The chances of a white Christmas are falling: More and more often it is green at Christmas | BR.de

Rain, mud, cloudy skies, gusts of wind and, in Bavaria, a foehn on Christmas night, green meadows and mountain slopes between the years: we should have got used to this long ago. Because in Germany we can only very seldom enjoy snow at Christmas, so the statistics are clear. The right soundtrack for Christmas is not “The snow is trickling quietly”, but “It is green so green”.

A blanket of white Christmas – a rare event

Meteorological definition for white Christmas

If one centimeter of snow or more is measured at a weather station on December 24th, 25th and 26th, meteorologically, it is called a white Christmas.

According to the meteorological definition of “white Christmas”, according to the German Weather Service (DWD), there were only six more or less white Christmases over three days in Germany over the past 120 years: in the years 1906, 1917, 1962 , 1969, 1981 and 2010. So the last time we could look forward to snow at Christmas was over ten years ago. Of course, there was more regional White Christmas. But their number is also decreasing.

White Christmas: probability down by 52 percent

The DWD’s meteorologists can tell whether there is a White Christmas at the earliest ten days in advance estimate the festival. A comparison of the two periods from 1961 to 1990 and from 1991 to 2020 shows, however, that the chances of a snow cover on all three days (December 24th to 26th) averaged 13 percentage points across Germany and even up to 44 percentage points regionally back. This means a decrease of 52 percent for three days with snow at Christmas, according to the current calculations of the DWD.

Less white Christmas: South particularly affected

The German Weather Service has calculated the decrease in the probability of a White Christmas for seven cities in Germany. It is noticeable that, statistically speaking, the chance of a white Christmas has decreased most in Munich – by 19.5 percentage points when comparing the two reference periods. In Leipzig, on the other hand, the probability has only fallen by 3.8 percent, in Berlin and Hamburg by 10, in Frankfurt am Main by 11.8 and in Freiburg by 12.2 percentage points.

Statistically speaking, according to the DWD, most people in Germany can only look forward to snow on the three public holidays every ten years. At higher altitudes above around 1,500 to 2,000 meters, however, sufficient natural snow for winter sports and mostly White Christmas can be expected in the next few decades, according to the DWD.

White Christmas in Bavaria: The balance of the past 50 years

An illuminated Christmas tree at the blue hour on December 21, 2010 at the frozen fishing port of Greetsiel in the Aurich district in East Friesland, Lower Saxony.  White Christmases with snow-covered landscapes are the exception here: a so-called weather singularity ensures that Christmas is mostly green in Germany.  |  Image: dpa-Bildfunk / Ingo Wagner

White Christmas – with us the exception instead of the rule

Since 1961, snow has fallen nineteen times on Christmas Eve in Munich. In 1962 the white splendor was even 28 centimeters high and therefore above average lush. The balance sheet looks different for the whole of Bavaria: there has only been five snowfall at Christmas in the past 50 years: in 1969, 1981, 1986, 2001 and 2010. Whining at a high level, some think on Heligoland, where there are only two on average Times in the century there is a white Christmas. There is only one place in Germany and Bavaria where you can expect a white Christmas every year: the Zugspitze! Measurements have been made since 1880.

Christmas thaw and premature Christmas

In addition to climate change, a regular exception is also to blame for the green misery: the so-called Christmas thaw. Christmas is just a bit inconvenient in terms of time: three days before Christmas night, winter only begins, because the day of the winter solstice is the astronomical beginning of winter. The fact that meteorologists always see December 1st as the beginning of winter is primarily due to statistical reasons: It pays off easier if winter also begins on the first of the month.

But the lowest level of the sun over the northern hemisphere is only reached three weeks later, just before Christmas. Flatter solar radiation for a few hours a day cools our planet half – the oceans quite slowly, the continents a little faster. The large land masses of Siberia cool down the fastest, where winter usually begins in November.

A high in the north brings us a white Christmas

Santa Claus on his sleigh pulled by a reindeer in the snow |  Image: picture-alliance / dpa

We have the best prospects for a white Christmas when the sun is smiling for the Russians: A high pressure area over Siberia, around which the air masses rotate clockwise, sucks in the cold air of the North Pole and blows it towards us as icy east winds. The polar air also brings us high above Lapland’s reindeer.

Where winter air meets summer warmth

Map: Winds and pressure areas in wintry Europe that cause Christmas thaw in Germany |  Image: BR

This is how the Christmas thaw occurs

Even in the frosty pre-Christmas season, the white Christmas in Bavaria is rather the exception. Even a cool high above Siberia doesn’t always bring us snow. Because woe, the winds branch off beforehand: If you pull north past England, then your winter dream is over with us. The cold air masses meet summer over the Atlantic.

Not only on the remainder of the summer heat, which is stored longer in the ocean, but on a very fresh summer from far away: Winter solstice here is also summer solstice in the southern hemisphere. There the sun shines high and hot for many hours a day and warms properly. And the large, global hot water pipe, the Gulf Stream, brings this warmth right into our vicinity.

The Icelandic low is to blame

Polar cold air from the east meets subtropical warm air from the southwest and there it is, the tiresome Icelandic low. The low pressure area rotates counterclockwise, shoveling the cold air further north and drawing in the warm, humid Atlantic air to us – with rainy westerly winds. And that’s it, our typical Christmas weather.

Green Christmas makes it easier to buy a Christmas tree by bike.  |  Image: picture alliance / Tobias Hase / dpa

Advantage of a green Christmas? Buying a Christmas tree by bike is much easier.

The south-west of Germany is particularly affected by the warm, humid weather, while the north-east of Germany still has more chances of the polar cold air. Sometimes a sharp dividing line then runs across the country. Where the cold and warm air masses collide, it gets turbulent: Heavy snowfalls, freezing rain and lightning ice occur there – a horror for everyone who crosses the country for the family Christmas party.

Typical, Christmas thaw!

Singularity

Meteorologists refer to a singularity as a weather situation that deviates from the normal course of the weather, but which occurs at certain times of the year with a high degree of probability. The singularity of the Christmas thaw is not alone – there are others:

Global warming isn’t the only cause of a green Christmas for us. The typical German non-wintry weather can also be to blame. It even has its own name: Christmas thaw. It is mostly from December 24th to New Year’s Eve. Because this weather behavior is so typical and regular here, meteorologists refer to it as Singularity. Like the ice saints in May or the sheep cold in June. Allegedly, people went swimming in the southern Rhine at Christmas time as early as the Middle Ages.

Before Christmas always milder

But in the past few years one could often not even speak of this singularity, because it would have had to have been colder beforehand. The mild temperatures in the run-up to Christmas increase:

“Before Christmas we often had our first long onset of winter with ice and snow all the way down to the plains. But especially around the Christmas holidays, the atmosphere felt a great ‘urge’ for mild westerly weather conditions with Atlantic air: the Christmas thaw. Since the mid-1980s Mild winters accumulate and with it the probability that the pre-Christmas weather with little ice and snow will seamlessly transition into the Christmas thaw phase.

Dr. Michael Sachweh, BR meteorologist

The singularity of the Christmas thaw seems to be dying out thanks to climate change – the green Christmas in Bavaria will remain and probably even increase: If global warming continues as it does now, the chances of a white Christmas in many parts of Germany could be significantly lower in the next few decades, says Andreas Friedrich, spokesman for the German Weather Service.

White Christmas are (only) a beautiful dream

Santa Claus stretched out in the sunshine on a landing stage |  Image: picture-alliance / dpa

Do we need to straighten our picture of Santa Claus?

Why is Christmas associated with snow in our minds at all? Most of the Christian world celebrates a green Christmas. The primeval Christmas in Bethlehem was also sure to be free of snow. So comfort yourself: White Christmas is (mostly) just a dream.

Reference-www.br.de

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