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ABSTRACT
A study has been made in wavenumber-freque"cy space of the 2oo mb
geopotential height field supplied by the German Weather Service
in the form of grid point data. The geostrophic wind components
have been similarly treated. The period of study covered eight years
(1969-1976) with a temporal resolution of 24 hours. The lowest temporal
mode considered was the annual cycle.
The first result of this study was that the maximum spectral energy
was to be found in the annual mean and annual cycle and that this
is principally contained in zonal wavenumbers one to four. At higher
frequencies the energy contained in the higher wavenumbers (5 to 8)
increases relative to that in the lower wavenumbers. In the case of
the higher wavenumber geostrophic wind components the energy in the
eastward propagating waves at a period of about ten days is almost
as large as that in the annual mean. There are however no significant
peaks in any particular frequency bands.
An attempt has been made to separate the purely standing waves from
the propagating components and it was found that the remaining purely
propagating contribution had a maximum between 4o 0 N and 6o 0 N at wavenumber
9 and with frequencies between 5o and 12o cycles per year.
A comparison of the annual mean field and the standing waves with
frequency one cycle per year allowed an investigation of the competing
effects of topography and thermal forcing to be made. This
showed that these two effects have an influence of the same order
of magnitude.
In the secend part of this study, time series and wavenumber-frequency
spectra of the turbulent meridional angular momentum transport were
investigated. The spectra show that at latitudes around 6o 0 N, where
the total transport is southward, the shorter high frequency waves
still transport momentum polewards.
Finally as a contribution to the discussion of parameterization the
linear fnfluence of the turbulent angular momentum transport on the