Wind and
Air
Masses
• An air mass is a volume of air that takes
on the conditions of the area where it is
formed.
• An air mass originating over an ocean
would contain a considerable amount of
moisture. When this moist air mass passes
over land some form of precipitation would
most likely be released.
• In contrast, an air mass originating over
land would probably be dry as it lacks a
ready source of moisture.
•-Air masses also take on the temperature
characteristics from areas where they form.
An air mass that forms over the Gulf of Mexico
would be warm and moist. An air mass
forming over a polar region would be cold and
dry.
•-A front is the leading edge of an air mass. A
cold front leads a cold air mass, while a warm
front leads a warm air mass.
•-Air moves along the surface of Earth from
high-pressure areas toward low-pressure
areas. This moving air produces wind.
• A high pressure system would produce sunny, dryer but
cooler conditions. In the winter, a high pressure system
produces sunny but very cold days. In the summer, the
days are sunny and not humid.
• A low pressure system produced cloudy wetter but
warmer days. In the summer, a low pressure system
would produce a warm rainy day. In the winter, the day
would have snow, and if the low pressure system was
intense, could produce a snow storm.
• Over most of Canada, winds blow from west to east
called the westerlies. These prevailing winds move air
masses that affect our weather.