Which air mass most commonly affects the UK?

The air mass that most commonly affects the United Kingdom is the maritime polar (mP) air mass. This air mass originates over the North Atlantic Ocean and is characterised by cool, moist air. The mP air mass is responsible for the UK's mild, wet climate.

The maritime polar air mass is one of the four main air masses that affect the UK. The other three air masses are:

* The continental polar (cP) air mass, which originates over continental Europe and is characterised by cold, dry air.

* The maritime tropical (mT) air mass, which originates over the tropics and is characterised by warm, moist air.

* The continental tropical (cT) air mass, which originates over continental tropical regions and is characterised by hot, dry air.

The UK's climate is influenced by all four of these air masses, but the maritime polar air mass is the most common. This is because the UK is located on the edge of the North Atlantic Ocean, and the prevailing winds in the UK are from the west or south-west. These winds bring the mP air mass over the UK from the Atlantic Ocean.

The mP air mass is responsible for the UK's relatively mild climate. The average temperature in the UK is around 10 degrees Celsius, and the average rainfall is around 1,200 millimetres per year. The mP air mass also brings with it clouds and rain, which is why the UK is known for its wet weather.

The maritime polar air mass can also bring extreme weather conditions to the UK. In winter, the mP air mass can bring cold spells and snowfall. In summer, the mP air mass can bring heat waves and thunderstorms.