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SUMMARY:Measuring greenhouse gas emissions from cities
DTSTART:20121106T161500
DTEND:20121106T171500
DTSTAMP:20260510T062851Z
UID:52ef98fedab6fa97a824061938560f1cdc40a583686d60c1feaa569a
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Andreas Christen\, Department of Geography / Atmospheric
  Science Program\, University of British Columbia\, Canada\n\nA reduction 
 of anthropogenic greenhouse gas emissions (GHG) is on the agenda of many g
 overnments and unsurprisingly cities are a focus for emission reduction ef
 forts. To reduce GHG emissions in cities\, several approaches are discusse
 d and implemented. Those include switches in the energy supply systems\, c
 hanges in technology and more broadly sustainable urban planning and desig
 n strategies (e.g. land-use-mix\, density\, vegetation). Such strategies m
 ust be informed and guided by rigorous scientific evidence and simulations
 .\n\nThis ENAC seminar will present how modeled GHG emissions from an enti
 re urban ecosystem (including emissions from traffic\, buildings\, diffuse
  sources\, soils and uptake by vegetation) can be validated against or inf
 ormed by direct flux measurements in the atmosphere above an urban area. W
 e will focus on GHG flux measurements using eddy-covariance (EC) systems o
 n fixed micrometeorological towers although aerial platforms would be also
  possible. In particular\, the seminar talk will explain how emission fact
 ors of carbon-dioxide (CO2) and methane (CH4) can be constrained by a stat
 istical analysis of long-term EC flux measurements\, if the location and b
 ehavior of the emission source are known but their magnitude is not.  Thi
 s is achieved by combining EC flux measurements with a backward dispersion
  model and a geographic information system (GIS) of the known location of 
 emission sources. \n\nTo demonstrate the potential and limitations of the
  EC approach\, we will use data from a relatively uniform 4 km2 residentia
 l neighborhood in Vancouver\, BC\, Canada with about 6’000 detached hous
 es and 23’000 inhabitants. The neighborhood\, called ‘Vancouver-Sunset
 ’ offers a long-term dataset of continuous GHG flux measurements of CO2\
 , and CH4 on top of a 30m research tower. The urban ecosystem surrounding 
 the tower has been characterized by a combination of urban object classifi
 cations (buildings\, trees\, land-cover) automatically derived from Light 
 Detection and Ranging (LiDAR) and optical remote sensing data. Further\, s
 patial census data\, assessment data\, traffic counts\, building energy mo
 dels\, and measured soil and vegetation models determine the location of e
 mission (and uptake) processes and their expected magnitude over time. Mod
 eled GHG emissions in a GIS and directly measured GHG fluxes are brought i
 n agreement using a backward-dispersion model (source area model) to attri
 bute measured fluxes to a given weighted spatial subset of the urban surfa
 ce. This attribution is repeated for many time steps with changing source 
 area configuration (wind direction) and temporal characteristics of emissi
 ons (day-night\, weekday-weekend\, summer-winter) - which allows a statist
 ical optimization / attribution of emission factors to GHG sources of know
 n location but unknown intensity.\n\nThe presented results demonstrate tha
 t direct GHG flux measurements based on the EC approach - if sites are car
 efully chosen - are a promising approach to validate fine-scale urban emis
 sion inventories/models and can inform emission factors under realistic co
 nditions. EC flux measurements fill a gap on GHG emission data at intermed
 iate urban scales - between known emissions of selected elements of an urb
 an system (cars\, space heating systems\, individual buildings) and data a
 ssimilation modeling using atmospheric concentration measurements on regio
 nal to continental scales.
LOCATION:GR A3 32 http://plan.epfl.ch/?room=GR%20A3%2032
STATUS:CONFIRMED
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