Analysis on Variation Characteristics of Diurnal Temperature Range in Xingtai of Hebei Province

Based on the daily average temperature,maximum temperature and minimum temperature data in Xingtai,Hebei province from 1954 to 2011,the variation characteristics of diurnal temperature range and its impact factors were analyzed. The results show:( 1) The annual diurnal temperature range in Xingtai had obvious decrease trend with inclining rate of-0. 683 ℃ /10 a in recent 58 years,and the average value of diurnal temperature range was 10. 9 ℃. In four seasons,the diurnal temperature range in spring was the largest and the smallest in summer. The diurnal temperature range in all seasons decreased clearly during 1954-2011,and the maximum declining rate was in winter and minimum in summer. The maximum monthly diurnal temperature range was in May and minimum in August,and in each month the decline trend was significant,but the maximum declining range was in January.( 2) There were 15 years and 4 to 7 years oscillations period for the annual diurnal temperature range in the past 58 years. The mutations of the annual diurnal temperature range occurred in 1972,1981 and 1995. The annual diurnal temperature range firstly increased,then decreased around the mutation points,and decreased in steps at the mutation points.( 3) The decline of diurnal temperature range was associated with the asymmetric variation of the minimum and maximum temperature. Furthermore,the annual diurnal temperature had significant positive correlation with sunshine hours and average wind speed and significant negative correlation with total cloud amount and vapor pressure,but had almost irrelevant with precipitation.( 4) The significant decrease of the diurnal temperature range in Xingtai would have disadvantage to crop yield and quality,but decrease the freezing injury to fruit trees in winter.