基于极值概率分布的河南冬小麦晚霜冻时空分布特征

为探究河南省小麦晚霜冻害的时空变化特征和分布规律,基于河南省1971-2019年111个气象站温度资料和17个农气观测站小麦发育期资料,采用Mann-Kendall趋势检验法对终霜日的时间及极值概率分布进行拟合分析。结果表明,河南省小麦拔节期常年值在第73-第91日(年积日),小麦晚霜冻终日均值在第80-第95日,小麦晚霜冻害发生频率均值为0.5～4.7次·10年~(-1)。河南省大部分地区的小麦拔节期和小麦晚霜冻终日均呈提前趋势,且终霜日提前幅度更大,但1990-2019年终霜日的变异度较1971-1990年间明显增大,提示晚霜冻发生的概率可能会降低,但潜在危险可能会加剧。93.1%的站点终霜日都满足极值概率函数分布,终霜日的10年、50年、100年重现期的空间分布规律与历史均值存在一定的差异;终霜日重现期水平与纬度、海拔均呈显著正相关,呈现出明显的地带性分布。由此可见,在气候变化背景下,小麦晚霜冻害的影响仍然不可忽视。

Statistical Characteristics of Late Frost in Winter Wheat Based on Extreme Value Distribution in Henan

In order to explore the spatiotemporal variation characteristics and distribution law of late frost hazard of wheat in Henan Province, the time of the last frost day and the probability distribution of extreme value were fitted by Mann-Kendall trend analysis and extreme-value distribution analysis, based on the temperature data of 111 meteorological stations and the wheat development period data of 17 agro-meteorological stations in Henan Province from 1971 to 2019. The results showed that the annual value of jointing stage of wheat in Henan Province was during 73rd to 91st day; the average of late frost ending date was from 80th to 95th day, and the average frequency of late frost injury was 0.5-4.7 times per decade. In most areas of Henan Province, a trend towards earlier wheat jointing stage and frost ending day was detected, with a greater advance in the frost ending day. However, the variation of the last frost date from 1990 to 2019 was significantly large, compared with that from 1971 to 1990, suggesting that the probability of late frost occurrence may be reduced, but the potential risk may be aggravated. Frost ending day in 93.1% stations is fitted with the extreme-value distribution. Certain differences are existed between the average distribution of historically observed frost ending day and 10-,50- and 100-year return periods value. The level of final frost day recurrence period is significantly positively correlated with latitude and altitude,showing a relatively obvious zonal distribution. Therefore, in the background of climate change, the effect of late frost hazard on wheat can not be ignored.