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  • Author or Editor: T. Yonetani x
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C. P. Jacovides
and
T. Yonetani

Abstract

The effectiveness of a number of forecasting indices for non-frontal thunderstorm activity has been investigated for the Greater Cyprus area. The indices include the humidity index (HI), the Pickup index (PI), the K-stability index, the Yonetani index in its original II and modified IIc, form, and the Showalter stability index (SSI) for the Mediterranean area. Combinations of some of these indices with information of the flow curvature are also considered.

Two data sets, representative of coastal and inland locations are used to evaluate the accuracy of these indices. Verification statistics indicate that Yonetani's indices II and IIc, are more successful than the HI, PI, and K indices in the forecast of air mass thunderstorms. The addition of the flow curvature at 500 hPa improves the effectiveness of most indices and its inclusion should be seriously considered for the Eastern Mediterranean area.

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T. Yonetani
and
Hal B. Gordon

Abstract

Following a transient increase in the atmospheric carbon dioxide to double the current level, and a subsequent maintenance at the doubled level, there is a climate shift toward a new equilibrium state. Changes in the mean temperature and precipitation, and changes in the occurrence frequencies of their extremes for the doubled carbon dioxide conditions have been assessed at the continental scale. There is a characteristic spatial pattern that involves a maximum annual mean warming in high northern latitudes and a minimum annual mean warming around Antarctica and in the northern North Atlantic. Under maintained doubled carbon dioxide, this interhemispheric asymmetry disappears except for an ocean–land asymmetry. A possible mechanism for this is considered in terms of changes in effective thermal capacity due to a reduction of overturning in the oceans that continues to decline after the atmospheric carbon dioxide stops increasing. It is also found that global warming becomes most noticeable in the occurrence frequency of high extremes in the annual mean temperature in the low latitudes, even though the temperature rise is largest in the high northern latitudes in autumn and winter. In addition, extremes of large (small) annual and seasonal total precipitation are recorded much more frequently in regions where the mean precipitation increases (decreases).

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