A Characteristic Feature of Ultra-Long Waves at the 500-mb Level in the Winter Season

Abstract

By making use of data at the 500-mb level during the winter season, the spectral densities of ultra-long waves in the frequency domain are examined. The result shows that the spectral densities for zonal wavenumbers k=1∼3 are approximately proportional to the minus second power of the frequency. From this result the day to day variations of the amplitude of ultra-long waves are examined as a stationary random process. In order to clarify the different characteristic features between ultra-long waves and baroclinic waves, the spectral density for zonal wavenumber of k=6 is also examined. In the case of the baroclinic wave (k=6), the maximum value of spectral density is obtained at the period of about a few days.