Urban Emissions of CO2 from Davos, Switzerland: The First Real-Time Monitoring System Using an Atmospheric Inversion Technique

Abstract

Anthropogenic emissions from urban areas represent 70% of the fossil fuel carbon emitted globally according to carbon emission inventories. The authors present here the first operational system able to monitor in near-real time daily emission estimates, using a mesoscale atmospheric inversion framework over the city of Davos, Switzerland, before, during, and after the World Economic Forum 2012 Meeting (WEF-2012). Two instruments that continuously measured atmospheric mixing ratios of greenhouse gases (GHGs) were deployed at two locations from 23 December 2011 to 3 March 2012: one site was located in the urban area and the other was out of the valley in the surrounding mountains. Carbon dioxide, methane, and carbon monoxide were measured continuously at both sites. The Weather Research and Forecasting mesoscale atmospheric model (WRF), in four-dimensional data assimilation mode, was used to simulate the transport of GHGs over the valley of Davos at 1.3-km resolution. Wintertime emissions prior to the WEF-2012 were about 40% higher than the initial annual inventory estimate, corresponding to the use of heating fuel in the winter. Daily inverse fluxes were highly correlated with the local climate, especially during the severe cold wave that affected most of Europe in early February 2012. During the WEF-2012, emissions dropped by 35% relative to the first month of the deployment, despite similar temperatures and the presence of several thousand participants at the meeting. On the basis of composite diurnal cycles of hourly CO/CO 2 ratios, the absence of traffic peaks during the WEF-2012 meeting indicated that change in road emissions is potentially responsible for the observed decrease in the city emissions during the meeting.

A multi-model approach to monitor emissions of CO<sub>2</sub> and CO from an urban–industrial complex

“…Additionally, Angevine et al (2014) have shown that using an ensemble mean of model simulations with different meteorology does not necessarily lead to a better representation of plume transport and dispersion in a Lagrangian model for area sources. We therefore speculate that assimilating observed wind fields in WRF-Chem, as was done by Lauvaux et al (2013), could be more beneficial to improve the modelled wind fields and as such improve the plume transport. Furthermore, the model performance under stratified and low wind-speed conditions needs to be addressed, since removing these data can lead to biased emission estimates.…”

The first 1-year-long estimate of the Paris region fossil fuel CO<sub>2</sub> emissions based on atmospheric inversion

“…Consequently, there is an increasing deployment of urban CO 2 monitoring networks with the objective of quantifying city emissions through the atmospheric inversion approach (Boon et al, 2016;Duren and Miller, 2012;Lauvaux et al, 2013Lauvaux et al, , 2016Kort et al, 2013;McKain et al, 2012;Strong et al, 2011;Turnbull et al, 2015). Bréon et al (2015), upon which this study builds, recently reported first estimates of fossil fuel CO 2 emissions of the Paris urban area during a 2-month period.…”

The potential of satellite spectro-imagery for monitoring CO<sub>2</sub> emissions from large cities

“…Initial results are based on dedicated urban ground-based atmospheric CO 2 measurement networks (Breon et al, 2015;Lauvaux et al, 2013;Turnbull et al, 2015). There has been no attempt at using SCIAMACHY or GOSAT data at this scale due to the low resolution and precision of the SCIA-MACHY data or to the scarcity of the sampling by GOSAT.…”