Climate Model Berlin - Evaluation Maps 2001
Map 04.11.1 Climate Functions
The Climate Functions map illustrates the actual condition of the climatic situation relevant to planning. Thereby bioclimatic burden conditions, equalisation benefits of cold air generating areas as well as spatial relations between compensation spaces and affected spaces are represented. Since both the equalisation effects and burdens are classifiable, planning priorities can be determined to point out which built-up areas are affected by changes in compensating spaces.
Green- and open space inventory
Vegetation-covered, open spaces with a considerable cold air production represent climate- and immission-ecological compensation areas. A high long-wave nocturnal radiant emittance during exchange-poor high pressure weather conditions leads to a strong cooling of the near-surface air layer, whereby particularly city parks near emitters must be considered of being perilled in terms of immissions. The quantity of the produced cold air depends on the prevailing type of vegetation, the soil characteristics and the associated nocturnal cooling rate. All in all 701 Green-space units were demarcated, whose qualitative classification regarding cold air mass flow is shown in Table 4.
The total area of the cold air producing surface amounts to approx. 43.854 ectares, which corresponds to an area percentage of around 49 % of the total urban area and can be regarded as very high.
Green and open spaces with a high cold air mass flow are predominately on the outskirts of the city. Usually the larger wooded and ruderal areas, graveyards and allotments are very cold air productive .The most important spatial urban climatic contributions for the city centre are from the Großer Tiergarten, the Airport Tempelhof and the allotments Am Priesterweg. These spaces are characterized by their extensive cold air affect ranges. A large part of the Grunewald also counts as a significant open space with a connection to the city centre. Green settlement types, which are aimed towards the city centre as well as occurring slope inclinations > 1°, assist the cold air flow considerably, so that the built-up areas in Schmargendorf and Wilmersdorf have a cold air penetration of up to 2000 m (also see the detailed explanation in the Map 04.10 (Climate Model Berlin). This, together with the allotments north of the Spandauer Damm, at the Heckerdamm as well as the Volkspark Jungfernheide and Rehberge result in a 10 km long cold air affecting area surrounding the western city centre. The green areas around the Volkspark Prenzlauer Berg and the central graveyard in Lichtenberg have a similar relevance for the eastern city centre.
Counting 58 green area units and a total size of approx. 37.820 Hectares, this category is spatially the largest. Its green area quota makes up approx. 86 % of the total green area, which can be traced back to the extensive wooded areas on the city outskirts.
The compensation benefits of areas with an average cold air mass flow are also to be regarded as important. In the city centre the Schlosspark Charlottenburg, the Volkspark Friedrichshain and the Volkspark Humboldthain show a significant cold air affect range. In the southern part of the city green settlement types without a connection to park or wooded areas possess an average mass flow. The areal sum of the open spaces classified as average amounts to 5.157 Hectares, which corresponds to about 12% of the total green area.
Green spaces which possess a low cold air mass flow make up a portion of 1,7 % of the total with 738 Hectares. This group is mainly composed of small graveyards, allotments and park areas with a size of up to 10 ha. These seldom possess an cold air affect range, as they are usually surrounded by buildings in a generally warmer area. An exception are those areas which are located within the affect range of green spaces with a stronger cold air production.
Green areas with a very low cold air mass flow usually cannot generate an affect range. These are small areas of about 2.5 ha, which are typically situated in developed areas. In burdened areas, however, even these small spaces can have a decisive function as climatic ecological comfort islands, as long as they feature a mosaic of different micro-climates, e.g. shadowed and sunny areas or cooling water surfaces (micro-climatic diversity). The percentage of this type of area is only 0.3 % with 139 Hectares.
The cold air generating areas of the surrounding countryside are often in direct contact with those of the city and can hence be seen as their extension. Due to the greater distance to the settled areas the flow field is at its maximum at around 6:00 a.m. The largest cold air generating areas can be found to the north-east of Berlin. The relatively conspicuous rise in terrain height here abets a wide-ranging in-flow of cold air into the city. Numerous smaller areas are concentrated at the southern city border, while the western edge of the city can offer only two cold air generating areas. The cold air mass flow is widely characterized as high. On the other hand the smallest cold air generating area west of Frohnau shows an average potential. The relevance of the surrounding areas rises with shrinking distance to residential areas, and is highest in the areas Spandau, Marzahn as well as on the southern city border.
As was already explained under Methology, the bio-climatic burden situation was calculated on the basis of parameters wind velocity and positive deviation from the PMV-value of the urban area. This composition allows a spatial partition of the settled area into bio-climatically burdened areas on the one hand, and non-burdened or less-burdened areas on the other hand.
The latter are characterized by cold air affect ranges, a moderate overheating and an adequate ventilation due to the flows from the cold air producing open spaces. The range of the cold air flowing into the built-up areas depends upon cold air productivity and the impediment properties of the surrounding development. Fig. 4 shows the situation in the periphery of the Großer Tiergarten, whereby the concentric, nocturnal out-flow of cold air as an affected area becomes apparent.
In the area between the John-Foster-Dulles-Allee and the Straße des 17. Juni north of the Großer Tiergarten an area of reduced flow velocities of less than 0.2 m/s is detected. From here the produced cold air is accelerated and, driven by the difference in temperature in consequence of the various land utilisation, infiltrates the surrounding development. Green settlement areas are unburdened, orange and red denote burdened housing blocks.
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.
Cold air stream channels in the districts of Marienfelde/Mariendorf, which in this case introduce cold air from the surrounding countryside, are denoted by the arrow signature. The Freizeitpark Marienfelde, as well as green settlement types act as stream channels. Due to the attribution to the aforementioned impact areas, a high urban climatic significance can be assigned to the green spaces and their function as a stream channel.
The illustration of potential traffic-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 most likely be exceeded. Inner city main roads are especially affected by the elevated burdens; of the total around 10 % of the analyzed transport network exceed the later boundary value.
In the Planning Advices Map cold air stream channels and outflows are divided into two categories, whereby the significance rises with growing proximity to the impact areas. Stream channels with a very high significance promote the penetration of cold air into the inner city area and to burdened district centres. Examples are the allotments at the S-Bahnhof Priesterweg, which carry the cold air from the graveyard on Bergstraße as well as from the Insulaner due north or the Volkspark Rehberge, which allows the transport of the cold air produced at the Airport Tegel towards Mitte. Further stream channels of this category are grouped north and south of the S-Bahn-Ring.
Merely the Grunewald has a broad extended cold air outflow with a high significance and at its eastern side a high cold air reach can be assumed. Stream channels with an average to high significance are situated mostly on the periphery of Berlin, which is also true of the spatial cold air outflow in this category. For these prominent structures or processes the following planning advices can be derived:
- Prevention of constructional barriers, which could induce a cold air congestion,
- Keep building heights as low as possible,
- Align new development to stream channels,
- Prevention of peripheral development and
- Conservation of green and open spaces.
The valley sections of the larger rivers Havel and Spree appear as spatial air-stream and ventilation channels, which exceed their local air exchange function. They benefit the air exchange in the bordering development even during strong, superordinated weather conditions. For planning purposes the river banks should be kept free, or at least be lightly developed.