CHARACTERISTICS OF 30--60 DAY OSCILLATION OF GENERAL CIRCULATION IN NORTHERN HEMISPHERE

摘要

Some characteristics of the 30- 60 day oscillation in general circulation are investigatedin this paper. In the tropical atmosphere, besides some results consisting with the knownfacts, we still find that the 30- 60 day atmospheric oscillations are very obvious in theequatorial eastern Pacific, and the zonal scale of the vorticity and divergence for the30- 60 day oscillation in the tropics is much smaller than wavenumber 1. There are the strongest 30- 60 day oscillations at the high latitudes in the Northern Hemi-sphere, but weaker at 20°-40°N latitudes. The 30- 60 day oscillations have an obviousbarotropic structure at mid-high latitudes and their zonal scales are smaller than those in thetropics. The 30- 60 day oscillations at the mid-latitudes propagate westwards and fast in thewintertime. At the high latitudes, 30- 60 day oscillations propagate westwards in the win-tertime but eastwards in the summertime. Meridional propagations of the oscillation arerather different in various regions.