Arctic Continental Vs Polar Continental

[Isolated Frost]

Here's a question I've been wanting to ask for a while... now I think Ac (arctic continental air) moves in from the arctic and then moves from the northeast and east on arrival to britain, and Pc (polar continental air) arrives due to siberian/scandi hp, and moves in primarily from the east.

Would I be correct in saying that the last couple of winters have been dominated by Ac air during cold snaps due to a strong greenland high, ridging off eastwards and southwards, thus delivering north-east and east winds to britain?

Here are a few questions:

What is arctic continental air and polar continental air, where are their hp sources located, and what is the usual outcome?

Which is more potent and for which parts of the UK?

Any examples please?

I think TWS is very advanced in knowing these airmasses, but any help would be lovely.

Ta, and have a brilliant christmas, boxing day, bank holiday and new year!

[Thundery wintry showers]

To my knowledge arctic continental is sourced from northern Scandinavia/Russia/Siberia whereas polar continental is sourced from central parts of Europe and/or western Asia, generally to the south of the Arctic Circle. In summer the term "polar continental" is perhaps misleading as those continental areas often get very hot in summer, but in winter polar continental air generally lives up to its description.

Thus a Scandinavian High setup is more likely to give us polar continental air although, if oriented right, a high centred over Scandinavia is also capable of bringing arctic continental airmasses across. The last two winters, dominated by Greenland High setups, mostly brought us a mix of arctic maritime air (straight down from the north) and arctic continental air (when the wind veered around to the east or north-east, most notably around 29 November to 2 December 2010).

I think arctic continental is the most potent in terms of cold, as polar continental is sourced from further south and arctic maritime is more heavily modified over the north Atlantic. However, in southern areas this is complicated by the fact that as it most often arrives via a north-easterly airflow, it is often associated with a longer sea track than polar continental air (which often arrives via an east to south-easterly regime) and so the arctic continental airmasses produce more snow showers over the North Sea but not necessarily lower temperatures.

[Isolated Frost]

Thanks TWS

Do you have many examples of Ac and Pc air on wetter? Thanks again, merry xmas

[damianslaw]

To my knowledge arctic continental is sourced from northern Scandinavia/Russia/Siberia whereas polar continental is sourced from central parts of Europe and/or western Asia, generally to the south of the Arctic Circle. In summer the term "polar continental" is perhaps misleading as those continental areas often get very hot in summer, but in winter polar continental air generally lives up to its description.

Thus a Scandinavian High setup is more likely to give us polar continental air although, if oriented right, a high centred over Scandinavia is also capable of bringing arctic continental airmasses across. The last two winters, dominated by Greenland High setups, mostly brought us a mix of arctic maritime air (straight down from the north) and arctic continental air (when the wind veered around to the east or north-east, most notably around 29 November to 2 December 2010).

I think arctic continental is the most potent in terms of cold, as polar continental is sourced from further south and arctic maritime is more heavily modified over the north Atlantic. However, in southern areas this is complicated by the fact that as it most often arrives via a north-easterly airflow, it is often associated with a longer sea track than polar continental air (which often arrives via an east to south-easterly regime) and so the arctic continental airmasses produce more snow showers over the North Sea but not necessarily lower temperatures.

How would you define the airmass which delivered the bitter cold of feb 91. Because of the long fetch easterly from siberia would you describe the synoptic as arctic continental? - it certainly delivered very cold conditions. Another example of an easterly borne from arctic continental air would be jan 87.

[feb1991blizzard]

Surely any airmass described as polar or arctic is the same thing, i can understand the differences between continental and arctic but not between polar and arctic as its the same region its just that arctic covers i wider area but its still an airmass sourced from very high lattitudes, continental can be polar or tropical,

[Lettucing Gutted]

Surely any airmass described as polar or arctic is the same thing, i can understand the differences between continental and arctic but not between polar and arctic as its the same region its just that arctic covers i wider area but its still an airmass sourced from very high lattitudes, continental can be polar or tropical,

I read a textbook called "Atmosphere Weather and Climate" and it said the biggest differences between Arctic and Polar airmasses are in the Upper Troposphere with the temperature there been much more colder in the Arctic airmass than the Polar airmass. Also at the 500 HPA level the temperatures in Arctic air is -40C or even colder whereas Polar air has 500 HPA temperatures above -40C. Edited December 28, 2011 by Craig Evans

[feb1991blizzard]

I read a textbook called "Atmosphere Weather and Climate" and it said the biggest differences between Arctic and Polar airmasses are in the Upper Troposphere with the temperature there been much more colder in the Arctic airmass than the Polar airmass. Also at the 500 HPA level the temperatures in Arctic air is -40C or even colder whereas Polar air has 500 HPA temperatures above -40C.

Ok, thanks for the reply, it seems to me, reading yours and TWS's post above that there are differences, but i would say that with regard to winter setups for the UK, they are only subtle differences and both can deliver really good snow events, i seem to remember another thread regarding this last year with a vote but i cant find it, i may have inadvertantly voted for the wrong airmass being my favourite going on what i have read in here.

[Thundery wintry showers]

How would you define the airmass which delivered the bitter cold of feb 91. Because of the long fetch easterly from siberia would you describe the synoptic as arctic continental? - it certainly delivered very cold conditions. Another example of an easterly borne from arctic continental air would be jan 87.

The classification can be very difficult, especially as it isn't well-documented, but I strongly suspect that the February 1991 easterly outbreak had arctic continental air- it originated north of the Arctic Circle and then headed south into central Europe before heading our way from the east.

This chart from mid-February 1986 is probably a good example of polar continental air, as the airmass comes straight from central Europe, with very cold surface temperatures but not so impressive at upper levels:

http://www.wetterzen...00119860217.gif

http://www.wetterzen...00219860217.gif

For a good example of arctic continental air we don't have to look back very far:

http://www.wetterzen...00120101130.gif

http://www.wetterzen...00220101130.gif

Quite a number of the famous "easterly" months had a strong polar continental influence in the SE and a strong arctic maritime influence in the NE, including the Februarys of 1947 and 1986- hence the fact that those months had long runs of cold dull dry weather in the SE due to limited instability over the southern North Sea, while further north conditions were often brighter with some snow showers.

In general polar continental air isn't particularly reliable for generating snow showers over the North Sea, though of course it can give rise to major snowfalls if it collides with Atlantic weather systems.

[johnholmes]

Quite a number of the famous "easterly" months had a strong polar continental influence in the SE and a strong arctic maritime influence in the NE, including the Februarys of 1947 and 1986- hence the fact that those months had long runs of cold dull dry weather in the SE due to limited instability over the southern North Sea, while further north conditions were often brighter with some snow showers..

sorry Ian that about 'often brighter' is simply not true, have a look at the charts on the link below for almost every day in 1947 February, 7-8/8 seems to be the general cover and 1947 is often quoted for almost all areas over and east of high ground as notable not only for its severe cold and snowfall but also its lack of sun.

http://www.winter1947.co.uk/

[Thundery wintry showers]

sorry Ian that about 'often brighter' is simply not true, have a look at the charts on the link below for almost every day in 1947 February, 7-8/8 seems to be the general cover and 1947 is often quoted for almost all areas over and east of high ground as notable not only for its severe cold and snowfall but also its lack of sun.

http://www.winter1947.co.uk/

The sunshine stats for stations in the eastern half of the UK for February 1947 from the Met Office's station data list (from south to north):

Manston 29.7

Waddington 24.7

Durham 42.8

Mairn 83.5

Wick 62.7

The table in the Weather article for February 1947 gave 17 hours for Kew (London) and 30 for Aberdeen.

I don't think the stats refute my "often brighter" claim, although one can certainly argue that "often less dull" would be more accurate in the case of February 1947. Although north-eastern districts generally reported a shortage of sunshine, in most cases the shortage wasn't quite as extreme as in south-eastern Britain. The spread of sunshine totals for February 1986 was similar, though shortages were generally smaller than in February 1947.

[cooling climate]

I was always of the view that continental Arctic was

when the air from the continent was excessively cold

IE Jan 87, Jan 85 etc,etc.

[Polar Maritime]

I was always of the view that continental Arctic was

when the air from the continent was excessively cold

IE Jan 87, Jan 85 etc,etc.

Do you mean Polar Continental ?

[cooling climate]

Do you mean Polar Continental ?

No I mean Arctic continental as apposed to polar continental.

The former being colder than the latter.