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# Lesson6b Atmosphere - PowerPoint PPT Presentation

Lesson6b Atmosphere. Weather patterns on the Planets. Figuring out weather patterns. Here in Kentucky we are moving about 700 MPH, due to the Earth’s rotation on its axis. Which direction is the Earth turning?.

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### Lesson6b Atmosphere

Weather patterns on the Planets

Image a trip from Lexington to Rome, Italy and back. Assume no wind on the trip.

Direction of Earth’s Rotation

. no wind on the trip

• The trip to Rome will take less time than the trip back to Lexington.

• The trip back from Rome takes less time than the trip to Rome.

• No effect

• It has no effect. no wind on the trip

• The plane flight is the same both ways.

• The plane before take-off is already moving 700 MPH, due to the Earth’s rotation. When it is flying it is traveling around 500 MPH relative to the ground plus the 700 MPH it had at take off.

• Same thing for the return trip. When the plane is flying back to Lexington, from outer space the plane will appear to be moving 200 MPH to the East. Lexington is approaching at 500 MPH

• Ancient Greeks used this kind of idea to say that the Earth was NOT rotating.

• What happens when you jump in the air?

• If you are in the air for one second, here in Kentucky, the Earth would rotate underneath you at 700 MPH.

• For one second you would land 300 meters to the west. That’s 3 football fields.

You land in the same spot. was NOT rotating.

700 MPH

700 MPH

700 MPH

You land in the same spot. was NOT rotating.

700 MPH

700 MPH

700 MPH

You land in the same spot. was NOT rotating.

700 MPH

700 MPH

700 MPH

You land in the same spot. was NOT rotating.

700 MPH

700 MPH

700 MPH

700 MPH

You land in the same spot. was NOT rotating.

700 MPH

700 MPH

700 MPH

700 MPH

700 MPH

You land in the same spot. was NOT rotating.

700 MPH

700 MPH

700 MPH

700 MPH

700 MPH

Canada launches an attack on the Panama Canal by firing a cannon ball. They aim directly at Panama.

. cannon ball. They aim directly at Panama.

• It should hit the target.

• It will hit West of the target

• It will hit East of the target.

• The first thing we need to consider is the rotation speed of the launch site in Canada.

• Let’s assume the launch site is at a latitude of 55o North.

• We know that everyone on Earth has the same length day, 24 hours. But not everyone is moving at the same speed.

• At the equator the rotational speed is

v = Circumference/time

v = 24,901 miles/24 hours = 1037 MPH.

Distance to rotation axis the launch site in Canada.

• What about the Canadian launch site?

35o

55o

2270 miles the launch site in Canada.

• What about the Canadian launch site?

35o

55o

Speed at Canadian launch site the launch site in Canada.

v = (circumference of circle)/length of day

v = (2π(2270 miles))/24 hours

v = 14,268 miles/ 24 hours

v = 594 MPH or about 600 MPH.

Panama is moving at about 1,000 MPH.

Now let’s see what this means.

From outer space. the launch site in Canada.

• Let’s assume the cannon ball travels 500 MPH and it was pointed due south.

• So, from outer space the cannon ball has a sideways component.

600 MPH East

500 MPH South

Real Velocity

Missed to the West.

What do we see on Earth? also. By the time the cannon ball arrives, Panama would have moved right into the path. BUT Panama is moving at 1,000 MPH.

• We know that Canada isn’t falling behind Panama on the surface of the Earth.

Missed to the West.

Panama returns fire. also. By the time the cannon ball arrives, Panama would have moved right into the path. BUT Panama is moving at 1,000 MPH.

• Panama laughs and thinks Canadians are a bad shot. So they aim directly at the launch site and fire due North.

• What will happen?

. also. By the time the cannon ball arrives, Panama would have moved right into the path. BUT Panama is moving at 1,000 MPH.

• Panama will miss the target and hit East of it.

• Panama will miss the target and hit West of it.

• Panama will hit the target.

What do we see on Earth? also. By the time the cannon ball arrives, Panama would have moved right into the path. BUT Panama is moving at 1,000 MPH.

• Panama is traveling 1000 MPH and Canada only 600 MPH.

Missed to the East.

• The curved path that is witnessed on the surface of the Earth makes it look like there is a force pushing the cannon ball off course.

• This is often called the Coriolis “Force”. But there is no force acting on the cannon ball. The path is the result of us on the surface thinking that we are not rotating. It is a perspective issue. From outer space the path makes perfect sense.

• Therefore, the correct name is the Coriolis Effect.

Hadley Cell Motion Coriolis Effect.Hot air on the equator, rises and moves North or South.

Hadley Cell Motion Coriolis Effect.When it cools it sinks down and heads back to the equator

. equator should bend to the East. Instead they are bending to the West.

• It is too hot for a Hadley cell to form

• There is no Coriolis Effect on Venus

• Venus is rotating the opposite direction

• Venus doesn’t have water clouds so the effect is different

On Earth the rotation is so rapid that the Hadley cell turns east before it reaches the North pole.

There are three major cells east before it reaches the North pole.

• The Hadley Cell, that moves from the Equator

• The Polar Cell, that moves from the poles

• And the Ferrell Cell, (or mid-latitude cell) that isn’t really a cell at all. It is the boundary region between the Hadley and Polar cells. This transition region is dominated by either the Hadley or the Polar cells. It is turbulent and has many different weather patterns.

The Ferrel cell east before it reaches the North pole.

• Many things can happen between the latitudes of 30o and 60o.

• For example, warm air from the south can collide with cold air from the north. The warm air can ride up on top of the cold air. And the two streams will mix and produce turbulence.

• Or one cell can over power the other cell and cause a front to move up into the Ferrel region.

Downward flow of the Hadley cell east before it reaches the North pole.

• In the region where the Hadley cell sinks, the air pressure is normally high.

• High pressure in a region means that the air tends to flow outward from the region to places where the pressure is lower.

As air sinks into the more dense air near the surface, it takes on the speed of the air in that region

Northward

Ferrel Cell

HIGH PRESSURE

Earth surface

Equator

Northward

Equator

High Pressure region in the Northern Hemisphere. takes on the speed of the air in that regionWhat will happen as the air leaves this region?

North

H

Equator

. takes on the speed of the air in that region

• The northern air flow will bend east, and the southern flow will bend west.

• The Northern air flow will bend west and the southern air flow will bend east

• The air will move straight out of the region.

High Pressure region in the Northern Hemisphere. takes on the speed of the air in that regionCoriolis Effect bends the air flow.

North

H

Equator

High Pressure region in the Northern Hemisphere. takes on the speed of the air in that regionAir circulation is clockwise around a high pressure region.

North

H

Equator

High Pressure region in the Southern Hemisphere. takes on the speed of the air in that regionWhat will happen as the air leaves this region?

Equator

H

South

High Pressure region in the Southern Hemisphere. takes on the speed of the air in that regionRotation is counter-clockwise for high pressure.

Equator

H

South

High Pressure regions takes on the speed of the air in that region

• High pressure regions on Earth are fair weather regions.

• In order to form clouds, air currents must raise up to altitudes where water vapor turns into water droplets and forms clouds.

• High pressure stops the ability for these type of air currents to form.

• The result is sunny weather.

Regions of low pressure in the Northern Hemisphere. takes on the speed of the air in that region

• When a region develops where the air pressure is lower than in surrounding regions the air flow is into the low pressure region.

North

L

Equator

. takes on the speed of the air in that region

• The southern air flow will bend west and the northern flow east.

• The southern air flow will bend east and the northern flow west.

• The air will flow directly in, collide and make a storm.

In Northern Hemisphere, low pressure systems rotate counter-clockwise.

North

L

Equator

Low Pressure Systems counter-clockwise.

• In the Southern Hemisphere, lows rotate clockwise.

• Low pressure means that air is flowing into the region and can develop air currents that move upwards, where the air is cooler.

• When this happens, water vapor condenses to from droplets and clouds form

Hurricane counter-clockwise.

Jupiter counter-clockwise.

Jupiter counter-clockwise.