Urban Heat Island research
The UHI intensity − i.e. the difference between urban and rural air temperature − has been frequently investigated. Table 1 (from Lee et al., Overview of urban heat island phenomenon towards thermal comfort, Environmental Engineering and Management Journal, 16(9), 2014) shows UHI values for several cities. See this table here.
Furthermore some simulation models on heat development in cities have been developed. Kikegawa's model, for example, subtly derives urban temperature dynamics from the location of buildings in relation to each other, roads, heat flux in and out of buildings, traffic intensity, wind, building use, etc. Such models are used to predict the future behaviour of local climate variables for a wide variety of UHI-mitigating policies.
A completely different approach is adopted in AHE (anthropogenic heat emission) computation models of Flanner, Allen, or Dong. Those models calculate the temperature variations purely as a function directly from primary energy consumption in a region, do not take into account other heat effects (such as fire etc.), but sometimes include the heat development of the human body. These models have a small grid spacing (in space and time), but do not elaborate the interaction between the local structure variables. They then show on a global scale the AHE, expressed in Watt per square meter (= W m-2), of urban areas. According to Allen et al. the global average of urban QF (= annual heat release) is somewhere between 0.7 to 3.6 W m-2. In most models (Steward et al., Dong et al.) values above 10 W m-2 annual heat release are calculated for megacities, with peaks of up to 80 W m-2. For vast areas with many urban agglomerations such as Europe, one arrives at mean values between 0.40 (USA) and 0.70 (EU) Watt for each square meter of the total zone.
Dong et al. therefore conclude that changes in AHE quantity and distribution will be a necessary parameter for future climate studies.
Literature
Y. Kikegawa, Y. Genchi, H. Kondo, K. Hanaki, Impacts of city-block-scale countermeasures against urban heat-island phenomena upon a building's energy-consumption for air-conditioning, Applied Energy 83 (2006) 649–66
M. G. Flanner, Integrating anthropogenic heat flux with global climate models, Geophys. Res. Lett., 36 (2) (2009)
L. Allen, F. Lindberg, C.S.B. Grimmond, Global to city scale urban anthropogenic heat flux: model and variability, Int. J. Climatol., 31 (13) (2011), pp. 1990-2005
Y. Dong, A. C. G. Varquez, M. Kanda, Global anthropogenic heat flux database with high spatial resolution, Atmospheric Environment, vol. 150, feb 2017, 276-294
I. Stewart, C. Kennedy, Estimating anthropogenic heat release from megacities, ICUC9 -9th International Conference on Urban Climate held jointly with the 12thSymposium on the Urban Environment,20–24 July 2015, Toulouse, France
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