上海中心城区二氧化碳通量特征分析

Study of carbon dioxide flux characteristics over central urban area in Shanghai

利用位于上海中心城区徐家汇站的涡动相关湍流通量资料,对该区域2012年12月至2013年11月二氧化碳(CO2)通量的时间变化、空间分布特征、年总排放量进行分析。结果表明:中心城区徐家汇为CO2通量的源区,CO2通量的日变化呈现与交通流量相对应的双峰现象,冬季的通量值普遍小于其他季节,尤其在早高峰时段更为明显。节假日CO2通量的早高峰效应并不明显,其峰值明显低于工作日,且有滞后的趋势。各方向CO2通量大小与其周边下垫面情况密切相关,夏季白天在商业建筑密集区和主要道路处,CO2通量明显高于其他季节。上海中心城区CO2通量的年总排放量为44.5 kg/(m^2·a),高于国内外其他城市的市中心或高密度住宅区的数值,这主要和观测时段相对偏晚、植被覆盖率偏低、周边高层建筑和主干道偏多有关。

Based on the eddy covariance turbulent flux data for a whole year from December 2012 to November 2013 in central urban area(Xujiahui)of Shanghai,the temporal and spatial distribution characteristics and annual emissions were analyzed.The results show that the Xujiahui central urban area is the source of CO2 flux.The diurnal variations of CO2 are typically characterized by two peaks,consistent with the traffic rush hour patterns.The CO2 flux in winter is smaller than that in the other seasons,which is more significant in morning traffic peak time.Moreover,the morning peak traffic effect in weekends is obviously less than that in weekdays,and it shows a lagging trend.The spatial variation patterns of CO2 flux are mainly determined by the surface characteristics.Due to the large fraction of commercial buildings and major roads,the CO2 flux in the daytime of summer is much larger than that in the other seasons.The total annual CO2 emission from the neighborhood around the flux tower is about 44.5 kg/(m^2·a),which is higher than that in other cities worldwide due to the relatively late observational period,low vegetation coverage,and the more surrounding of high-rise buildings and major roads.