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3.5.5 Meteorological data for model validation Limited meteorological data was available for the model validation. Temperature, wind speed and wind direction data were obtained from the British Atmospheric Data Centre (BADC) for the MIDAS (UK Met Office land surface weather stations) network in and around London. The MIDAS network (http://badc.nerc.ac.uk/data/ukmo-midas) comprises of daily and hourly rain measurements, soil temperature, daily temperature, mean wind measurements and hourly weather which form a long term record of UK weather conditions. The hourly weather data includes measurements of wind speed and direction, air temperature, as well as information on cloud types and amounts, and visibility. Each MIDAS network station is identified via a unique source identifier. General guidelines exist for the location of sites and measurement methods and heights 2 . Not all sites however meet these requirements, for example sites located in city centres may be located on roof tops, or close to large obstacles and this may compromise the validity of the measurements. The MIDAS stations used were the London Weather Centre (LWC), which is classified as an urban station; the Heathrow airport station (classified as peri-urban) and St James’s Park (classified as an urban green space station) (see Figure 3.6). These three stations were chosen because they provide the most comprehensive data sets and are located in the London area. All three have hourly measurements of air temperature, wind speed and direction for at least the last ten years, although data can be missing for some periods. 2 Met Office Surface Data Users Guide (UK Met Office document, taken from MIDAS Data User Guide), available at http://badc.nerc.ac.uk/data/ukmo-midas/ 82
Table 3.7 shows a summary of the MIDAS weather stations used in the model evaluation in Chapter 5. Table 3.7: Summary of available data for the MIDAS weather stations used in the model evaluation in Chapter 5 London weather centre London Heathrow St James' Park Bracknell Beaufort Park BADC Station ID 19144 708 697 838 Site elevation 43 m 25 m 5 m 74 m Location characteristics Roof top Airport Urban park Rural Latitude 51.521 51.479 51.504 51.39 Longitude -0.11 -0.449 -0.129 -0.784 Hourly temperature data Yes - for all detailed evaluation cases Yes - for all detailed evaluation cases Yes - for all detailed evaluation cases Yes - for all detailed evaluation cases Partial - missing data Partial - missing data Partial - missing data Partial - missing data Hourly wind speed data Station start date 1929 1947 1903 1965 Station end date Current Current Current 2003 83
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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
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(Peterson 1969; Changnon 1992; Coll
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2.3 Justification of modelling appr
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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 and 90: difficulties in the linking of the
Page 91 and 92: Table 3.3: Description of how the 2
Page 93 and 94: 3.5.2 Orography data Orography data
Page 95: epresenting suburban development a
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
Page 125 and 126: appropriate value for these paramet
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
Page 141 and 142: (a) Potential temperature [K] (c) T
Page 143 and 144: Figure 4.25 shows the vertical sect
Page 145 and 146: 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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