The expression “islet of heat urban” (ICU) made its appearance around the middle of the 20e century. It refers to a phenomenon of localized temperature rise in urban areas compared to neighboring rural areas. These heat islands are microclimates caused by human activities (power plants, heat exchangers, heat…) and urban planning (dark surfaces that absorb heat, like tar).
A time considered marginal, even beneficial in cities facing winters rigorous, in a context of global warming, the urban heat island phenomenon and its health implications potential are now taken more seriously, as they can aggravate episodes of heat wave and affect the biodiversity pushing back some species and attracting others, more thermophilic.
Different types of urban heat islands
Heat islands relate, for some, to measured temperatures at ground level and, for others, on temperatures observed in theair. The former are more intense during the day, when the urban ground heats up under the effect of solar rays. The second are more intense at night, when the materials of construction and others floor coverings return the stored heat. These islets can be observed up to two kilometers high.
Heat islands are also more intense in the city center than in the suburbs. The parks and green spaces as for them, constitute zones of freshness.
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