Temporal and spatial variations of high temperature in Ningxia wolfberry producing area, Northwest China from 1961 to 2023.

Better understanding the long-term and regional variation of summer high temperature weather in Ning-xia is of great significance for the cultivation, agricultural activities and high-quality development of Lycium barbarum industry. Based on the June-August meteorological data of 21 national meteorological observation stations in Ningxia from 1961 to 2023, we evaluated the long-term variations of average maximum temperature, extreme maximum temperature, number of hot days, heat wave frequency and maximum apparent temperature in summer, and analyzed the regional variations of hot weather after the abrupt change of trend. The results showed that the average maximum temperature of June, July, August in wolfberry producing area of Ningxia were 27.5, 29.2 and 27.4 ℃ from 1961 to 2023, respectively, and the warming rates were 0.39, 0.36 and 0.25 ℃·(10 a) ^-1, all of which had abrupt changes in the 2000s. The high temperature area after the mutation mainly concentrated in the middle and northern Ningxia producing area. The monthly extreme maximum temperature of June, July and August were 32.3, 33.7 and 32.5 ℃, respectively, which increased significantly at a rate of 0.30, 0.45 and 0.33 ℃·(10 a) ^-1. There was an abrupt change from 2002 to 2010, and most of the extreme maximum temperature in the middle and northern Ningxia wolfberry producing areas reached higher than 35 ℃ after the mutation. Accordingly, the number of hot days and heat waves showed an increasing trend, and the frequency of the two appeared the highest in July, and Wuzhong, Zhongning, Helan and other producing areas were greatly affected. The maximum apparent temperature increased significantly in summer, with the increase rates of 0.45, 0.41 and 0.31 ℃·(10 a) ^-1 in June, July and August. The abrupt change occurred around 2008, and the increase after mutation was 1.84, 1.77 and 1.54 ℃ compared with that before. Under the influence of wind speed and humidity, the average maximum apparent tempera-ture in June, July and August were 1.10, 2.42 and 2.29 ℃ higher than the average maximum temperature. Air temperature was the main factor driving the level of apparent temperature. Wind speed was a secondary factor in June to July, and relative humidity was a secondary factor in August. We should pay more attention to the influence of wolfberry high temperature stress caused by temperature change under the background of climate warming, and strengthen the ability of high temperature warning and defense.