Urbat heat island in Göteborg, Sweden
FC-02x Livable Future Cities (1st Run) - Compulsory Exercise 2
Uploaded on 2015-12-14 by PetraPalusova
[1]: https://edxuploads.s3.amazonaws.com/14501003723297071.png Göteborg is situated on the South-western coast of Sweden in valley landscapes. The most significant effect with a great influence on creating the urban heat island in case of Göteborg city are weather conditions and the topography. In a valley landscape the different valleys channel the flow and thus the vertical extent of the flow could be greater than the same flow on a flat landscape. One of the most significant features of the urban heat island in the Göteborg area is that the air flow in the lower layer is almost independent of the wind direction at higher levels. (The smoke emanating from the higher chimneys show a south-easterly air flow over the area. In the valleys, however, by the smoke plumes from chimneys lower than 30 meters, the urban heat island and the topography create an air flow directed towards the city center from the north, east and south.) The air flow from the valley in the north is the true urban heat island as it is directed almost opposite to the direction of the regional wind at a higher level. The urban heat island develops during anticyclonic weather conditions. The development of a urban heat island demands a large negative net radiation balance and little wind speed or calm weather. The questions are what limits in cloud cover and wind speed are required and how long must the conditions persist to develop the urban heat island. The heat island in area of Göteborg city is small due to the temperature gradient towards the sea. On the other hand, the weather conditions create an urban heat island in the eastern parts of the area. In the western parts of the city the urban heat island is not found. Instead there was an air flow through the mouth of the river towards the sea. Series of balloon measurements in the eastern area have shown the following pattern: first a cold air lake is built up in the valley and a ground level inversion is developed. When the urban heat island begins to blow the inversion is gradually broken up from below. The reason for the higher inversion base then probably depends on the greater temperature difference in the east. The urban heat island starts earlier and its vertical extension has time to grow to a greater height. The horizontal temperature gradient is supposed to reach the highest point at the border of the built-up area.