Climate in Germany
The climate in Germany belongs to the cool, temperate climate zone and is in the transition area between the maritime climate of Western Europe and the continental climate of Eastern Europe .
overview
The climate in Germany is largely determined by Germany's location on the west side of the continent in the area of the west wind zone. With the prevailing westerly winds in the mid-northern latitudes, humid and, due to the warm Gulf Stream, mild sea air is often brought in from the Atlantic, so that temperatures in Germany, especially in the winter months, are higher than its northern position would suggest. The Atlantic influence decreases from west to east within the country. On the coasts, the hinterland inland and as far as the Cologne Bay , a maritime climate type dominates with comparatively small temperature differences between summer and winter, while to the south-east, especially in eastern Bavaria and in eastern Germany, there is a clear continental influence with warmer summers and cold ones Winters. However, with easterly winds in winter up to the North Sea islands, permafrost periods of several days can occur, just as, conversely, a pronounced westerly wind in eastern Bavaria results in temperatures well above 0 ° C in winter.
Climate observation and mean values
To assess the climate and its changes, long-term mean values are used for the various measurement parameters such as B. temperature, precipitation or humidity, which are usually formed from the measured values of a 30-year series of observations, ideally at the same location and called the reference or normal period . The German Weather Service (DWD) works with the reference period 1961–1990, which is also widely used internationally, ie the averaged climate data from these 30 years, which is therefore always mentioned first here. In recent years, the DWD has also used the reference period 1981–2010, as this better reflects the drastic changes in the climate over the past few decades and thus our present climate. For these reasons, the mean values in the following sections are always given for both periods, unless otherwise stated. The new international reference period 1991–2020 will be available from 2021.
The so-called nationwide area mean value of the air temperature (i.e. an area mean calculated from the data from all DWD weather stations) is 8.2 ° C (normal period 1961–1990) and 8.9 ° C (normal period 1981–2010) with January as the coldest month with an average of −0.5 ° C and 0.4 ° C and July as the warmest month with 16.9 ° C and 18.0 ° C. The Upper Rhine Graben and the neighboring Neckar Valley have the highest annual average temperatures with over 11 ° C z. B. in Karlsruhe , Heidelberg and Stuttgart , while for example in Oberstdorf only 6.6 ° C are reached.
Climate change in Germany
In recent decades, as a result of global warming in Germany and worldwide, a general trend towards higher temperatures has emerged: As can be seen from the time series of air temperature in Germany , the average temperatures have been above that in all years since 1988 except for 1996 and 2010 long-term mean value (1961–1990) of 8.2 ° C (status of the count: up to and including 2019); since around the turn of the millennium there has been an accumulation of very warm years. The old record of 9.9 ° C from 2000 was achieved again in 2007 and 2015, and through 2014, 2019 (10.3 ° C each) and 2018 (10.5 ° C) - the new record holder - exceeded. 9 of the 10 warmest years since systematic weather records began in 1881 were between 2000 and 2019 (status of the count: up to and including 2019). Looking at the period from 1881 to 2019, the warming in the seasons turns out to be the same: For summer, autumn and winter, the evaluations by the German Weather Service show a linear trend of +1.5 ° C over this period and +1.6 for spring ° C.
These changes also have visible consequences for everyone: The typical phenological reference dates move forward about 2.5 days per decade. On average, the early spring, defined on the basis of the snowdrop blossom, now begins around 10 days earlier than it was 40 years ago, and the same applies to the apple blossom as a defining event at the beginning of full spring .
Temperature records
The lowest temperature ever measured in Germany, but not officially confirmed, was −45.9 ° C and was recorded on December 24, 2001 at Funtensee in the Berchtesgaden Alps . However, it is an uninhabited extreme location, because extremely cold air can form over a blanket of snow in the drainless depression on long winter nights. The German Weather Service gives a record value of -37.8 ° C, which was measured on February 12, 1929 in Hüll ( Wolnzach district, Pfaffenhofen district). The highest measured temperature in Germany was reached on July 25, 2019 at the Lingen (Ems) station in the Emsland with 42.6 ° C and thus the record value of 40.5 ° C measured only the day before at the Geilenkirchen station in North Rhine-Westphalia already exceeded again.
Precipitation
The mean annual precipitation amount is 789 mm and 819 mm 1981-2010, the driest month so far has been February, but April has even undercut February in the last 10-15 years. The wettest months are the summer months, the precipitation then often falls as comparatively short and heavy showers during thunderstorms and less as continuous rain. The amount of precipitation varies between well over 1000 mm in the Alps and the low mountain ranges and below 500 mm in the rain shadow of the Harz Mountains between Magdeburg in the north, Leipzig in the east and Erfurt in the south. In general, the humidity decreases from west to east. There is also a noticeable trend towards spring drought, especially in the east of the country, which in many years favors smaller vegetation fires.
From October to April, precipitation in Germany can fall as snow down to the lowlands, the frequency of snowfall increasing from west to east in line with the decreasing influence of the Atlantic. The altitude is also decisive for the frequency and longevity of snow cover. While in the lower elevations of western North Rhine-Westphalia ( Niederrhein , Kölner Bucht ), several years can now pass without a single day with a measurable snow cover , episodes lasting several days with snowfall and the formation of a snow cover belong to lower elevations in the east and south of the country despite the warming trend, almost every winter. So was z. In Düsseldorf, for example, between 1977 and 2007, the average annual snowfall was just under 11 days, while in Dresden, 600 km to the east, this was the case on 45 days. In Northern Germany the number of days covered with snow fluctuates a lot; In many years there is almost no formation of a blanket of snow, especially towards the west as on the Lower Rhine, but unlike there there are always winters that separate the mild air in the south from the cold air in the north due to recurring or stubborn air mass limits, run very cold and snowy, e.g. B. the winters 1978/79 or 2009/2010, both with regionally more than 100 days of snow cover in Schleswig-Holstein and Mecklenburg-Western Pomerania, while the same winters in the south were comparatively mild and with little snow. Also in the winters 2013/2014 and 2015/2016 the only notable winter phases were limited to the north-east half, the air mass boundary between the mild south-west and the cold north-east was both times almost immobile in a typical position across the country for several days Line from the mouth of the Ems to the Ore Mountains .
sunshine
The overall high temperature level in Germany, however, is bought with a high proportion of cloudiness in the winter half-year, since especially from November to February, i.e. the months with very low sun with correspondingly weak solar radiation and short day lengths, only cloudy periods can prevent longer phases of cooling. The combination of humid sea air under the influence of high pressure and weak solar radiation leads to long-lasting cloudy high fog in large parts of the country in late autumn and winter. Sometimes it is sunny and mild in these weather conditions on the peaks of the low mountain ranges and in the Alps with a supply of mild air from the southwest, while in the lowlands fog, high fog and sometimes even frost determine the picture. In low wind winter high pressure weather, the normal temperature stratification is canceled. The reason is the weak solar radiation and the property of the heavier cold air to flow into the valleys and lie there under the warm air in the heights. These weather patterns are called inversion weather patterns . They can often only be ended again by an advance of Atlantic air masses accompanied by wind, which leads to a normalization of the conditions with cooling at altitude and warming on the ground. In the context of an inversion weather situation, the lack of wind and the lack of air mass exchange between the lower and higher air layers in metropolitan areas can lead to a significant and dangerous increase in air pollution, which is known as smog .
Some areas, especially on the western / north-western low mountain range threshold, where the clouds moving in from the west accumulate - mainly parts of North Rhine-Westphalia, Lower Saxony, Hesse and Rhineland-Palatinate - are among the regions in Europe with less sunshine in some cases, with less than 1400 hours of sunshine annually . Comparable and even lower values are recorded in densely populated regions across Europe only in some areas of the British Isles and on Norway's west coast. Since around the end of the 1980s, there has been a trend towards more sunshine overall in Germany. For example, the German area average for sunshine (average value determined annually by the DWD from grid data) between the two reference periods 1961–1990 and 1981–2010 increased from 1544 to 1601 hours of sunshine and has even been 1,674 hours of sunshine for the last 15 years.
Germany's sunniest regions are on the northern and southern edges of the country. Germany-wide front runners in terms of sunshine are the West Pomeranian islands of Rügen and Usedom . With 1869 hours of sunshine per year, Kap Arkona on Rügen is the sunniest German weather station for the current reference period 1981-2010, until its task it was Zinnowitz on Usedom with even 1917 hours of sunshine per year in the period 1961-1990. The all-time monthly record has also fallen in this area: In July 1994, the Cape Arkona station registered 404 hours of sunshine, almost exactly 13 hours of sunshine per day. The capital region of Berlin and the neighboring Brandenburg are also comparatively sunny . In the south, the sunniest regions are the southern Upper Rhine between Karlsruhe and Lörrach , the Stuttgart region and the Bavarian foothills of the Alps including the state capital Munich , each with an average of 1800 hours of sunshine. Even if the total duration of sunshine in the regions mentioned is quite similar, the distribution over the year is very different: on the Baltic Sea coast, it is mainly sunny springs and summers that contribute to the high annual sums, while in the south, and especially in the foothills of the Alps, those Winters are much sunnier than the German area average. The western edge of the state from Saarland to East Frisia and northern Schleswig-Holstein benefit less from the general trend towards more sun. When evaluating these changes, however, it should also be borne in mind that the comparability of the sunshine measurements, which were only introduced across the board in 1951, is due to station relocations, technical problems (e.g. measurement failures), especially in the area of the former GDR and a conversion of measurement technology to digital recording of the Sunshine in the nineties is not entirely unproblematic.
Damage from extreme weather conditions
Extreme weather conditions such as long-lasting droughts, severe frosts or extreme heat waves are comparatively rare due to Germany's geographical location. In the autumn and winter months, however, there are storm or hurricane lows, which preferentially move east across the North Sea and mainly affect northern Germany and the northern low mountain ranges. In recent years, however, there have also been some storm lows that are more likely to affect central and southern Germany, such as the hurricane lows Anatol and Lothar in December 1999 or Kyrill in January 2007.
Floods and floods that occur after intense rainy periods in summer ( Oder flood 1997 , Elbe flood 2002 , flood situation June 2013 in Bavaria ), especially in the context of so-called Vb weather situations , can also assume catastrophic proportions. A low coming from the Atlantic moves south of the Alps over the northern Mediterranean and then back north towards eastern Central Europe, where the moisture absorbed over the warm Mediterranean leads to very abundant continuous rain in Austria, the Czech Republic, southeast Germany (especially Bavaria and Saxony). as well as Poland can come. Also as part of the snowmelt can cause flooding and considerable damage, especially if the thaw with heavy rainfall combined to snowy winters very suddenly and occur up to high mountain areas. Droughts mainly affect the east of Germany, which is already with little precipitation, especially the regions with sandy soils, but can sometimes also affect the whole country, as most recently during the heat waves in 2003 and 2006.
The thunderstorm frequency, which increases from north to south, is also potentially damaging. Cloud-earth lightning strikes are five times more frequent than on the edge of the mountains in Bavaria and Baden-Wuerttemberg as well as in the Ore Mountains in Saxony, where frequent summer heat meets topographical conditions that favor the formation of thunderstorms on the coasts. Thunderstorms occur most frequently in the summer half of the year, either in warm and humid, unstable stratified air masses that typically come to us from the Mediterranean region or when Atlantic lowlands reach into Germany with the introduction of cooler air from the west. In winter, under the influence of deep polar air with very large temperature differences between the altitude and the ground, thunderstorms can occur even when it is snowing.
In addition to the sometimes very high precipitation rates, which overload the capacity of the soil and the sewer system and thus lead to flooding, considerable damage to property and crops can result from hailstorms and (very rarely in Germany) fires from lightning strikes. Another phenomenon in the context of summer thunderstorms is the occurrence of tornadoes , popularly and in the media often referred to as " tornado ". In total, around 30 to 60 confirmed tornadoes per year can be assumed in Germany, in some years even more (122 confirmed tornadoes in 2006). The number of unconfirmed suspected cases is even significantly higher and in 2015 was e.g. B. 212.
See also
Web links
Individual evidence
- ↑ Temperature: Long-term mean values. dwd.de, accessed on April 9, 2016 .
- ↑ a b c d Kaspar, F., Friedrich, K .: Review of the temperature in Germany in 2019 and the long-term development , report by the German Weather Service , as of January 2, 2020
- ^ Friedrich, K .; Kaspar, F .: Review of 2018 - the warmest year so far in Germany , report by the German Weather Service , as of January 2, 2019
- ↑ Change in the seasonal development phases in plants. Umweltbundesamt.de, accessed on April 9, 2016 .
- ↑ Peter Bissolli, Thomas Deutschländer, Florian Imbery, Susanne Haeseler, Christiana Lefebvre, Jutta Blahak, Rainer Fleckenstein, Juliane Breyer, Michael Rocek, Frank Kreienkamp, Stefan Rösner, Klaus-Jürgen Schreiber: July 2019 heat wave in Western Europe - new national record in Germany . Report by the German Weather Service , August 1, 2019. Retrieved August 26, 2019
- ↑ Long-term mean values. montsprognose.de, accessed on April 9, 2016 .
- ↑ Average days of snow cover 1977–2007. imk-tornado.physik.uni-karlsruhe.de, accessed on October 3, 2010 .
- ↑ Area mean sunshine. montsprognose.de, accessed on April 9, 2016 .
- ↑ Sunshine: Long-term mean values 1981–2010. www.dwd.de, accessed on February 10, 2016 .
- ↑ Sunshine: Long-term mean values 1961–1990. www.dwd.de, accessed on February 10, 2016 .
- ↑ Extreme values map of the 20th century. In: Klimastatusbericht 2001. DWD, accessed on July 23, 2016 .
- ↑ Hannak, L., Friedrich, K., Imbery, F., Kaspar, F .: Comparison of manual and automatic daily sunshine duration measurements at German climate reference stations, Adv. Sci. Res., 16, 175-183, 2019; DOI: 10.5194 / asr-16-175-2019
- ↑ Frequency of cloud-earth lightning according to Kreisen 1999–2011. www.spiegel.de, accessed on July 23, 2016 .
- ↑ Reported tornadoes by years. tornadoliste.de, accessed on May 15, 2016 .
