近50年京津冀气候舒适度的区域时空特征分析

受气候变化影响,区域气候舒适期势必会发生不同程度的变化。从气候舒适性的视角出发,利用京津冀地区1966—2015年的170个观测站点50年逐日气象资料,以温湿指数、风效指数、着衣指数及其综合指数为气候舒适性的评价指标,统计分析区域气候舒适期的起止日期、天数及其年际间变化规律,揭示京津冀区域气候舒适度的时空变化特征,为区域人口合理分布和气候资源评价提供科学依据。此外,以日为时间尺度进行气候舒适期分析,有利于气候变化背景下区域间横向和区域内纵向的比较研究。结果显示:(1)京津冀气候舒适度指数近50年来的变化趋势基本相同,综合指数呈显著增加趋势;但各地间变幅存在一定差异,其中天津气候舒适度指数变化幅度最为明显,北京变化相对平稳。(2)从气候舒适度综合指数来看,京津冀地区气候舒适期年内分布呈"M"型,舒适期相对集中在4—5月、9—10月,舒适和较舒适等级的月累计日数均达到28 d以上,其中5月气候最为舒适,舒适等级日数最多,达到24—26 d;北京年平均舒适天数最多(100 d),天津最少(91 d)。(3)从单一气候舒适度指数来看,京津冀舒适和较舒适等级的初始日期大多呈显著的提前趋势;终止日期和天数大多略有增加,但变化趋势不显著。而综合指数显示,1966—2015年较舒适等级的初始日期变化最为显著,大约每10年提前3—4 d;天津和河北终止日期变化也达到显著水平,大约每10年推迟1—2 d,北京增加趋势不明显。(4)京津冀气候舒适期的空间分布显示,舒适等级的日数从西北向东南地区呈减少特征,河北北部舒适等级的年平均日数最多达115—120 d,东南部最少,不足90 d。

Spatial and temporal characteristics of the periods of climate comfort in the Beijing-Tianjin-Hebei region from 1966 to 2015

The periods of climate comfort have certainly changed over the last 50 years because of climate change. Based on daily climatic data from 170 observatories from 1966 to 2015, variations in the period of climate comfort in the Beijing-Tianjin-Hebei region over the last 50 years were examined in detail in terms of the temperature-humidity index (THI), wind-effect index (WEI), index of cloth loading (ICL), as well as the comprehensive comfort index (CCI). The start date, end date, and duration of comfortable days with annual variation characteristics were recorded so that analysis of spatial and temporal changes could be done. Evaluation of climate comfort is an important indicator of spatial distribution of the population, and assessment of climatic resources. This study on climate comfort period used daily climate data to precisely chart the intra- or inter- regional differences, especially under global climate change. Our study found:(1) In the past 50 years, the trend of change of the various comfort indices were the same for Beijing, Tianjin, and Hebei. The average annual CCI in the Beijing-Tianjin-Hebei region showed an obvious upward trend, while the various individual comfort indices showed variations among Beijing, Tianjin, and Hebei. The range of change was greatest in Tianjin, while the least change occurred in Beijing. (2) Analysis of time data showed the annual distribution of climate comfort appeared to be of the "M" type in the Beijing-Tianjin-Hebei region. By building the CCI, the comfortable period in the Beijing-Tianjin-Hebei region was concentrated mainly in the periods of April to May, and September to October, where there were more than 28 days a month graded as comfortable or less comfortable. Annually, the most comfortable period was in May, with 24-26 days graded as comfortable. Among Beijing, Tianjin and Hebei, the longest comfortable period per year occurred in Beijing, with an average of 100 days, followed by Hebei, with an average of 95 days, and the shortest comfortable period occurred in Tianjin, with an average of 91 days. (3) At the start date, as calculated by assessment of THI, WEI, and ICL, there was a significantly advanced tendency for comfortable and less comfortable grade days, whereas at the end date there was a slightly increased tendency for comfortable days, but this was not statistically significant. CCI showed that the start date of the less comfortable grade days varied greatly, advancing by 3-4 days per 10 years. The end date in Tianjin and Hebei increased at a rate of 1-2 days per 10 years, while this tendency in Beijing was not statistically significant during the 1966-2015 period of study. (4) Spatial distribution analysis showed the duration of comfortable days in the Beijing-Tianjin-Hebei region decreased from northwest to southeast. The longest duration of comfortable days was in northern Hebei, of which there was an average of 115-120 days per year, while the shortest duration was in southeast Hebei, where there was an average of less than 90 days.