邢台市近57年四季长短和极端气温变化特征分析

Change Characteristics of Season Length and Extreme Temperature of Xingtai City in Recent 57 Years

在全球气候变暖的背景下,近些年邢台气温明显升高,使得邢台市四季的起止时间和长度发生了明显的改变。通过分析多种季节划分方法,根据邢台市的气温分布特点,定义了适用于邢台市的四季划分方法,通过分析四季的变化,结果显示:①邢台四季分明,就常年平均而言,冬季最长,其次是夏季,秋季和春季长度很相近,秋季略短。②过去57年里,邢台各季节的长度和起止时间都发生了明显的变化,特别是自21世纪以来,这种变化速度明显加快。最主要的变化特点为,春季发生的时段向前移了近13 d;夏季明显变长,开始时间变化不太明显,结束时间推后;秋季的发生时段变化不明显;冬季持续时间明显缩短,比20世纪90年代缩短了10 d。③采用候温法和节气法划分的四季开始日,二者在春、夏、秋季存在明显差异,而冬季比较接近。日极端最低气温的增温幅度明显高于日极端最高气温的增温幅度,且日极端最低气温<3.0℃的天数(即霜日)明显减少、日最高气温>35℃的天数(即高温日数)变化不明显。

In the context of global warming,the temperature in Xingtai increased significantly in recent years,which brought obvious changes to the start and end dates and length of four seasons.According to the temperature characteristics of Xingtai,the method of marking off the four seasons which adapted to Xingtai had been defined.As indicated by the results,① Xingtai had four distinctive seasons,winter,in average,was the longest,then followed by summer,the length of autumn and spring was basically the same with slightly shorter autumn.② In the past 57 years,both the length and the start and end dates of each season in Xingtai changed,especially after 21st century.Spring moved ahead approximately by thirteen days,summer became longer with delayed end time;the start and end date of autumn did not change obviously;winter was shorter than 1990s by 10 d.③ The start and end dates of spring,summer and autumn marked by the methods of pentad temperature and solar term were different,while that of winter marked by those two methods were close.The rising range of daily minimum temperature exceeded that of daily maximum temperature.The numbers of cold days with daily minimum temperature below 3 ℃（frost days）reduced,but there was no obvious change in the numbers of hot days with daily maximum temperature above 35 ℃.