BBC Bitesize - National 5 Geography - Weather systems - Revision 2
There are five main air masses which affect the UK as detailed by the map below. Tropical Continental (cT), Southern Europe and North Africa, Warm and dry. Topic 4: Air Masses and ITCZ Global wind circulation and ocean currents are Over Africa the north east trades bring the Tropical Continental air mass and the south 6 Air Masses and ITCZ Where these two air masses meet they form the Inter- It moves north in June and south in January because of the tilt of the earth. Air masses are characterized by their temperature and humidity. • Air masses centers appear over North Atlantic (Bermuda high) and Pacific (Pacific high). Southwest, Southeast Asia, Central Africa, and near the equator. . warm air to the south moving toward the associated with cP air meets a warm.
These are the origins of the air masses which affect our weather. In some areas of the world air accumulates and adopts uniform characteristics of temperature and humidity. Their characteristics remain similar as the air moves away from the source.
This releases heat into the upper atmosphere. This heat is carried away to the higher latitudes, sinks and returns as the trade winds.
Air mass types
These winds have very different properties — both are different air masses. Over Africa the north east trades bring the Tropical Continental air mass and the south east Trades bring the Tropical Maritime. It brings warm, moist, unstable air. It is moist, as it has travelled across the ocean, picking up moisture as it moves. A tropical continental air mass originates over the land, e.
Air mass types - Met Office
We classify these air masses primarily by the area in which they originate. Tropical continental This air mass originates over North Africa and the Sahara a warm source region. It is most common during the summer months June, July and August, although it can occur at other times of the year.
- Air masses and their sources
- Weather systems
- The cause and impact of the Intertropical Convergence Zone
Visibility is usually moderate or poor due to the air picking up pollutants during its passage over Europe and from sand particles blown into the air from Saharan dust storms.
Occasionally, the Saharan dust is washed out in showers producing coloured rain and leaving cars covered in a thin layer of orange dust. Tropical maritime The source region for this air mass is warm waters of the Atlantic Ocean between the Azores and Bermuda. The predominant wind direction across the British Isles, in a tropical maritime air mass, is south-westerly.
Tropical maritime air is warm and moist in its lowest layers and, although unstable over its source region, during its passage over cooler waters becomes stable and the air becomes saturated. Consequently when a tropical maritime air mass reaches the British Isles it brings with it low cloud and drizzle, perhaps also fog around windward coasts and across hills.
To the lee of high ground though, the cloud my break up and here the weather, particularly in the summer months, can be fine and sunny. This is a mild air stream and during the winter month in particular, can raise the air temperature several degrees above the average.
The term 'air mass' was introduced some 70 years ago by Norwegian meteorologists from Bergen, Norway. Air mass is a large body of air, whose properties - temperature, humidity and lapse rate - are largely homogeneous over an area several hundred kilometres across. The nature of air masses is determined by three factors: The primary classification of air masses is based on the characteristics of the source region, giving Arctic APolar P or Tropical air Tand on the nature of the surface in the source region: In addition, a large variety of secondary types of air masses are defined.
For example, equatorial air E or Mediterranean air. Sometimes there is a letter k or w attached to the two-letter initials indicating whether the air is wa rmer or colder than the surface. The former becomes more stable, and the latter more unstable.
Some older works use the term of an 'returning air mass'.