Chapter 3 Section 1 Pages 76-82 Air Masses & Fronts Chapter 3 Section 1 Pages 76-82

Air Mass A huge body of air with similar characteristics: Humidity Temperature Air Pressure Classified based on two questions… Did the air mass form over water or land? In what climate did it form?

Continental Form over land, in the middle of continents Very dry air.

Maritime Form over oceans Water evaporates from the ocean creating very humid air.

Tropical Warm air masses form in the tropics and have low air pressure. Why? Particles are spread out, low density.

Polar Cold air masses form north of 50°N latitude and south of 50°S latitude Have high air pressure (are very dense).

Air Masses 1 2 4 3 Continental Polar Maritime Polar Maritime Polar Maritime Tropical Maritime Tropical 4 3 Continental Tropical

How Air Masses Move What moves an air mass from one place to another? The Global Winds move air masses The Prevailing Westerlies generally push air masses from west to east in the United States.

Exit Pass What are the two ways air masses are classified? Give an example of a type of air mass.

Fronts The area where air masses meet and do not mix Named after battle lines Cause storms and a change in weather Depends on the characteristics of the air masses and how they are moving.

Warm Fronts A warm air mass hits a cold air mass Warm air rises over cold air – Why? Warm air is less dense Weather: If humid air, light rain forms If dry, scattered clouds form After it passes, it is likely to be warm and humid

Warm Fronts

Cold Fronts Cold air bumps into warm air, pushing the warm air up As it rises, it cools and forms clouds Move faster than warm air mass, can cause abrupt weather changes Weather: Humid brings rain, T-storms, or snow Dry air forms cloudy skies After it passes, brings cool, dry air with clear skies and cooler temps.

Cold Fronts

Stationary Fronts Occurs when cold and warm air masses meet, but neither can force the other to move Water vapor in the warm air condenses into rain, snow, fog or clouds If it stalls over an area, it can bring these conditions for several days.

Stationary Fronts

Occluded Fronts Occurs when a warm air mass is caught between two cold air masses Pushes warm air up over colder air, cutting the warm air off from the ground Weather: Cool ground temperature Brings clouds, rain or snowy weather.

Occluded Fronts

What is a front? Briefly explain one type of front. Exit Pass What is a front? Briefly explain one type of front.

Surface Map

Surface Map

Surface Map

Cyclones Cyclone is Greek- meaning “wheel” A swirling center of low pressure. Spin counter-clockwise (due to coriolis effect winds are turned to the right in the NH) L is short for Low Pressure Air is moving towards the low Air is rising, forming clouds and precip. Bring LOUSY Weather

Anti-Cyclones Are areas of high pressure centers Winds spiral out from the center towards areas of lower pressure. Spin clockwise (due to coriolis effect winds are turned to the right in the NH) H= short for High Pressure Air is moving away from the high. Cool air is sinking, and warms as it falls. Clear, dry weather. (Brings HAPPY weather)

Mid-Latitude Cyclones H L

Mid-Latitude Cyclones