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Ann. Geophys., 21, 1183-1195, 2003
www.ann-geophys.net/21/1183/2003/
© European Geosciences Union 2003
Momentum flux associated with gravity waves in the low-latitude troposphere
S. R. Prabhakaran Nayar and S. Sreeletha
Department of Physics, University of Kerala, Kariavattom, Trivandrum-695 581 India
Abstract. The vertical fluxes of
horizontal momentum at tropospheric heights are calculated for four days, 25–28
August 1999. The mean zonal wind during these days show the presence of strong
westward wind at the upper troposphere. Both the symmetric beam radar method
and the power spectral method of evaluation of vertical flux of zonal and
meridional momentum shows nearly the same result for quiet conditions. The
temporal evolution of the momentum flux is estimated for a day with strong
zonal shear and convection. These results indicate that on 28 August 1999, the
strong downward vertical wind in the lower altitude range is associated with
upward vertical flux of zonal momentum, and strong upward vertical wind is
associated with downward vertical flux. Similarly, the strong shear in zonal
wind is associated with the increase in negative values in vertical flux in the
upper troposphere. Analysis of the role of wave periods in the transport of
momentum flux indicates that the vertical momentum flux magnitude is not evenly
distributed in all wave periods, but instead it peaks at certain wave periods
in the range 10 to 100 min.
Key words. Meteorology and
atmospheric dynamics (convective process; tropical meteorology; precipitation)
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