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3.5 Data sources This section describes the data sources which were used for the construction of the model domains, the initialisation of the model runs, and the validation of the model results. 3.5.1 Land cover data The CEH Land Cover Map 2000 (LCM2000) was used to derive the land cover classification for the model domain. The LCM2000 is a 1 km x 1 km raster dataset covering Great Britain which was created from a 25 m x 25 m pixel resolution dataset within a 1 km x 1 km grid. The dataset is a digital map made by analysis of spectral reflectance data from Earth observation satellites. LMC2000 has two urban land use classes, representing continuous urban land cover and discontinuous suburban land cover. These were used in order to classify the urban land cover into two BEP urban classes with characteristics representing urban and suburban land cover. All large areas of vegetation in LMC2000 (>0.5 ha) are distinguished by the appropriate land cover class, and these will be likewise represented in METRAS by the most appropriate land cover class. Since LCM2000 has 27 land cover classes, compared to the 10 classes used in the METRAS model, the classes must be summarised into the METRAS classes. A FORTRAN programme was written to convert the LCM2000 data set into the 10 METRAS land cover classes. On the basis of the description of the LCM2000 classes provided, the CEH land cover percentages were aggregated into the 10 METRAS land cover classes using summary in Table 3.3. 76
Table 3.3: Description of how the 27 land cover classes in the CEH Land Cover Map 2000 are summarised into the 10 METRAS land cover classes. CEH land class CEH Description METRAS land class METRAS Description 1 2 Sea/Estuary Water (inland) 0 Water 5 Salt marsh 1 Mudflats 3 Littoral rock 4 6 Littoral sediment Supra-littoral rock 2 Sand 7 Supra-littoral sediment 27 Unclassified 3 Mixed land use 14 Arable cereals 15 Arable horticulture 16 Non-rotational horticulture 17 Improved grassland 4 Meadows 18 Set-aside grass 19 Neutral grass 20 Calcareous grass 8 Bog (deep peat) 9 Dense dwarf shrub heath 10 Open dwarf shrub heath 5 Heath 11 Montane habitats 26 Inland bare ground 21 Acid grass 22 Bracken 6 Bushes 23 Fen, marsh, swamp 12 Broad leaved woodland 7 Mixed forest 13 Coniferous woodland 8 Coniferous forest 24 25 Suburban, rural developed Continuous urban 9 Urban Figure 3.4 shows the percentage of the ‘Meadows’ and of ‘Mixed forest’ land cover in the domain. 77
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MODELLING THE IMPACT OF URBANISATIO
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Abstract Urban areas have well docu
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Abbreviations aLMo Meteo Swiss oper
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4.2.2 Impact of the urban area on t
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List of figures Figure 2.1: Scales
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Figure 4.21: Diurnal variation of t
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Figure 6.16: Mean horizontal wind s
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Chapter 1: Introduction Urban areas
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with trends derived from a statisti
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scheme, and therefore it was necess
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The effects of future urban expansi
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2.1 Urban climate modification Urba
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latitudes (Taha 1997), and this is
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100 - 200 m 1 - 2 km 10 - 20 km 100
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epresentatively sample the underlyi
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over the city centre, convergent fl
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Cold islands can also occur in urba
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of the atmosphere. For example, it
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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
Page 71 and 72: y the implementation of a specific
Page 73 and 74: A prognostic equation is used to re
Page 75 and 76: At the surface the temperature is c
Page 77 and 78: The boundary conditions used for th
Page 79 and 80: are defined in the file m1tini_TAPE
Page 81 and 82: The terms representing the impact o
Page 83 and 84: 3.2.1 Calculation of dynamical effe
Page 85 and 86: θ k ∆z / 2 H Siu (Equation 3.12)
Page 87 and 88: 3.3 Implementation of BEP in METRAS
Page 89: difficulties in the linking of the
Page 93 and 94: 3.5.2 Orography data Orography data
Page 95 and 96: epresenting suburban development a
Page 97 and 98: Table 3.7 shows a summary of the MI
Page 99 and 100: 3.6 Summary In this PhD study the m
Page 101 and 102: temperature, air pressure and air d
Page 103 and 104: Potential temperature [K] Figure 4.
Page 105 and 106: Wind speed [ms -1 ] Figure 4.2: Ver
Page 107 and 108: 4.2.1 Horizontal cross sections of
Page 109 and 110: affected, as the flow bends around
Page 111 and 112: Downwind of the city on the other h
Page 113 and 114: the city, which is expected since t
Page 115 and 116: Potential temperature [K] Figure 4.
Page 117 and 118: simulation this effect is verticall
Page 119 and 120: differences are expected during day
Page 121 and 122: tend to cool the surface, but can a
Page 123 and 124: Figure 4.15 shows the vertical prof
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Page 127 and 128: 0.61) and that of conventional grav
Page 129 and 130: Difference in potential temperature
Page 131 and 132: educed near surface temperatures of
Page 133 and 134: fraction was increased in steps of
Page 135 and 136: works. In the control simulation th
Page 137 and 138: characterised by the albedo, therma
Page 139 and 140: 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
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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).
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Bottema, M. (1997). "Urban Roughnes
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Craig, K. J. and R. D. Bornstein (2
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Grimmond, C. S. B. and T. R. Oke (2
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Jin, M. and J. M. Shepherd (2005).
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Lemonsu, A. and V. Masson (2002). "
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Nitis, T., Z. B. Klaic and N. Mouss
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alance in urban areas - Recent adva
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Seaman, N. L. (2000). "Meteorologic
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Therry, G. and P. Lacarrere (1983).
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Yague, C., E. Zurita and A. Martine
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