The basis for the evaluation and separation of areas based on their climatic functions are the simulation findings for a radiation weather condition with low interexchange, as they were presented and specified by the results of the Climate Model Berlin – Analysis Maps. The insights gained by the regional climate model FITNAH are the foundation for the analysis of the actual climatic state, from which the interrelation of functions can be deduced.
Contrary to the previous widespread – drawing primarily on VDI directive 3787 sheet 1 – static considerations based on climate zones, in which a land use related uniform micro-climate was assumed independent from the position of the climatopes, the model-based approach provides now area-wide quantities of different parameters regarding the cold-air balance in Berlin. Furthermore, the dynamic aspect within the climate balance is considered sufficiently. The detailed calculation of wind and temperature conditions in Berlin was carried out using the FITNAH model (Flow over Irregular Terrain with Natural and Anthropogenic Heat Sources). A precise mathematical and physical description of the model can be found in the Digital Environmental Atlas and Groß (1993).
During summer high-pressure weather conditions with low wind speeds, local climatic peculiarities can develop particularly well in landscapes. Said weather conditions are characterized by cloudless skies and a very weak synoptic wind of less than 4 m/s. In the numeric simulation carried out here the spacious synoptic basic conditions are determined as follows:
- coverage ratio 0/8,
- geostrophic wind speed 0 m/s
- relative air moisture 50 %.
Beside the highlighting of the interrelation and neighbouring correlation between cold air producing green spaces and urban areas also a quantitative and qualitative evaluation as well as an illustration of the climatic burden and compensation potential of the variously structured spaces in the urban area takes place. Also the effects of the surrounding and undeveloed open spaces on the urban area were assessed. For this purpose the block areas of the Digital Map Berlin 1 : 5,000 (ISU5) were assigned all parameters, e.g. wind speed, air temperature at a height of 2 m and cold air volume flow. If a building block takes up more than one grid cell of a parameter, an average value is generated from the single values of the cells. Consequently, each building block has available a range of climatic parameters. Based on this, the variously structured spaces were awarded evaluation indices, more on which can be found in the chapter Methodology.
To identify areas with slope inclinations of > 1°, on which extensive cold air out-flows occur, a relief analysis was carried out, using the FITNAH Terrain-Elevation-Model. To determine the traffic-related air pollution during weather conditions with a low air exchange (inversion), the immission field for the air pollutant nitrogen dioxide (NO2) has been calculated area-wide with FITNAH and potentially loaded areas within green spaces have been defined. In addition to the FITNAH results, the potential traffic-based air pollution is figured out by the annual average nitrogen dioxide concentration in the street space, calculated with the programm IMMIS, for the year 2005 (cf. detailed description [in German] SenGesUmV 2008).