Effects of urban density on carbon dioxide exchanges: Observations of dense urban, suburban and woodland areas of southern England

Abstract

Anthropogenic and biogenic controls on the surface-atmosphere exchange of CO2 are explored for three different environments. Similarities are seen between suburban and woodland sites during summer, when photosynthesis and respiration determine the diurnal pattern of the CO2 flux. In winter, emissions from human activities dominate urban and suburban fluxes; building emissions increase during cold weather, while traffic is a major component of CO2 emissions all year round. Observed CO2 fluxes reflect diurnal traffic patterns (busy throughout the day (urban); rush-hour peaks (suburban)) and vary between working days and non-working days, except at the woodland site. Suburban vegetation offsets some anthropogenic emissions, but 24-h CO2 fluxes are usually positive even during summer. Observations are compared to estimated emissions from simple models and inventories. Annual CO2 exchanges are significantly different between sites, demonstrating the impacts of increasing urban density (and decreasing vegetation fraction) on the CO2 flux to the atmosphere.

Diurnal Variation of CO₂ Flux in an Urban Area of Tokyo

“…6). The weekday/holiday contrast is consistent with the results in London and Swindon, UK (Ward et al 2015), and in Lodz, Poland (Pawlak et al 2015) although the contrast in Lodz is not evident in winter likely due to similar use of domestic heating regardless the day of week. The diurnal pattern and weekday/holiday difference, which differs site to site, should the attributed to those of human activities in the flux footprint.…”

“…Having two peaks is consistent with several findings, e.g. in Melbourne, Australia (Coutts et al 2007), Firenze, Italy (Matese et al 2009), Swindon, UK (Ward et al 2015), Lodz, Poland (Pawlak et al 2015) although the peaks are small, but contrasts with the single, small daytime peak found in London, UK (Helfter et al 2011;Ward et al 2015). Here, winter has the largest amplitude diurnal variation, summer the least.…”

“…vegetation than that of Kugahara area. Synthesis comparison of urban sites in world-wide (Nordbo et al 2012;Ward et al 2015) showed that the annual total CO 2 flux increases as the vegetation cover decreases. In 8 months denoted with shade in Fig.…”

“…These studies, however, focused on seasonal variations, not diurnal-scale variations. Revealing the controlling factors of diurnal scale variations is still limited (Velasco et al 2009;Ward et al 2013;Ward et al 2015;Lietzke et al 2015).…”

Evaluation of Urban Local-Scale Aerodynamic Parameters: Implications for the Vertical Profile of Wind Speed and for Source Areas

“…2a) are used, where prior analyses have been undertaken (e.g. Kotthaus and Grimmond 2014a, b;Björkegren et al 2015;Ward et al 2015). Instrumentation at the Strand campus of King's College London (KCL) has been mounted on towers upon the King's building (KSK), the Strand building (KSS), and to the west on the Strand building (KSSW) ( Table 3).…”