Urban Climate Flashcards
What is the Urban Heat Island effect
The area around and above a city that is hotter then the surrounding area
Why are cities hotter then other areas
Citys are primarily made of concrete and asphalt which absorbs and retains heat
Less trees in cities, which means less cool air is being drawn into the city
Big glass structures reflect solar radiation onto streets
Cities have industries which produce lots of water vapour
Cities have more vehicles which release pollution
What is a micro climate
Small scale variations in temperature, wind speed, humidity, precipitation and evaporation
What is Albedo
The reflectivity of a surface
What is a temperature inversion
Air temperature increases with height
How do thunderstorm’s form
Occur more in late afternoon
Occur more with the urban heat island effect
Hot air rising
Rapid conventional uplift under conditions of extreme instability
Latent heat is released during condensation further fueling the uplift process
Low air pressure draws in water from the surrounding area
How does precipitation form
Lots of vertical motivation in cities which transports water
Cars release hygroscopics which absorb moisture from the air
Cities produce large amounts of water vapour, which condenses to form rain
Water vapour condense into water droplets then falls as precipitation
How does wind form
Warm air meets cool air
Warm air expands and rises, causing the cool air to rush in and take its place
Wind speed is less in cities due to urban structures such as high rise buildings
What produces fog
The ground cools
Causes the air near it to cool as well
When air cools it can’t hold as much water vapour
Vapour condenses into droplets
Water molecules suspended in the air
Last longer in cities due to more hydroscopic which attracts water
What are the three types of rainfall
Frontal
Relief
Conventional
What is frontal rainfall
Warm air meets cool air
Warmer less dense air rises
Warm air cools
The cooling in the air causes the water vapour to condense forming a cloud
When the water droplets becomes to heavy it falls as precipitation
What is relief rainfall
Warm air meets with mountain
Warm air rises up the maintain
The air cools and condenses due to altitude, forming a cloud
When water droplets become to heavy they fall on the opposite side of the mountain
What is convevtional rainfall
Sun heats the ground
Causes rapidly rising pockets of warm air - know as convection currents
Air cools and condenses forming a cloud
When the condensed water droplets become too heavy they fall as heavy rainfall, often with thunderstorms
