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 Urban Green Space to Provide Local Climate Regulation

Von Saddroddin Alavi Panah (30.04.2014)

For thousands of years, humans have used landscaping to serve their wellbeing. During the last 300 years – in response to the industrial revolution - the trends to such activities affecting land surface have accelerated (Lambin, 2006). Urbanization is an extreme form of this activity. The process of urban sprawl has been more intensely than ever before and it continues to grow.

One of the results of urbanization is replacing natural vegetation with buildings and roads which tends to significantly higher air temperature in relation to temperatures in rural surrounding areas; known as Urban Heat Island (UHI) (Oke, 1982). Most of the world’s cities show higher temperatures in their urban core than in surrounding rural areas (except cities in arid and semi-arid). Most importantly, the increasing mean temperatures due to climate change compound the importance of evaluating UHI (EPA). It is likely that climate change will cause more frequent occurrences of extreme events, like prolonged period of excessively hot weather called heat waves (Frisch et al, 2002). Heat waves are a significant threat to human health in cities (Rizwan et al., 2008). For example, a heat wave in 2003 increased mortality by +7.6% only in Munich (Germany) (D'Ippoliti et al., 2010) and was blamed for 70.000 deaths in Europe (Robine et al., 2008). Undoubtedly, more energy will be consumed for cooling buildings and maintaining infrastructure (Kikegawa, 2003).

A big challenge presented to contemporary scientists is to adapt and mitigate cities to climate change.
This study applied satellite images and ecosystem services to assess the cooling effect of urban green space, especially during extreme warm periods. Consequently, it was first hypothesized that; the larger proportion of urban parks within certain area are to expected stronger cooling effects than smaller proportions (hypothesis 1) and secondly; the threshold of the cooling effect from urban parks during an extreme warm period such as a heat wave (hypothesis 2) while a threshold is expected for any natural system. Trees and vegetation reduce heat islands in two main ways. Firstly, by shading that keeps the land surface cooler and reduces the amount of heat transfer to the air above; and secondly, during the process of photosynthesis in which plants use the sun’s energy, water is evaporated and this prevents the released energy from heating up the city. Therefore, fully vegetated area was expected to have cooler surface. The results of this study demonstrated that the relationship between surface temperature and the presence of urban green space is a non-linear trend and showed a remarkable decrease in surface temperature in regions where the proportions of vegetation cover recorded as 70 to 79 percent of 1 km2. It is also demonstrated that surface temperature for urban green space is related to the temperature of its urban surrounding. This dependency may differ according to the size, shape and as discussed location of the park. Although there is a dependency between urban parks and urban LST, the results show that the cooling effect of urban park still takes place under extreme hot weather conditions such as the heat wave in 2003. Studies on thermal properties of UHIs and urban green space not only undoubtedly improves our understanding to a better adaptation to regional and global climate change; but also helps to moderate urban outdoor thermal comfort; and more important decreasing power consumption needed for cooling in cities which cause to more CO2 emissions and pollution.

Scientific career
  • 2004 - 2009
  • B.Sc. in Biology of Plant (Botanic Science), University of Teheran
  • 2010 - 2013
  • M.Sc. in Environmental Global Change Ecology

  • * Alavipanah, S.K., Hamzeh, M., Alavi Panah Seyed Sadroddin, Goudarzi, S. Macroscopic and Microscopic Thermal Infrared Remote sensing Approaches for Global Warming, 35th International Symposium on Remote Sensing of Environmental (ISRSE). (in press)
  • * Alavi Panah, Sadroddin, Koellner, T., Wegmann, M., Qureshi, S. Relationship Between Land Surface Temperature and the Ratio of Urban area and/or Urban Parks. Journal of urban planning and development, American Society of Civil Engineers. (submitted)