Types Of Arctic Highs

[Lettucing Gutted]

I get the impression that there is at least two types of Arctic High Pressure system. An Arctic High is a high with its centre north of 80deg North.

The Cold Arctic High

This is the true beast for cold weather fans and are affectionately known as "cold blocks". The great feature of this Arctic High is that it can send big pools of cold air all over the mid lattitudes such as Britain, for long periods and with hardly warming out of the Arctic cold pool due to displaced warm airmasses as long as both the polar and subtropical westerly jet streams flow at low latitudes. The fact that the Arctic cold pool doesn't warm out in a cold Arctic High is important for sustaining cold spells otherwise the warming of the Arctic troposphere creates cyclogenesis leading to strong low pressure systems and secondary features near the North Pole which cut of the flow of cold air and strengthens the Ferrel cell which can bring very warm weather to the mid latitudes associated with the subtropical high pressure systems.

The cold Arctic High was responsible for almost all of the cold months and seasons upto the end of the 20th Century. As the name suggests the cold Arctic High is related almost directly to the intensity, depth and extent of the Arctic cold pool. The intensity, depth and extent of the Arctic cold pool is in turn dependent on the extent of the Arctic ice sheet. There was a large Arctic ice sheet and cold Arctic High in the cool Arctic summer of 1985 and there was an even larger Arctic sheet and large cold Arctic High in the cold Arctic winter of 1969. An interesting feature of the best cold Arctic Highs is that eventhough the cold high forms in a deep cold Arctic airmass there is anticyclonic circulation at all levels of the Arctic atmosphere from the surface, through the troposphere and into the stratosphere. Although the Arctic upper troposphere is colder than normal there is anticyclonic circulation in the upper arctic troposphere and stratosphere due to direction of planetary wave energy from Siberian snow cover and the intense surface Arctic High and/or Siberian Highs themselves.

Below is an example of a cold Arctic High in the cool Arctic summer of 1985:-

http://www.wetterzentrale.de/pics/archive/ra/1985/Rrea00119850601.gif

In the chart below notice that in addition to the plus 5C, 0C and even the -5C 850 HPA isotherms plunging into the Western Mid lattitude North Atlantic Ocean the Arctic is also under sub -5C 850 HPA air associated with the cold Arctic High:-

http://www.wetterzentrale.de/pics/archive/ra/1985/Rrea00219850601.gif

Below is an example of a cold Arctic high in the cold Arctic winter of 1969. The central pressure of this high is 1045mb and is north of Novaya Zemlya:-

http://www.wetterzentrale.de/pics/archive/ra/1969/Rrea00119690117.gif

In the chart below notice that in addition to the -5C and even the -10C 850 HPA isotherms plunging into the Central Mid lattitude North Atlantic Ocean the North Pole is also under sub -22C 850 HPA air associated with the cold Arctic high:-

http://www.wetterzentrale.de/pics/archive/ra/1969/Rrea00219690117.gif

The Warm Arctic High

Effectively this is a displaced subtropical high pressure system. Eventhough deep cold cutoff lows can be displaced into mid lattitude locations such as Britain (hence a Negative North Atlantic Oscillation and Negative Arctic Oscillation)the warm "Arctic" High brings record breaking "warmth" to the Arctic itself. This happened during the very warm Arctic summer of 2007 which saw a record low Arctic ice extent.

Below is an example of a warm Arctic High in the warm Arctic summer of 2007:-

http://www.wetterzentrale.de/pics/archive/ra/2007/Rrea00120070807.gif

In the chart below notice that eventhough the 5C isotherm at 850 HPA surges towards Spain there is a pool of very mild plus 0C and even plus 5C air at 850 HPA associated with the warm Arctic High over the Arctic:-

http://www.wetterzentrale.de/pics/archive/ra/2007/Rrea00220070807.gif

Edited December 24, 2009 by Craig Evans