In this section, you will learn: zz what air masses are and how they form fronts zz about the various types of air masses zz about the different types of fronts that are formed.
Air mass Polar
Maritime Tropical Isobar Millibar
Front Warm Cold
Occluded Anticyclone Depression
Air masses
Air masses are large moving pockets of air that are distinct from the surrounding atmosphere. Warm air masses carry more moisture or water vapour than cold air masses. All air masses have the following characteristics:
• They are large, often stretching more than 1,500 km across the landscape and extending several kilometres into the atmosphere.
• The temperature, pressure and moisture are similar at any point within the air mass. • They travel across the atmosphere as a single unit.
Ireland experiences a range of air masses with different sources and paths. This gives us our variable weather. The following air masses affect Ireland:
Polar maritime These air masses from the north-west Atlantic bring cold, wet air and showery conditions.
Arctic Air masses from the North Pole bring cold weather conditions.
Polar:
Polar continental Air masses from north-east Europe bring dry, cold and frosty nights and heavy snowfall in winter.
Tropical continental Air masses from the Sahara bring dry sunny weather.
Polar Tropical maritime
Air masses from the south-west bring rain all year round.
Maritime:
to do with the sea or oceans.
Tropical Maritime
: Figure 13.9 Sources of air masses over Ireland 232 Tropical Continental Maritime Arctic Polar Continental
