PERIODIC VARIATION OF AUGULAR MOMENTUM TRANSPORT SPECTRA AT 500MB SURFACE

Daily values of the geostraphic angular momentum transport at 500 mb surface are computed as a function of wave numbers(1 through 12) for fifteen months during three winter seasons, 1975-1978.Medium range periodic variation at middle latitude is studied. It is found that the total amount of transport shows a quasitwo week variation. The amount of transport of wave number three also shows the same periodicity. The two kinds of transport are in phase variation, and the contribution of the transport of wave number three to the total transport is more than 50%.Power spectral and cross-spectral analyses are made. It is revealed that the above qualitative results are reliable. It is found that the variation of the orientation of the trough and ridge line of wave number three obtained from zonal harmonic analysis for selected examples, is in agreement with the quasi-two week variation of the momentum transport.