urban climate Flashcards
urban heat island effect
when urban inner citys are a higher temperature than rural areas
how much hoter are urban areas
8% hotter. in some areas like london temps in the inner city can reach 5 degrees hotter in seasons compared to rural areas
what reasons are there for urban heat island
-darker surface albedos
-higher population which radiates and traps heat
how much heat do each surface type absorb
-tarmac 90% and reflects 10%
-vegetation 68% and reflects 32%
-ice/snow absorb 15% and reflect 85%
what is the urban canopy layer
tall buildings absorb sunlight which creates a layer of warm air below the height of skyscrapers.
what is a pollution dome
the urban heat island effect traps heat over the city and there is a dome where the air is much hotter than the area outside. prevailing wind pushes the heat away and spreads it.
why is UHI a problem
-it creates health problems for people in the city such as: heat stroke and asthma
-increased rates of evapotranspiration which leads to higher rain in citys
-increased air con usage
-higher pollution levels
-increased water consumption
fog and smog
when fog mixes with polluting air particles, it creates a substance known as smog. the great london smog of 1952 killed over 2000 people.
how does UHI lead to higher rates of precipitation
hotter albedo surface areas generate convection currents in citys. higher rates of evapotranspiration creates cumulus clouds over the city. precipitation can be 20% greater in urban areas.
wind in urban areas
convection currents in citys from the UHI.
skyscrapers in citys trap the wind.
reducing UHI.
-urban greening
-cool surfaces
-cool cars
milan- vertical forest on skyscrapers
chicago city- installed green roofs which are 21 dgerees lower than other buildings.
los angeles- white pavements
why does china suffer from air pollution
smog build up has made the area highly polluted. the citys are darker and harder to see in and 2000 have died from the smog.
what is the clean air act
it is a policy introduced in 1956 which brought about smoke free zones and pollution monitoring
why is carbon monoxide bad
it is a greenhouse gas which traps heat and pollution. it is estimated that transport is responsible for 90% of all carbon monoxide emissions. breathing in can cause health problems.
pollution reduction schemes
-ulez
-congestion charge
-park and ride
-cycle super highways
-improvemnst in public transport
-electric cars
-car sharing
-laws
