Seasonal variations of the 40-50-day oscillation in atmospheric angular momentum

Abstract

Intraseasonal variability (including 40-50-day fluctuations) of global momentum is largest in late boreal winter and smallest in boreal autumn; however, the 40-50-day spectral peak is most pronounced in boreal summmer when lower-frequency intraseasonal variance is depressed. The 40-50-day spectral peak in global momentum is much less pronounced and apparently is restricted to a narrower frequency band, than corresponding peaks in zonal wind spectra from individual tropical rawinsonde stations. Contributions to global momentum fluctuations from three near-equal-area latitude bands (tropics, Northern Hemisphere, and Southern Hemisphere) are compared, confirming that intraseasonal momentum fluctuations are tropical in origin. -from Authors