weather patterns air masses and fronts section 17.1
TRANSCRIPT
Weather PatternsAir Masses and Fronts
Section 17.1
Air Masses
Huge bodies of air that have similar temperature, humidity, and air pressure
Maritime polar
Maritime tropical
Continental tropical
Continental polar
Arctic
OK
Fronts
• When an air mass moves into an area and interacts with other masses, it causes the weather to change.
• The boundary where air masses meet becomes a front
Cold Front
Since cold air masses move fast they can cause abrupt weather changes (thunder storms)
After a cold front passes, colder, drier air moves in bringing clear skies
Fast moving cold dense air pushes slow moving warm air up
Warm air cools and precipitates
Warm Front
Less dense warm air moves over dense cold airCan produce rain or snowArea likely to become warm and humid
Fast moving warm air overtakes slow moving cold air
Warm Front
Stationary Fronts
Cold air and warm air meet but neither can move the other.
Produces rain, snow or fog
Can last for several days
Standoff between two air masses
Stationary Fronts
Standoff between two air masses
Occluded Front
A warm air mass is caught between two cold air massesThe denser air mass pushes the warm air mass upThe two cold air masses may mix underneath the warm oneThe warm air mass is cut off (occluded) from the groundThe warm air cools, condenses and may precipitate
Cyclones & Anticyclones
• Fronts become distorted because of things like mountains or jet streams (bending)
• Bending can cause swirls which can create low pressure centers
Cyclones
• Swirling low pressure system
• Air pressure decreases as warm air rises
• Cooler air blows inward toward the low pressure area
• Coriolis effect causes the wind to spin counterclockwise in northern hemisphere
• Associated with clouds, wind, and precipitation
Anticyclones
• High pressure systems
• Air swirls outward in clockwise direction in northern hemisphere
• Cool air moves downward and heats up lowering relative humidity
• Associated with dry, clear weather