• 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...

Introduction

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.

Middle

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.

Conclusion

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. Peri-glacial areas

    The thermal conductivity of the stones is greater than that of the soil; as a result the area under the stone becomes colder than the surrounding soil and ice crystals form. Further ice expansion widens the capillaries in the soil, allowing more moisture to rise and freeze.

  1. Rain by Somerset Maugham - Comment on the significance of the recurrent image of ...

    this again shows how the weather is winning the battle between the white men and the island. It also shows though how it has not stopped for as long as we thought it had, which shows its persistence. The description of the rain is in great detail.

  2. To ehat extent is climate change a lot of hot air?

    In addition to this the extent and the thickness of the Arctic sea ice has declined rapidly over the last several decades. Also, there is proof that glaciers around the world have been shown to be retreating. Had I been asked a couple of years ago if I believed in

  1. Energy tranfers within the atmosphere

    Reigning on Earth's Climate - Only about 70% of the solar energy that reaches Earth is absorbed, while the other 30% is reflected back into space by atmosphere and aerosols, ocean/land and clouds as a consequence due to the albedo.

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

    This is because fuels contain compounds of nitrogen formed from the proteins contained in organisms. When the fuel is burnt, these nitrogen compounds are oxidised to form fuel NOx .At the high temperature of combustion, atmospheric nitrogen and oxygen combine to form thermal NOx .

  1. Acid rain study

    Human activity is responsible for 65 million tonnes of sulphur dioxide deposited into the atmosphere in 1985 in contrast with natural sources which are responsible for only 25 million tonnes a year. It is accountable for 21 million tonnes annually of nitrogen oxides and this is about the same for natural sources with 15-20 million sources a year.

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

    Outline Method On Wednesday the 8th of March 2006 I will go to Chaldon Church in Coulsdon, Surrey. I will use a random sampling method to pick out the gravestones that I will be using in my experiment. For data calculations afterwards I will need at least 20 samples.

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