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types, building heights, and different amounts of vegetation coverage, it is possible to consider how urban planners can design cities which maximise comfort and sustainable energy use. There are also important links between this work and climate change, since London could be particularly vulnerable to future changes in its climate, such as increased flooding events and exacerbated summer heat waves. 1.2 Structure of this thesis A review of the current literature is presented in Chapter 2. Chapter 3 describes the mesoscale model METRAS which is used for this study, the urban scheme BEP chosen to be implemented in the model, as well as the methods used in the implementation and the data sources required to configure the modelling system for the London domain and to evaluate the model. The results from the implementation of the urban scheme in METRAS are presented in Chapter 4. The model is initially run for an idealised domain, and sensitivity tests are carried out to enable a full understanding of the model performance and the underlying processes which determine the urban impact on the model results. The model is then run for London, and the results are evaluated against meteorological data from London weather stations (Chapter 5). In Chapter 6 the effects of past urbanisation scenarios are investigated for a particular meteorological case for which the model was evaluated and for which a significant urban effect was identified. The effects of urbanisation on the regional climate are isolated from other effects by comparing simulations performed with a land cover map representing urban land use in 2000 and hypothetical land cover maps based on a literature survey. 6
The effects of future urban expansion scenarios are investigated for London in Chapter 7. Conclusions and recommendations for future work are made in Chapter 8. 7
Page 1 and 2: MODELLING THE IMPACT OF URBANISATIO
Page 3 and 4: Abstract Urban areas have well docu
Page 5 and 6: Abbreviations aLMo Meteo Swiss oper
Page 7 and 8: 4.2.2 Impact of the urban area on t
Page 9 and 10: List of figures Figure 2.1: Scales
Page 11 and 12: Figure 4.21: Diurnal variation of t
Page 13 and 14: Figure 6.16: Mean horizontal wind s
Page 15 and 16: Chapter 1: Introduction Urban areas
Page 17 and 18: with trends derived from a statisti
Page 19: scheme, and therefore it was necess
Page 23 and 24: 2.1 Urban climate modification Urba
Page 25 and 26: latitudes (Taha 1997), and this is
Page 27 and 28: 100 - 200 m 1 - 2 km 10 - 20 km 100
Page 29 and 30: epresentatively sample the underlyi
Page 31 and 32: over the city centre, convergent fl
Page 33 and 34: Cold islands can also occur in urba
Page 35 and 36: of the atmosphere. For example, it
Page 37 and 38: amount of solar radiation absorbed
Page 39 and 40: (Peterson 1969; Changnon 1992; Coll
Page 41 and 42: 2.3 Justification of modelling appr
Page 43 and 44: Trusilova (2006) carried out a stud
Page 45 and 46: constant flux surface layer in the
Page 47 and 48: the vertical distribution of vegeta
Page 49 and 50: using different building parameters
Page 51 and 52: Table 2.2: SWOT analysis for the ME
Page 53 and 54: Fraction of urban land cover [%] Fi
Page 55 and 56: The built up area of London can cur
Page 57 and 58: Figure 2.5(a-f): Builtup area of Lo
Page 59 and 60: • Mainly high density development
Page 61 and 62: climate of London, and currently on
Page 63 and 64: For mid-latitude cities, of which L
Page 65 and 66: warming of 0.04 °C per decade, in
Page 67 and 68: out differences in the urban heat i
Page 69 and 70: adopted in previous studies ranges
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y the implementation of a specific
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A prognostic equation is used to re
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At the surface the temperature is c
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The boundary conditions used for th
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are defined in the file m1tini_TAPE
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The terms representing the impact o
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3.2.1 Calculation of dynamical effe
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θ k ∆z / 2 H Siu (Equation 3.12)
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3.3 Implementation of BEP in METRAS
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difficulties in the linking of the
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Table 3.3: Description of how the 2
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3.5.2 Orography data Orography data
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epresenting suburban development a
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Table 3.7 shows a summary of the MI
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3.6 Summary In this PhD study the m
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temperature, air pressure and air d
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Potential temperature [K] Figure 4.
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Wind speed [ms -1 ] Figure 4.2: Ver
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4.2.1 Horizontal cross sections of
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affected, as the flow bends around
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Downwind of the city on the other h
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the city, which is expected since t
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Potential temperature [K] Figure 4.
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simulation this effect is verticall
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differences are expected during day
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tend to cool the surface, but can a
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Figure 4.15 shows the vertical prof
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appropriate value for these paramet
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0.61) and that of conventional grav
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Difference in potential temperature
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educed near surface temperatures of
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fraction was increased in steps of
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works. In the control simulation th
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characterised by the albedo, therma
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is higher by a similar amount. The
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(a) Potential temperature [K] (c) T
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Figure 4.25 shows the vertical sect
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tests also reproduced well document
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Chapter 5: Evaluation of the urbani
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Fraction of urban land cover [%] Fi
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For the summers of 1995-2000 the an
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Table 5.2: Selected periods of simu
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commonly used as a rural reference
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newly urbanised version of the METR
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adiation trapping in the street can
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the second day of simulation (31 st
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Air temperature ( o C) 35 30 25 20
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the model. The smaller percentage o
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Wind speed (ms -1 ) Wind direction
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London Heathrow Airport (LHR) Wind
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A full set of hourly wind speed and
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contain both roofs exposed to direc
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Chapter 6: The effects of urban lan
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simulations with two hypothetical s
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dependent on the r(i,j), the radial
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centre of the domain was more than
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6.2 Effects of the current state of
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During daytime the shape of the are
Page 187 and 188:
The calculation was performed for t
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ecause finding a rural reference po
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development (GLA 2006) and differen
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6.2.4 Wind speed and direction Klai
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Wind speed and direction (ms -1 ) F
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“urban” cells to be affected by
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the urban surface. Many other studi
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eason the near surface potential te
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Mean potential temperature at 12:00
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where A(x) is the area affected by
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Table 6.8: REI for the RADIUS, DENS
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COMBINED series also show a reducti
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for all runs in the series, and cor
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The runs are then combined into one
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to be more linear than the smaller
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The total reduction in mean wind sp
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The REI showed that for all the var
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Higher temperatures in the urban ar
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Over the next ten years the populat
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7.1.1 EXPANSION series The first sc
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Another cause of this form of expan
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7.2 Effects of urbanisation for the
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Mean near surface potential tempera
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UHI intensity (K) 4 3.5 3 2.5 2 1.5
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temperature, an increase in the mea
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7.2.3 Wind speed The effect of the
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7.3 Effects of urbanisation for the
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mean near surface potential tempera
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7.3.2 Wind speed Changes in the mea
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expansion strategies such as the re
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should also be considered to avoid
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models, for example Martilli et al.
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cities (Baker et al. 2002). Already
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uses, painting the roofs white to r
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The full influence of different met
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References Abercrombie, P. (1945).
Page 259 and 260:
Bottema, M. (1997). "Urban Roughnes
Page 261 and 262:
Craig, K. J. and R. D. Bornstein (2
Page 263 and 264:
Grimmond, C. S. B. and T. R. Oke (2
Page 265 and 266:
Jin, M. and J. M. Shepherd (2005).
Page 267 and 268:
Lemonsu, A. and V. Masson (2002). "
Page 269 and 270:
Nitis, T., Z. B. Klaic and N. Mouss
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alance in urban areas - Recent adva
Page 273 and 274:
Seaman, N. L. (2000). "Meteorologic
Page 275 and 276:
Therry, G. and P. Lacarrere (1983).
Page 277:
Yague, C., E. Zurita and A. Martine
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