CITY WEATHERS: METEOROLOGY AND URBAN DESIGN

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1 TITLE: Birmingham Urban Climate Change with Neighbourhood Estimates of Environmental Risk. A Knowledge Transfer Partnership. AUTHOR: Richard Bassett INSTITUTIONAL AFFLIATION: University of Birmingham ADDRESS: 412 GEES, University of Birmingham, Edgbaston, B15 2TT ADDRESS: r.bassett.1@bham.ac.uk 1

2 Introduction The BUCCANEER (Birmingham Urban Climate Change with Neighbourhood Estimates of Environmental Risk) project is an exciting two year knowledge transfer initiative involving Birmingham City Council and the University of Birmingham. This Knowledge Transfer Project (KTP) is helping to provide the necessary evidence to ensure the effective delivery of the Council s long term vision that the City will be the UK s first sustainable global city with a low-carbon energy infrastructure and well prepared for the impact of climate change. Birmingham, UK is a large metropolitan city located in the Midlands with a population in excess of one million inhabitants. A rise in mean annual temperature from 9.4 o C ( ) to 10 o C ( ) has already indicated that Birmingham is likely to be impacted by the effects of climate change (LCLIP,2007). The UKCP09 expect this increase to continue with estimates that the 2080 summer mean daily maximum temperatures rising by up to 6.6 o C under a high emissions scenario in Birmingham. However, absent to these climate projections is the complex morphology of Birmingham which creates a warming effect when compared to surrounding rural areas. This effect is strongest several hours after sunset (Oke, 1987). Termed the urban heat island (UHI), past studies have found the exact nature to be related to city size, moisture availability, land-use, anthropogenic emissions, building materials and geometry. Research into the exact nature of Birmingham's UHI has been limited when compared to the extensive UHI research on other UK cities. Unwin (1980) identified that city centre nocturnal minimum temperatures could be in excess of 5 o C warmer under anti-cyclonic conditions. However Unwin's (1980) study was not truly representative of city centre conditions, with the site located in suburban Edgbaston. Johnson (1985) furthered this research by conducting transects through Birmingham with the UHI found to be up to 4.5 o C during clear, calm conditions. More recently surface UHI investigations from MODIS satellite images found night time surface UHI to be typically around 5 o C and up to 7 o C under extremely stable heatwave conditions (Tomlinson et al. 2010). The UHI effect can lead to heat stress and air pollution problems which are a major health concern. In particular heatwaves have been shown to exacerbate cardiovascular diseases, cerebrovascular diseases, respiratory diseases and heat stroke. The estimated increase in overall mortality during heatwaves is reported to be between 7.6% and 33.6% with the significant majority of people affected being aged 75 and over (Health Effects of Climate Change in the West Midlands, 2010). 2

3 The 2003 European heat wave was one of the hottest summers on record in Europe. It led to a health crises in several countries and combined with a drought to create a crop shortfall in Southern Europe. More than 40,000 Europeans died as a result, including 2,045 excess deaths in England and Wales (UK Office for National Statistics) where temperatures reached 38 o C. Climate projections show that there could be an average of 3 heatwaves during July and 2 during August by 2080, leading to an increase in deaths, particularly for the elderly and vulnerable. A heatwave experienced in 2020 may lead to 53% more deaths by the 2020s than during the 2003 heatwave (Health Effects of Climate Change in the West Midlands, 2010). The problem lies that unlike any other significant weather event, heat is not treated as an atmospheric hazard. High temperatures may have a direct impact on road surfaces, railway networks, air conditioning and machinery, as well as creating uncomfortable conditions in houses, factories, offices and public areas. High temperatures are often associated with forest fires, low water flows and a reduction in water quality in ponds and rivers. During these periods sudden rainfall can flush heavy metals and sooty deposits from roads and sewage from misconnected drains into streams and rivers. Whilst city morphologies have been extensively researched and found to cause increased night time temperatures in urban areas, UKCP09 assume that Birmingham has an agricultural landscape. These projections therefore underestimate the temperature fluctuations caused by the UHI. Thus in order to inform new planning policies it is vital that the influence of the UHI is accounted for. Birmingham's UHI Birmingham s UHI is not currently modelled. The inclusions of Birmingham's urban areas in a land surface model should show the intensification of temperatures within the city centre. In the present study, the JULES (Joint UK Land Environment Simulator) model has been setup and run for Birmingham and surrounding areas. The model is run using satellite derived land use data and Meteorological data from Coleshill, a rural weather station outside of the urban boundaries. The JULES model performance has been evaluated against air temperature measurements at two UK Met Office standard sites, Edgbaston (urban) and Winterbourne (rural). Averaged annually over 2010, the UHI for Birmingham was found to be 0.37 o C. Split diurnally, the night time UHI was found on average to be 0.89 o C. A slight urban cool island was shown to develop during the day. The maximum UHI 3

4 00:00 01:00 02:00 03:00 04:00 05:00 06:00 07:00 08:00 09:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 CITY WEATHERS: METEOROLOGY AND URBAN DESIGN intensity modelled over 2010 was found to be 5.24 o C.These modelled temperature patterns were found to be consistent with previous research findings for Birmingham (Unwin (1980), Johnson (1985)) and correlate strongly with observed temperature data at Edgbaston and Winterbourne weather stations. The temperatures predicted by the JULES model show a strong correlation with observations over a 12 month simulation (2010) for Birmingham. The model predicts well the diurnal UHI intensity when hourly averages over a year are taken (Figure 1). On an hourly basis some variability was found with a root mean square error (RMSE) of approximately +/- 1 o C. The model evaluation is also being complemented by a further UHI project using tiny-tag data logger temperature measurements around Birmingham and proposals to set up further sensors in the city centre. Annual mean temperature differences as little as 0.05 o C were found between the observed and predicted sites. This indicated the models suitability for use in the BUCCANEER project. In general the model was found to under predict the night time UHI intensity and over predict the day time cool island effect, particularly when modelling a heatwave scenario. When considering the sources of uncertainty the model does perform well. For example, the point locations of the observation may have an entirely different land use to the average land use of the 500m grid cell around it. At this scale small scale meteorological effects such as shading, frost hollows could alter the temperatures enough to explain the slight differences between observed and modelled results. Further to this, limitations in data driving the model, such as the long wave radiation input required for the model being estimated as a function of the atmosphere could lead to deviations between observed and predicted values C 0.60 C 0.40 C 0.20 C 0.00 C C C C C Observed UHI Modelled UHI Figure 1 Observed and Modelled UHI intensities averaged over a 12 month simulation (2010) between Edgbaston (urban) and Winterbourne (rural) weather stations. 4

5 Currently the validation of the model is continuing as new data becomes available. Several new projects starting at the University will put Birmingham at the forefront of urban climate research. An additional project (HiTemp) which aims to establish a high-density urban climate network in Birmingham will provide abundant data for further validation. The data validation will also be complimented by a new met-office standard weather station, located in the city centre which is expected to be fully operational from July Several key urban heat island features became apparent when the model simulations for Birmingham were run (Figure 3). For example a marked temperature gradient, the so called urban temperature cliff (Figure 2) was found when moving from the Edgbaston area to the city centre. Under a heatwave condition the model was showing a temperature gradient in excess of 1 o C per kilometre. Spatially the pattern of the UHI was found to resemble the satellite derived urban heat island for Birmingham (Figure 3). Direct comparisons have not yet been established due to the characteristic difference between the surface and the near surface urban heat islands. Figure 2 UHI Transect showing the typical temperature profile across a city (Oke, 1987) 5

6 Figure 3 Birmingham's modelled UHI during the 2006 heatwave (18th July, 01:00) Figure 4 Satellite derived surface UHI (Tomlinson et al. 2010) 6

7 Knowledge Transfer and Resulting Action One of the main focuses of this project is the sharing of information between the University of Birmingham and Birmingham City Council. Ensuring that the science and findings of the research can be applied directly to inform policy decisions has been a key deliverable throughout the project. The task of transferring research findings into a simple, easy to understand format that is both transferable and widely available to project partners is an ongoing challenge. It is ideally thought that the BUCCANEER project can be a means in which different service areas from within Birmingham City Council and the University can communicate, interact and share data. In order for this to be achieved, a user-friendly web interface has been created - The BUCCANEER Planning Tool (Figure 5). The tool aims to: Visually display information in a user friendly format. Address the impact of the combined effects of the urban heat island and climate change on different temporal and spatial scales across the city. Highlight vulnerable social and environmental areas through risk mapping layers. Allow users from other projects to upload and compare information layers. The tool will allow the UHI heat layers to be overlaid, using GIS (Geographical Information Systems) with vulnerability layers developed from a risk mapping project at the University of Birmingham. These layers use social, economic and environmental data to create risk maps with a particular focus on heath and demographic vulnerabilities. For example proportion of people with ill health in high density housing that will be exposed to excess heat. By overlaying these layers the BUCCANEER project will provide a greater understanding of the interlinked social, economic and environmental risks presented by extreme weather events and future climate change. The project will equip service areas such as planners and health protection agencies with the necessary tools needed to adapt to the impacts of climate change in Birmingham. Already the tool has been incorporated into Birmingham s planning process with inclusion in the Emerging Core Strategy (see section 5.40). Birmingham s Climate Change Adaptation Action Plan which is currently being produced also highlights the BUCCANEER as a primary planning tool. The Action Plan will highlight the risks and vulnerabilities Birmingham faces as a result of climate 7

8 change and the core actions both underway and future actions that need to be developed. This will be a key document outlining the strategic direction both BCC and its partners must take to ensure Birmingham is prepared for a changing climate. The report pulls together the various studies undertaken (including the BUCCANEER) to provide a holistic assessment of the best way forward to benefit from the economic, social and environmental benefits of adapting to climate change. The action plan will assess the actions necessary in different sectors as well as at a community level. These will be further identified in the context of both short and long term measures. Crucially this action plan will provide the framework for developing individual neighbourhood action plans in the following year. The BUCCANEER Planning Tool (Figure 5) will thus become: A valuable aid for planners. An instrument to help inform and develop strategic policies. Figure 5 Example of the BUCCANEER Tool User Interface displaying the UHI for Birmingham under a heatwave example 8

9 Conclusion and Future directions of the Project The next stage of the project is to drive the JULES model on statistically plausible future hourly weather sets from the UKCP09 weather generator. The intention is to identify any spatial heat distribution changes in Birmingham and the difference in number of heat related events compared with not incorporating the UHI into future climate predictions. The model will also be run to assess the effectiveness of climate change adaptation strategies, for example the cooling effect of adding an extra 10% green infrastructure in the city centre. These future climate and hypothetical adaptation scenarios will then be fed into the BUCCANEER tool as layer sets. The tool will also include what if? scenarios, i.e. the user will be able to select their location in Birmingham and then modify the land use and model properties to mimic adaptation strategies to assess their strengths and weakness' in adapting to climate change. 9

10 References Birmingham City Council, Emerging Core Strategy 2010: lobheader=application%2fpdf&blobheadername1=content- Disposition&blobkey=id&blobtable=MungoBlobs&blobwhere= &bl obheadervalue1=attachment%3b+filename%3d the+birming Johnson D.B., Urban Modification of Diurnal Temperature Cycles in Birmingham UK. Journal of Climatology 5: Joint UK Land Environment Simulator: Kotecha R., Thornes J., Chapman L., Birmingham s Local Climate Impacts Profile (LCLIP). May E., Bairdi L., Kara E., Raichand S., Eshareture C., Fisher P., Kemm J., Beckett S., Crompton T., Reeves C., Health Effects of Climate Changes in the West Midlands: Technical Report. Oke T.R., Boundary layer Climates, 2nd Ed. Methuen, London. Tomlinson C.J., Chapman L., Thornes J.E., Baker C.J., Derivation of Birmingham's summer surface urban heat island from MODIS satellite images. International Journal of Climatology UKCP09: UK Climate Impacts Programme: UK Office for National Statistics: Unwin D.J., The Synoptic Climatology of Birmingham s Urban Heat Island, Weather 35: