An arctic maritime air mass has similar characteristics to a polar maritime air mass, but because of the shorter sea track the air is colder and less moist. Arctic air is uncommon during the summer, but when it does occur it may bring heavy showers or thunderstorms and unseasonably low temperatures. Between October and May, the air is cold enough to produce hail showers or snow, and these are most frequent over Scotland and along the coasts exposed to northerly winds.
Polar low-pressure systems forming in this air mass can sometimes lead to widespread and heavy snowfall, but otherwise inland areas remain free of cloud in the winter months. In northern Scotland, arctic maritime is usually the coldest air mass, but over the rest of Britain, this air mass is not as cold as polar continental. Returning polar maritime is another version of polar maritime, but this time with a longer sea track which takes the air first southwards over the North-Atlantic, the north-eastwards across the British isles.
During its passage south, the air becomes unstable and moist but on moving north-east it passes over cooler water making it stable in its lowest layers. Although the weather across the British Isles in this air mass is largely dry, there can be extensive cloud cover. Air mass types. There are a total of six air masses that affect the British Isles, they are classified as follows: Tropical continental This air mass originates over North Africa and the Sahara a warm source region.
Tropical maritime The source region for this air mass is warm waters of the Atlantic Ocean between the Azores and Bermuda. Polar continental This air mass has its origins over the snow fields of Eastern Europe and Russia and is only considered a winter November to April phenomena.
Polar maritime This air mass has its origins over northern Canada and Greenland and reaches the British Isles on a north-westerly air stream. Arctic maritime An arctic maritime air mass has similar characteristics to a polar maritime air mass, but because of the shorter sea track the air is colder and less moist. An arctic maritime air mass has its origins over the North Pole and the Arctic Ocean. The map and explanation above shows the direction of the air mass movement and the weather characteristics they bring with them.
The names of the air masses hold clues as to where they originated and hence the weather they will bring. As it passes over the North sea it can pick up some moisture, bringing snow to the East coast in winter. It originates in Greenland and North West Canada. They bring a mixture of conditions to the country, from sizzling Spanish heat on day to frosty arctic blasts the next, which are typically named after the area they originate from.
The six basic types include arctic or antarctic, tropical, equatorial, polar, continental or maritime. Continental or maritime are dependent on whether the air masses come from over land or sea.
While arctic or antarctic, equatorial, tropical, and polar depend on the particular region in which they form. The most severe weather usually occurs when warm, humid maritime tropical air collides with dry and cold continental polar air. The nature of air masses is determined by three factors: the originating area of the air mass, the age and the modifications that may arise as the air travels away from its starting point across the surface of the earth.
Originating from desert regions like North Africa and the Sahara, this hot and dry air mass is most common during the summer months, but it can occur at other times of the year. Often sand particles and pollutants blown across Europe from Saharan dust storms can reduce visibility and can leave a thin layer of orange dust on surfaces with when mixed in with rain.
Weather fronts: What are they and how do they affect the UK? How high and low air pressure affects UK weather. Tropical maritime: This air mass comes from the Azores Islands, and when approaching British Isles from the west, it usually leads to long periods of rain, and overcast skies, with some drizzle for the east. In summer, tropical maritime air tends to feel very warm and muggy, bathing much of the southeast in plenty of sunshine.
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