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Urban flux towers

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Investigators: Erik Velasco

Description: Direct flux measurements to the atmosphere of greenhouse gases and heat at neighborhood scale.

Surface-atmosphere exchange of mass
and energy in urban environments

​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​CENSAM stopped activities on Dec. 2017. For updates and information contact to Erik Velasco (

The eddy covariance (EC) method has been widely used to investigate the surface–atmosphere exchange of energy, carbon dioxide (CO2), other trace gases (e.g., methane, olefins, toluene, benzene, acetone, etc.), and aerosols over natural ecosystems, such as forests, crops, grasslands, etc. Since the late nineties the EC method has also been used in urban environments. Until now, over 30 urban EC flux systems (i.e. flux towers) have been deployed, mostly in mid-latitude cities located in the northern hemisphere. Singapore and Mexico City have been the only (sub)tropical cities where EC flux measurements have been reported. Our team has participated in all short- and long-term initiatives in both cities.

Instrumentation installed at the top of these towers is able to directly measure the total exchange of energy and mass (including all major and minor anthropogenic and natural emission sources and sinks) within a sensor footprint that is usually representative of the local scale (i.e. hundreds of meters or similar to the size of a complete neighborhood).

cartoon urban_flux_tower bis.jpg

Since 2010 we have been measuring in collaboration with Prof. Matthias Roth (NUS-Geography) fluxes of CO2 and energy (sensible and latent heat, and solar radiation) from a low-rise neighborhood of Singapore. Results of these measurements have been used to investigate the potential of urban vegetation to offset the anthropogenic emissions of CO2. The energy flux data have been used to evaluate the performance of meteorological models, as well as to gain knowledge on the variables driving climatological phenomena, such as the urban heat island.

To learn more about Singapore's flux tower and get an updated list of publications visit the NUS Urban Climate Lab website.

In Mexico City we have measured fluxes of energy, CO2, selected volatile organic compounds and chemically-resolved aerosols as part of two large field campaigns in 2003 and 2006. More recently in 2011-2012, in collaboration with the Molina Center for Energy and the Environment (MCE2), the National Institute of Ecology and Climate Change (INECC) and the Air Quality Monitoring Network of Mexico City we deployed during 15 months a flux tower to measure fluxes of CO2 and energy. Results of these studies have been used to evaluate the accuracy of gridded emissions inventories, improve the performance of air quality models, and assess the efficiency of control measures and environmental regulations.

Lead researcher
- Erik Velasco (SMART, Singapore;
- Matthias Roth (NUS-Geography, Singapore)
- Luisa T. Molina (MCE2, USA)
- Armando Retama (SIMAT, México)
- Rodrigo Vargas (Univ. of Delaware, USA)
- Brian Lamb (WSU, USA)
- Shelley Pressley (WSU, USA)
- Hal Westberg (WSU, USA)
- Matthias Demuzere (KU Leuven, Belgium)
- Suraj Harshan (NUS-Geography, Singapore)
- Sok Huang Tan (NUS-Geography; now at MEWR, Singapore)
- Michelle Quak (NUS-Geography; now at URA, Singapore)
- et al.


(*partially supported by SMART through EV)


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