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Methods of Information Acquisition
for Planning (Nature measurements, Wind tunnels, Modelling) |
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4.3.3 The
Cold-Air Flow Model KALM
The model KALM (SCHAEDLER, LOHMEYER 1996) is a cold-air flow model. It calculates the time-elapsed progression of cold air flows when provided with temporally-constant cold-air production rates. The horizontal wind velocity and the volume of cold-air flow are calculated along with the density of the cold air layer. Through the coupling of wind fields calculated by KALM with dispersal models, e.g. LASAT (JANICKE, 1996), pollutant dispersal in cold-air flows can also be calculated. Figures 4/35a-c shows examples of the KALM model for the flow-density volume of cold air in the city area of Stuttgart. The cold air flow-density volume is the amount of cold air in m3 that flows per second through a 1-m wide strip spanning the vertical distance between the earth’s surface and the top boundary of the cold air layer. Its unit is m3/ms. The Neckar Valley and the Nesenbach Valley, among others, belong to the significant flow systems in Stuttgart. The entire flow of cold air in the Nesenbach Valley amounts to about 100 million m3/h, whereas the magnitude of the cold air flow reaches up to 95 m. Higher-lying areas and the upper sections of valleys are known as primary sources of cold-air production, while the middle and lower sections of valleys as well as low-lying areas are cold-air collection and blockage areas. Since the latter areas are often densely settled, they can exert a "cold-air negating" effect via the warming and flow obstruction associated with their structures. A similar cold-air flow model as KALM is the model KLAM from the German Weather Office. |
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