How wind field calculation works for the Stuttgart region
General information:
The wind distribution in a certain region depends on various factors. These factors are among others the large-scale inflow, topographic conditions and land use.
"Diagnostic flow models" calculate the three-dimensional wind distribution in a broader region on the basis of wind speed and wind direction measured in various stations with simultaneous consideration of topographic conditions and land use.
The calculation for Greater Stuttgart is based on 30-minute average values collected by the measuring stations Stuttgart-Zentrum, Berger Tunnel, Branddirektion and Geschwister-Scholl-Gymnasium.
Data representation:
The diagnostic wind field model "DiWiMo2" calculates the wind fields every 30 minutes for an area of 20 by 20 km and portrays the wind field for the ground layer (5 m above ground).
The wind field is charted in a vector diagram. The vector arrows are aligned in the direction of the wind. The length of the arrows indicates the wind speed: the longer the arrow, the harder the wind.
Two different types of maps are available for the wind field representation. The city map helps you to orientate quickly in Stuttgart. The relief map clearly shows the topographic influences on the wind field in the Stuttgart region.
Wind field calculation with the diagnostic wind field model "DiWiMo2":
"DiWiMo2" is a diagnostic wind field model. It is based on the theories of N. Moussiopoulos, Th. Flassak and G. Knittel (1988). A diagnostic wind field model is a model for calculating a flow field in a topographically structured region on the basis of wind measurements. Obstacles, like buildings, trees and walls, are not directly eliminated but are considered as topographic surface roughnesses. Diagnostic models require little disk space and calculating time and thus work very well with online calculations and representation.
"DiWiMo2" receives the collected values for wind speed and wind direction from four measuring stations. It works out a vertical wind profile and interpolates and extrapolates between the data in order to receive a three-dimensional initial wind field. The second step consists of a correction of the three-dimensional initial wind field in order to comply with the conservation of mass in the assumed area. This is achieved thanks to the solution of an elliptic differential equation.
Literature:
Moussiopoulos N., Flassak Th. und Knittel G. (1988): A refined diagnostic wind model, Environmental Software 3, 85-94.
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| © City of Stuttgart, Office for Environmental Protection, Section of Urban Climatology |
