1983 Volume 61 Issue 2 Pages 263-268
In order to estimate space-time spectra correctly from uneven twice-daily data sampled by a polar-orbiting satellite, the wavenumber transform method (Hayashi, 1980) is modified by the use of a nonorthogonal Fourier inversion. The space-time spectra are obtained from the time-Fourier coefficients of the space-Fourier transforms of the asynoptic field with respect to its frequency-shifted wavenumber. Since this method requires the spatial interpolation of asynoptic data, it is effective only for ultralong waves. The wavenumberfrequency aliasing characteristics are examined and the computer code is exemplified.