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Analyses of Unusual First and Last Frost During the Last 40 Years in the Changjiang and Huaihe River Valley
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摘要: 该文用地面最低温度资料，以≤0℃作为霜冻指标，定量地确定出现异常霜冻的判别标准，研究了近40年初终霜冻异常的气候特征。结果表明：初终霜冻的异常明显存在地区差异。其变化周期以2～3年和准12年最普遍。其偏离均值大致有两种波型：反向变化和同向变化。前者在淮河流域较突出，后者在长江流域较普遍。当其出现反向变化趋势，且二者偏离均值达最大时，该时期为初霜冻异常偏早(偏晚)，终霜冻异常偏晚(偏早)的活跃期。同样，当初、终霜冻出现同向变化时，初、终霜冻异常活路期亦呈现同向变化。Abstract: According to the frost index defined by the soil surface minimum temperature ≤0℃, the criterion for the unusual frost was quantitatively given and the climatic features of the unusual first and last frost during the last 40 years were studied. The results show that there distinct geographical differences in the unusual first and last frost days, and 2~3 year and guasi－12 year cycles are universal. Roughly, two fluctuation patterns are discovered. One is the opposite tendency between the first and last frost days and the other is the same fluctuation tendency between them. The former is obvious in the Huaihe River Valley and the latter is generally in the Changjiang River Valley. When the departures of the first or last frost come into being the opposite tendency or the same one and their departures to the average reach the largest, the frost periods are defined as unusual active one.
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