Urban Climates Flashcards
Describe the temperature of Urban areas in comparison to other areas?
Warmer
What is the name given to urban areas as a result of their temperature characteristics?
Urban Heat Island
How do Windows help to increase temperature?
Enhance and reflect heat from the sun towards the ground. (E.g Walkie Talkie building in London was burning through cars)
How do air conditioning units make urban areas warmer?
They release the warm air into the atmosphere
How do factories and cars increase the temperature of urban areas?
They produce a lot of greenhouse gases which constantly thicken the greenhouse gas layer which make it difficultly for heat to escape. Therefore they act as a pollution dome
How do tall buildings help to heat up an area?
Because they are tall they cause conditional instability forcing clouds to form which similar to the greenhouse gas layer traps, like a blanket, the heat in the urban areas
How do building materials such as concrete and brick lead to an urban heat island?
They retain heat better than most materials so therefore surrounding them is a hotter area
How do drainage systems lead to an urban heat island?
Because they transport water away from the surface underground, this means the heat used to evaporate them normally is used to heat up the urban area
How do people lead to an urban heat island?
We produce terrestrial heat and so in urban areas there are lots therefore lots of heat
How does a lack of greenery in urban areas lead to a heat island?
Because plants retain heat through photosynthesis and don’t release to atmosphere so is stored where it can’t warm up area
What is the rate at which temperature increases the closer you get to the city from the edges?
2-4Celsius
Describe the amount of rainfall in urban areas?
There is likely to be more
How do high rise buildings lead to more rain?
They cause conditional instability which forces cloud to form
How does the urban heat island effect lead to more rain?
Increased heat also encourages cloud formation
How do factories help to increase rainfall?
They release water vapour and hygroscopic nuclei that attract water towards them and so assist with droplet formation
How does the undercutting of air at ground level altitudes lead to increased precipitation?
The undercutting at grounds level altitudes forces air to rise faster and thus produce precipitation
Why does fog occur in urban areas?
The urban area is significantly warmed during the day, in winter especially, at night the increase amount of darker hours and less incoming heat radiation means there is a temperature inversion and the urban area cools. The cooler area means that the water vapour released by factories, and hygroscopic nuclei that assist with droplet formation, can reach their dew point and so low altitude clouds/fog forms.
When does fog mostly occur in urban areas?
Autumn and Winter seasons
What are winds like in urban areas?
They can be very powerful
What are 3 ways buildings cause increased wind speeds and turbulence?
- Uneven heights and surfaces of them means there isn’t a smooth flow for air therefore there is increased turbulence of air
- They can force air downwards if high enough into canyons of air which increases their speed and power
- Tall buildings may force air around them and in grid like cities e.g New York this may produce channels or tunnels of air in the streets
What is the Venturi effect?
The forcing of air downwards by buildings into canyons where their speed increases with change of directions and can knock people over
How can urban areas counteract increased wind speeds?
Buildings on stilts
What is the difference between primary and secondary pollutants?
Primary pollutants are those that are produced directly from one process, however secondary are usually primary pollutants that have reacted with another or gone thorough a second process such as reacting with the sunlight
Describe the quality of urban area’s atmosphere in comparison to rural areas
Bad quality
What are 3 primary pollutants?
Sulphur oxides
Nitrogen Oxides
Carbon Monoxide and Dioxide
Volatile Organic Compounds such as Hydrocarbons
What is an example of a secondary pollutant?
Ozone (Usually produced when a primary pollutant reacts with sunlight)
What leads to the formation of photochemical smogs?
When primary pollutants react with sunlight to turn into Ozone. This smoke them reacts with existing fog or clouds in a hydroscopic manner to assist with more smog that now has dangerous Ozone in it
Where is photochemical smog a massive problems?
Los Angeles> lots of cars, lots of sunshine, and topography traps the chemicals.
Why is ozone and photochemical smog a massive problem?
Because Ozone is bad for respiratory system
What are some examples of particulate matter?
Tobacco, Cement, Ash, Coal, Pollen, dust and sea salt
When is the air quality in urban areas likely to be worse?
Winter, because the temperature inversions trap the chemicals in Smog and photosmog over the city
When was Smog a real problems for London?
In 1952 when they lead to 4000 deaths
What are some of the sources in urban areas that produce the pollutants that produce photochemical smog?
Things that burn fossil fuels such as factories and cars
How is a temperature inversion created and how does it lead to worse air conditions?
During an anticyclone air is forced downwards and trapped at the surface with all the moisture. At night, odd even day, the temperature suddenly drops and so does the atmosphere. Due to the cold air it is unable to support the moisture at the low levels and so condenses to form a low layer of cloud or fog. The chemicals and particulate matter in urban areas then produces smog that mixes with the clouds. Due to the continued presence of the anticyclone these can be trapped close to the surface and therefore worsen air quality.
What is particulate matter?
An incredibly small solid in the atmosphere that are around 10 micrometers in diameter
Give some examples of the action being taken to reduce the effects of the urban areas climates
Oyster Cards, Boris Bikes, Congestion charges, pedestrianising, expensive parking, DLR, Low emission zones, park and ride, 1952 clean air acts, catalytic converters, lead free petrol
What are 5 the sources in urban areas that produce particulate matter?
Cars and vehicle exhausts, smoking, building sites, mines, sea and plants
Give 5 examples of particulate matter
Cement, sea salt, pollen, brick, ash, nitrates, sulphates, tobacco
Why are particulate matter bad for air quality?
They can be so small that it is difficult for our respiratory systems to flush out. This can therefore lead to respiratory and cardiovascular problems. They can also react with fog to produce smog that creates thick air that is bad for respiratory system
