Model-based urban climate analysis
Under the complete project, two model runs were conducted with the meso-scale climate model FITNAH for a high-summer weather situation with a horizontal resolution of 10 m. The first model run is based on an allochthonous west wind weather condition occurring relatively frequently in Berlin during the summer months. The second model run is based on an autochthonous weather condition without higher-level wind influence used regularly for an analysis of the urban climate. Additional data, differentiated in space, were derived for the specific climatological parameters from the resulting meteorological fields. On the whole, therefore, three supplementing extensive data sets are available.
It is state-of-the-art technology that only one meteorological situation can be consulted for deriving the PHK. The autochthonous peak-summer high pressure weather condition without the higher-level wind influence was selected to do this for PHK 2015. It represents the weather condition, in which the urban climatic process sequence is most clearly pronounced, and accordingly on whose basis useful planning instructions can be derived. Since for specific questions (e.g. B-plan process, effect analyses of measures) the results of the analysis phase can also become relevant, its data can also be retrieved in the geo-portal.
Structure of planning advice map
The 2004 and 2009 editions of the planning advice map for urban climate consisted respectively of a map as well as brief, explanatory texts for the environment atlas. The PHK 2015 consists, for the first time, of three supplementary maps as well as an explanatory accompanying document:
- a main map
- supplementary planning instructions, as well as
- measures.
This method accommodates, on one hand, the high complexity of the topic, the enhanced significance within the inclusion of urban-climatic aspects in the urban development policy as well as the enhanced user requirements for accuracy of statements.
The “Main map” 04.11.1 is (enhanced in content and substantiated spatially) the equivalent to the PHK 2004 and 2009 editions. The map contains an extensive evaluation of the urban-climatic stress situations during the day and in the night (as well as summarised for an overall evaluation) and relief functions, and thus represents the technical basis for evaluation and decision-making for plans aligned to entire city as well as to partial spaces. In the “supplementary planning instructions” 04.11.2, selected partial topics of urban development were linked with the evaluation results shown in the main map as well as with further spatially high-resolution technical and geo-data. They act as basis for decision-making for specific technical plans or queries (e.g. urban redevelopment, sensitive uses, demography).
The “measures level” 04.11.3 contains, depending upon area type and actual space, the assignment of 30 individual measures to all ISU5 block (partial) areas as well as to all sections of “Detailed network” of the road network of Berlin. The level primarily focuses on improving or maintaining the status quo in the stock. However, those measures have also been expressed, which are relevant especially for the intensive new construction projects in Berlin.
Spatial units observed
The PHK main map differentiates mainly between three spatial evaluation units:
- Settlement area
- Green and open spaces
- Public roads, paths, places.
Those areas are assigned to the settlement area, which primarily fulfil the functions of living, working and public facilities. The human being stays mainly in the residential areas during the day as well as in the night. Green and open spaces comprise of all areas, which are primarily meant either for human relaxation (e.g. parks, gardens, forests) or provide other climate-ecological services (e.g. arable lands). From the perspective of urban climate, the green and open spaces can provide a dual benefit. Firstly, they are visited actively during the day and form an counter-weight to the possible thermal or air-hygienic stress in the road and settlement areas. Secondly, they produce and/or transport cold and fresh air, especially in the night and enable the adjacent population to have a relaxing sleep even during bio-climatic stressful weather conditions. Public roads, paths and places, on the other hand, play a role during the day as temporary staying places for the human being. They are visited either for longer stays (e.g. town squares) or as means to an end, in order to reach a destination (e.g. going to work or shopping).
The units of the ISU5 block map form the geometric space reference. In doing so, each area has been assigned uniquely to one of the three usage categories. The assignment was done on the basis of the so-called area types (see SenStadt 2010). The spatial unit “Public roads, paths and places” represents a special case. Their partial areas are recruited partly from ISU5 area types with a traffic-related usage allocation (incl. town square, promenade, parking place). The major part of the around 22,000 individual areas were derived from the detailed map of Berlin road network and represents actual screen sections so that in this way a spatial link could be made possible between the air-hygienic and thermal stress levels on the roads.
Out of the approx. 890 km² of Berlin city area, 373 km² (41.9 %) have been classified as settlement area, and 351 km² (39.5 %) and 121 km² as road space (13.7 %). The remaining 5 % of the total area of Berlin constitute flowing and stationary water bodies. Owing to their climatic compensation function, the open water bodies occupy an essential position in the city-climatic process sequence of Berlin. However, since the water bodies are normally not subject to any conversion or development pressure, they are shown in the PHK only for the purpose of information.
Approach, data basis and method of the process used for updating the climate data take into account a largest possible, simultaneously extensive detailing of the resulting statements. However, owing to the dynamic development in the city, the initial prerequisites for the evaluation on individual areas change faster than the possible update cycle of the maps in the environment atlas. Therefore, it is recommended to use the overlay function with the respectively latest air patterns in the geo-portal for an area check as well as for a comparison with the technical data of the PHK. From this, one can drawn inferences for the usability of the evaluation results.