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Xin Hai Gao
and
John L. Stanford

Abstract

Low-frequency analyses are reported for four years of 3-day-mean satellite microwave and infrared data representative of temperatures in the stratosphere. In data representative of 30–150 mb temperatures oscillations with 39–51 day periods are observed as a tropical dipole pattern in the Indonesia/central Pacific. In addition, the first evidence is presented for such oscillations in the southeast Pacific. Furthermore, significant 39–51 day oscillations are observed in the mid- and upper stratosphere, centered near 60°S latitude.

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Xin-Hai Gao
,
Wen-Bi Yu
, and
John L. Stanford

Abstract

Four years of satellite-derived microwave and infrared radiances are analyzed for the three-dimensional and seasonal variation of semiannual oscillations (SAO) in stratospheric temperatures, with particular focus on high latitudes, to investigate the effect of stratospheric warmings on SAO. Separate analyses of individual seasons in each hemisphere reveal that the strongest SAO in temperature occur in the Northern Hemisphere (NH) winter polar upper stratosphere. These results, together with the latitudinal structure of the temperature SAO and the fact that the NH polar SAO is nearly out of phase with the lower latitude, SAO, are consistent with the existence of a global-scale, meridional circulation on the SAO time scale. The results suggest that polar

stratospheric warmings are an important source of SAO in both high and low latitude stratospheric temperature fields. Interannual variations, three-dimensional phase structure, and zonal asymmetry of SAO are also detailed. The SH stratospheric SAO is dominated by a localized feature in the high-latitude, eastern hemisphere which tilts westward with height.

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