Climate in cities. Advanced
The presence of buildings and roads affects the radiation, heat and water balance of an area. This means that the local climate in a city is different to that in the surrounding countryside. Urban bioclimatologists study how the urban climate affects living organisms, particularly humans.
Air pollution in urban areas affects human health. Energy production, industrial processes and vehicles emit many different air pollutants into the atmosphere. For example acid rain, caused by emissions of sulphur and nitrogen oxides, causes not only soil degradation and lake acidification, but also faster corrosion of metals and decay of buildings constructed of limestone and marble.
There have been many attempts to reduce air pollution. Monitoring now occurs in endangered areas and international agreements are now in place which are helping to improve air quality on a global scale.
Industry, energy production and transportation are heavily concentrated in the cities. These sectors of the economy are the main sources of air pollution, delivering large amounts of gases, particles and dust into the atmosphere. Each sector delivers a different cocktail of pollutants but as energy production and transport are both based on the combustion of fossil fuels they emit similar chemicals into the air. The effect of the pollutants include the modification of our climate and the deterioration of both human health and the natural environment.
Many attempts have been made to reduce air pollution. At present, the concept of sustainable development is the most widely accepted strategy. Its assumption is that economic growth can be permanent and well-balanced so as to satisfy the needs of society and that this can occur without degrading our natural environment. To make this a reality, new technologies are being introduced to reduce air pollution and more recycling is encouraged. Better monitoring is being introduced and, since air pollution is a global problem, international agreements to help improve the situation are being sort.
There are large differences in solar radiation and heat and water balances between urban and non-urban areas.
The urban atmosphere contains lots of pollution in the form of solid particles. Together with the strongly altered mostly artificial urban surface, these significantly change the radiation balance in a city compared to non-urban areas. The radiation balance and the heat balance are closely correlated. The heat balance of an urban area is complex due to the large number of buildings and includes heat exchange through conduction by the ground, streets and walls as well as the heat from the combustion of fossil fuels. In a city, the water balance is also controlled by these same elements, but their proportions are significantly different. In urban areas, the amount of rainfall is higher than in non-urban areas.
The urban climate may have a negative effect on people primarily through air pollution and noise. Urban air pollution from vehicles is particularly harmful, it can cause acid rain and can reduce the amount of solar radiation reaching the ground. Increasing the amount of parks can help reduce the negative impacts of the urban climate on humans.
Acid rain, acid fogs and acid snow directly and indirectly affect our health. Breathing acid fogs can damage our respiratory system and acidic waters contain higher than average levels of heavy metals. Drinking these waters can cause many serious diseases.
The main pollutants responsible for acid rain are the nitrogen oxides and sulphur dioxide. It's easier to reduce emissions of these gases by saving energy and reducing car use than it is to prevent damage by acid rain. Once the acid rain is formed all we can do is partially neutralise its effects with liming being the most widely used method.