近60a长三角地区极端高温事件变化特征及其对城市化的响应

基于长三角地区1951~2014年56个国家级气象站点逐日气温记录资料,通过计算极端高温事件相关指标(极端最高温TXx,极端最低温TNn,高温日数Htd和低温日数Ltd),利用GIS空间分析技术和Mann-Kendall时间趋势分析方法分析了长三角地区近60 a极端高温事件的空间分异特征和时间变化趋势,并探讨了城市化发展对区域极端高温事件时空变异的影响。结果表明:(1)长三角地区极端高温事件指标均表现为一定的上升趋势,极端低温指标(TNn和Ltd)线性变化趋势比极端高温指标(TXx和Htd)更为显著,变化趋势最显著的地区集中在经济和城市化水平较高的城市及周边地区(如上海、杭州等)。(2)极端高温指标(TXx和Htd)多年平均总体表现为南高北低,西高东低的趋势,而极端低温指标中TNn多年平均为由中部向南北两侧降低,Ltd多年平均呈现自中部向南北南侧增多的趋势。(3)从1990~2000到2000~2010年,城市化对极端高温事件的影响增强,快速城市化对北部城市极端高温事件的影响高于南部城市。

CHARACTERISTICS OF EXTREME HEAT EVENTS VARIATIONS AND THEIR RESPONSE TO URBANIZATION IN YANGTZE RIVER DELTA REGION IN RECENT SIXTY YEARS

Based on daily temperatures data at 56 national meteorological stations in the Yangtze River Delta region during 1950 to 2014, the extreme heat events indices (extreme maximum temperature TXx, extreme minimum temperature TNn, high temperature days Htd and low temperature days Ltd) were calculated to explore the temporal and spatial distribution characteristics of extreme heat events in the region of the Yangtze River Delta for the past 60 years with the aid of GIS spatial analysis technology and Mann-Kendall trend analysis method. Furthermore, their intrinsic relation with urbanization was also studied in this paper. The results showed that:(1) Extreme heat events indices of Yangtze River Delta were all characterized by a rising trend. The linear trend of extreme low temperature indices (TNn, Ltd) was more significant than that of extreme high temperature indices (TXx, Htd). In addition, trend of extreme heat events indices of cities with higher level of economy and urbanization was the most significant. (2) Extreme heat events indices were heterogeneously distributed in the region of the Yangtze River Delta. Multi-year average of extreme high temperature indices (TXx, Htd) was high in southern and western area while relative low in northern and eastern area in this region. For extreme low temperature indices, multi-year average for TNn descended from the central to the north and south on both sides. On the contrary, multi-year average for Ltd was gradually increasing from the central to the north and south on both sides. (3) The impact of urbanization on TXx was more important than TNn. From the decade of 1990-2000 to the decade of 2000-2010, the impact of urbanization on extreme heat events indices has been enhanced with a larger influence on northern cities rather than southern ones.