. It is 30% more likely to rain in urban areas due to the UH high effect
. Concrete holds 2000 times more sunlight than an equal volume of air
. Urban areas compared to rural areas has a temperature difference of up to 0.5 degrees
Temperatures
Temperature- the urban heat island effect is when urban areas have higher temperatures than rural areas. This is due to the albedo effect and the rates of evapotranspiration. The land use in urban areas especially in the CBD is tall concrete skyscrapers and tarmac roads, which are low albedo surface is. Therefore, incoming solar radiation is absorbed by the surface is during the day. Then in the early evening, the stored radiation is released as shortwave radiation which warms up the surrounding areas leading to a warmer temperature. Also, in the CBD, due to the lack of vegetation, there is a decrease in the rate of photosynthesis. This leads to a decrease in the release of cool water vapour, which would call the surrounding areas. Some ways to counteract the warmer temperatures is through installing green roofs on skyscrapers like in Charlottesville North Carolina where this will lead to an increase in the rates of evapotranspiration and improve urban drainage. Also, the walls and roofs at the Atlanta food bank have been painted white, to increase the number of albedo surfaces leading to an increase in the reflection of solar radiation back into the atmosphere.
Precipitation
this is when warmer temperatures lead to an increase in the magnitude of apple transpiration. Therefore, the warmer particles rise up in the atmosphere creating a cyclonic environment [low pressure environment] on the surface. The rising of the particles will continue until it loses its kinetic energy and begins to cool down and condense. These particles will clump together to form cumulus clouds, which once heavy enough will release the particles as precipitation called convectional rainfall. Or a graphic rainfall takes place when the rising particles create a frictional force with the sides of the skyscrapers which mimic mountainsides.
Thunderstorms
this is very similar to the formation of precipitation, but the rate of apple transpiration is much greater leading to the formation of cumulus limbus clouds. These clouds will produce torrential rainfall which is high levels of rainfall in a shorter period of time , leading to flash storm events. these storms are most likely to take place during the early evening when UHI effect is at its maximum.
Fog
this is mist on ground level an forms in specific conditions. These form in temperature inversions where the cool air lies below warm air which creates an anti cyclonic environment [high pressure environment]. During cool overnight temperatures, the water particles will condense to form mist. These mists can last for a long duration of time if there is a high level of vehicle emissions. These emissions contain condensation nuclei which attracts water particles, thus producing a larger and more persistent fog.
Air quality
- Particulate pollution- this is pollution that was common during the industrial revolution, where factories where the combustion of fossil fuels produced pollution which contained suit and dust particles.
- Photochemical pollution- this is when vehicle pollution which contains nitrous oxide reacts with sunlight producing the pollution. These have hazardous impacts in dry hot areas like LA and Tokyo. In Tokyo, this has become a major issue where citizens now have to wear masks on a regular basis.
Pollution reduction policies
- The introduction of the Clean Air Act in 1952 and subsequent reforms in 1956 was in response to the great London smog.
- In 2020, the low emission zone and the ultra low emission zone were introduced to prevent vehicles older than 2007 from entering the zones, with older vehicles facing a 15 pound charge to do so.in October 2021 these zones were expanded to include the inner London ring roads with lobbying to push the zones to cover the entirity of the M25 by 2023.
- The congestion zone in 2007 located in central London prohibited polluting vehicles to enter the zones without paying the congestion zone charge.though this was deemed ineffective becausr most of the affluent residents that are located inside the zone can afford private healthcare.
- Cycle for hire schemes in 2012 in conjunction with the cycle superhighways made cycling more accessible.
- 200 electric buses added to the London bus fleet however in late may 2022 six of these electric buses caught fire in Hertfordshire when it was charging which led to 100 electric buses to be decommissioned for further inspection. This shows that full electric buses still need much work.
- The hopper fare of £1.55 for making unlimited journeys in a one hour period is meant to incentivise the use of public transport.
- The government grants of 3000 pounds to be put towards a brand new electric vehicle purchase though the government only set aside a set amount of money for which this can happen.
- Crossrail and the HS2 railway projects to expand the public transport network allowing more people to use it.
- The introduction of E10 petrol in July 2021, where 10% of the petrol is made up of bio ethanol.