Mean (top) and anomalous (bottom) 200-hPa stream function (106 m2s-1)for the last 30 days. The non-divergent component of the flow is directed along the contours with speed proportional to the gradient. Thus, high (low) stream function corresponds to high (low) geopotential height in the Northern Hemisphere and to low (high) geopotential height in the Southern Hemisphere. Anomalies are departures from the 1979-95 daily base period means.
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