Models WG Urban Climate
Measurements and model simulations complement each other in the investigation of urban climate issues, as this is the only way to obtain evaluated, transferable statements covering the entire area. 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.
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. 1: Air temperatur 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.
Fig. 2: Heat load in Dresden-Gorbitz for a cloudless, hot day in mid-July, averaged over the period between 9:00 - 18:00 based on model simulations with ENVI-met. Maximum loads are found on unshaded, sealed squares and streets. Shading by trees in parks and on paths reduces the "perceived temperature" (UTCI: Universal Thermal Climate Index) by about 10°C.