A NOTE ON THE DISTRIBUTION OF TRENDS BELOW 10HPA - THE EXTRATROPICAL NORTHERN-HEMISPHERE

The trend in the zonally averaged temperature, 1964-1993, was positive in most of the extratropical troposphere. It was negative in the annual mean in the stratosphere. In January a positive trend appeared in the middle stratosphere in the arctic which progressed downward through the winter. This is reflected in a reversal of the trends in the geopotential heights at 30 hPa and 10 hPa in late winter. The trends in the annual mean geopotential heights in both troposphere and stratosphere were positive south of about 60 degrees N and negative to the north. The zonally averaged geostrophic westerly wind between middle and high latitudes therefore increased during the period.