1971—2012年平凉市霜冻变化特征分析

Characteristics of Frost in the Pingliang City During 1971-2012

以≤0℃地面最低气温作为霜冻指标，利用平凉地区7个气象观测站1971—2012年的逐日地面最低气温资料，采用现代气候诊断方法，分析了初、终霜冻和无霜冻期的变化特征。结果表明：在近42a间，平凉市初霜冻发生频率减小，终霜冻发生频率增加，初、终霜冻日数呈减少趋势；平均初霜冻日呈推迟变化趋势，终霜冻日呈提早变化趋势，无霜期呈延长变化趋势，其气候倾向率均〉2d／10a，并均通过a=0．05的显著性检验；平凉地区初霜冻日普遍推后1～5d，终霜冻日普遍提前1～5d，无霜期普遍延长1-9d。平凉各地霜冻受灾程度差异较大，灵台和庄浪在受灾人口、直接经济损失和农业经济损失方面受灾较重。

Authors defined the frost processes with zero degrees centigrade or lower temperature, based on the method of modem climate diagnosis and daily ground minimum temperature data from 1971 to 2012 in Pingliang , analyzed the climatic features of the first/last frost dates and frost-free period changes. Results show that the first frost clays showed a trend of decrease, while frost-free period was lengthening during the past 42 years. The frequency of the first frost events was decreased, but the frequency of the last frost events was increased. It＇s found that the first frost dates postponed, while the last frost dates occur earlier, leading to the significant lengthening of frost-free period in Pingliang . The climate tendency rate of the first frost date, the last frost date and frost-free period were all more than 2 d/10 a, and have passed the test of significance of a= 0.005. It can be seen from the linear change trend that the first frost date has 1 to 5 days delay, the last frost date was 1 to 5 days ahead of time and the frost-free days prolonged 1 to 9 days. The frost disaster degree was different in Pingliang. There were heavier direct economic losses and more ool3ulations affected at Lingtai and Zhuanglang.