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HURD C. WILLETT

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HURD C. WILLETT

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Hurd C. Willett

Abstract

Following a brief discussion of the pertinent sunspot cycles, four extended samples of climatic data are presented in support of the contention that solar-climatic cyclical relationships are of sufficient significance and amplitude to be of practical value in climatic trend forecasting. In this connection it is noted that recent climatic trends have followed earlier expectations based on this assumption. In conclusion, some recommendations are offered for further development of this predictive potential.

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Hurd C. Willett

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The seasonal regimes of temperature in the arctic and the antarctic stratospheres are contrasted, with special reference to the sporadic winter warmings of the arctic and the explosive spring warming of the antarctic stratospheres. There follows a discussion of the inadequacy of the usual advective-dynamic explanation, at least in terms of any model presented to date, to account quantitatively for any of these phenomena in their more extreme manifestations. The seasonal regimes of total atmospheric ozone in the arctic and in the antarctic are likewise contrasted, again with special reference to the differing thermal regimes and sudden stratospheric warming. The strong annual period of auroral frequencies and the belts of maximum auroral frequency are discussed in relation to the arctic and the antarctic thermal regimes as is the relationship of sudden stratospheric warmings to auroral and solar activity. Finally, variability of the solar wind, i.e., of solar corpuscular penetration of the higher atmosphere, is tentatively suggested as a possible alternative explanation to the advective-dynamic hypothesis to account for the variation in common of polar stratospheric temperature, ozone and auroral activity.

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Hurd C. Willett and John Prohaska

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It is shown that previous evidence of a high cyclical correlation between total atmospheric ozone and relative sunspot number on the one hand, and the mean latitude of the total area of solar spottedness on the other hand, cannot he explained away by the seasonal, geographical and chronological non-homogeneity of the total ozone data. The same basic relationships are found with only little reduction of significance in the data of the only two stations of relatively complete record, and in calendar seasonal and even monthly data. Further investigation shows that the relationship to sunspot latitude is not continuous, but that the ozone stimulating effect of sunspots apparently is cut off rather sharply when the mean latitude of solar spottedness moves poleward of about 12°.

By analysis of the ozone data separately for the months February, March, August and September when the earth is farthest from the solar equator and for the months May, June, November and December when it is closest, Rasool has found further evidence of a rather sharp cutoff of the ozone stimulating effect of sunspots when the earth lies outside of a sunspot cone of some 15° radius.

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