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Environ Sci Technol. 2002 Jul 15;36(14):3139-46.

Micrometeorological measurements of the urban heat budget and CO2 emissions on a city scale.

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  • 1Centre for Ecology and Hydrology, Edinburgh, Midlothian, Scotland.


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.

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