Micrometeorological measurements of the urban heat budget and CO2 emissions on a city scale.
Direct measurements of urban CO2 emissions and heat fluxes are presented, made using the eddy covariance technique. The measurements were made from the top of a tower, approximately 65 m above the street level of Edinburgh, Scotland, and the fluxes are representative of footprint source areas of several square kilometers. The application of a stationarity test and spectral analysis techniques shows that at this height, the stationarity criterion for eddy covariance is fulfilled for wind directions from the city center for 93% of the time, while for other wind directions this declines to 59%, demonstrating that pollutant fluxes from urban areas can be measured. The average CO2 emission from the city center was 26 micromol m(-2) s(-1) (10 kt of C km(-2) yr(-1)), with typical daytime peaks of 50-75 and nighttime values of 10 micromol m(-2) s(-1). The correlation between CO2 emission and traffic flow is highly significant, while residential and institutional heating with natural gas are estimated to contribute about 39% to the emissions during the day and 64% at night. An analysis of the energy budget shows that, during the autumn, fossil fuel combustion within the city contributed one-third of the daily anthropogenic energy input of 3.8 MJ m(-2) d(-1), with the remainder coming from other energy sources, dominated by electricity. Conversely, the total energy input in late spring (May/June) was found to be approximately half this value.
Centre for Ecology and Hydrology, Edinburgh, Midlothian, Scotland. en@ceh.ac.uk
Eiko
E
Nemitz
Kenneth J
KJ
Hargreaves
Alan G
AG
McDonald
James R
JR
Dorsey
David
D
Fowler
D000393:Air Pollutants / Q000032:analysis*; D002245:Carbon Dioxide / Q000032:analysis*; D002947:Cities; D004784:Environmental Monitoring; D006798:Housing; D008685:Meteorological Concepts; D012621:Seasons; D013696:Temperature; D001335:Vehicle Emissions / Q000032:analysis; D014919:Wind
D000393:Air Pollutants; D001335:Vehicle Emissions; D002245:Carbon Dioxide