Urban Climates Flashcards
What is an urban climate
Set of climatic conditions that differ from the surrounding area
What is the urban climate affected by?
-pollution
-dark surfaces
-albedo
-industry
-lack of vegetation
Why do urban surfaces have a low albedo?
There are lots of dark surfaces eg. Tarmac
These absorb heat during the day
Release it slowly as long wave radiation
Give an impact of urban form on weather
Sunlight hitting skyscrapers in London caused cars below to melt as the sun reflected off the buildings
What is the urban heat island
The theory that urban areas are warmer than rural ones
What causes the urban heat island?
-albedo
-heat from anthropogenic activity
-air pollution
-less evapotranspiration
What makes the urban heat island stronger
-summer
-night
-anticyclone conditions (clear skies)
How does less evapotranspiration cause the urban heat island
Water is quickly removed by drainage systems
There’s little surface water to evaporate. There isn’t much vegetation so there’s little transpiration. Evapotranspiration uses heat energy, so less evapotranspiration means higher temperatures
How does air pollution lead to the urban heat island
Creates a pollution dome and increases cloud coverage
Trap outgoing heat radiation and reflect it back to the surface
Where are temperatures in urban areas highest?
The CBD
Why are there higher rates of precipitation in urban areas?
Warm air can hold more water
There is lower pressure due to rising air
Dust and pollution from industry act as condensation nuclei
What is the percentage increase for the chance of thunder in urban areas?
25%
Give an example of differing levels of fog in urban and rural areas
Kew (An inner suburb in London) experiences 79 hours of fog a year
Rural areas in south east England experience 20 hours
What type of map can be used to show differing temperatures in urban areas?
Isotherm map
