冬小麦晚霜冻害时空分布与多时间尺度变化规律分析

Spatial-temporal distribution and multiple-temporal scale variation analyses of winter wheat late freezing injury.

冬小麦晚霜冻害主要发生在中国的黄淮区域,河南占黄淮区域面积较大,是中国小麦的主要产地,又是晚霜冻害的重发区,因此文章以河南为例,从构成晚霜冻害的最低温度和小麦发育期两个因素出发,提出了晚霜冻害指数构建方法,使晚霜冻害指标定量化,并从多年数据库中计算出逐年晚霜冻害发生强度和发生天数。由于小麦发育期观测资料序列较短,影响了大尺度小麦晚霜冻害变化规律的分析,因而提出了冬小麦发育期资料推算方法;对计算出的近50年晚霜冻害资料进行EOF分析和Morlet小波分析,以发现晚霜冻害的时空分布与多时间尺度变化规律。结果表明:冬小麦晚霜冻害发生频率较高,高发区频率超过40%,且在20世纪70—90年代有增多的趋势;发生强度和天数变化趋势基本相似,具有发生强度较重区对应着发生天数较多区的趋势,且前者对小麦产量的影响大于后者;晚霜冻害发生强度的重发区分布在豫东南和豫西南,轻发区主要分布在淮河以南及豫西部分地区,其中第1模态分布型存在16年、第2模态分布型存在准2年的多时间尺度变化规律;发生天数的多发区主要分布在豫北北部和豫西南边界,少发区在豫东北及豫西南中部,其中第1模态分布型存在着准4年、第2模态分布型存在准3年和准6—7年的周期。

The winter wheat late freezing injury （WFI, or frost damage） mainly occurs in the Yellow River and the Huaihe River area, of which Henan Province possesses the most part. Henan is both the major producing area of wheat and the harder-hit area of WFI. In this paper, we present a WFI index based on minimum temperature and winter wheat development period （WDP）, and cal- culate the WFI degrees and days at 30 agrometeorological stations of Henan Province in 1981 - 2004. For the large-scale variation analysis of WFI, the 24-year WDP observation sequence is relatively short, therefore it is expanded by using the relation between the tuning 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 base of 2.5 ℃ . And then the expanded data of WFI in the last about 50 years are analyzed by EOF and Morlet techniques to reveal the regulations of spatial-temporal distribution and multiple-temporal scale variability of WF1. The results show that the frequency of WFI was higher, above 40 % in high-incidence areas in Henan Province; and the WFI exhibited a rising trend in the 1970s- 1990s. The trend of WFI degrees was similar to that of WFI days, and the areas of heavier WFI de grees usually corresponded to the areas of more days of WFI. The impact of winter wheat frost damage degree on the winter yield was more remarkable than that of the frequency of WFI. The incidence areas of heavy WFI degree lay in the southeast and southwest of Henan, and the areas of light WFI degree in the south side of the Huaihe River and parts of western Henan. The first/second EOF mode of WFI degrees displayed 16 years/quasi-2 years multiple time scale variability, respectively. The high/low frequent areas of WFI were distributed in the north of northern Henan and the southwest border of Henan/the northeast Henan and the middle part of southwest Henan, respectively. The first/second EOF mode of WFI days exhibited quasi-4 years/quasi-3 years and quasi-6-7 years multiple time scale variability, respectively.