500毫巴角动量输送波谱的周期变化

用三年冬半年15个月500毫巴逐日资料,计算写成谱函数形式的角动量涡动输送,研究其周期变化。输送总值(波数k=1—12的总和)盛行准两周的周期,逐年差别不大。k=3波输送值也盛行准两周周期,近于同输送总值同位相,而且负担了50％以上的输送总值。其他波数,k=2盛行26天左右周期,k=4盛行12天左右周期,但这些波的变化幅度比k=3波小得多。初步考察了准两周周期同寒潮的关系。 用解纬圈谱法,选例考察k=3波的槽脊走向和振幅,有同角动量输送准两周变化相应的变化。 最后采用功率谱和交叉谱的分析法,对1976—1977年角动量输送进行统计上处理,得到一些与定性分析相同的结果。

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.