Abstract
Abstract. A procedure of revealing parameters of internal gravity waves from meteor radar wind measurements is presented. The method is based on dividing the measuring volume into different parts and, using wavelet analysis, calculating the phase progression of frequency peaks in the vertical and horizontal direction. Thus, the distribution of vertical and horizontal wavelengths and directions of IGW energy propagation, using meteor radar data, has been obtained. The method was applied to a 4-month data set obtained in July and August, 1998 and 1999. As expected, the majority of waves have been found to propagate upwards, although a considerable number seem to propagate downwards as well. High-frequency (intrinsic periods T* of less than 2 h) waves are dominating. The distribution of waves over the course of an average day is only weakly structured, with weak maxima in the morning and evening.
Highlights
Studies of the wind regime in the mesosphere/lower thermosphere (MLT) regions have shown the essential influence of internal gravity waves (IGW) on dynamic processes and energy transport and dissipation in these height layers (e.g.McLandress, 1998)
The method is based on dividing the measuring volume into different parts and, using wavelet analysis, calculating the phase progression of frequency peaks in the vertical and horizontal direction
The obtained distributions of time-spatial IGW parameters agree with the results of other authors (Vincent and Reid, 1983; Manson and Meek, 1988; Gavrilov et al, 1996, 1997; Kalov and Gavrilov, 1985; Gavrilov and Medvedev, 1997), who have presented results about the horizontal IGW structure
Summary
Studies of the wind regime in the mesosphere/lower thermosphere (MLT) regions have shown the essential influence of internal gravity waves (IGW) on dynamic processes and energy transport and dissipation in these height layers We use only the zonal component both for wind estimation, and for gravity wave estimation This means that the horizontal wavelengths are not uniquely determined, depending on the north-south component. A sliding window low-pass filter is applied to suppress random errors in the high frequency component of the meteor radar wind time series in each sub-volume. Data are accepted, where the horizontal phase change of the wavelets satisfied a linear dependence This procedure was repeated for each height bin. For each altitude layer hi the mean values of phase and altitude are calculated, from which the vertical phase dependence is constructed, again using a robust least-squares fitting and the hypothesis of linear regression. The prevailing wind changes with height, from westward winds in the mesosphere to eastward winds in the lower thermosphere
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