Urban climate

• what does urban areas have ?

  their own microclimate
• what is another term that refers to the microclimate of an urban area?

  a 'climate dome
• what are the climatic differences between in the 'climatic dome'?

  climatic differences between urban areas and the surrounding countryside
• climatic differences between urban areas and the surrounding countryside in terms of TEMPERATURE

  an increase in both annual mean and winter minimum temperature
• climatic differences between urban areas and the surrounding countryside in terms of RELATIVE HUMIDITY

  a decrease in annual mean, winter and summer levels
• climatic differences between urban areas and the surrounding countryside in terms of PRECIPITATION

  an increase in quantity
• climatic differences between urban areas and the surrounding countryside in terms of VISIBILITY

  increase in winter and summer fog
• climatic differences between urban areas and the surrounding countryside in terms of AIR QUALITY

  increase in dust particles
• climatic differences between urban areas and the surrounding countryside in terms of WIND SPEED

  decrease in annual wind speed and gusts
• what is the urban heat island effect?

  the phenomenon of urban areas being warmer than rural areas
• what are urban heat islands?

  urban areas with higher air temperatures than the surrounding rural areas
• what temperature can the urban heat island effect fluctuate between?

  between 1 and 3 degrees C
• what factors affect the urban heat island effect?

  season, weather conditions, sun intensity and ground cover
• where are the highest temperatures found?

  in industrial areas and in the most densely built up areas (CBD)
• what are temperature sinks?

  pockets of cool air above parks and bodies of water
• what are temperature plateaus?

  when areas within the city with the same land use generally have the same temperature
• what are temperature cliffs?

  rapid changes in temperature as theres a change in land use
• ABSORPTION OF HEAT BY URBAN SURFACES - what do the building materials in urban areas do?

  absorb and store more hear from the sun during the day than rural areas
• ABSORPTION OF HEAT BY URBAN SURFACES - how is this heat stored in urban building materials released?

  its slowly released as long wave radiation
• ABSORPTION OF HEAT BY URBAN SURFACES - when is the release of heat from urban building materials most noticeable?

  at night when it warms the air
• ABSORPTION OF HEAT BY URBAN SURFACES - what is lower in materials in urban areas than rural areas?

  urban areas have a much lower albedo
• ABSORPTION OF HEAT BY URBAN SURFACES - what is albedo?

  the reflectivity of a surface
• AIR POLLUTION - what does air pollution from cars and factories increase?

  cloud cover over the city
• AIR POLLUTION - what does air pollution create?

  creates a pollution dome
• AIR POLLUTION - what is a pollution dome?

  a layer of pollution over the city
• AIR POLLUTION - what does both cloud cover and a pollution dome do?

  traps outgoing heat radiation and reflects to back to the surface
• HEAT FROM HUMAN ACTIVITY - what releases heat?

  cars, factories, offices, central heating, ac units and people
• LESS EVAPOTRANSPIRATION - what happens when it rains?

  the water is quickly removed by drainage systems so theres little surface water to evaporate
• LESS EVAPOTRANSPIRATION - what happens as theres little vegetation?

  there is little transpiration
• LESS EVAPOTRANSPIRATION - what type of energy does evapotranspiration use?

  heat energy
• LESS EVAPOTRANSPIRATION - what does less evapotranspiration lead to?

  higher temperatures
• EFFECT OF UHI ON HUMAN HEALTH

  respiratory problems, heat stoke and high pollution levels
• EFFECT OF UHI ON DISEASE

  high temperatures increase the spread of vector and waterborne disease
• EFFECT OF UHI ON AIR CONDITIONING SYSTEMS

  they use high amounts of energy
• EFFECT OF UHI ON URBAN FABRIC

  increased risk of the deterioration of parts of the urban fabric
• when is the UHI effect stronger?

  at night
• how much warmer are urban areas at night than rural areas?

  3-4 degrees warmer
• how much warmer are urban areas during the day than rural areas?

  0.6 degrees warmer
• why is there a bigger temperature difference at night between rural and urban areas?

  rural areas cool down at night but urban areas don't cool as much because urban surfaces continue to release heat that they have absorbed
• why is the UHI effect stronger in summer?

  theres more solar radiation in summer so urban areas absorb more heat