RECOMMENDATIONS FOR PLANNING
6.4 Planning-Related Urban Climate Studies

Air-hygienic and meteorological studies can provide significant support to solutions to planning problems. Meteorological measurements as well as the other study methods introduced in Chapter 4 require appropriate operational timeframes. Thus a series of stationary climatic measurements should include each meteorological season, thereby comprising at least one year. Beyond that, there is also the time needed for evaluating the results. Various time requirements come into consideration for other methods, such as the time for model construction (wind tunnel), waiting for suitable weather conditions (tracer gas studies; ambulatory measurements), the obtaining of permission for access to the study area or for setting up measurement instruments, as well as the preparation of useable maps or databases for model calculations.

To avoid urban planning delays due to outstanding expert opinions, the necessity of planning-related studies should be determined as early as possible. If basic data on the local climate was systematically collected in time, processing timeframes can usually be reduced significantly. A further big advantage is that climate and air quality maps provide information on site-related restrictions and thus on the climatic relevance of the project even in the run-up to planning. Many cities have already carried out urban climate studies. These studies become inevitable also in the context of climate change adaptation strategies (see Chapter 2.11.3). Generally, only very small local changes of the climate arise from building measures. When considered separately, the change caused by a specific measure is close to detection limit and falls within the natural spatial and temporal fluctuation range of climatic parameters. The reference to the total climatic effect on existing buildings does not admit to the irrelevance of planning but constitutes a perfectly appropriate argument with regard to the real features of urban climate. Small-scale climatic changes as a result of a change of use are only relevant for spatial planning when they can be used for the evaluation, like a "favourable" or "unfavourable" note.

As there is no universally valid evaluation of climate, it can often be hard to judge whether a particular planning project will have negative climatic impacts or not. As practice shows, expert opinions are often required for very specific issues, like profit cuts at frost-sensitive specialised crops from stagnant cold air. Another frequent reason for neighbourhood complaints is the depreciation of a property due to interferences from the neighbourhood or the "theft" of light, air and sun. The following meteorological disciplines can contribute their expert opinion to find a settlement for disputes:

• Human biometeorology (for questions of thermal stress, pedestrian disturbances through draughtiness, cooling strains, air pollution)
  
• Agricultural meteorology (for cultivation conditions for specialised crops)
  
• Technical climatology (for questions of technical safety, wind and snow loads, forma-tion of black ice, frequency of fogs, dimensioning of sewer systems and rainwater catchment basins, heating requirements, the best location for power supply installa-tions, the use of alternative renewable energies)
  
• Immissions climatology (for questions of the dispersion of pollutants and its technical evaluation)