气候变化背景下黄淮冬麦区冬季长寒型冻害时空变化特征

Spatial and temporal patterns of freezing injury during winter in Huang-Huai Winter Wheat Area under climate change

冻害是影响我国北方冬小麦生产主要的农业气象灾害之一,明确气候变化背景下冻害发生规律和演变特征,对防御冻害具有重要的意义。以黄淮冬麦区为研究区域,利用1960—2010年47个气象台站逐日气温资料,在分析越冬期负积温和越冬期长度变化特征基础上,以越冬期负积温为指标分析了黄淮冬麦区冬季长寒型冻害发生频率及站次比演变特征,并利用冻害实际灾情资料对研究结果进行验证。研究结果表明:(1)黄淮冬麦区越冬期负积温绝对值在过去50a平均为17.3—240.8℃·d,空间上呈南少北多的纬向分布特征,且近50a呈减少趋势,全区负积温绝对值每10年减少1.8—38.3℃·d,这种变化趋势表现为南低北高的空间分布特征;(2)研究时段内全区越冬期长度呈波动性缩短趋势,尤其是研究区域北部地区,南部地区越冬期长度年际间变化不显著,且个别站点有些年份没有稳定越冬期,多集中在1985年以后;(3)黄淮冬麦区较轻冻害发生频率较高,为40%以上,空间上由北向南逐渐增大,站次比年代际呈增加趋势;中度冻害和较重冻害发生频率较低,多数站点在10%以下,空间上由北向南逐渐减小,站次比呈减少趋势;全区无严重冻害和极严重冻害风险。气候变化背景下,黄淮冬麦区冬季长寒型冻害风险较小,各站点冻害程度随年代变化逐渐减轻,较轻冻害的站点逐渐增多。

Freezing injury is one of the most serious agro-meteorological disasters of winter wheat in North China, restricting yield and its suitability. Under the background of climate change, the warming trend in China is significant, especially in winter. However, freezing injury of winter wheat during winter still happened sometimes in Huang-Huai Winter Wheat Area （HHWWA）, therefore, identify the spatial and temporal patterns of freezing injury during winter under the background of climate change is very important to defense the freezing injury. In this study, based on the daily temperature data of 47 meteorological stations in HHWWA from 1960 to 2010, the trends of accumulated negative temperature and over-wintering durations were analyzed, and spatial and temporal variation of freezing injury during winter in HHWWA were identified, taking the accumulated negative temperature as freezing injury indices. Over the past 50 years, the average absolute values of accumulated negative temperature were ranged from 17.3 to 240.8 ℃·d, increased from south to north. Moreover, the accumulated negative temperature decreased at a rate of 1.8-38.3℃·d per decade from 1961 to 2010, and the higher values of trends were in the north. The over-wintering durations was also one of the important indicators of over-wintering conditions of winter wheat. In the study area, over-wintering durations decreased over the past 50 years, especially in the north areas, however there were no significant decreasing trends for the south areas, and no stable over-wintering periods for some south stations in some years, especially after 1985. Based on the analysis of accumulated negative temperature and over-wintering durations, the frequency and station ratio of freezing injury of different grades was studied. In HHWWA, the frequency of slight freezing injury was more than 40%, and increased from north to south. The ratio of existing station increased during the past 50 years. The frequencies of moderate and slightly severe freezing injury of most stations were under 10%, and decreased from north to south. The ratio of existing station decreased during the past 50 years. There was no severe freezing injury and extreme severe freezing injury over the whole region. Overall, in HHWWA, the risk of freezing injury during winter is low. The degree of the freezing injury reduced from 1961 to 2010, but the stations with slight freezing injury increased gradually. The results may reflect freezing injury during winter to a certain extend. However, there were many factors related to freezing injury, including meteorological conditions, soil conditions, management measures and so on. Therefore, a deeper and more systematic study on freezing injury involving all factors as well as on the effect of freezing injury on winter wheat yield is needed in the future.