Precipitation in Urban Microclimates

Distribution of rainfall over a town or city is very much influenced by topography
1. Largest values occurring over the more hilly regions
2. Lowest values in more low— lying areas.
Higher levels of rainfall in urban areas than surrounding counrtyside
1. Rain is more intense
  1. Why?
    1. The Urban Heat Island effect means that the air in urban areas is warm, which can hold more water. The warm moist air rises - convectional uplift
      1. As it rises it cools, and water vapour condenses and it rains - convectional rainfall
    2. Urban areas generate large amounts of dust and pollution. These particles floating in the air act as condensation nuclei.
      1. Condensation nuclei cause water to condense around them
      2. This encourage clouds to form, rather than allowing the warm, moist air to disperse.
    3. A mixture of building heights causes air turbulence, which promotes increased vertical motion
2. Higher number of thunderstorms
  1. Likely in late afternoon and evenings in the summer months

Zusammenfassung der Ressource

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