• Urban Microclimate & Urban Heat Island
  • Ø What is Urban Heat Island?
  • Definition of Urban Heat Island (UHI) is the abnormal atmospheric temperature differences between the central of urban and ambient suburban/rural area, occurred from difference of the characteristics of urban surface. (Howard, 1810)
  • Ø Urban Surface Characteristics
  • Urban surface has several distinctive characteristics compared to natural surface. Such as dense building rates, less vegetation area, large heat capacities, are contributing to the UHI. Large heat capacity can keep the heat inside of the urban surface. Shadow effect of the building, lack of evaporation caused by less vegetation surface are contributes to raise the temperature of urban area. Another important characteristic is the density of people live or working in urban area. Human activities produce the anthropogenic heat, which significantly and directly affects to the urban atmosphere temperature. These features are contributing to intensify the UHI.
  • Ø Phenomena associated with UHI
  • UHI keeps the urban temperature higher than surroundings, both daytime and nighttime. And generally, the temperature difference becomes significant at the nighttime.
  • The most important, popular phenomenon would be the tropical night phenomenon. Tropical night is the extreme case of the UHI, which temperature of urban air is higher or equal to 25℃. When the UHI become intensified, the intensity and frequency of tropical night become increase.

  • Relationship between ozone maximum-reach probability and temperature. (Lin et al., 2001)

  • Map of maximum ozone concentration and ozone-related mortality. (Knowlton et al., 2004)
  • Another important phenomenon is the chemical pollution related to the atmospheric temperature. Like tropospheric ozone, it is very harmful to people who exposed, but when the temperature of atmosphere increase, the probability of the ozone concentration reaches maximum become higher. This can severely damage the people live in urban area. The reason of researching about urban climate is predict the urban abnormal climate phenomena and prevent the people from harmful urban phenomena that described above.
  • Study associated with Urban Climate
  • Ø Weather Research and Forecast (WRF) and Urban Canopy Model (UCM)
  • To simulate the mesoscale phenomena, regional climate is preferred. WRF has been evaluated for regional climate simulation coupled with UCM. WRF simulates well with regional climate, and with UCM (Kusaka et al., 2001), we can adjust the urban parameters that define the statement of urban surface, to improve the simulation. With improved simulation, prediction of future climate based on the Representative Concentration Pathway (RCP) scenario or investigate the dispersion of pollutants will be set for further experiments.
  • References
  • Luke Howard, The Climate of London, Deduced from Meteorological Observations, Made at Different Places in the Neighborhood of the Metropolis, 2 vol., London, 1818-20
    C.-Y. Cynthia Lin, Daniel J. Jacob, Arlene M. Fiore, 2001, Trends in Exceedances of the Ozone Air Quality Standard in the Continental United States, 1980-1998, Atmospheric Environment 35 (2001), 3217-3228
    vKim Knowlton, Joyce E. Rosenthal, Christian Hogrefe, Barry Lynn, Stuart Gaffin, Richard Goldberg, Cynthia Rosenzweig, Kevin Civerolo, Jia-Yeong Ku, and Patrick L. Kinney, 2004, Assessing Ozone-Related Health Impacts under a Changing Climate, Environmental Health Perspectives, Nov2004, Vol. 112 Issue 15, 1557-1563
    H. Kusaka, H. Kondo, Y. Kikegawa, F. Kimura, 2001, A Simple Single-Layer Urban Canopy Model for Atmospheric Models: Comparison with Multi-Layer and Slab Models, Boundary-Layer Meteorology, Dec2001, Vol. 101, Issue 3, 329-358
    Updated at 28th June, 2013
    Contact: Ganghan Kim (ganghan2000@unist.ac.kr)
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