陕西榆林地区1954—2013年极端气温变化特征

Extreme Temperature Changes from 1954 to 2013 in Yulin,Shaanxi,China

对1954—2013年横山站、榆林站、绥德站的每日气象资料,运用线性拟合及累积距平、Mann-Kendall突变检验、主成分分析和Morlet复数小波等方法对WMO发布的10种极端气温指数进行了计算和分析。结果表明:榆林地区近60年极端最高气温、极端最低气温都呈上升趋势,冰日天数、霜日天数、冷夜天数、冷日天数呈下降趋势,夏日天数、热夜天数、暖夜天数、暖日天数呈现稳步上升趋势。近60年,榆林市极端气温的变化存在明显的阶段特征,并有突变现象发生。各指数的突变主要发生在20世纪90年代。暖指数的变化是榆林地区近60年气温呈上升趋势的主要原因。榆林地区冬春季气温升高是年平均气温上升的主要原因。33a左右的周期是10个指数比较稳定的周期,共同反映榆林地区极端天气的周期规律。极端暖指标在未来持续上升,极端冷指标则持续下降。研究区极端高温天气增加,会导致旱灾等极端天气增加的概率,并对森林防火产生一定的压力。极端低温天数的减少导致易发生森林和草原的病虫灾害,应做好预防工作。

Using the daily temperature data of weather station of Hengshan,Yulin and Suide from1954 to2013,adopting the linear fitting,accumulative anomaly,Morlet complex wavelet analysis,we calculated and analyzed ten kinds of extreme temperature indices released by WMO.Results indicated that the extreme maximum temperature and extreme minimum temperature in Yulin in last 60 years have a escalating trend,but the ice day,frost day,cold night,cold day number decreased,and summer day,hot night,warm night,warm day present steady rising trend.In the past 60 years,the change of extreme temperature in Yulin had obvious change characteristics in phase and the mutation phenomenon.The mutations of the extreme temperature and cold and warm indices mainly occurred in1990 s.The variation of warm indices is the main reason why the temperature of Yulin rose in the last 60 years.The increasing of temperature in spring and winter is the main reason that annual average temperature rose.The 33 a cycle is a relatively stable one for the ten kinds of indices in Yulin.Warm extremes and annual temperature range would keep rising while cold extremes would decrease.In the study area,increasing of the extreme high temperature days would have enhance chance of extreme weather such as drought,and will have a pressure on prevention of forest fires.Reducing of extreme low temperature days prone to forest and grassland pests and diseases.