• 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)

    For example, in Winter there has been 100% increase in fog in urban areas, compared to rural areas. The significance of the impact of pollution can be seen in the various measures being taken to reduce its effect in urban areas.

  2. Marked by a teacher

    B)Explain why the amount of solar radiation absorbed by the earth's surface varies from ...

    4 star(s)

    The earth's tilt means that when the North Pole almost directly faces the sun it will have constant daylight, whereas the South Pole will be in complete darkness for almost the entirety of the day.

  1. Peri-glacial areas

    Valleys Wind Windblown Loess Stone Polygons are a result of frost heave, which includes several processes causing either fine grained soils such as silts and clays to expand to form small domes, or individual stones within the soil to be moved to the surface.

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

    So this is the real results table we developed. We were helped by 1 person in identifying some of the rocks, she was called Lucy and she was an instructor for this course. On the actual day we collected 20 samples from each site both the terminal moraine and the slip off slope.

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

    climate change, I would have said yes without a shadow of a doubt. I would have been armed with research to prove that global warming was happening, and that we, as humans especially in the MEDW, were to blame for the rising temperatures.

  2. 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.

  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. Energy tranfers within the atmosphere

    it is re-radiated to be absorbed by another object. This radiation allows Earth to lose heat at the same rate it gains from the Sun. The solar radiation emitted by the sun as a result of the furnace like processes that occurs in the sun reaches the peripheral boundaries of the atmosphere before being absorbed.

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