中国沿海城市热浪时空特征与人口暴露研究

Spatial and Temporal Characteristics and Population Exposure of Heat Waves in China’s Coastal Regions

沿海区域既是陆地向海洋延伸的陆海相互作用最强烈的地带,又是受径流、潮汐和人类活动与气候变化作用多重影响的地球表层自然空间单元。结合2003~2018年度精细时间分辨率的近地表气温和地表温度产品,系统对比研究中国沿海城市热岛和热浪的时空分布格局及其协同作用。研究表明:①中国沿海地区极端高温事件呈现强度增大、持续时间增长的趋势。具体表现为在夏季城市热岛强度均高达2.25°C以上,整个沿海区域基于地温的平均热浪频次为24.59次,基于气温的热浪频次为16.33次,分别占全年热浪频次的90.81%和96.68%;②城市热浪频次与城市热岛强度在沿海的暖温带与亚热带地区呈现显著正相关,且在暖温带地区最为明显。平均地表温度增加1°C能够导致热浪事件平均增加两次。其中,暖温带的热浪频次在三大区域中增加速率最快,基于地温和气温的热浪频次复合增长率均超过5%;③从2003年到2018年,中国沿海区域城区人口增加了59%,而受高温热浪的人数增加近370%,超过总城市人口的5%(约4000万人)。我国沿海地区的城市热环境虽然与海域厄尔尼诺和拉尼娜现象呈现时空上较为一致的分布,然而城市总体变化与人口增长如何推动不同区域高温热环境模式的变化,仍待亟需更长时序、高时空分辨率的数据进一步进行讨论分析。

China's coastal areas are not only the most strongly interacting zones extending from land to sea,but also the natural spatial units on the surface of the earth affected by runoff,tides and the effects of human activi⁃ties and climate change.In this paper,using with the 2003~2018 high quality temporal resolution Land Surface Temperature(LST)and Near Surface Air Temperature(NSAT)products,the spatial and temporal distribu⁃tion pattern and synergy of urban heat islands and urban heat waves in coastal cities in China are systematically compared.The results show that:(1)Extreme high temperature events in China's coastal regions show a trend of increasing intensity and duration.Specifically,the intensity of urban heat islands in summer is as high as 2.25℃,the average heatwave frequency based on ground temperature in the entire coastal area is 24.59 times,and the temperature-based heat wave frequency is 16.33 times,accounting for 90.81%and 96.68%of the annu⁃al heat wave frequency,respectively;(2)The frequency of urban heat waves and urban heat island intensity is significantly positively correlated in the North Temperate Zone and North Subtropical Zone along the coast,and is most obvious in the North Temperate Zone.An increase of 1°C in average LST can lead to an average in⁃crease in heat wave events twice.Among them,the heat wave frequency in the North Temperate Zone in⁃creased the fastest in the three major regions,and the compound growth rate of heat wave frequency based on LST and NSAT exceeded 5%;(3)From 2003 to 2018,the urban population of China's coastal regions in⁃creased by 59%,and the number of people affected by heat waves increased by nearly 370%,exceeding 5%of the total urban population(about 40 million people).Although the urban thermal environment in China's coastal regions and the El Niño and La Niña phenomena in the sea show a more consistent distribution in time and space,how the overall urban change and population growth promote the change of high temperature and ther⁃mal environment patterns in different regions still need to be further discussed and analysed using longer time se⁃ries and high spatial and spatial resolution data.