Earlier studies have shown that an urban park at night-time establishes its own cold climate in situ (i.e. Oke, 1989; Spronken-Smith, 1994). Daytime studies, on the other hand, are less numerous and show conflicting results (i.e. Bründl et al.,1986; Jauregui, 1990/91). Since temperatures usually are higher during daytime, when people also are most active, the influence of green areas during daytime is of large interest. Thus, the aim of this work is to study:
1. Air temperature development in a park and its built-up surroundings during daytime.
2. Influence of local factors as sky view factor (SVF) and distance from the park border on the air temperature pattern.
3. Influence of meteorological factors as global radiation, cloud cover, wind speed and wind direction on the air temperature pattern.
The study was carried out in the city of Göteborg (700 000 inhabitants) that is situated on the Swedish westcoast. Swedish cities have a quite high density of green areas and in Göteborg the fissure valley landscape gives a lot of natural green spaces. For the study a large park, together with its built-up surroundings, were selected. The park, Slottsskogen, which is the largest park in Göteborg, has an area of 156 ha.
The study has been concentrated on the daytime conditions and the results are based on data from June 18 until September 30, 1997. Measurements have been done with the help of automobile traverses and permanent stations, including 14 tinytalks and 2 masts with logger equipments. The instruments have been protected with specially designed radiation shields. A number of locations have been chosen to represent different distances from the park border and areas with different SVF. In addition to the above mentioned stations, data from two standard meteorological stations have also been used.
Preliminary results indicate that there are large differences in air temperature between urban built-up and green area during day-time. The magnitude of the differences vary during the day and are influenced by geographical factors, such as for example SVF, and by meteorological factors, such as global radiation and wind speed.
More results will be presented at the conference.
References:
Bründl W, Mayer H, Baumgartner A (1986) Untersuchung des Einflusses von Bebauung und Bewuchs auf das Klima und die lufthygienischen Verhältnisse in bayerischen Grosstädten. Stadtklima Bayern, Abschlussbericht zum Teilprogramm "Klimamessungen München", Lehrstuhl für Bioklimatologie und Angewandte Meteorologie der Universität München (in German)
Jauregui E (1990/91) Influence of a Large Urban Park on Temperature and Convective Precipitation in a Tropical City. Energy and Buildings, 15-16, 457-463
Oke TR (1989) The micrometeorology of the urban forest. Phil. Trans. R. Soc. Lond. B 324:335-349
Spronken-Smith RA (1994) Energetics and cooling in urban parks. Unpubl. Ph.D. Thesis, The University of British Columbia, Vancouver, p 204