The reasons for the cold snap in Europe?

The reasons for the cold snap in Europe? Weather and Climate

While U.S. residents dream of a frosty snowy winter, most of Europe and Asia remains terrified of abnormally cold weather, due to the deaths of more than three hundred people. Entire communities in Italy, Bosnia and Romania covered with snow, and completely cut off from the outside world due to damaged power lines. In Bulgaria from heavy rains and massive melting of ice broke through a river dam, resulting in four deaths of local residents. In Bosnia, Serbia, Macedonia, and Turkey in the next few days is expected to increased snowfall.

Such rapid winter attack can exacerbate economic instability European countries, because some of them are not going through the best of times.

A 93-s stations Czech Hydrometeorological Institute February 5 was a record low for the country's temperature — 38,89 ° C. In Ukraine, at least 131 people survived the harsh weather conditions, another 2000 seeking treatment at health facilities because of hypothermia.

In Austria, the thick ice, it was decided to close the Danube navigation. The qualified freezing Venetian canals.

Fig. 2.Otkloneniya air temperature at geopotential heights of 500 mbar. Red indicates the areas of the middle strata of the atmosphere with an abnormally warm air near Norway. Dark blue areas are marked with an uncharacteristically low temperature over Europe and Asia. 28.01. — 03.02.2012.

What's going on?

Weather system that brought the region stable cold and snowy weather, called the Arctic Oscillation (AO). Depending on the phase in which, positive or negative, is a joint-stock company, it can generate a warmer or more severe climate over the North Atlantic and the Arctic, and neighboring areas.

Currently Arctic Oscillation is in a negative phase, making the weather very cold in Europe. The reasons for the variable valve AO are not fully understood, so the forecasting of its behavior is very challenging. It is interesting that in the winter of 2012 started just with the positive phase of the oscillation, but later there was a dramatic switch, and the weather is fundamentally changed.

Fig. 3. Change in pressure over the sea. Bright red indicates the areas of abnormally high pressure over Russia and Europe. The end of January — beginning of February 2012.

Fig. 4. Map winds circled area where cold air gets to Europe.

In recent years, the Arctic Oscillation phase often alternated. Thus, in December 2009 there was a "Snegapokalipsis," especially in the north of the United States, in February 2010, "Snow Armageddon" when the negative phase dominated by AO. Replaced by a positive phase in the form of numerous tornadoes in North America in April 2011.

In 2012, together with frost in Russia formed a region of stable high pressure. From Siberia cold continental air running into an obstacle in the form of an anticyclone over Scandinavia and north-western Russia, moved to Western Europe, pushing warm air masses further to the British Isles.

Another cause of such movement of cold air could become weakened circumpolar winds in the stratosphere at an altitude of 20 km, which occurred in early January 2012. This apparently caused a change in the charge of the weather, the troposphere, which is located at 10 km below. There form a weak westerly winds that blow in the middle latitudes of the Northern Hemisphere, or negative phase of the Arctic oscillation.

The transition from AO one phase to another is also influenced by the decrease in Arctic ice due to global warming. Melting ice triggers' Arctic paradox "when winter in the Arctic Circle becomes softer, while in the winter in more southern regions established abnormally cold weather.

This year, the Arctic Oscillation has not yet reached the United States, covering only Europe. But forecasters say that some of the facts about the imminent onset of cold on the other side of the ocean, as it was in December last year.

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