To What Extent Do Urban Areas Modify Their Climate?

Urban areas climate can often be very different to the surrounding rural areas, this is why urban areas are often described as having their own “microclimate” the differences in urban climates are due to number of different factors. In which the modify themselves to an example of the difference between urban and rural areas is somewhere like Calgary in Canada that experiences less extreme forms of weather to it surrounding area which include villages such as Banff and Canmore which get significantly more snow in winter and and normal slightly cooler than Calgary in summer.

Urban areas normally form a phenomenon known as urban heat island which is a zone of hot air around and above an urban area this results in higher temperatures than the surrounding rural areas this results in cities being warmer than rural areas and the temperatures becomes progressively lower as you move further away from the city, with the highest temperatures being in the city centre. Heat islands form due to a number of factors which occur within cities and are not really found in rural areas. The first reason is building material such as concrete and tarmac absorb large quantities of heat during the day as they are dark colours and when temperatures are cooler so normally during the night the heat is released which warms up the surrounding area. This explains why the effects of the heat island are more clear at night time as the city remains warm whilst the rural areas are much cooler and colder. Secondly there are a large amount of buildings with glass windows within the urban areas especially the CBD normally they have a high reflective capacity and reflect heat towards the streets were it is absorbed. A third factor influencing the heat island formation is the heat energy being emitted from industry due to the burning of fossil fuel which releases heat this also includes house heating as it contributes towards THISis a very small way. The heat energy warms up the air within the urban area contributing to the dome of warm air which is the heat island. Car emissions also act as particles in the air forming condensation which results in smog.

Urban heat islands can also have an effect on pressure. On a local scale as warm air rises over an urban area it draws in heat from the surrounding area and creates an area of localised low pressure. Pressure is also another factor in influencing the climate of an urban area. Strong pressure gradients develop between the windward and leeward side of buildings which can result in eddying occurring. Pressure gradient is the main driving force that causes the movement of wind from areas of high pressure to areas of low pressure. High pressure conditions create calm country breezes which move from colder rural areas to warmer urban areas. This is due to the