CERC — Environmental Software and Services

Atmospheric boundary layer and Urban heat island

ADMS Temperature and Humidity modelling system

The ADMS Temperature and Humidity modelling system has been developed to assess at high spatial resolution the spatial variation of temperature over complex urban areas. The system consists of two components:

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  • A land use model in which the temperature perturbations to the mean temperature are related to the spatial variation of surface type and building morphology; the land-use features are defined in terms of the following: surface roughness, albedo, thermal admittance, and parameters representing surface resistance to evaporation and building volume; and
  • An anthropogenic heat model, which allows for the dispersion of the heat emitted from anthropogenic sources. The hourly variation of heat generated from sources such as buildings and traffic can be modelled at a high resolution (tens of metres).

The system has a number of applications, including the assessment of the effect of new building developments on the local climate, and investigations into climate change mitigation scenarios, such as cool roofs and green roofs.

Learn more

  • Researchers using the model at the University of Bologna have published results of their model evaluation exercise
  • The ADMS Temperature and Humidity model has been used to assess the impact of roofing materials on energy use
  • A system to forecast temperatures over the Olympic Park was developed using previous research; this system was live during the London 2012 Olympics

LUCID: the intelligent design of cities[top]

The Development of a Local Urban Climate Model and its Application to the Intelligent Design of Cities project (LUCID) was a 3-year research project investigating how cities are able to adapt to a changing climate.

CERC worked on this project, with partners in the academic sector (University College London, London School of Hygiene and Tropical Medicine, University of Reading and Brunel University) as well as other consultancies. It ran from June 2007 to December 2010.

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The role of CERC within the project was to develop a tool that is able model local changes in temperature and specific humidity on a neighbourhood scale (i.e. over areas of a few square kilometres) due to changing land use. This was achieved by modifying the CERC model FLOWSTAR to calculate local perturbations to the upwind temperature and humidity fields based on local land use parameters, specifically: surface roughness, albedo, thermal admittance, and parameters representing surface resistance to evaporation and building volume. In addition, for the purpose of full model validation against temperature measurements, anthropogenic heat from traffic and buildings has also been modelled.

Funded by the UK Engineering and Physical Sciences Research Council (EPSRC).

Learn more

  • Further details of this project can be found on the LUCID website.

Modelling of wind shear at Hong Kong International Airport with FLOWSTAR

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Significant wind shear at Hong Kong International Airport, situated on Lantau Island, can occur as a result of wind flow over the mountain ridges to the south of the airport. A particularly severe event occurred on the morning of 27 December 2009, when seasonal easterly winds affected the south coast of China: this event was sufficiently serious that a number of aircraft were required to divert.

CERCís FLOWSTAR model was used to simulate the complex airflow over Lantau Island using observed data for the extreme wind event of the 27 December 2009. A sensitivity study showed how large variations in wind speed, wind shear and wind direction occur on the approach path when the upwind flow from the southeast is stably stratified above the boundary layer with a significant inversion no more than a few hundred metres above the mountain ridges (height about 450 m). There was found to be satisfactory agreement between the wind speed measured by a landing aircraft and predictions from FLOWSTAR.

The results from this work suggested that near real time application of the model and near real time monitoring with remote and in situ instruments can be used to predict these extreme flow events and hence give warnings about them.

The research for this project was carried out in collaboration with Hong Kong Observatory.

Learn more

  • Carruthers D, Ellis A, Hunt J and Chan PW,2012:Modelling of wind shear downwind of mountain ridges at Hong Kong International Airport.Meteorological Applications, DOI: 10.1002/met.1350 (Abstract)

Dispersion around buildings: comparison with wind tunnel and CFD[top]

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Mitsubishi Heavy Industries Ltd (MHI) of Japan contracted CERC to assist in evaluating the CFD dispersion model HYPACT, interpreting results, and improving the model for the case of an accidental release in the vicinity of a single block building. The flow field around the building was calculated using the RAMS model.

HYPACT was evaluated against wind tunnel data and results were interpreted by using the COST-732 Model Evaluation Guidelines (http://www.mi.uni-hamburg.de/Home.484.0.html). Based on the results and performance achieved, CERC used their expertise to suggest improvements to the model.

In the comparison exercise, ADMS 4 was used to model the concentration from an area source placed in the lee of an isolated building, at ground level. Mean concentration results from ADMS 4 were compared against wind tunnel and HYPACT, showing satisfactory agreement.

Supported by Mitsubishi Heavy Industries Ltd.

Mesoscale modification of FLOWSTAR for sharp changes in surface roughness

Coastal meteorology is complex and of great practical importance, for instance for coastal wind farms and flooding predictions. In 2005 and 2006 CERC developed modelling tools to compute wind flows in coastal regions, where there are sharp changes in surface roughness. These tools extend CERC's FLOWSTAR model and produce results in high spatial resolution on a standard Windows PC. The work built on the research of CERC's technical director Professor Julian Hunt.

The mathematical model is a general linearized shallow-layer perturbation model, where the approximately neutral lower layer of thickness h0 is situated below a stable upper layer (i.e. an inversion with temperature change ΔT), is developed for steady, mesoscale atmospheric flows over low-lying topography whose height is less than h0. With the Coriolis parameter f, sharp changes in surface conditions (surface roughness, terrain elevation, heat flux) are modelled as a distributed body force through the lower layer. The Froude number of this layer is small.

The project was supported by Mitsubishi Heavy Industries and Kyoto University.

Learn more

  • Hunt JCR, Orr A, Rottman JW, and Capon R,2004:Coriolis effects in mesoscale flows with sharp changes in surface conditions.Q. J. R. Meteorol. Soc., 130:2703-2731. (Abstract)
  • Orr A, Hunt JCR, Capon R, Sommeria J, Cresswell D, and Owinoh A,2005:Coriolis effects on wind jets and cloudiness along coasts.R. Meteorol. Soc. Weather, 60:10:291-299. (Abstract)

Parameterisation of the atmospheric boundary layer for offshore dispersion

Under a contract with the UK Department for Trade & Industry, CERC developed a marine boundary layer scheme for calculating surface roughness and heat fluxes over the sea that can be used, for example, for dispersion modelling of stacks on oil extraction platforms. To use this scheme all sources and receptors should be over the sea; it is not suitable for coastal modelling.

The scheme has been incorporated into ADMS 5 as the marine boundary layer option which is described in Section 8.9 of the ADMS 5 User Guide (see the User guide page).

Supported by the UK Department of Trade and Industry (DTI).

Learn more

  • Development of boundary layer profiles report(.pdf, 1MB)

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