What are the four different types of climatic variations?
precipitation wind fog thunderstorms
How much more rainfall do urban areas have compared to rural areas?
10% more rainfall than surrounding areas
Why do urban areas have increased rainfall?
- due to higher urban temperatures - this encourages the development of lower pressure + convectional uplift consequent conventional rainfall - this increase no of thunderstorms and increased rainfall
Where are the chance of thunderstorms increased?
in urban areas, particularly during afternoon/early evening in summer months
How are thunderstorms produced?
convectional uplift over conditions of extreme instability
What then occurs for a thunderstorm to form?
- cumulonimbus clouds develop in height where inversion produced stability - up draught of air through the central area of the towering cloud causes rapid cooling and condensation
What does this then lead to the formation of?
precipitation which coalesce through collisions in the air
What is then released during condensation?
latent heat - further fuels conventional uplift as raindrops split in draught - positive electrical charge builds up in the cloud
What did fog increase with in cites?
industrialisation
What occurs to cause fog?
particles acted as condensation nuclei + encouraged fog formation at night - usually under high pressure weather conditions
What does this combination cause?
there is a high incidence of fog in urban areas - particularly under anticyclonic conditions
How can fog be dangerous?
cities such as Beijing and New Delhi suffer regular winter fogs + hazardous to human health
What is channeling?
wind = redirected down long, straight streets where there is less friction (urban canyons)
What is the venture affect?
when air flows in a gap between two buildings causing the winds to pick up high speeds
How do urban structures affect wind speed?
buildings exert a frictional drag on air moving over and around them - can cause change to wind direction
How do wind speeds differ?
#NAME?
How do high-rise buildings affect wind speed?
may slow air movement - also channel air into the canyons to create the Venturi affect
How does the Burj Khalifa (tallest building in the world) cope with wind?
1) due to statement architecture buoying = able to withstand gusts of 240km 2) building has narrow top + softened edge = can deflect wind 3) buildings = built at angle relative to the prevailing wind