2. Climate and air as planning factorsWind
Information on wind speed
and wind direction
is necessary in order to characterize wind.
In contrast to temperature measurements, the identification of the wind conditions near the ground is carried out at a measuring altitude of 10 m above flat and undisturbed terrain (VDI guideline 3786, Part 2, 1988). Measuring altitudes of 6 m are also common in climatological analyses.
About 200 stations constantly record the wind conditions in Germany and therefore allow for the drawing up of wind statistics.
An equivalent to wind speed is the term "wind force", which is preferentially used in the context of the Beaufort wind scale containing 12 levels to describe wind speed. The coast line of regions in Northern Germany has an annual average of about 6 m/s, flat inland regions about 4 m/s, Southern Germany about 2-3 m/s. City centres have an average annual wind speed that is still significantly lower.
The wind rose indicates the frequency of occurrence of the individual wind directions from which the wind is blowing.
Indications on the wind speed complete the information on the average wind conditions. The wind rose combining frequency of occurrence and wind force (force wind rose) indicates the frequency of occurrence of particular wind direction sectors (force sectors) for each wind direction separately.
For many purposes it may be useful to examine force wind roses separately according to different months and seasons. As for the question of heating requirements or insulation of a building, it is mostly the winter half year that counts.
What plays a major role in the planning phase are local wind systems that may develop as a result of the surface structure or topographic conditions. These wind systems, like valley and mountain winds or slope and cross field winds, may be completely decoupled from supraregional winds. They are of significance for land use planning in the context of heat islands and air pollution situations. As these winds generally only occur near the ground, they are highly influenced by building measures. Knowing these wind systems is essential to guarantee thermal comfort and reduce air pollution in the cities. Special measurements are often necessary for this purpose. The use of smoke grenades usually is evidence enough for local wind systems.
|© City of Stuttgart, Office for Environmental Protection, Section of Urban Climatology