Temperature and Moisture Conditions in Medium Low-exchange Nocturnal Radiation Periods 1992
Map 04.04.4 Measuring Routes and Measuring Stations
In this map part all measuring routes and climate stations are contained which were used for the climate maps in the Environmental Atlas as a Statistical Base. That means beside the current measuring routes, those routes driven in West Berlin in the years 1981-83 are also contained. For reasons of clarity only the smaller auxiliary routes have been omitted.
The air temperature and the humidity at an elevation of 2 m and the wind speed and wind direction at elevations of 2.70 m and 6.70 m were measured using of the TU Berlin Department of Bioclimatology mobile monitoring vehicle.
The operating period of the stations was not uniform. In the eastern part of the city measurements were taken from June 1991 to May 1992. The data at Alexanderplatz and at Ostkreuz was provided by the Berlin weather bureau of the Deutscher Wetterdienst. In the western part of Berlin, most measurements were taken between 1981 to 1983. However in order to make comparisons with the data from 1991/92 some stations in the western part were reactivated and/or installed anew.
Map 04.04.1 Distribution of Air Temperature
The temperature differences within the city boundaries are much higher in nocturnal radiation periods than the long-term means (c.f. Map 04.02, SenStadtUm 1993a). Since one is concerned with a selection of certain weather conditions the temperature levels cannot be carried over for the entire year. However it can be assumed that the spatial distribution of the isotherms is comparatively representative.
The most overwarmed areas with mean temperatures over 19 °C are to be found where the development is densest, above all in Charlottenburg, Mitte, Kreuzberg, Schöneberg and the northern part of Wilmersdorf. However the warmest areas are not necessarily to be seen as distinct as they appear from the density of development. So in heavily built-up Moabit, but also in Friedrichshain and Prenzlauer Berg the temperature lies under 19 °C. A possible explanation therefore is, that in the summer 1991 the winds blew predominantly from eastern and northwest directions so that the heat island was displaced leeward. Temperatures over the 18 °C characterize the area within the city rail circle line, but also Spandau, Tegel, the old town of Köpenick and the high-rise developments Märkisches Viertel and Gropiusstadt. The comparably lower temperatures in the large settlements of Marzahn and Hellersdorf can be explained by the large open spaces in the neighborhood.
Clearly green spaces and allotment gardens are distinguished from the inner city by temperatures under 17 °C, while larger open spaces near the outskirts (e.g. parts of the Königsheide and the adjacent allotment gardens) record values of under 16 °C display. The large bodies of water lie in the area between 16 and 17 °C.
Forest areas are distinguished generally by temperatures under 15 and/or 16 °C. Low lain forest glades like Saubucht and Teufelsfenn even lie under 14 °C. Parts of the Krummendammer Heath northeast of the Greater Müggelsee Lake are especially cool with values around 13 °C.
Map 04.04.2 Distribution of Relative Humidity
Since the vapor pressure varies slightly within the city boundaries occasionally and locally according to source or sink, but displays on the whole no great differences, the relative humidity depends essentially on the air temperature. Thus the distribution of relative humidity is in many areas of the city inversely proportional to the temperature.
The densely built-up residential areas of the center of town, above all in Charlottenburg, Schöneberg, Wilmersdorf, Mitte, Prenzlauer Berg, Friedrichshain and Schöneweide are, with under 60 % relative humidity (RH), the most dry. The adjacent, sparsely greened areas lie at between 60 and 65 % R.H. With decreasing density of development and increasing greening, the relative humidity clearly increases. The southern outskirts and outer areas as well as the greater part of the Grunewald reach 70 to 75 % R. H.; in the Grunewaldseenrinne lake channel and the sinks in the Grunewald (Pechsee Lake, Saubucht, Teufelsfenn, Postfenn) the humidity even reaches 75 to 80 %. This applies also to the larger surface waters, broad parts of the agricultural and forest management areas in the surrounding countryside and along the entire northern outskirts.
The high moisture deficit in the inner city even in the night hours causes a substantial potential evaporation rate. The high values for relative humidity include on the contrary areas which distinguish themselves through an increased fog risk. The fog frequency is to be classified as greater in the surrounding countryside than in the inner city.
Map 04.04.3 Equivalent Temperatures under Low-exchange Weather Conditions
The absolute value of the equivalence temperature depicted is not determining because of the selection of weather conditions and the night hours. The essential information is carried rather by the relative differences in the city landscape. This allows only humidity risk areas to be delimited.
The areas with the highest equivalence temperatures (over 40 °C) are found in the core area of the western part of Berlin, in the industrial areas of Tegel (Borsigwerke) and in the Spree valley (Siemensstadt, Haselhorst). The densely built-up areas of Charlottenburg, Wilmersdorf, Schöneberg, Spandau, Tegel, Neukölln, Köpenick, additionally some high-rise development and industrial areas on the Teltow canal as well as also the Greater Müggelsee Lake and some part of town centers lie at 39 to 40 °C. Other heavily built-up areas in the western and eastern part of the city as well as some bodies of water, likewise also the industrial area of Hennigsdorf show values exceeding 38 °C. It is particularly noticeable that the areas of dense development in the eastern part of Berlin like Mitte, Prenzlauer Berg, Friedrichshain, with 38 to 39 °C, show lower values than comparable areas in the western part. Probably the predominant easterly winds play a role here, i.e. from the broad, less humid open spaces of the outskirts.
The southern outskirts and the southern outer areas, with an equivalence temperature of 36 to 37 °C, lie clearly under the values of the center of town. In the northern, western and eastern surrounding countryside, the values lie still lower. The lowest equivalence temperatures with under 31 °C can be found in the low-lying Saubucht in the Grunewald.