves are then used to fit the observations by varying the strength of the background wind shear and the eddy diffusion coefficient. Molecular and eddy dissipative processes can only limit the wave amplitude growth, whereas presence of vertical wind shear can result both in increase and decrease of the wave temperature amplitude, which is also accompanied by corresponding variations in the vertical wavenumber. This effect could be very large for waves with a horizontal phase speed comparable to the background horizontal wind.
We demonstrate the developed technique in a study of Jupiter's stratosphere and lower thermosphere using the temperature profiles retrieved from the 1999 HIP 9396 stellar occultation by the northern polar region of the Jovian atmosphere (Raynaud et al. submitted to Icarus). The quality of the data allows us to successfully identify and reconstruct three dominant wave modes, which peak at different altitudes and compare them to model results.
This work is supported by the Marie Curie Fellowship Program of the European Community under contract HPMF-CT-2000-01005.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.