polar vortex collapsed! This message is becoming widely used again, if it is in North America or Europe, above-average cold. Meteorologists try because of this relationship now, to use the state of the vortex for longer-term weather forecasts.
Darker high-pressure
Shortly after Christmas, the vortex has broken down once again into two or even three parts. A few experts are convinced that Now it will be cold. Because time and again, has opened in the past, in such a situation, the door of the Arctic Eisschranks in the direction of the South. Will it be this Time?
To drops at the beginning of each winter the sun because of the wrong position of the earth’s axis in the high Northern Latitudes permanently below the horizon. The cooling and heavier masses of air sink down, the air pressure in the height decreases. In the stratosphere, above 20 km, is developed around the North pole, around a stable low-pressure area in the flows from the outside due to the pressure difference air. The rotation of the earth in turn requires that the inlet flows of air against the clockwise to set the height Low. Ready for the polar vortex with wind speeds of up to 200 kilometers per hour.
for the Winter of the Northern hemisphere, the typical vortex of wind at the top of the stratosphere you realize on the ground nothing. Because the weather plays happen in the underlying layers of the atmosphere up to about 15 kilometers altitude. Somehow, but what is happening at a great height in the thin stratospheric air seems to be, as yet, poorly understood way, to the atmosphere including the impact of. And as the Berlin-based meteorologist Richard Scherhag in 1952, discovered, done, occasionally, in the vortex there is at the very top of strange things.
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of the Opposite spins
Normally, the Winter temperatures in the Northern stratosphere at minus 70 degrees. However, at 23. In February 1952 reported a degree of the probe, the Scherhag like any other day, from the Tempelhofer feld on a balloon in the stratosphere had to rise, in 30 km height and a significant temperature rise: only minus 12. A few days later, the STRATO was a sphere, but cooled down again to its normal state. Meanwhile, it is known that such temperature rises occur irregularly, but on average every other Winter. The meteorologists call them “Berliner phenomena”. As before, you puzzles, but why always re-heat without any warning from the deeper layers of air in the stratosphere will be transported. The consequences of a Berlin phenomenon can be observed clearly: The sudden warming of the stratosphere changes the pressure and thus also the flow conditions in their more or less strong. The stratospheric polar vortex weakens or splits into several smaller sub-vortices. Sometimes in the winter, change vortex of wind even completely its direction of rotation and starts wafting the Pole in a clockwise direction. This reversal of the normal wind conditions in the stratosphere due to their short-term warming effect sometimes, but not always, the underlying atmosphere of the floor. There, in the troposphere, around is blowing at altitudes up to 15 kilometers, constantly the so-called Jetstream counter-clockwise around the Northern globe. The Jetstream is strong and his speed is high, it blows without any major detour from West to East. And even further down, in the near-surface layers of air in the lower troposphere, the air flows in this case, as a rule, stable in this direction.
Positive oscillations
This mild European Winter, the typical condition produced by a state, the meteorologists as “a positive North Atlantic oscillation” refer to: the Azores high-pressure system with a vortex of wind in a clockwise direction. At the same time a low pressure vortex that paddles the air in a counter-clockwise direction around is more in the North Island. And both of these wind, the air transport blades together between quickly from West to East from the Atlantic ocean to Europe. Nice for winter haters: For it is with this wind blows across the thanks to the Gulf stream, the mild air of the Atlantic ocean to Europe.
Weak Jetstream
This basic flow pattern in mild winters, however, changes sometimes. And sometimes, even after a Berlin phenomenon. In particular, if the resulting weakening of the vortex in the stratosphere persists sphere longer, or the stratosphere begins sphere fluidized in to blow against the direction of spreading this disorder also downwards into the troposphere. That weakens the jet stream, and this, in turn, the tracks on which this flows around the globe are changing: In sweeping arcs, the jet-stream meanders-winds far up North and then back South. The northward buckling jet stream bows warm air masses up in Arctic climes. Conversely, the open to the South and Jetstream-loops are transformed into so-called “cold-air troughs”, in the polar air from the Arctic far to the South can flow.
“The normally prevailing West-to-East track of low pressure areas will be interrupted, therefore, so that you with cold air from polar Latitudes far to the South opt-out,” writes meteorologist Adrian Leyser from German weather service in a post on the Website of his authority. These Blockade-weather conditions provided “in the Winter, often for long periods of colder phases in Central Europe.”
Depending on which regions of the arches are straight, is it warm or cold, often for weeks. Because often, the loops of a weakened jet stream are progressing only slowly to the East, and remain virtually on the spot. In addition, the floor areas near the high pressure on the Baltic States or Russia to intervene in the proceedings, which form in the cold, heavy air. These cold highs can be uncomfortable to be stable and to steer a longer period of time cold air from the North-Eastern regions of the us.
Negative temperatures
a Long, cold Winter, with significant sub-zero temperatures can have many causes. How often and how much the polar vortex is crucial here, the meteorologists discuss controversial.
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Germany, Europe and the USA, meteorologists more weeks of cold wave
Also, climate change is expected to play a role. A study by Marlene Kretschmer from the Potsdam Institute for climate impact research and colleagues suggests a mechanism: Due to the in comparison to the Rest of the world strong warming of the Arctic, there is “in the polar vortex in the stratosphere, a change to longer-lasting Debility”. The allow cold air to flow to Russia and Europe. “Actually, this explains most of the observed cold extremes in the Eurasian winters since 1990.”
