Prediction of high temperature disaster risks during summer maize flowering under future climate warming background in Henan Province

To predict the risk of high temperature disasters during the summer maize flowering period under future climate change scenarios, a high temperature risk index was established based on the long-term observational data of the summer maize booting period from 19 agro-meteorological observational stations in Henan Province and future climate change scenarios (representative concentration pathways, RCPs). Based on the high temperature risk index, the spatio-temporal characteristics and risk of high temperature disasters during the summer maize flowering period were analyzed in Henan Province. The climate change scenarios (RCPs) included the baseline climate scenario (RCP-rf, 1951-2005) and two future climate change scenarios with moderate emission (RCP 4.5) and high emission (RCP 8.5) during 2006-2050. The summer maize flowering period at each site was defined as the period from the booting stage to 7 days after booting, and then, it was interpolated into the whole province to match the gridded date of climate scenarios. The maximum temperature of higher than 32℃ and 35℃ during flowering were used as the threshold for occurrence of light and heavy high temperature disasters. A comprehensive risk index was successfully established, and the risk level was divided by integrating high temperature frequency and accumulation of temperature higher than 32℃ and 35℃ during the summer maize flowering period. The results showed that under the RCP-rf scenario, the high temperature frequency during the summer maize flowering period was 20.5%-81.0% (≥ 32℃) and 3.9%-51.9% (≥ 35℃). Compared with the baseline, the frequency of high temperature days of more than 32℃ during the summer maize flowering period increased by 9.1% (RCP 4.5) and 11.0% (RCP 8.5), and that of higher than 35℃ increased by 8.7% (RCP 4.5) and 8.3% (RCP 8.5). Under the RCP-rf scenario, the accumulation of temperature higher than 32℃ during the summer maize flowering period ranged 48.5-200.9℃·d, and that of higher than 35℃ ranged 9.8-138.5℃·d. Compared with the baseline, the accumulation of temperature higher than 32℃ during the summer maize flowering period increased by 25.4℃·d (RCP 4.5) and 25.6℃·d (RCP 8.5); and that of higher than 35℃ increased by 25.8℃·d (RCP 4.5) and 31.4℃·d (RCP 8.5). According to the comprehensive risk analysis of high temperature during the summer maize flowering period, the high-risk zones under RCP-rf scenario were distributed in the eastern and northern areas, which adjacent to Xinxiang, Zhengzhou, Xuchang, Luohe, and Zhoukou, except Shangqiu, accounting for approximately 30.1% of the main summer maize planting area. The high-risk areas covered most of the areas in the east of Luoyang and Nanyang, accounting for 63.4% of the main area of summer maize planting under the RCP 4.5 scenario and 76.3% of the main area of summer maize planting under the RCP 8.5 scenario.