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Climatic Conditions (Winds (Channeling - Wind redirected down long…
Climatic Conditions
Winds
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Urban Canyons - Relatively narrow streets bordered by high rise buildings funneling ans so concentrating winds
Venturi Effect - The squeezing of wind into an increasing narrow gap resulting in a pressure decrease and velocity increase
Urban areas have a much greater friction due to high rise buildings, which slows down wind altering its direction
Case Study - Burj Khalifa
- Over 828m tall
- Withstands winds of 240km/h
- Series of aerodynamics improvements
- Softened edges preventing whirlpools/vortices
- Large base = lower centre of mass = more stable
- Sheer concrete rods to ensure stability
- Still wobbles by about 2m at the top
Precipitation
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The UHI generates convection as ground surfaces are heated, rapid evapotranspiration takes place
City pollution can increase cloud formation and rainfall, polluntants act as water attracting nuclei and assist in raindrop
Cities also produce large amount of water vapor from industrial sources and power plants contributing to the increasing precipitation
Urban Heat Island
During extreme UHI, the cases of heat stroke, asthma, organ damage and even death increases
In warmer periods, the added heat from thr UHI can lead to increased water consumption
The earlier flowering times of plants and trees in cities and prolonged growing season may cause discomfort for city residents for city residents who face a longer allergy season
Thunderstorms
Develop in hot humid air and characterised by heavy precipitation associated with thunder and lighting. 25% more storms and 400x more hailstorms
The rising heat can trigger heavier and more frequent late afternoon and early evening thunderstorms
Due to the warm air rising so fast it cools and condenses rapidly, forming water droplets, ice and hail which charge the thundercloud and discharge lightning
Fog
If less dense, is effectively cloud cover at ground level
The higher concentration on condensation nuclei over cities encourages their formation, especially during cooler overnight temperatures
In London on the 1st December 2017, 25 trains were delayed and 6 were cancelled