The ENVIBASE-Project

Documentation / Online Handbook

Climate

Description of the Problem

Metropolitan areas are subject to fundamental modifications in their thermal balance compared to the surrounding countrysides. Reasons for this are:

• modifications in heat storage capacity and conductivity, and changes in wind and exchange relationships due to masses of built-up structures;
• the decrease of evaporating surfaces caused by the high degree of surface sealing and the lack of areas covered with vegetation;
• the warming of the atmosphere by the so-called greenhouse effect (especially due to increases of CO₂);
• inflows of energy and water vapour from anthropogenic sources.

Spatial planning is no abstract profession. It has to handle urban and landscape areas as the surroundings of plants, animals, and human beings. Spatial planning is responsible for, as well as influenced by, special development plans and the aggregate planning instruments. In every case, all the different public and private environmental projects and plans are based on the existing environmental laws, orders, or guidelines. Especially in Germany, knowledge of and political organisation regarding climate issues are not as widely spread through the population as knowledge about other environmental problems like water and air pollution. Improving the legal situation for climate protection seems to be more difficult under the current economic situation.

The deficit in handling these problems is therefore not only caused by the different legal situations but also by the economic and political climates, the competition of the single-planning disciplines, and the level of science. In addition to these challenges, the availibility of "hard- and software" is urgently needed for the success of solving climatic problems.

Results of the human biometeorological analysis of different spaces are of interest because of their possible application in the fields of:

• urban and landscape planning, for instance regarding investigations of impacts of big construction projects;
• medicine, for instance for the analysis of thermal stress situations;
• tourism, for instance for the selection of holiday areas or the duration of holidays;
• advice concerning the location of residential areas.

Data Sources

Besides the satellite interpretation and the new model application in late 1996, the investigation for the climate section of the Environmental Atlas Berlin was undertaken by the Technical University, Institute of Ecology, Special Group Bioclimatology. Together with these experts, we decided to use a more traditional concept of investigation, i.e. to measure at located stations on the one side and at defined measuring points while a measurement trip (transect) on the other side.

The measurements for the climatic maps of the Environmental Atlas Berlin were made at a height of 2 m. They were made in 1981-1983 for West Berlin, in 1991 for East Berlin, and in 1992 for the surrounding countryside. Overall 150 monitoring trips (West Berlin 60, East Berlin 60, surrounding countryside 30) were made along 34 monitoring routes (WB 24, EB 6, SC 4) with 1800 monitoring points (WB 1000, EB 500, SC 300). Data from 38 other monitoring stations were included for processing.

For West Berlin, the yearly average for 1982 was used as a basis for calculating the twenty-year average for 1961-1980 (Environmental Atlas 1985, 04.02). This temperature distribution was brought into line with the thirty-year average for 1961-1990 after comparison with the readings of the long-term monitoring stations in Dahlem and Tempelhof. Correctional adjustments were made, particularly in Grunewald, with the aid of a West-East connection route.

For East Berlin and the surrounding countryside, the average yearly temperature distribution for 1991/1992 (unpublished) was calculated from the monitoring trips conducted in 1991 and 1992 and from station readings. The adjustment of the thirty-year average was also carried out with the aid of the reference values of the Dahlem and Tempelhof stations (see below).

For the ground-level wind investigations, the mobile climate monitoring vehicle of the Department of Bioclimatology of the Technische Universität Berlin was used. The databases for the existing maps were 29 day and 70 night-time measurement trips during the 4-year period of 1980 to 1984 in the area of the western boroughs of Berlin, as well as 21 day and 42 night-time measurement trips in the year 1991 with the emphasis on the eastern part of the city. The wind speed was measured with an anemometer at a height of 2.70 m at, altogether, 770 measuring points. Statements as to the wind comfort for pedestrians along with the near ground wind field can thereby be derived. Data on the wind speed at the least disturbed station, Tempelhof Airport, at the time of the measuring trips were provided by the German Weather Service. In addition, research on block courtyard and forest locations were evaluated.

All data were stored in data banks and used for the different statistical and spatial evaluations. These elaborations are explained in detail in the accompanying texts to each map.

Methods

Different databases required the separate calculation of long-term mean temperatures for West Berlin and East Berlin/surrounding countryside. The calculation procedures were, however, largely corresponding. The procedure should be briefly outlined, since the entire procedure had to be performed for East Berlin/surrounding countryside.

The assignment of individual measuring points, according to the (development) structure of their surroundings, to continuously monitoring climate stations is of central importance for various stages of calculation. It was assumed that the course of temperatures at the climate stations can be depicted with respect to the monitoring points. This assignment enabled the different measurements of a monitoring trip to be, as a first step, synchronised to a point in time. The results of the monitoring trips were then averaged for each monitoring point. The long-term wind statistics of 1950 to 1970 from Berlin-Dahlem were applied for the weighting of individual surveys: the relevant air temperature value was weighted in the determination of average values by means of wind direction at the referenced point in time of each survey and its percentage of all wind directions in the long-time averages.

The projection of these results onto the mean annual values for 1991/92 again proceeded by the monitoring points assigned to the climate stations. The climate stations monitored temperature continuously in 1991/92. This enabled the determination of average values for any given point in time. The projection of monitoring point average values required the climate station mean annual values and the corresponding temporal average value for monitoring points. It was assumed that the monitoring points at these other locations behaved like their associated climate stations. Thus the difference between these two values measured at the station was carried over to the associated monitoring points. Figure 3 reproduces this procedure schematically.

The next step was the inclusion of the corresponding monitoring trip results for the surrounding countryside. This first step enabled the determination of mean annual temperatures for East Berlin and the surrounding countryside for each monitoring point from June 1991 to May 1992.

A transition was now necessary to the long-time averages of 1961 to 1990, or, for West Berlin, the conversion of mean annual values for 1961-80 into mean annual values for 1961-90. This transition could only be realised with the help of the two long-term stations at Dahlem and Tempelhof.

The long-term average at both stations for 1961 to 1980 was around 0.2 °C lower than the newly calculated values for 1961 to 1990. The adjustment of the West Berlin long-term averages to the new period proceeded on the assumption that this difference of 0.2 °C was valid for all western monitoring points of the monitoring network, and thus a general increase around this quantity of difference is justified. Forest locations were the only areas where no changes were undertaken, because of results given by two stations operated in Grunewald since 1986.

The calculation of long-term temperature values in East Berlin and the nearer surrounding countryside, based on the average values calculated for 1991/92, proceeded and were differentiated according to three different use types. Climate stations were selected which presented a suitable database for the inquiry of the projection factors because they had been in operation for several years. The Tiergarten park station was representative for park/forest locations. The Alexanderplatz station was assumed to be representative for dense development. A 5-year test series between 1975 and 1980 was available for both stations. It was assumed that these stations could be assigned between the Dahlem and Tempelhof long-term monitoring stations for the period 1975-80, just as it was for the long-term mean. This enabled the determination of long-term mean annual values for Tiergarten and Alexanderplatz. The difference of these means to the mean annual temperatures for 1991/92 was then used in the projection for the associated monitoring points. Figure 4 shows the principles of this procedure. The examples used in Figure 4 are the Alexanderplatz station and the monitoring points for dense development.

This process gave a long-time average to use in projections for park and forest locations. It is approximately 1.3 °C below the mean annual temperature for 1991/92. The difference for densely developed locations was about -0.8 °C. The long-term monitoring station Dahlem represented the third use type of sparse development. Its directly measured 30-year average was approximately 1.0 °C below the mean annual temperatures for 1991/92. Use-referenced values were increasingly included in the projection of 30-year mean temperature values for East Berlin and the surrounding countryside. The interpolation of individual values to area was performed manually.

The total portrayal in the map cannot take into consideration the sometimes serious changes in use in certain parts of the study area. These took place between 1961-90. They include the establishment of the large settlements in Hellersdorf, Hohenschönhausen, and Marzahn. Statements are thus always related to present use.

Results and Uses

The approached form of publishing the data for the Environmental Atlas are maps covering the whole area of Berlin; in the field of climate, the following maps were created: Long-Term Mean Air Temperatures 1961-1990, Ground-Level Wind Conditions, Temperature and Moisture Conditions in Medium and Low-Exchange Nocturnal Radiation Periods, Urban Climate Zones, Surface Temperatures Day and Night, Climate Functions, Long Term Precipitation 1961-1990.

The most actual result is the application of the Human-Biometeorological Assessment of Climate for Urban and Regional Planning. This new model, described in the guideline 3787 VDI for the human energy balance is the UBIKLIM from the German Weather Service. UBIKLIM uses the assessment index PMV. PMV makes it possible to assess thermo-physiologically indoor and outdoor air as point calculations or in the form of maps.