• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Urban Micro-climates

Extracts from this document...


Geography - Atmospheric Systems Essay a) Outline the characteristics of urban heat islands. (5) First and foremost the urban heat island can be defined as an effect whereby inner city areas tend to have higher mean annual and also higher winter minimum temperatures than the surrounding rural areas. The differences in heat usually become more substantial towards the centre of the urban areas. Heat is given off by factories, vehicles and home, all of which burn fuel and produce heat which aids the urban heat island effect. Also urban surfaces, such as concrete and tarmac, absorb substantial amounts of solar radiation before releasing it during the night. This occurrence therefore attributes to the much higher night time temperatures found in the centres of urban areas. Smog and pollutants found in the urban areas form a pollution zone which allows short wave insolation to enter, however the smog consequently traps the outgoing terrestrial radiation as this is of a longer wavelength. ...read more.


The release of heat from buildings is slow; consequently changes in urban temperatures often lag behind seasonal patterns. The wind is another key factor which has an influence on the extent of the urban microclimate. Usually built up areas tend to have lower wind speeds than surrounding areas, this is because taller buildings provide a frictional drag on air movements. Consequently, wind turbulence is created, providing rapid changes in both its direction and speed. Therefore a general decrease in wind speed occurs as the air travels to the city centre from the suburbs. In rare cases, the urban heat island effect may actually alter the local wind patterns completely. Indeed a low pressure area may develop as warm air rises over the urban area. As a result winds in urban areas tend to be 20-30% lower than average. However planners must consider the importance of a well designed urban area, as efficient air flow is essential so that damaging pollutants can be dispersed. ...read more.


On the other hand, thunderstorms are much more common in built up areas, due to the intense convection that can occur, particularly during hot summer evenings. An interesting example of an influential factor that specifically affects an urban heat island is the urban rainfall in Manchester - a city in northwest England. Recent research undertaken by a local university has suggested that the erection of a band of high rise tower blocks in Manchester during the 1970s has brought more rain to certain parts of the city. The level of rainfall has increased by approximately 7% over recent decades. This has occurred as a consequence of the turbulence made by the micro scale effect of tall buildings, which forces the air to rise. Also the heat island effect means that the temperature can be up to 8�C higher in the centre of the city in comparison to the surrounding countryside. This contributes further to the above average rainfall, by causing the air to rise further as a result of convection. ?? ?? ?? ?? Alex Potter 6N2 23rd March 2009 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Atmosphere & Weathering section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Atmosphere & Weathering essays

  1. Marked by a teacher

    Urban Areas have a significant impact on climatic characteristics Discuss.

    4 star(s)

    The presence of pollutants also raises temperature as the pollutant dome, present in urban areas, can absorb heat and prevent some escaping. This pollutant dome will re-radiate heat down to the urban surface. Similarly the height and arrangement of buildings will also impact the temperature.

  2. Experiment to Compare the Percentage Area Covered by Lichen on Gravestones and the Age ...

    Once the first gravestone in the sample has had its age and percentage lichen coverage noted down then move on to the next in the sample and repeat the measuring process for all 20 gravestones. In the case of a pilot study, before I undertake the whole experiment I will

  1. Photochemical smog is the most widely known and perhaps most serious air pollutant. It ...

    Favourable conditions for photochemical smog Certain conditions are required for the formation of photochemical smog. These conditions include: 1. A source of nitrogen oxides and volatile organic compounds. Industrialization and transportation create these pollutants through fossil fuel combustion. [1] 2.

  2. A comparison of Fluvial and Glacial Sediments (deposits) In the Glen Rosa area of ...

    I will measure Roundness by- comparing sediment sample to the guide shown below, this may be difficult to decide which category the rock goes into however for the sake of speed it was my primary choice.

  1. Acid rain study

    Acid rain is a global problem and requires international co-operation to help solve the problem. It is a global problem because air currents that produce our daily weather also carry pollutants over long distances. When pollution travels between countries like this it is known as trans-boundary air pollution.

  2. Describe and explain the variety of landforms found in periglacial areas.

    Or if an old pingo, and no water is being added, decays an ognip is left. This is a circular rampart of sludged material with a hollow/basin where the pingo once was. This may also fill with water. Another periglacial process, which creates landforms, is mass movement.

  1. Distinguish between the terms active layer and permafrost.

    and ground contraction (Figure 5.7). Frost-heaving results in small dome-shaped polygons with larger stones found to the outside of the circles, whereas ice contraction produces larger polygons with the centre of the circles depressed in height and containing the bigger stones. The diameter of an individual polygon can reach over 30 m.

  2. Climate in different cities around the world

    clothing, fatigue and hunger, even if the air temperature is above freezing. Use a strong sunscreen, hat and barrier cream for your nose and lips. Calamine lotion and aloe vera are good for mild sunburn. Protect your eyes with good-quality sunglasses, particularly if you will be near water, sand or snow)

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work