Air Masses and Fonts Chapter 8 Section 3

Standards S 6.4.e Students know differences in pressure, heat, air movement, and humidity result in changes in weather.

Anticipatory

Language of the Discipline Air masses Front Tropical Occluded Polar Cyclone Maritime Anticyclone Continental

Air Masses A huge body of air that has similar temperature, humidity and air pressure at any given height Types: maritime tropical Continental tropical Maritime polar Continental polar

Maritime Polar Warm, humid air masses form over tropical oceans. In summer they bring hot humid air. Gulf of Mexico, and the Atlantic Ocean Winter: can bring heavy rain or snow

Maritime Polar Cool, humid air masses form over icy cold North Pacific Summer: brings fog, rain and cool temperatures to the West Coast

Continental Tropical Hot dry masses form in dry Southwest and northern Mexico Hot dry weather to the southern Great Plains Covers a smaller area than other air masses

Continental Polar Central and Northern Canada, and Alaska Air masses bring bitterly cold weather with very low humidity Winter: Air masses bring clear, cold, dry air Summer: milder

How Air Masses Move In the US, air masses are commonly moved by the prevailing westerlies and jet streams. Prevailing Westerlies: major wind belts and push aim asses from west to east. Jet Streams: bands of high speed winds above Earth’s surface Fronts: huge air masses collide with each other but do not mix. They have different temperatures and humidity collide. Storms and changeable weather develops.

Review cold air is dense and sinks. Warm air is less dense and rises. When they run into each other the cold air slides under the lighter air. Warmer air is pushed up.

Types of Fonts Colliding air masses can form 4 types of fonts: Cold fronts- move quickly and cause abrupt weather changes. After it passes, drier air moves in and brings clear skies, a shift in wind and lower temperature Warm fronts- move slowly weather may be rainy or cloudy. After is passes through the weather is warm and humid

Stationary fonts- where warm and cool air meet, the water vapor in the warm air condenses into rain, snow, fog or clouds. It will stall over an area, it may bring clouds and precipitation Occluded fronts- temperature near the ground become cooler. Warm air mass is cut off. As warm air cools, it condenses and weather becomes cloudy and rain or snow may fall.

Cyclones Wheel Swirling center of low air pressure Cyclones and decreasing air pressure are associated with clouds, wind and precipitation Warm air in the center rises and air pressure decreases Cooler air blows towards a high pressure area

Anticyclones High pressure centers of dry air “highs” on a weather map. H Descending air in an anticyclone generally causes dry, clear weather. Winds spiral outward from the center and moves to areas of lower pressure.

Checking for Understanding Where do continental polar air masses come from? What type of weather do cold fronts bring? What in an anticyclone?

Guided Practice Independent Practice Worksheet Stop! Have your answers checked Workbook pages