Continental Air Masses

[Kentish Man]

In very old textbooks there was a distinction made between Polar Continental, air largely drawn from central Europe and Southern Russia typically giving daytime maxima of around 3C in the winter months and night minima just above freezing because of the cloudiness of the airstream and Artic Continental, air drawn from Scandinavia and Artic Russia which in midwinter was cited as the only airstream that will produce freezing days with sunshine and snow showers in central England.

Is this a distinction still made?

[Thundery wintry showers]

I remember Philip Eden's 1995 book Weatherwise had a discussion on polar and arctic continental airmasses, but concluded that polar continental air was better described as "European" (something that I would personally agree with). The BBC weather site also mentions the two airmasses.

Temperatures and weather types vary according to the detailed history of the airmass, but the general points are correct, as far as I'm aware.

Polar continental (European) airmasses tend to be moderately cold and very stable, 850hPa's may be unspectacular but the surface is often almost as cold as the upper atmosphere. As the airmass approaches us from the east or south-east, the moisture picked up off the North Sea is often trapped underneath an inversion, giving rise to stratocumulus layers. The warm sea air is also trapped underneath the inversion, so temperatures rise appreciably by the time they reach Britain, giving the highs of 3C and minima of 0C.

Arctic continental air is also very dry, but tends to be much colder at upper levels (that's usually where you get the -15 to -25C cold pools at 850hPa level), so the atmosphere ends up more unstable as it crosses the North Sea. It is also more likely to arrive from the east or north-east, with a longer track over the North Sea, and the result tends to be sunshine and snow showers. Although these airmasses often take a longer sea track, in practice that doesn't always mean that they are modified more, as the lack of an inversion means that the warm sea air mixes with a greater portion of the atmosphere above, reducing the rate at which the airmass warms at low levels.