西安地区近50年极端气温变化研究

摘要

为了揭示西安地区近50年极端气温的变化和可能造成的灾害，本文根据1959—2008年间的气象数据，利用线性倾向估计法、Mann-Kendall突变检验法、主成分分析法以及相关性分析法，研究了西安地区年最低气温、年最高气温、暖夜、暖日、夏天日数、热夜日数、冷夜、冷日、霜日、冰日的变化特点、趋势以及周期。结果表明，西安地区1959—2008年间气温总体呈上升趋势，尤其暖夜日数上升最明显，速率为18.82 d∙10a−1。霜日、冰日、冷夜呈下降趋势，下降速率分别为0.5 d∙10a−1、6.45 d∙10a−1和4.22 d∙10a−1。西安地区1959—2008年间夏天日数、热夜日数、暖日日数、暖夜日数呈上升趋势，上升速率分别为2.35 d∙10a−1、5.38 d∙10a−1、6.48 d∙10a−1、18.82 d∙10a−1。极端高温呈先下降后上升趋势，极端低温呈略上升趋势。西安地区1959—2008年间极端气温存在突变，突变主要发生在1990年代，夏日日数和暖日日数的突变发生在2000年代。暖指数的增加是西安市1959—2008年间气温呈上升趋势的主要表现。小波分析显示西安地区极端气温普遍存在27 a左右的主控周期，极端最高气温、夏日、暖日、冷夜、冷日、霜日、冰日存在15 a左右的振荡周期。极端暖指数增加和极端冷指数的减少表明高温灾害与旱灾发生的机率可能增大，需要做好防范工作。%In order to analyze the variational characteristics of extreme temperature and disasters in Xi'an area, meteorological data from 1959 to 2008 which contains daily average temperature, the highest temperature and lowest temperature, methods of linear fitting, Mann-Kendall examination, principal component analysis and correlation analysis were comprehensive employed to analyze each year's variation trends, mutation and the oscillation period of extreme temperature indicators, such as the extreme minimum temperature, extreme maximum temperature, warm nights and warm days, summer days and hot nights, cold nights, cold days, frost days, ice days. The results showed that: the overall temperature of Xi'an area from 1959 to 2008 had an upward trend, especially warm nights increased signiifcantly at 18.82 d∙10a−1 rate. Frost days, ice days, cold nights had downward trends, the decline rate were 0.5 d∙10a−1, 6.45 d∙10a−1 and 4.22 d∙10a−1 respectively. Summer days, hot days, warm days and warm nights of Xi'an area rised from 1959 to 2008, the rate were 2.35 d∙10a−1, 5.38 d∙10a−1, 6.48 d∙10a−1, 18.82 d∙10a−1 respectively. The extreme maximum temperature increased firstly and then decreased, the extreme minimum temperature had a slightly rising trend. From 1959 to 2008, extreme temperature mutation mainly occurred in the 1990s, while warm days and summer days mutation occurred in the 2000s. The increasing trend of temperature from 1959 to 2008 was mainly due to warm indices. Wavelet analysis showed that extreme temperatures of Xi'an area had around 27 a master cycle, extreme maximum temperature, summer days, warm days, cold nights, cold days and ice days had about 15 a oscillation. Both the increasing number of extreme warm indices and the reducing number of extreme cold indices would increase the probability of high temperature and drought disasters, and needed some preventive work.