The inner city itself profits from the welfare benefits of more sizable open spaces such as the Airport Tempelhof or the Volkspark Friedrichshain. Smaller, preliminary open spaces serve as “green stepping stones” and facilitate the infiltration of cold air into the developed areas.
The favourable areas are juxtaposed to burdened areas with an above average heat load and ventilation deficits. This pertains to following boroughs:
The peripheral, concentrated district-centres, however, also exhibit a raised potential bio-climatic impact, as e.g. in the boroughs or districts
- Ober- und Niederschöneweide,
In addition, almost all districts feature insular housing blocks with a potential burden. However, structurally, high-rise settlements tend to have a better ventilation than portrayed in the map. Sporadically, the burden can be so great that even an existent cold air flow cannot compensate it.
The illustration of potential transport-induced air pollution along main roads complements the spectrum of occurring burdens. This is a model-based calculation for the reference year 2001, showing for single street sections the boundary values of the 22. BImSchV for NO2 as an annual mean, which should be adhered to by 01.01.2010, and which will likely and most likely respektively be exceeded. Inner city main roads are especially affected by the elevated burdens; of the total around 10 % of the analyzed road network exceed the later boundary value.
Structures which allow air exchange and introduce cold air are the central link between compensation spaces and bio-climatically burdened affected spaces. Air-stream channels should usually offer a low surface roughness, whereby lesser wooded valley and floodplain areas, larger green spaces and tracks offer the required attributes. Wide roads, because of their immission load, can only aid the climatic balance, but not the transport of fresh air. The air-stream channels are sub-divided according to process in the Climate Functions Map, where a cold air producing (partial) area can also fulfil an air-stream channel function.
The predominant form of air-stream channels are thermally induced types in combination with a compensation space, which can be led back to the utilisation-based temperature differences. Exemplary for such inner city channels are the allotments at the Priesterweg which transport the cold air northwards coming from the graveyard on Bergstraße in Steglitz and from Insulaner. Furthermore the allotment am Heckerdamm as well as the Volkspark Rehberge channel a fraction of the cold air produced at the Airport Tegel towards the city centre. A number of further thermally induced air-stream channels can be found north of the axis Tegel – Lichtenberg as well as in the south between Lichterfelde and Bohnsdorf. In the western part of the city the channels are grouped around Spandau and lead cold air directly out of the northern Grunewald and the bordering regions towards the city. If a green space borders directly on a developed area, an air channel becomes obsolete.
Predominantly orographically induced air-stream channels are concentrated in the eastern part of the city. These are about valleys, e.g. Wuhle and Mühlenfließ, which, because of their alignment, width and terrain attributes, can be used as air-stream channels. To that effect, one can class in the western part of the city the depth line from Grunewald trough Hundekehlsee – Dianasee – Koenigssee – Halensee.
The lowlands of the larger rivers like Spree and Havel exceed this function and also possess a characteristic for superordinated air-stream and ventilation channels. They benefit the air exchange in the bordering developed areas even under strong, dominating weather conditions.
A spatial cold air out-flow is limited to areas with an inclination of > 1°, and is, because of the relatively low height differences, scarce in Berlin.
For that reason this process is interlinked to the few areas with a noteworthy inclination like that of the Grunewald and the Köpenicker Bürgerheide. Furthermore, in the northern part of the Tegeler See, Kaulsdorf and in the Forst Düppel one can assume cold air flow. The cold air delivery is above average on these wooded slopes because the long-wave emission is very high, and with that the primary cooling rate. This occurs not from the ground, but from the upper treetops. Due to the size of the emanating surface the cold air can flow in and over the treetops, instead of first subsiding into the trunk area. (Groß 1989).
Map 04.11.2 Planning Advices Urban Climate
The Planning Advices Urban Climate Map is an integrated evaluation of the facts relevant to planning shown in the Climate Functions Map. Protection and development measures for the improvement of the climate and also – by means of attenuation and removal effects – of the air. The goals of
- Development and
- Reconstruction of
climatic and immissions-ecologically important surface structures (Mosimann et al. 1999) correspond to the main idea of these efforts. The associated planning advices provide information on the sensitivity against usage changes from which climate-founded requirements and measures in the course of areal planning can be deduced. Below, the planning classification of climate-relevant elements in Berlin is considered.
Green- and open space inventory
Urban green spaces and green spaces near settlements have a substantial effect on the urban climate and positively influence the direct surroundings micro-climatically. Larger coherent green spaces constitute the climatic regeneration potential. The produced cold air mass flow as a qualifying parameter, however, takes a back seat in this regard. The spatial position and with it the question which bioclimatic load a respective building development involves, is much more important for a classification in the planning process. Ultimately, a green space with only minor production of cold air can also bring with it a significant benefit in densely settled areas.
Of very high importance concerning the urban climate are green and open spaces with an impact on bio-climatically stressed settled areas. These are above all large, inner-city green spaces such as Großer Tiergarten and Volkspark Friedrichshain, and open spaces on the premises of the Airport Tempelhof. Vitally important are furthermore smaller parks, ruderal areas and wasteland, as well as sports grounds that are only sealed up to a moderate extent, as far as they can achieve a relieving effect on the neighbourhood. This results in the highest sensitivity of these areas against intensification of utilisation and the following planning advices:
- Avoidance of exchange barriers against built-up border areas,
- Reduction of emissions and
- Cross-linking with open spaces.
This means that edificial works and utilisation contributing to the sealing of these areas can lead to further alarming climatic damage. Alongside the aforementioned and other individual areas of this class the larger distant areas such as open spaces adjoining Blankenfelde or in the Wuhlheide can also be assigned to this category. The largest coherent area in this context extends from the Grunewald over the green coined settlements in the district of Lichtenrade to Rudow.
Green and open spaces with a connection to urban areas with a low level of pollution or even a favourable microclimate possess a high to medium importance to the urban climate. They are mostly located in a considerable distance from the city centre and are connected to the urban areas with a minor bio-climatic load that is situated beyond the course of the outer urban railway line (S-Bahn-Ring). Among these are the following areas:
- Green spaces and suburbs pervaded by greenery between Bucher Forest and Malchow,
- Krummendammer- and Köpenicker Bürgerheide,
- Forest Grunewald northwest of the Avus as well as the Airport area Tegel and
- Forest Spandau.
These areas possess a high sensitivity regarding utilisation intensification, whereby air exchange with its surroundings should be especially considered.
The third category constitutes green and open spaces of low urban climatic importance. These are areas which either possess a minor influence on – burdened – developed settlements, or have an insignificant cold air production. The latter can often only offer a small area size and are usually situated in the inner city. These areas can by all means take on a role as climatically ecological comfort islands, provided that they feature micro-climatic diversity (e.g. bodies of water, shadowed and sunny areas).
The Gatower Heide and the green settlements in Frohnau and Heiligensee are sizable areas which have a minor relevance. Constructional intervention in these areas would only carry minor climatic changes, as long as the air exchange is not significantly compromised.
The settlement areas situated in the cold air affect range of a green space are typically sufficiently ventilated and exhibit a small to no bio-climatic importance, (see Map 04.11.1 Climate Functions). To preserve this favourable state, the high sensitivity regarding utilisation intensification has to be considered. Planning-wise exchange barriers and further aggregation have to be avoided.
Climatically favourable settlement areas are sparsely developed and green settlements, e.g. mansions with a low sealing level, a high vegetation level and a relatively high nocturnal cooling rate. These areas are cold air producers themselves, to a certain extent, and aid the cold air flow of neighbouring open spaces. Green settlements are usually found outside of the S-Bahn-Ring, but some are near the city centre (e.g. Garden City Tempelhof west of the Airport). These areas lead neither to an intensive bio-climatic impact, nor do they impede air exchange. They typically have a low sensitivity against utilisation intensification, as long as the building heights are kept low and the parts of the structures are aligned to the cold air flow. Spaces bordering directly on burdened areas will have a high sensitivity due to the climatic relevance.
Lesser burdened settlements are also non-ventilated settlement areas with a low bio-climatic burden. Crucial for this classification is not so much the non-existent cold air affect range, but rather a low potential heat load. This results in a high sensitivity regarding utilisation intensification and the avoidance of further aggregation.
Impacted areas, on the other hand, usually exhibit ventilation deficiencies and an above-average heat load. These are divided into settlement areas with a low, in some cases moderate as well as with an average, in some cases high bio-climatic load. Under consideration of the impact level, a high or very high sensitivity regarding utilisation intensification results. Under urban climatic aspects, these areas are in need of rehabilitation, which results in the following planning advice:
- No further aggregation,
- Improvement of ventilation and increase of vegetation,
- Conservation of all open spaces and
- De-sealing and, if necessary, planting of inner courtyards.
Beside the inner city area there are also districts with strongly developed centres, e.g. Spandau, Weißensee or Hohenschönhausen. Furthermore, a low to average local impact may occur in the entire city area and is not limited to the aggregation areas. In isolated cases a bio-climatic impact can occur despite an existing cold air affect range. In such a case the potential impact situation can be so high that even a cold air flow is not able to achieve a significant compensation.
The situation in the peripheral area of Tempelhof is shown in Fig 6. The bio-climatically impacted industrial areas along the S-Bahn tracks are especially visible, in particular in the district of Mariendorf.