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

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/(m²·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.