Learning Target: Today we will begin learning about weather systems and fronts.

Transcription

1 October 31st, 2014 Thank you for not chewing gum Materials: Pencil, science notebook, Science book Today s Agenda: Bell work Vocabulary quiz Finish reading 3.1 Notes Learning Target: Today we will begin learning about weather systems and fronts. Daily Question: Which is more dense warm air or cold air?

2 Vocabulary- review Air mass- a large volume of air in which temperature and humidity are nearly the same in different locations at the same altitude. Front- a boundary between air masses. High-pressure system- formed when air moves all the way around a high pressure center. Low-pressure system- a large weather system that surrounds a center of low pressure.

3 Air Masses are large bodies of air Form when air over large region sits in one place for many days Air takes on characteristics of land below Earth cold air cold Earth wet air moist When air mass moves, brings temp. and moisture to new location

4 Characteristics of air mass Some regions produce air masses again and again Characteristics depend on where it forms Hot desert= dry, hot air mass Cool ocean waters= moist, cool air mass Classified into categories by characteristics

5 1 st word = moisture Continental- over land Air dries as loses moisture to land below Maritime- over water Air becomes moist as gains water vapor from water

6 2 nd word = Temperature (distance from equator) Tropical- near equator Warm Gains energy from warm land or water Polar- far from equator (closer to poles) Cool Gains energy from cold land or water

7 Combination of two words = characteristics of air mass Maritime tropical = moist, warm air mass Continental polar =? Dry, cool air mass

8 Movement of an air mass Air masses Travel away from regions where they form Move with global patterns of winds In MOST of US, move from west to east Move with jet stream

9 When move to new region Carries characteristics with it Characteristics of surface begin to change air mass Changes begin when air touches surface May take days or weeks for change to spread upward through entire air mass When moves quickly, may not change

10 Weather changes where air masses meet New air mass = weather change Front is boundary between air masses Weather near front different from weather inside air mass Clouds can form when one air mass pushes another and air pushes upward Weather becomes cloudy or stormy as front passes Afterward, experience temp. and humidity of air mass that moved in

11 Fronts and weather Different types of fronts produce different weather patterns

12 4 Types of weather fronts: Cold Front Warm Front Stationary Front Occluded Front

13 Cold Front When a fast moving cold air mass runs into a slow moving warm air mass and the thicker cold air slides under the lighter warmer air.

14 A cold front symbol The direction the teeth point indicate the direction the front is moving.

15 Warm Front hen a moving warm air mass collides with a lowly moving cold air mass and the warm air moves over the cold air.

16 Warm Front symbol The directions that the bumps face is the direction the front is moving.

17 Stationary Front When a cold air mass and warm air mass meet, but neither air mass has enough force to move the other air mass.

18 Stationary Front Symbol

19 Occluded Front When a warm air mass is caught between two cooler air masses and the thicker cold air masses move underneath the thinner warm air mass and push it upward.

20 Occluded front symbol The directions that the bumps face is the direction the front is moving.

21 High-Pressure system Air sinks slowly down Spreads out toward low pressure area as nears ground Coriolis effect makes air turn clockwise in Northern Hemisphere Formed when air moves all the way around a high-pressure center

22 Most are large and change slowly When stays for long time, air mass may form Generally bring clear skies and calm air or gentle breeze Air sinks to lower altitude, warms a bit Water droplets evaporate and clouds disappear

23 Low-pressure system Small area of low pressure can become larger system Large weather system that surrounds a center of low pressure Begins when air moves around and inward toward lowest pressure, then up to higher altitudes Upward motion lowers pressure so air moves faster

24 Produce stormy weather In Northern Hemisphere, circles in counterclockwise direction Can develop wherever there is low pressure Often along boundary between warm and cold air mass Large weather systems in North America usually move west to east Wind can blow in different directions within a weather system