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contact:
dublin energy lab,
focas institute,
dublin institute of technology,
dublin 8,
ireland.

t/ +353 1 402 7912
f/ +353 1 402 7904

e/ dublinenergylab@dit.ie

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Energy Balance & CO2 Fluxes :  Urban Climate Observation Site

As part of an ongoing project with DIT partnering NUI Maynooth and UCD, a suite of instruments is deployed on the roof of DIT Kevin St measuring net radiation (solar and terrestrial), wind velocity in three dimensions (u,v and w), air temperature, humidity, the turbulent fluxes of sensible heat (H) & latent (LE), and atmosphere concentrations of CO2 and H2O. Dublin can now add its name to this small, but growing, international research effort to measure energy balance and CO2 fluxes in the urban environment.

The radiation sensor measures total energy (Q*) within the local-scale climate system, taking into account in-coming and reflected solar radiation and incoming and out-going terrestrial radiation. The magnitude of Q* on any given day will determine the amount of energy available for (1) evaporating water and (2) for heating the atmosphere, these energy fluxes are known as latent (QE) and sensible (QH) heat. One of the outputs is the diurnal pattern of the turbulent fluxes of LE and H. Another output is the CO2 flux and turbulence. Turbulence is reliant upon solar energy inputs that drive vertical temperature gradients—as a result night time turbulence is significantly lower than during the day. Fluxes of CO2 are influenced by (1) the form (i.e. the presence of vegetation) and (2) the function of a city (i.e. the timing of the working week and the associated traffic flow). Large peaks in CO2 coincided with the morning rush hour, this pattern is less evident at weekends when traffic flow is reduced. In summer fluxes tend to be lower as a result of benign weather conditions and reduced fuel consumption. Winter on the other hand sees increased emissions in response to higher heating demands and the reduced carbon storage capacity of vegetation. The magnitude of the flux will also be influenced by turbulence—strong turbulence will serve to mix atmospheric concentrations of CO2 into a deeper layer of the atmosphere hence lowering the flux.

kevin street observatory

Long term datasets from sites such as this one in Kevin street will be important for parameterising and validating urban climate models worldwide, in addition to providing urban dwellers and policy makers with local-scale, high-resolution climate information.


Contact:
Keith Sunderland
School of Electrical Engineering Systems
e: keith.sunderland@dit.ie
ph: +353-1-4024882