邢台市气温日较差的变化

利用1954—2011年邢台市逐日平均气温、最高气温和最低气温资料，对邢台市气温日较差的变化特征及其影响因子进行了分析。结果表明：（1）近58a来，邢台市年平均气温日较差为10．9℃，呈明显下降趋势，变化速率为-0．683℃／lOa；四季平均气温日较差中，春季最大，夏季最小，且均呈下降趋势，其中冬季下降幅度最大，夏季最小；1—12月气温日较差中，5月最大，8月最小，均呈显著下降趋势，1月气温日较差下降幅度最大。（2）年气温日较差在近58a存在15a的低频振荡周期和4～7a的高频振荡周期，并在1972、1981、1995年发生突变，在突变点前后，年平均气温日较差均表现为增加珲仃减少趋势，且年气温日较差在突变年呈阶梯下降趋势。（3）最低、最高气温非对称的变化是气温日较差下降的直接原因。另外，年气温日较差与日照时数和平均风速呈显著正相关，与总云量、水汽压呈显著负相关，与降水量几乎不相关。邢台市气温日较差显著减小，对各类作物的产量、品质有不利影响，但冬季气温日较差的下降减少了果树冻害发生。

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 -O. 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 min- imum 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 de- creased around the mutation points, and decreased in steps at the mutation points. （3） The decline of diurnal temperature range was as- sociated 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 Xing- tai would have disadvantage to crop yield and quality, but decrease the freezing injury to fruit trees in winter.