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The Research Group in Theoretical Physics of the Hungarian Academy of Sciences and the Research Center for Astronomical and Earth Sciences investigated the effect of climate change on polar atmospheric processes using novel simulation methods. There were disturbing results.
Recent years have brought increasingly volatile winters in the northern temperate zone. It is not uncommon for extreme snowstorms to hit the continents of North America or Eurasia, and other times they also experience fairly mild weather conditions in the far north.
Over the North Pole area, air is constantly circulating in a large vortex in the upper atmosphere. This rotating mass of air thousands of kilometers across is called a polar vortex. Because the strength of the polar vortex is determined by the difference in temperature between the equator and the heel, it is weaker in summer and more intense in winter. At the edge of the polar vortex, the meeting of cold, dry air masses in the north and hot, humid air masses in the south, at an altitude of about 7-12 km, a strong air current circulates over the continents and oceans of the northern hemisphere – the so-called running current or jet stream.
If the polar vortex is strong, so is the current, and its trajectory extends further north, preventing cold air masses from leaving the Arctic. However, when the polar vortex is weak, the running flow also weakens, spreads further south in sections, and often cannot get in the way of a detached mass of cold air, the researchers write.
The force of the polar vortex is related to the pressure conditions of the air masses around the Arctic. The change in these is called the arctic oscillation. If the air pressure around the Arctic is lower than average, the Arctic oscillation is said to be in its positive phase, the polar vortex will intensify, and fewer gusts of winter cold can be expected. However, if the air pressure around the pole is higher than average (the arctic oscillation is in its negative phase), the polar vortex weakens, the polar air can penetrate the southern areas and cause severe snow storms. . This is exactly what happened in the winter of 2010, when three record snow storms hit the United States.
What did the researchers study?
The study analyzed the expected future changes in the Arctic Oscillation based on the results of two state-of-the-art climate models and various climate scenarios. From the map resulting from the analysis, it was possible to read in which areas in the future the amplitude of the pressure fluctuation related to the oscillation will be greater and where it will be less.
The forecasts for the different models differed a bit, but basically there was agreement: in general, fluctuations in air pressure are expected in the area around the Arctic.
Translated into practice, this means that we can expect increasingly abrupt and increasingly cold intrusions from the south, while at the same time unusually mild and calm winter periods can also be expected.
At the same time, changes are expected in the so-called long-distance relationships associated with the Arctic Oscillation, that is, in the relationships between the climate in distant parts of the Earth. Meteorologist György Babolcsai’s December Anomaly Index, which characterizes the relationship between the value of atmospheric pressure in early autumn in the North Atlantic region and the average temperature in December in the Carpathian Basin, can be linked to the oscillation arctic and is also important for forecasting winter weather in the Carpathian basin.
Hungarian researchers have found that the strength of the Arctic oscillation temperature connections in Europe is expected to decrease with climate change. That is to say, it is not enough that the amplitude of the Arctic oscillation increases on average, but, at least here in Europe, it is becoming increasingly difficult to predict the specific climate that all this means on the basis of the oscillation phase index.
Since the publication of this study, researchers have already applied the same method to the El Niño-Sur oscillation phenomenon, with similar results. It was found that in the future the amplitude and strength of the southern oscillation may increase, and in this case, there will also be changes in the strength of long-distance connections.
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