January 15, 2013. In recent days in many parts of the northern hemisphere there is cold and snowy weather. It seems or actually harsher winter than usual? You can even hear the question: "Is there a relationship between the observed cold weather and sudden stratospheric warming?" Clearly, the answer to this question is quite difficult.
Indeed, now in the stratosphere over the northern hemisphere there is a sudden thaw.
Sudden stratospheric warming (GSP), which occur in the winter, causing the most intense interest. Meteorologists continue to actively explore the mechanism of their relation to changes in the troposphere, especially in the lower layers, where a weather, we feel.
Sudden Stratospheric Warming — A strong and sudden increase in temperature "explosive nature" in the polar and sub-polar stratosphere in winter, sometimes up to 50 ° or more in a few (about ten) days. This occurs at altitudes of 10 to 50 km. In this case, the sign of the meridional temperature gradient over the hemisphere, is formed stratospheric anticyclone and the overall transport of air varies from west to east. SP occurs in the upper stratosphere, in layers, which are located above the stratonulya (about 24 km) and then extends to the lower stratosphere. A return to normal winter mode is slower than the development of warming. GSP. occur almost every year. Apparently, the immediate cause of the GSP. is lower, and adiabatic heating of stratospheric air associated with the restructuring of the conditions of circulation.
The history of observations of the GSP has a little more than 60 years. It was first seen in 1952, according to the observations in Berlin. The most comprehensive monitoring of the stratosphere is from 1979, it accounted for radiosonde data and satellite information.
GSP should be distinguished. "Explosive" type of normal warming of the stratosphere during the year.
Sudden stratospheric warming (GSP) remains one of the most dramatic events in
Nature stratospheric warming lies in the connection of tropospheric and stratospheric dynamical processes. Quite clearly, this relationship can be traced to an altitude of 30 km. Large-scale intensity of tropospheric processes are reflected in the structure of stratospheric temperature fields, geopotential and wind. But unlike the troposphere, the conversion of these fields occur over a much longer time intervals.
For stratospheric warming that occur almost every winter, characterized by uneven geographical distribution. Their frequency is high in the Asian region.
Sudden stratospheric warming involve significant changes in circulation in the winter stratosphere.
Usually in the winter over the hemisphere, when the sun's heat flow is very limited (or no), formed by the circumpolar vortex, the center of which migrates near the pole. It surrounds the jet stream at the edge of the polar night at high latitudes — a zone of strong winds blowing from west to east. In this period the GSP scheme "breaks" when a strong perturbation of the troposphere, such as extensive and powerful anticyclone may be blocking extends upward. He was "outraged" polar night jet stream, significantly weakens the westerly winds and can even reverse them. When this occurs, the air starts being sucked into the stratosphere vortex center and shrink. As a result of compression is his warm-up, and begins the GSP and increased vertical circulation. At some time in the polar region can be established anticyclone.
The first signs of warming in the stratosphere were observed in December (
Emerging in late November, a split of the circumpolar vortex led to its substantial deformation and movement, so in early December storm center was located over Greenland. The axis of a deep stratospheric troughs, sometimes with an independent center over northern Scandinavia, has been focused on Western Siberia. Over the Aleutian you celebrated with stratospheric anticyclone, and the situation was generally similar to that observed usually at stratospheric warming. However, the temperature in the polar regions of the stratosphere in October and November were significantly below the average, and a transient increase in the first half of December, only to bring it closer to the norm.
In the second decade of the cyclone has recovered and has deepened, so geopotential at its center was about 70 ladies below normal. Center was located mainly in the northern Barents Sea.
In late December storm center moved further south, to the area of the New Earth. The warming trend is maintained, as evidenced by the stratospheric anticyclone over the Korean Peninsula and the comb, it is spreading from the north Pacific and Canada. In late December — early January, there was a sharp rise in temperature in the polar regions of the stratosphere to extremely high values.
In the equatorial stratosphere continued weakening of the eastern phase of the quasi-biennial cycle of the winds. "
Anticyclone in winter troposphere — the phenomenon of short-term and unsustainable. Circumpolar vortex and westerly winds due to astronomical factors, the characteristics of solar wind and the Earth's rotation is gradually restored. A easterly waves, gradually fading, will descend into the troposphere, influencing our weather — hence all the cyclones in the movement have a tendency to move to the south, southwest and west. They block the flow of warm air, which could come from the Atlantic, but it brings cold air from the Arctic or of cooled continental regions.
GSP is often, but not always, accompanied by such phenomena. During such events simply increases the frequency of cold weather. This is just one of the "ways" to make cold weather, more precisely, to reallocate the field of cold and warm weather accordingly modified scheme of atmospheric circulation.
Today, meteorologists are based on monitoring with a good lead time to a week to predict and monitor the emergence and evolution of the GSP and to determine the nature of the atmospheric circulation.
A more accurate prediction, which allows for the passage of certain weather systems (cyclones, anticyclones, atmospheric fronts) through certain regions and the specific values of weather elements by numerical models, as usual.