weather winds, air masses, air pressures, fronts

• Draw square• Get density activity ready• Get out jar, green food coloring and hot plate• Gather jars, cans, saran wrap, rubber bands,

straws and index cards for barometers

BellworkWhat kind of weather can we expect in the next few days according to the map?

Us

Why Do We Have Weather?

WHY DO WE HAVE THE WEATHER ?

• Just think about it!• Why is there wind? Why does it blow

from one direction one day and another the next?

• Why is it rainy one day and dry the next?

• How come it’s cold in the winter?• How can we have hail in the

summer?• What causes snow and freezing rain?

If we were to pick one term to help explain why we have weather, what do

you think would be a good word?

You might pick heat or sun….but another good choice would be

Convection

Convection: the transfer of heat,usually in gases or liquids.

Convection Demo

• How does convection work?• See if you can watch the demo

and make sense of convection

Warm Air - How do air molecules act? The walls of this room are the walls of our container.

You are all air molecules. Lots of nitrogen, some oxygen and a little carbon dioxide.

Warm air is active. It moves around quickly and will bounce off the walls.

Say:Say:I’m moving FAST.I’m moving FAST.I can hold lots of moisture.I can hold lots of moisture.

Cold Air - How do air molecules act? The walls of this room are the walls of our container.

You are all air molecules. Lots of nitrogen, some oxygen and a little carbon dioxide.

Cold air moves slowly. It moves around very slowly and will move closer together.

Say: Say: I’m moving slowly.I’m moving slowly.I can’t hold much moisture.I can’t hold much moisture.

Density???• how close together the molecules of a substance

are or how much mass a substance has in a given space

• Density Demo– Hold each– What is the size of the two canisters?– Does one feel heavier than the other?– Mass the two and write down the mass of each.

FlourSugar

Which one is more dense?How do you know?

FlourFlour SugarSugar

After the atmosphere is warmed by radiation (sun) and conduction, the heat is transferred throughout

the atmosphere by convection.

• Warmed air: has more space between the molecules, it’s less dense and rises

• Cooled air is more dense and tends to sink

• In general, air near the equator tends to rise and air near the poles tends to sink

Density of Air – Square on the Floor

• Everyone stand inside the square

• You are all air molecules (lots of nitrogen, some oxygen, and a little carbon dioxide, etc.)

• You are cold air. What will you do?

• Half the class stand outside the square.

• The ones inside the square spread out.

• You are warm air.• What will you do?

Density of Air

• Can you explain why warm air rises with what you know about density now?• Can you explain why cool air

sinks with what you know about density now?

How Do Clouds Form?

• First let’s review evaporation• Evaporation: the process of a liquid becoming

a vapor (gas)• Cut and Paste Image• Phet: http://phet.colorado.edu/sims/states-

of-matter/states-of-matter-basics_en.jnlp

How Do Clouds Form?

Step 1 – Warm, moist air risesStep 2 – That warm air hits the cooler air in the upper atmosphereStep 3 – When it hits the cooler air, it condenses onto dust particles in the air into water droplets

Teach Your Neighbor Using Gestures

I’ll I’ll DemonstrateDemonstrate

How Do Clouds Form?

Step 1 – Warm, moist air risesStep 2 – That warm air hits the cooler air in the upper atmosphereStep 3 – When it hits the cooler air, it condenses onto dust particles in the air into water droplets

Did You Know?

How Does Air Behave?

•Cold air can hold less moisture than warm air•Warm air can hold more moisture than cold air

Consequences of Rotation: The Coriolis Effect - Video

The Weather HighwaysCoriolis Effect

• Created by the ROTATIONROTATION of the Earth

• Causes the air and water to be pushed to the right north of the equator.

• This creates global weather highways

• Cut and paste Coriolis Image

The Westerlies• Winds that blow from the west to the east• most of our weather comes from the west• Cut and Paste Global Wind Image

What Weather Should We Expect?

Trade Winds• Winds that blow from the east to the west• These affect the paths of hurricanes

Let’s break for a short review:

1.Transfer of heat in liquids or gases_____.

2. _____ air is dense and tends to sink.3. Cold air holds _____ moisture than

warm air.4. The Coriolis effect causes the air

and water vapor to be pushed to the _____ to the North of the equator.

How did you do?

1. CONVECTION

2. COLD

3. LESS

4. RIGHT

Cloud in a Bottle Demo

Cloud in a Bottle Lab

C.H.A.M.P.S. – Group Work, Voice Level 2, Complete Lab, Finger Signals, Jobs

1.We will add water to 1/3 of the bottle.2.We will

Let’s Play a Game

• Weather Game

Now What?

• Ok, so we know that the weather moves around on these highways and that warm air rises and cold air sinks.

• But why is it sunny one day, and rainy the next?

Let’s take another look at the weather map:

• Notice that there are H’s and L’s on the map

• There are also blue lines with spikes and red lines with half circles

• Let’s take a closer look!

High and Low Pressure - Video

High Pressure Areas

• Cooler air sinks and is warmed• This usually means sunny skies

Low Pressure Areas

• When warm air rises and cools• Precipitation

and stormy weather

So, if you see a big H on the weather map over the area you

live, you can expect fair weather.

When you see a big L in your area, there will probably be stormy

weather

Teach Two of Your Neighbors• Action of High PressureHigh Pressure: Push Down on neighbor’s

shoulders and say:– You are a bunch of air molecules.– You’re experiencing a high pressure high pressure that doesn’t allow

you to rise and make clouds– No clouds means no rain

• Action Low PressureLow Pressure: Let go of his or her shoulders and say:– You are still a bunch of air molecules.– You’re experiencing a low pressure low pressure that allows you to

rise and make clouds. – Clouds that fill up with moisture will mean rain.

How do Air and Water Molecules Act Under Pressure

• Half the class stand outside the square box.

• Half the class stand inside the square box.

• I’m going to add air and water molecules to box.

• Those outside move to the inside.

• You are under a lot of pressure.

• You can’t rise. (no clouds)

• Now, I’m going to stop adding air and water molecules to the box and we are going to take the lid off of it.

• Start slowly moving to the front of the room.

• As you rise to the front, what will you do?

• Condense and become clouds.

Barometer

•Barometers are used by meteorologists to keep track of pressure in the air.

Understanding the Barometer

• If you see the barometer pointer moving downward, what does that mean?– The pressure is

increasing.• If you see the barometer

pointer moving upward, what does that mean?– The pressure is

decreasing.

These highs and lows move along the jet stream and bring

us our weather changes.

• Video

• A fast flowing river of air found in the atmosphere at around 12 km above the surface of the Earth.

• They form at the boundaries of air masses with large differences in temperature, such as of the polar region and the warmer air to the south.

Jet Stream

Jet Stream Demo

Using: Hair Dryer, ping pong ball•The hair dryer shoots a column of air up between air that is also in the room.•When I tilt the hair dryer left and right, the ping pong ball stays in the column of air. •Jet streams are columns of air in upper atmosphere. •These weather columns are like currents. These columns of air move throughout the year.

Fronts and Air Masses

• Air mass: a large body of air whose temperature and moisture are fairly

similar at a given altitude• Fronts: boundaries separating

different air masses

• There are four different air masses that affect the United States

Warm and Cold Fronts - Video

Ok, now we see the difference in the air masses

• Let’s look at the different fronts and their impact on weather

• Can you see the four different types of fronts on the map?

Warm Fronts

• A warm front is warm air taking over the cool air

• The front edge of warm air must “overrun” cold air

• Slow moving

Cold Fronts

• Cold air advances into region of warm air

• Rain and Thunderstorms

• Clearing conditions after front passes

Video

Cold Front is Moving In – 5:28

• As the warm air was pushed up (low pressure allowed it to rise), the warm air cooled and condensed.

• The condensed water vapor (gas) caused clouds, which could not hold as much moisture (water vapor [gas]).

• This caused rain and thunderstorms.• What will the weather be like after the cold front passes

through?

Stationary Fronts

• Surface positions of the front do not move

• Often a region of clouds

• Neither the cold or the warm front are ‘winning’.

Quiz

1. Get out a sheet of paper.2. Spread out around the room.3. C.H.A.M.P.S.• Voice Level of 1• Come to my desk for help• Quiz• Finger Signals• Complete the Quiz

1.• What causes a low

pressure system to create clouds and sometimes precipitation? LL

2.• What type of

front can be found close to point D ?

3.• Which of these

fronts would you expect to have greater precipitation, but be short lived as the front passes?

4.• Give the name

of the air mass that would have the following characteristics:

• cool, moist, unstable

5.That important weather word that

refers to the transfer of heat

6.In general, air near the equator

tends to_____ ( rise or fall ).

7.

________ causes air and water to be deflected to

the right north of the equator.

8.Which of the weather highways

usuallycontrols our weather

9.

Warm air holds ( more or less ) moisture than cold air?

10.

• If there is a big

H on the weather map

where you live, would you

expect fair or stormy weather?

HH

How did you do?

Let’s check the answers!

Answers

1. The low pressure allows the warm air to rise. As the warm air rises, it cools. Water vapor cools and condenses into clouds. Cold air can hold less moisture, so eventually it might rain.

8. Westerlies 2. Cold front 9. More 3. Cold front 10. Fair 4. Maritime polar (mP) 5. Convection 6. Rise 7. Coriolis Effect

Predict the Weather Game

• Game

Centers

• Vocabulary