Anticipation Guide #2

Transcription

1 Weather Systems

2 Anticipation Guide #2 Density differences in the atmosphere are responsible for redistributing earth s heat When air is heated it rises, cools and expands releasing energy mt air masses are warm and dry air masses Air masses exchange heat and moisture with the surface over which it travels Air masses can never modify and will always be associated with their source regions

3 Focus Question How can the weather conditions in Canada affect our weekend?

4 VA SOL SOL 3 The student will investigate and understand how to read and interpret maps, globes, models, charts, and imagery. Key concepts include a. maps (..weather) and SOL 13 The student will investigate and understand that energy transfer between the sun and the Earth and its atmosphere drives weather and climate on Earth. Key concepts include b. prediction of weather patterns

5 Enduring Understanding Energy transfer between the Earth s surface and the atmosphere creates the weather. The atmosphere remains in balance until acted on by an outside force.

6 As air rises, it expands and cools.

7 Weather Systems Heat energy on Earth is in constant motion as it flows from areas of higher temperature to areas of lower temperature. This heat flow creates our global wind systems that transport colder air to warmer areas and vice versa in a constant balancing act of heat energy

8 Coriolis effect If Earth did not spin predicting weather would be much easier. Cold air at the poles would flow towards the equator and displace the warm air which would rise and flow back towards the poles as it cools in the upper atmosphere, but since it does spin and since air is a fluid material the prediction is far more difficult

9 Coriolis effect The Coriolis Effect on Earth causes moving particles (air molecules ) to deflect to the right in the northern hemisphere and to the left in the southern hemisphere

10 Coriolis Effect

11 Global Wind Patterns For thousands of years mariners have utilized predictable wind patterns to navigate the globe. There are three basic zones per hemisphere. Meteorology now provides an understanding of the reasons for these reliable winds

12 Global Wind Patterns Trade Winds occur at where the warm, rising air from the equator begins to cool and sink. They occur below 30 degrees latitude and blow in an east to west direction

13 Question How do you think this wind pattern got its name?

14 Horse Latitudes Along the 30 degree line the sinking air causes a belt of high pressure with very little horizontal movement. Sailors used to refer to these as the horse latitudes because they would sometimes become stranded in the calm seas and have to throw their horses overboard because they couldn t feed them

15 Global Wind Patterns Prevailing Westerlies flow between 30 and 60 degrees latitude and blow from west to east. This pattern is responsible for much of the weather in North America

16 Global Wind Patterns Winds are named for the direction they blow from

17 Global Wind Patterns Polar Easterlies blow from east to west between 60 deg and the poles and are characterized by very cold air

18 Global Wind Patterns

19 Jet Streams Often the weather report will state that the jet stream is affecting today s forecast in some way. Earth weather is strongly influenced by atmospheric conditions and events between the wind zones

20 Jet Streams Jet Streams are narrow bands of fast, highaltitude, westerly winds and flow at speeds of 185 km/hr Their position varies and drives large-scale weather systems

21 Fronts Since air masses of different characteristics are constantly in motion some of them are bound to eventually collide

22 Fronts Front is the narrow region separating two air masses of different densities Density differences are caused by differences in temperature, pressure, and humidity

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24 Fronts There are four main types of fronts and the interaction of colliding air masses often causes dramatic changes in weather

25 Fronts Cold Fronts occur where cold, dense air displaces warm air and we see clouds, showers, and thunderstorms

26 Fronts-Cold Front Generally, with the passage of a cold front, the temperature and humidity decrease, the pressure rises. e.com/books/earth_ science/terc/conten t/visualizations/es2 002/es2002page01. cfm?chapter_no=vi sualization

27 Cold Front-crossing NYS - October 2008 (metars and satellite)

28 Fronts Warm Fronts are where advancing warm air displaces cold air and we see extensive cloudiness and precipitation

29 Fronts-Warm Generally, with the passage of a warm front, the temperature and humidity increase, the pressure decreases. sszone.com/b ooks/earth_sci ence/terc/cont ent/visualizatio ns/es2002/es2 002page01.cf m?chapter_no =visualization

30 Fronts Stationary Fronts are where the two air masses meet but neither advances. Little cloudiness and precipitation is seen

31 Fronts Occluded Fronts occur where a cold air mass overtakes a warm front and wedges it upward. It then collides with another cold front and causes precipitation on both sides

32 Fronts-Occluded Occluded front is formed when a cold front overtakes a warm front.

33 Pressure Systems The vertical movement of air combined with the coriolis effect results in the formation of rotating low and high pressure systems

34 High Pressure System High Pressure Systems are formed by dense, sinking air and move in a clockwise direction (in the northern hemisphere) High pressure is associated with fair weather

35 Low Pressure Systems Low Pressure Systems form by low density rising air moving in a counterclockwise direction Low pressure is associated with stormy weather