Abstract:

Under global climate change, frequent extreme heat during summer maize growing season has brought great uncertainty to summer maize yield and attracted wide attention. The interannual and seasonal distribution characteristics of extreme heat during summer maize growing season in Haihe plain was systematically analyzed. The daily maximum temperature data at 26 meteorological stations in the study area from 1960 to 2019 were used to detect extreme heat events, and 35°C was taken as the extreme heat threshold of summer maize. Extreme heat characteristics, including the number and duration of extreme heat events, the number of extreme heat days and the extreme heat degree days during summer maize growing season were analyzed in this study. The results showed that the four extreme heat characteristics all showed an increasing trend from the northeast coastal area to the southwest inland area. The interannual variations of extreme heat characteristics during summer maize growing season from 1960 to 2019 had two obvious change points in 1972 and 1996, and these two change points divided the study years into three periods: strong, weak and strong. From mid June to early July, the number of extreme heat days was the biggest, accounting for 69.8% of the total extreme heat days during June to September. The interannual variation of extreme heat days from late June to late July were most similar with the interannual variation of extreme heat, and could be regarded as the main period affecting the variation of extreme heat during summer maize growing season. The results have certain significance for comprehensively grasping the spatial and temporal distribution characteristics of extreme heat in the study area and guiding the production of summer maize.

Key words: summer maize, extreme heat, Haihe plain, spatio-temporal, growing season