Variations of high temperature from 1961 to 2019 in Liaoning Province, China

Better understanding of the changes in high-temperature would be helpful for improving the monitoring of hot extremes and mitigating their impacts towards a sustainable regional development. Based on the data of daily maximum temperature, relative humidity, and wind speed from 23 meteorological stations in Liaoning Province in summer (June to August) during 1961 to 2019, we analyzed the variations of daily maximum temperature (Tx), daily maximum apparent temperature (AT), and heat wave events (3 consecutive days ≥35 ℃). The effects of meteorological variables on daily maximum apparent temperature were examined by the grey relational analysis method. The results showed that the average Tx (AT) of all stations was 26.19 (27.35), 28.29 (31.13), and 28.14 (31.08) ℃, respectively, while the average trends in Tx (AT) was 0.17 (0.38), 0.20 (0.35), and 0.17 (0.28) ℃·(10 a)^-1, respectively, in June, July and August during 1961 to 2019. The average AT and its trends in each month were larger than the Tx. From June to August, there was significant negative correlation between Tx (AT) and its climate tendency rate, indicating that the range of warming in the area with low Tx and AT was larger than that in the area with high values. We should therefore pay more attention to the protection against high temperature in the low value area of Tx and AT in summer. From June to August, the average number of hot days with AT ≥ 35 ℃ was 0.85 d·a^-1, with an average increase rate of 0.20 d·(10 a)^-1. Hot days were signifi-cantly more in June and July than in August. The area with more hot days was mainly located in the west of Liaoning, and the area with less hot days was mainly located in the south and coastal areas. The number of heat wave events was 0.071 times per year, which was large in western Liaoning. There was no high temperature heat wave event in the southern and coastal areas of Liaoning. The correlation analysis showed that the AT in June was strongly associated with relative humidity, while AT in July and August had the closest relationship with Tx. Therefore, the importance of relative humidity on the monitoring and forecasting of high temperature and hot weather cannot be ignored.