Berlin Environmental Atlas

04.04 Temperature and Moisture Conditions in Medium and Low-exchange Nocturnal Radiation Periods (Edition 1993)

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Humidity Load and Equivalence Temperature

The humidity load is caused by different climate parameters. These include the vapor capacity of the atmosphere, the sunshine, the wind and the air temperature standing. Thus the equivalence temperature has been applied to determine the level of humidity. It consists of the air temperature and the latent heat which would be present at a given level of condensation from a specified vapor capacity.

Again using the example of the very hot summer day, it becomes clear that the inner city residential areas exhibit very high equivalence temperatures at noon and still in the evening hours (see Fig. 5). The station in Zehlendorf is, especially in the evening hours, already to be classified as essentially favorable. The outer areas like the Grunewald and especially the Dahlemer Feld are the least burdened during the course of the day.

Fig. 5: Daily Course of Equivalence Temperature on a Hot Low-exchange Radiation Day (8 July 1991) at Various Locations in Berlin

[Statistical base of this Figure is also available as Excel-File (MS-Excel is required).]

On the basis of investigations in Berlin (Wedler 1970), health burdens are to be anticipated in areas in which the daily average equivalence temperature exceeds 50 °C. Other authors (Linke and Baur 1957) define the humidity limit at 56 °C. In health spa climatology, the limit has already been reached at 49 °C according to Jendritzky et. al. (1979). Based on these values, the number of hours in which the limits are exceeded in the inner city residential areas during the months of July and August is very high. This is a period in which the risk of excessive humidity is especially high (see Table 1). That applies also for the high-rise settlement in Hellersdorf on the outskirts of town. In the heavily greened residential areas, as well as at forest and field locations the number of the burdened hours is considerably lower. The absolute number of hours are subject to the annual variations. However the relative differences at the individual locations may be taken as representative.

Tab. 1: Number of Hours with an Equivalence Temperature over 49 °C and/or over 56 °C as Measure of the Humidity Load at Various Locations in Berlin

[Table is also available as Excel-File (MS-Excel is required).]

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