Variations of Stratospheric Zonal Winds, 20–65 km, 1961–1971

A. D. Belmont Control Data Corporation, Minneapolis, Minn. 55440

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D. G. Dartt Control Data Corporation, Minneapolis, Minn. 55440

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G. D. Nastrom Control Data Corporation, Minneapolis, Minn. 55440

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Abstract

The observed variability patterns of monthly mean zonal winds over an 11-year period, from 80°N–70°S and from 20–65 km, are explained in terms of component patterns of a long-term mean, quasi-biennial, annual and semi-annual periodic variations. Interannual variations are displayed by monthly mean height-time sections for each of eleven years, and Northern Hemisphere–-Southern Hemisphere differences are seen from 11-year mean, latitude-month sections for each 10 km. An 11-year mean, height-month section at the equator shows the transition of the easterly regime at low levels to a westerly one at highest levels. Summer easterlies extend from equator to pole, from 30 to 50 km, but winter westerlies extend from equator to about 70° only at 60 km. Also, only at 60 km are there westerlies from pole to pole during the equinoxes. The stronger Southern Hemisphere westerly circulation of the troposphere is found to extend to at least 40 km, and possibly to 60 km. Southern summer easterlies are the same as, or stronger than, those in the Northern Hemisphere. Improved latitudinal rocket network coverage is needed in the Southern Hemisphere. Finer time resolution is essential everywhere to obtain diurnal variations.

Abstract

The observed variability patterns of monthly mean zonal winds over an 11-year period, from 80°N–70°S and from 20–65 km, are explained in terms of component patterns of a long-term mean, quasi-biennial, annual and semi-annual periodic variations. Interannual variations are displayed by monthly mean height-time sections for each of eleven years, and Northern Hemisphere–-Southern Hemisphere differences are seen from 11-year mean, latitude-month sections for each 10 km. An 11-year mean, height-month section at the equator shows the transition of the easterly regime at low levels to a westerly one at highest levels. Summer easterlies extend from equator to pole, from 30 to 50 km, but winter westerlies extend from equator to about 70° only at 60 km. Also, only at 60 km are there westerlies from pole to pole during the equinoxes. The stronger Southern Hemisphere westerly circulation of the troposphere is found to extend to at least 40 km, and possibly to 60 km. Southern summer easterlies are the same as, or stronger than, those in the Northern Hemisphere. Improved latitudinal rocket network coverage is needed in the Southern Hemisphere. Finer time resolution is essential everywhere to obtain diurnal variations.

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