Aspects of the stratospheric circulation as derived from SSU data

Five years of global data are available for the stratosphere up to 1 mb from Stratospheric Sounding Units (SSUs) on board NOAA satellites. These data form the basis for a climatological study which concentrates on the seasonal and inter-annual variability of the stratosphere and the connection between the stratospheric circulation and that of the troposphere. Particular emphasis is on the structure of the Southern Hemisphere and how it compares with that of the Northern Hemisphere. The characteristic difference in the vertical structure and propagation of disturbances in the two hemispheres is related to differences in the tropospheric flow and the long-term variation of the basic state of the stratosphere. Disturbances in both hemispheres occur in preferred geographical locations. The final warming, marking the transition from westerly to easterly winds, is an example. These occur asymmetrically with respect to the pole as warm air moves over the pole, usually from the same region.