Local Climates

Local climates describe those climates which have influence over very small geographical areas, perhaps only a few miles or tens of miles across. Under certain conditions local climatic effects may predominate the more general pattern of regional or latitudinal climate. Examples of local climates include land and sea breezes, the orographic effects of mountains and heat island effects of cities.

The development of the sea breeze mimics on a much smaller scale the circulation cells of rising and descending air that make up the Earth's general circulation. On a warm summer's day at the coast, the land heats up faster than the adjoining sea, and the warm surface air rises. Cooler air offshore is drawn in to replace the rising air inland, and a cool sea breeze develops. Usually, the effects of the sea breeze can be felt over only a few miles, but occasionally the air blows inland much further. At night, the land cools down quickly radiating heat to the atmosphere, whilst the sea remains relatively warmer. Under these conditions the sea breeze may reverse to form a land breeze.

The presence of mountains can significantly influence the local climate. Mountains force air to rise, and consequently assist the development of clouds and precipitation. It is not uncommon for rain to be falling at the top of a mountain, whilst further downwind it may be dry and even sunny in the rain shadow.

Cities contains a lot of concrete structures like streets and buildings which soak up sunlight during the day. At night, they release this heat, which warms urban areas several degrees Celsius above nearby rural areas. This phenomenon is known as the urban heat island effect.