Abstract:

Based on the data such as daily maximum temperature, precipitation from 20:00 to 08:00 the next day and from 08:00 to 20:00, air relative humidity at 14:00, and wind speed at 14:00 observed at 17 national surface meteorological stations in Shijiazhuang from May 20 to June 15 during 1972−2025, this study analyzed the temporal and spatial variation characteristics of dry−hot wind using statistical methods, and it also clarified the correlation between temperature, humidity and wind speed on annual typical dry−hot wind day. The results showed that: (1) the number of dry−hot wind days in Shijiazhuang increased at rates of 0.6d·10y⁻¹ from 1972 to 2025 and 2.1d·10y⁻¹ from 2000 to 2025. The decadal average of dry-hot wind days was the lowest in the 1990s (8.4d·y⁻¹) and the highest in the 2020s (14.8d·y⁻¹). Moderate dry−hot wind days from 1972 to 2025 and severe dry−hot wind days from 2000 to 2025 showed a significant increasing trend (P<0.05). (2) Among the 17 stations in Shijiazhuang from 1972 to 2025, moderate dry−hot wind events occurred with the highest frequency, mainly concentrated from June 3 to 15. Moderate dry−hot winds occurred frequently throughout the first and second pentads of Harvesting and Sowing, and its days increased year by year in the second and third pentads of Approaching Fullness. (3) Abrupt changes were detected in the total number of dry−hot wind days as well as the days of mild, moderate and severe dry−hot winds in Shijiazhuang from 1972 to 2025. The most recent abrupt change relative to 2025 was an abrupt increase for all categories: mild dry−hot wind days increased abruptly in the late 1980s, while the others increased abruptly after 2016. (4) The decadal average number of total dry−hot wind days and that of mild, moderate and severe dry−hot wind days at the 17 stations in Shijiazhuang from 1972 to 2025 ranged from 4.7 to 8.3, 0.6 to 1.4, 2.4 to 4.3 and 1.1 to 2.6d·y⁻¹, respectively. All showed high−value areas in the southwestern parts of the study region, and the spatial distribution of decadal average moderate dry−hot wind days was basically consistent with that of the decadal average total dry−hot wind days. (5) Annual typical dry−hot wind days in Shijiazhuang from 1972 to 2025 mainly occurred from June 4 to 15 (accounting for 75.9%), with the highest frequency in the first pentad of Harvesting and Sowing, followed by the second pentad of Harvesting and Sowing, and the distribution of affected stations showed regional characteristics (affecting no less than 9 stations per day). On these days, the relative humidity at 14:00 was negatively correlated with both the daily maximum temperature and the wind speed at 14:00, and the correlation between the relative humidity at 14:00 and daily maximum temperature passed the significance test (P<0.05). The results of this study can provide scientific guidance for the management decision−making of winter wheat in Shijiazhuang during the grain−filling and maturation stages, as well as provide meteorological support to ensure high grain yield and increase farmers′ income.

Key words: Solar term, Dry?hot wind, Temporal?spatial variation characteristics, Correlations between temperature, humidity and wind speed, Shijiazhuang