City-surrounding wind system
The city-surrounding wind system is a local wind system that is pronounced in cities , which ideally is oriented towards the city center and occurs at night or in the morning. It is induced by temperature and pressure differences between the city and the surrounding area and develops especially in warm, dry, low-exchange and low-wind high pressure weather conditions .
The heat island above the city is considered to be the engine for the wind system . The buildings in the area of the city have a good heat storage capacity , which sometimes contributes to the development of such a heat island. This results in a pressure and temperature gradient from the surrounding area to the heat island. The size of the city is decisive for the characteristics of a heat island, so the likelihood of winds directed into the city also increases with the size of the city.
The air heated up during the day rises convectively over the urban area and cooler air from the surrounding area flows in near the ground. The winds seldom reach wind speeds greater than 1–2 m / s and are very easily slowed down or even completely dissolved by frictional influences such as vegetation or buildings. The thickness of the air flow varies in the meter to decameter range.
In terms of urban climate , the wind system is quite useful because it serves as a fresh air feeder in the urban area and the polluted air is renewed or disposed of upwards.
See also
literature
- CD Schönwiese: Climatology . Ulmer Verlag, Stuttgart 2003, ISBN 3825217930