Unit 4 Flashcards
What is a microclimate?
is a distinctive climate that exists in a localised area, such as a city ( the climatic characteristics in this local area will differ from the prevailing regional conditions)
What are the reasons for higher temperatures in urban areas?
darker surfaces, cement, brick, tar
A.C forces hot air outside
What are the reasons for low humidity in urban areas?
low number of trees, so there is less evapotranspiration as drainage systems get rid of rainwater
What is the reason for fewer frosts in urban areas?
heating, and darker surfaces absorb heat
What are the reasons for more air particulates (dust) in urban areas?
particulates are released from cars, creates high levels of precipitation
What are the reasons for higher rainfall levels in urban areas?
more condensation nuclei, to form precipitation, air pollution and warmer temperatures
Since what year has more of the world’s population lived in urban areas than rural?
2010
By 2050, it is predicted what % of the population is predicted to live in urban areas?
70%
What is the definition of a megacity?
those cities with more than 10 million inhabitants
In 1950, how many Megacities were there and what were they called?
2, New York and Tokyo
How many Megacities where there in 2018?
37
What is an example of a developing megacity?
Dhaka in Bangladesh
When did Bangladesh gain independence and what was the population of Dhaka?
March 1971
pop of 250,000
economic growth and rural poverty
What proportion of the population in Dhaka are housed?
1/3
How much does traffic cost the city of Dhaka annually?
$2 billion
What particular issues of urban climate do cities like Dhaka face?
flooding
What is the meaning of Urban heat island?
urban areas are warmer than surrounding rural areas thus creating a localised warm area
What are the main causes of urban heat island?
- limited surface water, bare earth
- less vegetation
- decreased albedo (reflectivity)
- low surface water = less latent heat
What is the proportion of Asphalt reflectivity compared to grass?
Asphalt = 0.05 - 0.2
Grass = 0.25 - 0.3
Why do urban areas trap more heat than rural areas?
they have less vegetation and low albedo, which means heat is retained overnight
However, rural areas have more albedo and higher albedo and high surface water = latent heat, which is cooler
What is the case study for Urban heat islands?
Birmingham
By how much have temperatures risen over the last 15 years in the rapidly growing cities of New Delhi and Mumbai?
temps in both cities have risen 2-3 degrees in only 15 years
Nasa satellites show the cities being 5 - 7 degrees warmer than surrounding rural area
Why do high pressure anticyclonic systems lead to a more pronounced temperature difference between an urban and rural area?
air is sinking, which means there is a small pressure gradient
because it doesn’t rain sun provides insolation which increases the temp
When does the heat island affect become more pronounced?
between 5 and 6pm, until morning
What does a diurnal period mean?
24 hour period
What is friction drag and how does it affect urban winds?
speed is generally lower in urban areas, they are deflected over and around buildings which creates the friction on the air movement
How does side view wind against face work?
pressure gradient is set up between the windward and leeward side of buildings
How does the windward side create an area of high pressure?
(the side facing the direction of the wind)
windward side of a building tends to have a high pressure due to the air pushing against it, its forced up
How does the leeward side create an area of low pressure?
side which blocks the straight path of the wind has an area of low pressure
How does a turbulent wind flow pattern occur?
wind moves around the building from the high pressure to the area of low pressure creating a localised turbulent flow pattern
What is the venturi effect?
where wind is funnelled down certain streets creating localised strong winds
Where is an example of where the venturi effect is used to create wind turbine systems between high buildings in windy cities?
Chicago
How much more rainfall do UK urban areas experience compared to surrounding rural areas?
30% more rainfall
How do urban areas experience more rainfall, than rural areas?
- insolation
- dark surfaces in urban areas, low albedo, more heat absorbed
- warm air rises = low pressure
- cars, release particulates
- condensation nuclei = precipitation
= heat island
How can understanding the urban rainfall effect be useful in managing water?
- can cause orographic rainfall, important for urban planning
- will know where to place reservoirs, and water storage areas, but also a way to reduce flooding events
Why are urban areas less humid and why?
urban areas can be 6% less humid
1. air temps are higher which means that dew point is reached quicker, not much moisture left in the air
2. Land surface and water stores, urban areas have less in water stores compared to rural areas (runoff, evapotranspiration, infiltration)
What are examples of air particulates?
co2
suphur dioxide
nitrogen oxide
What are the weather conditions associated with pollutants?
pollution, photochemical smog and acid rain
According to the World Health Organisation (WHO) how many premature deaths do pollution cause each year?
7 million
What are the effects of pollution on people?
both short term and long term
can cause respiratory disease and implications on peoples health
What conditions does photochemical smog tend to form under?
calm anticyclonic conditions, high pressure
How does photochemical smog form?
when primary pollutants (volatile organic compounds) interact with sunlight produce a mixture of different hazardous chemicals known as secondary pollutants such as Ozone
How are volatile organic compounds formed?
created from incomplete fossil fuel combustion
How does photochemical smog affect humans?
causes serious health problems and can be extremely toxic to all living organisms
What is the case study for photochemical smog? How many died?
The London smog December 1952, when there was a 5 day smog, claiming 4000 lives
What does the clean air act of 1856 implicate?
UK government introduced these regulations on emissions of smoke and gas from industrial, commercial and domestic premises to improve air quality in urban areas
Between 1970 and 2000, what has been the reduction in public power in emissions and why?
switching to renewable energy
from 250pm emissions to 30 pm emissions (in kilo tonnes)
What is the definition of acid rain?
any form of precipitation with high levels of nitric and sulfuric acid
How does acid rain form?
- nitrogen dioxide emitted from burning fossil fuels
- nitrogen dioxide is soluble, dissolves into clouds
- wind can carry this away up to 800km away from source
- crops can be stunted
- can damage marine ecosystems
What are the different strategies used to reduce the level of pollution in cities?
- transport policies and legislation
- technological solutions
- land use planning and improved urban design
What is the UK vehicle taxation introduce by the government?
- introduced a series of road tax bands based on the CO2 emissions of a vehicle
- purpose to use more fuel efficient vehicles that reduce the levels of C02 reduced
What is the pug in grant and what does it offer in the U.K?
encourages people to buy electric vehicles, the grant will pay for 35% of the purchase price for these vehicles, up to maximum of £4,500
How many deaths per year are caused by pollution in the U.K?
40,000
What does the ULEZ stand for and where was it introduced?
Ultra Low Emission Zones, introduced in London
What does the ULEZ charge per day for the cars that are not allowed to drive in these zones?
£12.50
How much lower are the nitrogen levels in London thanks to ULEZ?
46% lower than if ULEZ had not been introduced
What are the 4 major cities that have moved to ban diesel vehicles by 2025?
Paris
Mexico City
Madrid
Athens
In Paris which vehicles have neem banned?
Those registered before 1997
What is titanium oxide and why is it useful?
it reacts with ultra violet light to neutralise elements of air pollution such as nitrogen oxide, breaking them down into harmless compounds
What are the 2 places which have coated buildings with titanium oxide to reduce air pollution?
- Manuel Gea Gonzalez Hospital, which negates the effects of 1,000 vehicles every day (covers 2,500km sq)
- Palazzo Italia, Milan, covers 13,000 km sq (6 floor building)
What is the name of the substance that contains titanium oxide and decreases nitrogen oxide levels by 25 - 45%?
Photocatalytic Concrete, could be used in urban development
What is the case study for how land use planning and urban design can reduce the levels of air pollution in urban areas?
Copenhagen
How has the capital city of Denmark gone about tackling the air pollution problem?
re-designed the urban transport system to encourage cycling
9 out of 10 Danes own bikes
modern, made it convenient for people
What % of commuters in Copenhagen cycle to work?
34%
What % of school children cycle to school in Copenhagen?
49% of children aged between 11 and 15
How has planting urban trees reduced the effect of the urban heat island?
The University of Indiana discovered that on hot days (35 degrees) the ground temp below trees was 10 degrees lower than ground exposed to the sun
What city in the U.K is one of the greenest in the World? What is the % cover of trees?
London, with 20% of its surface covered in trees (8 million trees), removes 2.4 million tonnes of air pollution
Which city has the worst air pollution in the world?
New Delhi
Why is Delhi’s air pollution so bad?
due to farmers burning fields to get ready to plant crops
fireworks for Diwali
What is the case study for a sustainable city?
Curitiba Brazil
What is the population of Curitiba?
18 million people
What is the green exchange and when was it introduced in Curitiba?
introduced in 1990, helps 30,000 families
where people collect garbage and trade its weight in for foods
collects 300 tonnes of garbage per month
What was involved in the solution of the parks in Curitiba?
introducing green spaces in urban areas
(solved flooding problems and stopped creation of slums)
builders allowed 3 extra stories for free if they create green space below/ pay cash towards conservation
What proportion of garbage is recycled in Curitiba?
2/3s
How does Curitiba’s integrated transport links work?
Bus lanes in the centre of roads (they are up to 25m long) and go from the centre of the city outwards and vise versa
