Microclimates

• What is a microclimate

  the climate of a small area is different to its surroundings
• urban temperatures


  • warmer in urban areas than rural (6c difference in summer 2c in winter)
  • lower albedo- concrete can absorb 2000x more heat
  • less vegetation to offer shade and evotranspiration
  • buildings leak heat
• precipitation 


  • 6% less vegetation in urban areas and lack of evotranspiration
  • higher concentration of cloud cover results in 5-15% more precipitation
  • 400% greater incidence of hail storms
  • 25% greater risk of thunders
• why is there more fog and cloud formation in urban areas

  as the pressure is lower (air rises) moisture is drawn from the rural to the city
• air quality 


  • dense population means more primary emissions from vehicles and industries = more fossil fuels burnt
  • more cloud cover as there is 7X more dust particles from fossil fuels
  • higher temperatures and reduced sunlight
• wind 


  • wind velocity is reduced by 30% in cities as there is increased frictional drag because of buildings
  • narrow spaces create a canyon effect
  • buildings forcing wind down a narrow gap alters wind direction called the venturi effect
• what is the Venturi effect

  when buildings force winds down narrow gaps which alerts wind direction
• What is a Venturi effect

  Wing filling gaps left by canon effect