Boundary-Layer Group (BL Group)

Urban Meteorology

Urban Meteorology is the study of the effect of urban areas on local weather variables, such as temperature, winds and fluxes.

Most of the world's population lives in cities, which are already responsible for 80% of the world's carbon emissions. London's energy consumption soared during the 2003 heat-wave as offices and public buildings switched on air conditioning systems across the city. Such extreme temperatures are predicted to be a regular occurrence by the 2050s, at which point 70% of our current buildings will still be around. They are not designed to function in what will be the equivalent of the current-day Mediterranean climate.

The underlying aim of our research in this area is to develop simple models of these effects, based on the insight generated from experimental work (both laboratory and field), numerical simulations and analytical models.

Research Projects

ACTUAL (Advanced Climate Technology Urban Atmospheric Laboratory) (Janet Barlow, Curtis Wood & Rosy Wilson)

  • This EPSRC project (2009-2013) will investigate the impact that buildings themselves have on London's changing climate. Results will be integrated directly into engineering and policy areas which impact on urban infrastructure. ACTUAL will collect and analyse data using cutting-edge remote sensing techniques such as lasers and sodars to probe the air above the buildings at a distance. It will also be developing new techniques to monitor the impact of buildings on local, urban climate change. The project aims to provide robust, representative climate data for London within 5 years.
  • Note we have a project website

DYCE (Dynamic deployment planning for monitoring of ChEmical leaks using an ad-hoc sensor network) (Alison Rudd & Stephen Belcher)

  • The DYCE consortium will develop a capability for the rapid deployment of sensors to gather data on chemical agents following their malicious or accidental release into an outdoor (industrial/urban) environment. The validity of chemical composition measurements is reliant upon the ability to gather air samples that are representative of the whole environment. To build an accurate picture of this it is currently necessary to deploy large quantities of chemical sensors, which is prohibitively time consuming and expensive. We will mitigate this limitation through the development of deployment planning tools that react to gathered data and instruct the dynamic redeployment of a limited set of wireless sensor nodes, thereby optimising their data gathering capability.
  • In this collaborative Technology Strategy Board (TSB) project (2009 - 2011) we are performing inverse modelling (to predict an unknown source strength and location of a release), laboratory testing (wind tunnel experiments) and field data collection to validate urban deployment.

LUCID (The Development of a Local Urban Climate Model and its Application to the Intelligent Design of Cities.) (Sylvia I. Bohnenstengel & Stephen Belcher)

  • The LUCID project is a collaborative EPSRC research project led by UCL. The project is investigating how cities can adapt to a changing climate. The project brings together people from very different research areas covering meteorologists, buildings scientists, planners, urban and building designers and epidemiologists. The project has the following three core objectives:
  • To develop a new integrated tool to model the local climate in urban areas based on the dynamical and thermodynamical processes associated with land use and building form;
  • To use the model to explore the complex relationships between the projected changes to regional climate and local urban climate and the impact on energy use;
  • To evaluate the impacts of local temperature and air quality on health as a result of a changing climate.
  • Within this project we are running the Met Office Unified model version 6.1 with the newly developed Met Office Reading urban surface energy exchange scheme MORUSES to determine the processes shaping the spatial and temporal structure of the London urban heat island. For further more detailed information please have a look at the following websites:
  • official LUCID project website
  • My group website
  • My personal website

DAPPLE (Dispersion of Air Pollution & Penetration into the Local Environment) (Curtis Wood, Janet Barlow & Stephen Belcher)

  • DAPPLE is a collaborative research project, involving leading UK universities, aiming to answer important questions about air quality near busy urban roads. Its aims include determining what controls the amount of pollution to which we are exposed and developing tools needed to assess localised pollution "hot-spots". Field measurements will be made around the junction of Marylebone Road and Gloucester Place in London. Understanding gained through these measurements, alongside windtunnel observations, will be used to improve on existing modelling techniques. More information is available at DAPPLE

Modelling Winds over Urban Areas (Omduth Coceal & Stephen Belcher)

  • Urban areas affect incident winds by offering resistance to the air flow. Here we compute mean properties of the wind velocity by treating an urban area as a porous region of distributed drag. In this so-called urban canopy model, numerical and analytical computations are performed with the addition of an extra drag force to the averaged Navier-Stokes equations. We investigate the adjustment of a rural boundary layer to an urban canopy, and also flow through an inhomogeneous canopy characterised for example by a change in building density and building height. We also perform Large Eddy Simulations and Direct Numerical Simulations of air flow over arrays of cubical obstacles, with the ultimate aim of developing rigorous parametrizations of turbulence and drag that will then feed into the urban canopy model.

Atmospheric Response to Urban Heterogeneity (Anil Padhra & Janet Barlow)

  • The urban surface consists of a complex combination of buildings, roads, rivers, fields and reservoirs. Flow travelling over these land patches experiences changes due to differences in roughness, temperature and humidity. Our understanding of how the atmosphere responds to such changes is somewhat limited yet it has major benefits to the prediction of pollution dispersion, extreme temperatures and wind gusts. Spatial analysis of building distribution across a suburban to urban area has shown that there is a gradual decrease in building spacing. Current work involves the use of wind tunnel modelling to evaluate drag over such a surface with particular emphasis on turbulence characteristics, scalar transport and roughness-sublayer depth. The goal is to establish if there is universal flow behaviour over surfaces of various building morphology. Comparison of laboratory results to that of the real urban atmosphere will help to strengthen the reality of the findings.

Scalar Transport from Urban Streets (Janet Barlow, Frauke Pascheke & Stephen Belcher)

  • Transport of heat and pollution out of streets is not currently understood, and hence scalar fluxes cannot be quantified. As the fluxes determine concentrations within the street, it is essential to quantify turbulent transport over rough urban surfaces. I have developed the naphthalene sublimation technique to study transport from a model street canyon in a windtunnel experiment. Initial results have shown that street geometry is the most important factor influencing the rate of ventilation of a pollution source at street level, but also that large upstream surface roughness reduces the dependence of ventilation on street geometry. The technique has been further developed to study heat transport out of a street, which is important in terms of quantifying the urban energy balance. Future work using this technique includes transport from street canyons at varying distances downstream of a change in roughness, and transport from streets amongst an array of buildings. In addition, I plan to do full-scale measurements in a street canyon to determine coupling between in-canyon flow and the flow above roof height. This involves using synchronised sonic anemometers.Click here for more details.

Modelling the Urban Boundary Layer and Energy Balance (Ian Harman & Stephen Belcher)

  • Recent increases in the resolution of numerical weather prediction models means that urban areas can now be resolved. This implies that advanced parameterisation schemes for the surface exchange processes in urban areas need to be developed so that the numerical weather prediction models can accurately forecast the weather within urban areas. However few physically based models of the surface exchange procesess, and in particular the surface energy balance, exist which are appropriate for use in operational numerical weather prediction models. This works aims to develop an such energy balance model for an urban area. Tests on the combined model will enable the identification of key features of the urban environment and the quantification of the causality of urban-rural cliamte differences. The fully developed and tested model will then be linked to a separate urban dynamics model to create a full parameterisation scheme for the surface exchange processes in urban areas for numerical weather prediction models. This research is to be carried out in conjunction with the UK Met. Office.

Urban Meteorological Influences on Vehicular Aerosol Emmisions (Petroula Louka, Stephen Belcher & Giles Harrison)

  • The transportation and mixing of pollutants is determined by the mean and turbulent flow within an urban street and within the roughness sub-layer aloft. Because sources of pollution are situated both at ground level (cars) and roof-top level (chimneys), the complex morphology of an urban area creates a highly disturbed flow up to several metres above the buildings. Understanding these flow dynamics is crucial to understanding the distribution of pollutants within an urban environment and to improving air pollution dispersion. We are looking at the flow dynamics in urban areas and the impact it has on air pollution.

Urban Pollution Measurement with a Gerdien Condenser (Karen Aplin & Giles Harrison)

  • Better measurements of atmospheric aerosol are necessary in order to understand urban pollution and to assess the impact of aerosol on climate change. I am making such measurements using a novel electrical method. The instrument used is a Gerdien condenser, a cylindrical capacitor that collects atmospheric ions. This provides a measurement of the air's electrical conductivity, which is directly related to the aerosol concentration. The Gerdien condenser can also be used to obtain particle mass spectra across a wide size range and can therefore be applied to monitor particle formation events, which are currently poorly understood.


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BLMet research

  • Urban meteorology
  • Air-sea interactions
  • Orographic processes
  • Mesoscale processes