Long-term Development of Selected Climate Parameters 2013

The Berlin-Tegel measurement station is located on the airport compound in the northeast of the municipal area of Berlin, about 9 km from the city centre. The area to the north and northwest of the airport is characterised by large forest and lake areas, whereas partly dense development is found from northeast to south. The wind measurements are performed at a height of 10 m above ground. The measurements for the station go back to the beginning of 1963.

Long-term mean values

Table 5.2 gives an overview of the long-term monthly mean values of selected climate parameters at the Tegel station in the 30-year period 1981 to 2010 under consideration.

The climate diagram of the Berlin-Tegel station is shown in Figure 5.1. It shows an averaged history of temperature and precipitation of the individual months of the 30-year period from 1981 to 2010. August is the month with the most rainfall; the least precipitation occurs in the transitional seasons.

The sunshine diagram follows the temperature curve, as expected (cf. Fig. 5.2).

The following figures show wind direction distributions at the Tegel aviation weather station in the period from 2001 to 2010. In addition to the mean long-term wind direction distribution, distributions for low-wind conditions with speeds up to 2 m/s as well as conditions with wind speeds above 2 m/s were evaluated. Low-wind conditions were recorded in 24.6 % of the cases in the period under consideration. Calms (windless conditions) were observed in 0.6 % of the situations. Wind speeds above 2 m/s occurred in 75.4 % of the evaluated period. The red ring lines in the diagrams indicate the mean frequencies of occurrence of the wind direction in the respective period under consideration in percent. The distance between ring lines corresponds to 1 %.

Developments, trends

Figure 5.5 shows the history of the annual mean temperature of the years 1963 to 2013. The trend is increasing in the course of the measurement series, as for all other stations. In Berlin-Tegel, this increase amounts to more than 1.5 Kelvin, the largest increase among the six stations under consideration.

Figure 5.6 illustrates the history of the threshold days occurring in summer for the entire observation period 1963 to 2013. Both the summer days and the hot days exhibit a positive trend. The number of summer days per year increased by about 16 days, the number of hot days by about four. The number of tropical nights shows no clear tendency.

Although the temperatures at the Berlin-Tegel station rose by 1.6 °C in the last 50 years, there is no marked difference in the increase of summerly threshold days in comparison with the other five stations. In the trend, the number of summer days in 2013 was 16 days above the initial values in 1963; the number of hot days increased by four days.

With respect to the number of tropical nights, the Tegel station has a middle position together with the one in Tempelhof. The highest nocturnal temperature values as well as the highest number of tropical nights (in total and related to individual weather events) are recorded at the inner-city Alexanderplatz (cf. Fig. 2-3). The lowest number is recorded at the peripheral sites Dahlem and Grunewald. This close relationship with the urban location comes about mostly because the nocturnal minimum temperatures more closely reflect the degree of development of the surroundings than the daytime maximum values.

In the period under consideration, a stretch of 8 days with consecutive tropical nights was observed in the time from July 23 to July 30, 1994. This value was not surpassed even in the ‘hundred-year summer’ of 2003 with 67 summer days, 31 of them consecutive from July 14 to August 13, at the Tegel station (cf. Fig. 5.7).

Figure 5.8 shows the history of the threshold days frost day and ice day for the period 1963 to 2013. The trend shows a decrease both in the number of frost days and for the ice days. The frost days decreased by 15 days on average, the ice days by 9 days. However, this development is not discernible if only the 30-year period 1981 to 2010 is considered. No trend can be observed in this case (cf. Fig. 5.9).