MERIDIONAL PROPAGATION OF EAST ASIAN LOW-FREQUENCY MODE AND MIDLATITUDE LOW-FREQUENCY WAVES^*

Based on June to September 1981 ECMWF grid datasets analysis is done of the characteristics of thepropagation and structure of low-frequency(quasi 40 day) oscillation over eastern Asia. Results show aseparating(confluence) belt for the meridional propagation of low-frequency zonal(meridional) winds at higher(lower) levels over subtropical latitudes at 120°E, revealing that the oscillation of the zonal winds is quasi-geostrophic in pature and in phase in the high- and low-level. It is also found that the eastward propagationof the high-level zonal winds around 35°N in East Asia is the result of eastward march of midlatitude low-frequency waves with 60-90 longitude wavelength and speed of 1.5-2.0 longitudes per day. In addition, suchlow-frequency vortices, when moving over the coastwise region, tend to develop, accompanied by sharp oscil-lation in the westerly jetstream over eastern Asia.