中文摘要：

冬季小麦迟了的霜灾难(世界聋人联合会) 主要在黄和 Huaihe 河区域，河南省，省盖住大多数部分发生。河南省是在中国的小麦生产的主要区域，但是它被 WFD 严重地撞击。在这研究，我们基于最小的温度和冬季小麦发展时期(WDP ) 构造一个世界聋人联合会索引。在 30 点的世界聋人联合会度和 agrometeorological 在 19812004 的时期期间在河南省省驻扎的天是计算的。为世界聋人联合会的大规模时间的变化分析，24年的 WDP 观察系列是相对短的，它被在 2.5 的批评价值上面使用在冬季小麦和在茎延伸之间的温度和那分阶段执行的5天的跑平均数和有效累积温度的转弯的绿日期之间的关系因此扩展

英文摘要：

The winter wheat late frost disaster（WFD） occurs mainly in the Yellow and Huaihe River area,of which Henan Province covers the most part.Henan is the major area of wheat production in China,but it is severely hit by the WFD.In this study,we construct a WFD index based on the minimum temperature and the winter wheat development period（WDP）.The WFD degrees and days at 30 agrometeorological stations in Henan Province during the period of 1981-2004 are calculated.For the large-scale temporal variation analysis of WFD,the 24-yr WDP observation series is relatively short,so it is expanded by using the relation between the turning green date of winter wheat and the 5-day running mean temperature and that between the stem elongation phase and the effective cumulative temperature above a critical value of 2.5 ℃.The WFD data are also expanded for the last 50 years and are analyzed by using the empirical orthogonal function（EOF） and the Morlet wavelet methods.Characteristics in the spatial distribution and temporal variation of WFD are revealed.The results show that the frequency of WFD is generally high,exceeding 40% in parts of Henan,and exhibits a rising trend in the period of 1970-1990.The variation trend of WFD degrees is similar to that of WFD days,and the areas with higher WFD degrees coincide the areas with more WFD days.Moreover,the WFD degree has a greater impact on the winter wheat yield than the WFD days.The areas with high WFD degrees lie in the southeast and southwest of Henan,and the areas with low WFD degrees lie in the south of the Huaihe River and parts of western Henan.Temporal variations of the first and second EOF modes of the WFD degree display 16-and quasi-22-yr periodicities,respectively.The areas of high（low） WFD frequency are distributed in the northern Henan and the southwest border of Henan（the northeast Henan and the middle part of southwest Henan）.The temporal variation of the first（second） EOF mode of WFD days exhibits a periodicity（periodicities） of quasi-4 yr（