ROSSBY-WAVE PROPAGATION AND TELECONNECTION PATTERNS IN THE AUSTRAL WINTER

Observational evidence of and theoretical support for the Northern and Southern Hemisphere teleconnection patterns in the austral (Southern Hemisphere) winter are examined through an upper troposphere streamfun ction teleconnectivity map and time-lag cross-correlation analysis usi ng ECMWF initialized analysis 200-hPa winds for the 11 June-August per iods from 1979 to 1989. As was previously found for the Northern Hemis phere winter, the regions of strong teleconnectivity, particularly in the winter hemisphere, tend to be oriented in the zonal direction and coincide with the location of the major jet streams. Although equatorw ard propagation from the Northern and Southern Hemispheres is observed , little evidence of cross-equatorial propagation has been found. For comparison, the response of a barotropic model, linearized about a cli matological 300-hPa June-August time-mean flow to localized forcing is determined It is found that the activity tends to be trapped inside e ach of the Southern Hemisphere subtropical and polar jet streams, with these acting as waveguides. In the Northern Hemisphere a weak wavegui de belt is found near 40 degrees N around the whole hemisphere. The pa tterns simulated by the model are generally in good agreement with the teleconnectivity study described above. Both the observations and the model support the existence of the Pacific-South American pattern.