海河平原夏玉米主要生育期发生高温干旱并发事件的气候学分析

Climatological Analysis of Extreme Heat and Drought Concurrent Events in Main Growth Periods of Summer Maize in Haihe Plain

利用海河平原27个气象站1960-2019年逐日最高气温、降水数据,采用标准化降水指数识别干旱,百分位法确定高温阈值,利用Cramér-von Mises(CvM)突变检验、累积分布函数(CDFs)等方法分析夏玉米全生育期及各主要生育期(播种-拔节、拔节-开花、开花-成熟)不同阈值水平下的高温干旱并发事件长期演变特征及空间分布情况。结果表明:(1)夏玉米各主要生育期不同阈值水平的高温干旱并发事件发生范围均无长期变化趋势,在20世纪90年代存在显著突变,突变后发生范围明显大于突变前,特别是开花-成熟期并发事件发生范围最大且突变后增大最多;对于不同阈值水平,高温阈值下并发干旱事件的发生范围增大最明显。(2)夏玉米各生育期并发事件发生频率均为研究区西北部较高,并向东南部减少,发生频率较高的北部地区自突变后增加幅度也最大。海河平原近60a夏玉米主要生育期高温干旱并发事件在20世纪90年代存在显著突变,自突变后,并发事件发生范围及各站点发生频率均明显增多,开花-成熟期高阈值水平下并发事件增多尤为突出。

The simultaneous occurrence of different climatic events(e.g.,low precipitation and high temperatures)which means concurrent events,may cause significant impacts on the ecosystem and society.Maize is one of the main food crops in China,but extreme heat and drought concurrent events bring great instability to summer corn production,which has become important factors threatening food security.Based on daily maximum temperature and precipitation data from 27 meteorological stations in Haihe plain from 1960 to 2019,the Standard Precipitation Index(SPI)was used to identify drought and the extreme heat threshold was determined by percentile method.The Cramér-von Mises(CvM)mutation test and Cumulative Distribution Function(CDFs)were used to analysis long-term evolution characteristics and spatial distribution of extreme heat and drought concurrent events during different threshold levels in the whole growth period and main growth periods of summer maize(sowing to jointing,jointing to flowering,flowering to maturity).The results showed that:(1)the summer maize extreme heat and drought concurrent events were no long-term trend at all threshold levels of main growth periods.There was a significant mutation occurred in the 1990s.And the scope of occurrence after mutation was significantly larger than before mutation,especially the flowering to maturity concurrent events had the largest scope and increased the most after mutation.For different threshold levels,the scope of high extreme thresholds concurrent drought events was increased obviously.(2)The frequency of summer maize decreased at the whole periods from northwest to southeast in the study area.The concurrent events occurred at higher frequency in the north of the study area,and the increment was also greatest after mutation.The extreme heat and drought concurrent events during the main periods of summer maize in Haihe plain during nearly 60 years was significantly mutated in the 1990s.After the mutation,the range of concurrent events and the frequency at each stations have increased significantly,flowering to maturity as well as high threshold levels of concurrent events particularly.