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Weather Patterns Air Masses and Fronts. Section 17.1. Air Masses. Arctic. Maritime polar. Continental polar. Huge bodies of air that have similar temperature, humidity, and air pressure. OK. Maritime tropical. Continental tropical. Fronts.
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Weather PatternsAir Masses and Fronts Section 17.1
Air Masses Arctic Maritime polar Continental polar Huge bodies of air that have similar temperature, humidity, and air pressure OK Maritime tropical Continental tropical
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 Fast moving cold dense air pushes slow moving warm air up Warm air cools and precipitates 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
Warm Front Fast moving warm air overtakes slow moving cold air Less dense warm air moves over dense cold air Can produce rain or snow Area likely to become warm and humid
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 masses The denser air mass pushes the warm air mass up The two cold air masses may mix underneath the warm one The warm air mass is cut off (occluded) from the ground The 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