Tools WG Urban Climate
Tools
Measurements and model simulations complement each other in the investigation of these topics, as this is the only way to evaluate comprehensive and transferable statements. Model simulations provide insights into the temporal and spatial characteristics of the urban climate and the effect of the urban climate on stressors and burdens of the population. This allows effective adaptation and development scenarios to be derived and projections of previously unobserved situations to be simulated. From stationary and mobile measurements, in combination with detailed structural information, insights for the further development of model approaches are drawn and implemented.
The continuously supervised urban climate stations (example: Model project Integral Water Management MIW) provide the temporal course at representative points in the city. These measurements are characterized by high-quality sensors. Among other things, infrared cameras are used (Fig. 1), which effectively scan the thermal properties of different surfaces.
Fig.1: Surface temperatures on the Straße des 17. Juni in Berlin, detail from a time series of several days (1 min cycle), recorded with VarioCAM HR from InfraTek. The shading effect of buildings and tall vegetation, as well as the heating of different building materials is visible.
We record the spatial variability of the measured variables in the urban area using our mobile measuring systems (Fig. 2). The high temporal resolution of the measurement (1 Hz) allows the exact spatial assignment of the measurements.
Fig. 2: Mobile measuring systems to record the exposure of city dwellers. The ambient conditions (radiation, air temperature, humidity and wind) are recorded every second and assigned spatially.
The models used in the WG Urban Climate complement each other in their scales and scope of application. An overview is given in the model matrix. In the microscale, the urban climate models ENVI-met, PALM-4U and the radiation model SOLWEIG are applied, the next larger scale is covered by the Weather Research and Forecasting Model WRF. Data sets from various mesoscale climate models (including COSMO-CLM) and ensembles from global and regional models are used to drive the microscale urban climate models. ENVI-met is suitable to represent the effects of three-dimensional urban structures on the diurnally and seasonally variable urban climate. With its user-friendliness, it is an ideal tool for scenario analysis of urban areas, including the derivation of effective climate change adaptation measures. At the same time, ENVI-met is also used for the qualification of students. PALM-4U is a new urban climate model with enormous potential in basic research of near-surface processes in the urban atmosphere. The turbulence-resolving simulations possible with it provide realistic representations of the flow and the urban climate, especially for critical dispersion calculations. Due to its very good scalability, entire large cities can be simulated with adequate resolution.
Fig. 3: Air temperatures simulated with PALM-4U for the city center of Dresden at 15:30. The greatest warming shows the central old town and south of the shopping area up to the main station. The situation shows the cooling effect of parks and green areas (Großer Garten southeast of the city center). The points south of the Großer Garten represent mobile measurements.