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Basic NavigationLecture 5

ACP32 Vol2

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Basic Navigation

By the end of this lecture you should know:

The 6 Major Air Masses

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Major Air Masses

The Earths atmosphere is constantly

moving as warm air rises, cold air descends

and the Earth spins.

There are 6 Major Air Masses that influence

British weather.

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Major Air Masses

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Major Air Masses

Arctic Maritime

Originating in the very cold Arctic seas, picks up a

little moisture as it travels south. Typical weather

conditions are:

Summer - Very cold with frequent heavy showers.

Winter - Very cold strong north, north-easterly

winds. Heavy snow showers in north.

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Major Air Masses

Polar Continental

Originates in Siberia. In southern Britain the weather is dryas it has not crossed much water. In northern Britain theair mass has travelled over the north sea, losing heat and

picking up moisture.

Summer - Warm and dry, cloud free. East coast tends tobe cool and showery with coastal fog in the north.

Winter - Sleet and snow showers in the north. Cold strongeast winds.

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Major Air Masses

Tropical Continental

Originates in North Africa, warm air moves north over

Europe and has little opportunity to pick up water vapour.

Typical weather conditions are:

Summer only - Very hot and dry, hazy with occasional

thunder storms.

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Major Air Masses

Tropical Maritime

Originates in warm tropical oceans around theequator. Brings warm and wet air. Typical

weather conditions are:

Summer - Warm south-west winds. Low stratuscloud over west coast.

Winter - Stratus cloud, hill fog and drizzle. Warmwith prolonged rainfall.

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Major Air Masses

Returning Polar Maritime

Originates in Canada as very cold, dry air. Initiallyit moves south, gains warmth and moisture. Bythe time it reaches the Britain. Typical weather

conditions are:

Summer - Warm with squally showers and stormsinland.

Winter - Stratus cloud. Showers in the westernmountains.

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Major Air Masses

Polar Maritime

Originates in north Canada and Greenland, crosses theAtlantic Ocean picking up water vapour before reachingBritain. Typical weather conditions are:

Summer - Cool winds, heavy showers, thunder storms inmountains

Winter - Heavy showers in west with snow in mountains.Clear skies at night in the east giving frost.

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