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Harry Van Loon and Roy L. Jenne

Abstract

We have tested three methods of estimating the level of a coming season's mean temperature at a station where the statistical association between two selected seasons is as high as one can expect in extratropical regions. The methods are contingency tables, regression equations, and the use of the last few decades if there is a trend at the station which will separate the mean of these decades a fair distance from the long-term mean. A moderate amount of skill was achieved, but the degree of seasonal association in our test case was exceptionally high, and generally these methods will provide only a small improvement over a probability based on knowing only the observed frequency distribution.

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Harry van Loon and Roy L. Jenne

Abstract

In the tropics of the Southern Hemisphere the zonal wind in the troposphere above the 500-mb level has a well defined half-yearly oscillation with westerly maxima (easterly minima) in May and November. It is demonstrated that the oscillation is associated with second harmonics of opposite phase in the temperature above the equator and in the subtropics. The temperature oscillations are tentatively explained as being the result of an intensification of vertical motions from autumn to winter. The half-yearly temperature oscillations reverse phase near the tropopause, and again near the 50-mb level. Above this level they are thus in the same phase as in the upper troposphere. The phase reversals imply that the second harmonic of the zonal component of the thermal wind likewise changes phase twice.

A marked longitudinal asymmetry is observed with the oscillations being considerably stronger in the Eastern than in the Western Hemisphere.

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Harry van Loon, Karin Labitzke, and Roy L. Jenne

Abstract

This note deals with the standard deviations of 24-hr changes in 10-mb temperatures and heights. The standard deviations are differently distributed in disturbed and in quiet winter months. In the disturbed months their largest values form a coherent area at high latitudes; in the quiet months they surround the polar region as a ring with its center on the Atlantic side.

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Harry Van Loon, Roland A. Madden, and Roy L. Jenne

Abstract

Two patterns dominate changes of monthly mean temperature and pressure-height in the stratosphere. In the one, the middle latitudes vary oppositely to low and high latitudes, and in the other the changes at higher latitudes are out of phase with those at lower latitudes.

A shorter trend consisting of opposite changes at middle and high latitudes is superposed on the above variations which a cross-spectrum analysis shows has a preferred time scale of one to three weeks. The contrast between middle and high latitudes thus undergoes a series of corresponding fluctuations and we show that these are associated with amplitude changes in waves 1 and 2 in that the meridional contrast decreases when the amplitude of one or both waves is large, and vice versa.

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John M. Wilcox, Philip H. Scherrer, Leif Svalgaard, Walter Orr Roberts, Roger H. Olson, and Roy L. Jenne

Abstract

The solar magnetic sector structure has a sizable and reproducible influence on tropospheric and lower stratospheric vorticity. The average vorticity during winter in the Northern Hemisphere north of 2ON latitude reaches a minimum approximately one day after the passing of a sector boundary, and then increases during the following two or three days. The effect is found at all heights within the troposphere, but is not prominent in the stratosphere, except at the lower levels. No single longitudinal interval appears to dominate the effect.

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