Regional warming induced by urban surface expansion in Shanghai

如何量化城市下垫面扩张对增暖的贡献,减小气候变化评估和预估的不确定性,是城市化影响研究中的一个难点。本文基于卫星遥感得到的反映过去三十多年城市下垫面扩张的土地利用数据,开展高分辨率的嵌套数值试验,量化了城市下垫面扩张在上海不同空间尺度上对增暖的贡献。城市下垫面扩张对整个区域增暖的贡献在19%左右,而城市下垫面扩张区(N2U)的贡献比一直是城市下垫面区域(U2U)要高得多,分别在42%和17%左右。同时城市下垫面扩张对最低温度的增加强于最高温度的变化,日较差减小,尤其在城市下垫面扩张区更加显著。

To detect the impacts of urban surface expansion on surface air temperature at 2-m（SAT） in Shanghai, China, nested numerical integrations based on satellite-derived urban data between the 1980 s and 2010 s were performed using the Weather Research and Forecasting（WRF） model. Urban surface expansion induced an annual-averaged warming of 0.31 °C from 1980 to 2016 across the whole of Shanghai, showing the greatest intensity between 2010 and 2016. The values were 0.36, 0.78, and 0.75 °C over grids that were classified as urban in both time periods（U2 U）, landuse grids that changed from non-urban to urban（N2 U）, and urban areas（including U2 U and N2 U）, respectively, and revealed weak warming over the inner-ring areas because the urban surfaces had been there since the 1980 s, whereas warming areas were coincident with the outward expansion of the urban surface. Meanwhile, marked seasonal variations could be detected, which were greater in spring and summer but less in autumn and winter. The approximately homogenously distributed SAT maximum（weaker） and heterogeneously SAT minimum（stronger） contributed to the decreased diurnal temperature range. Regional warming induced by urban surface expansion was approximately 0.12 °C per decade, which accounted for 19% of the overall warming across the whole of Shanghai. The values were 0.11 °C per decade and 0.39 °C per decade over U2 U and N2 U, which accounted for approximately 17% and 42% of the overall warming, respectively, and resulted in approximately 41% of the overall warming over urban areas.