Meteorology / Weather Chapter 38

Standards  5 a, b  6:a, b  Objectives:  Student will be able to describe weather and climate.  Students will be able to describe effects on climate of latitude, elevation, topography and proximity to large bodies of water and cold or warm ocean currents.

What is Meteorology?  The study of atmospheric phenomenon.  Clouds, raindrops, snowflakes, fog, dust, and rainbow.  Hydrometers- water droplets and precipitation  Lithometers- smoke, haze, dust, and condensation nuclei.

 What is weather?  Give three examples of weather.  Explain hydrometer  Explain lithometer

Weather vs. Climate  Weather- the current state of the atmosphere  Climate- Long term variations in weather for a particular area

 Explain the difference between weather and climate.

How is radiation distributed?  Earth feels hotter in the afternoon than in the morning or evening.  The suns rays hit the Earth at different angles. –Morning and Evening it is at a low angle therefore spreading out more  Same amount of energy over a larger area –Afternoon Suns rays hit Earth more directly

 Why is it hotter in the afternoon than in the morning or evening?

 This explains why the tropical regions are hotter and the poles colder  Tropical regions remain at a fairly constant temperature because the heat is redistributed.  Continual motion of air and water relocate heat on Earths surface, ocean and atmosphere. Creates a balance.

 Why does tropical regions stay at a fairly constant temperature?  What happens to all the heat in the tropical regions?

Air Masses  Air Mass is a large body of air that takes on the characteristics of the area over which it forms.  Area where it forms is called a source region, take on the temperature of that area. –Land air masses contain less moisture –Water air masses contain more moisture

 Explain an air mass.  How do land air masses and water air masses differ?  Identify what is a source region.

Air Mass Modification  An air mass is modified by the exchange of heat or moisture with the surface over which an air mass travels.

 Explain the modification of an air mass.

Wind Formation  Wind is caused by the uneven heating of Earth which creates areas of high pressure differences in the atmosphere  Wind is the movement of air from an area of high pressure to an area of lower pressure

 How is wind formed?  Explain how wind flows.

The Coriolis Effect  The effect of Earth’s rotation on the movement of air masses  Changes the direction of the air flow  Wind influences weather  Determines when and where ships and planes can travel

 Explain the coriolis effect?  What does the coriolis effect influence?  In what pattern does the coriolis effect move currents in the Northern and Southern Hemispheres.

Review Sheet # 1  1. What is meteorology?  2. Define weather, climate, hydrometers and lithometers  3. Explain how radiation is distributed to earth.  4. Why do tropical regions stay hot?  5. How is a balance maintained on earth?  6. What are air masses and how are they modified?  7. How is wind formed?  8. Explain the coriolis effect

Wind Systems  Doldrums are windless zones at the equator 3 Types of Surface winds  Trade Winds  Prevailing Westerlies  Polar Easterlies

 Name the 3 types of wind systems.

Trade Winds  Between the equator 30 degrees latitude north or south  Steady winds flow that flow to the southwest in the northern hemisphere  In the southern hemisphere, they blow toward the northwest

 Where are trade winds located?  What direction does the trade winds travel in the northern hemisphere?  What direction does the trade winds travel in the southern hemisphere?

Prevailing Westerlies  Blow in the opposite directions of trade winds  Between 30 degrees and 60 degrees latitude north and south of the equator  Responsible for most of the movement of weather across the U.S. and Canada

Prevailing Westerlies  In the northern hemisphere, the winds blow from the southwest to the northeast  In the southern hemisphere, the winds blow from the northwest to the southeast

 What wind system is responsible for the movement of weather in Canada and US?  What direction does the prevailing winds blow?  What latitude are the prevailing winds located in the northern and southern hemispheres?

Polar Easterlies  At the North Pole the winds blow from the northeast to the southwest  Near the South Pole the winds blow from the southeast to the northwest

Jet Streams  Narrow belts of strong winds that blow near the top of the troposphere

Daily and Seasonal Winds  Convection currents cause sea breezes and land breezes  Sea breezes occur during the day  Air overhead is heated by conduction, which becomes less dense and is forced upward by cooler denser air moving in land from the ocean  This results in convection currents

Land Breezes  Movement of air toward the water  The cool dense air from the land moves out over the water, pushing the warm air over the water upward  This occurs at night

Review Sheet # 2  1. Name three types of wind systems.  2. Define doldrums  3. Explain trade winds, prevailing winds, polar easterlies, and jet streams.  4. Explain convection currents  5. Explain land breeze circulation.  6. When do sea breezes occur?  7. When do land breezes occur?

Fronts  A front is a narrow area where two air masses meet. Different types of weather results from different fronts. –Cold front –Warm Front –Stationary Front –Occluded Front

Cold Front  Cold air forces warm air up.  Moves very quickly  Clouds, showers, and thunder storms are associated with this front.  Represented with a blue line with triangles.

Warm Front  Warm air displaces cold air.  Moves slowly  Extensive cloudiness and precipitation  Represented by a red line and half circles

Stationary Front  Two air masses meet and do not advance on one another.  Caused by both air masses to have been so modified that their pressure gradient and temperature differences are small.  Some rain and clouds can occur  Represented by a blue line with triangles on one side and half circles on another.

Occluded Front  Cold air mass over takes a warm air mass.  Precipitation occurs at this type of front.  Purple line with alternating triangles and half circles.

Hurricane  Large, low pressure, rotating, storms called tropical storms or cyclones.  The strongest tropical storms are called hurricanes.  Formed from warm water and a disturbance that pushes the warm air up and stay suspended.  Warm air is a hurricanes fuel.  Category 3 tropical storms are called hurricanes.

Tornado  A tornado is a violent, whirling column of air in contact with the ground.  Tornados are associated with severe storms, called super cells.  Tornados vary in size and intensity.  Usually form in the spring in the late afternoon or evening.

Lightning  In a cumulonimbus atoms are separated.  A negative atom “step leader” descends from the cloud towards earth.  A return stroke from earth made up of positive ions rush to meet the negative atoms.  The illumination of lightning is the exchange of energy.  Thunder is the sound of the energy produced from the exchange of energy

Review Sheet # 3  1. Name the four types of fronts.  2. Draw the symbol that represents each of the fronts.  3. What type of weather results from a cold front?  4. What type of weather results from a warm front?  5. What type of weather results from an occluded front?  6. What type of weather results from a stationary front?  7. Identify the difference between a hurricane and tornado.  8. How does lightning form?