Weather: A study in Variables

Coriolis Effect & Mid-Latitude Cyclones

Coriolis Effect & Mid-Latitude Cyclones

ReviewReview Atmosphere

Structure composition

Heat Global Heat uneven Convection, conduction, radiation

Pressure Gravity, depth Water, temperature Causes wind

Atmosphere Structure composition

Heat Global Heat uneven Convection, conduction, radiation

Pressure Gravity, depth Water, temperature Causes wind

Review. . .Review. . . Water

Relative humidity Amount in air affected by

temperature (capacity/cups) Air masses

Consistent throughout Don’t mix Boundaries are fronts Warm = less dense, cool = more

dense

Water Relative humidity Amount in air affected by

temperature (capacity/cups) Air masses

Consistent throughout Don’t mix Boundaries are fronts Warm = less dense, cool = more

dense

Things are never as simple as they seem!

Things are never as simple as they seem!

Let’s start with wind Blows from areas of high pressure to

areas of low pressure Opposed by friction near the surface Also have to account for the rotation

of the Earth for any wind that travels a significant distance

Let’s start with wind Blows from areas of high pressure to

areas of low pressure Opposed by friction near the surface Also have to account for the rotation

of the Earth for any wind that travels a significant distance

Global winds, no rotation (pg 540)

Global winds, no rotation (pg 540)

Cold = High pressure

Hot = Low pressure

With RotationWith Rotation Last slide = Space frame of reference Our frame of reference = Northern

hemisphere = winds curve to the RIGHT In Southern hemisphere, winds curve to

the LEFT. Earth rotates counterclockwise when

viewed from above the north pole. Rotation makes stuff happen.

Last slide = Space frame of reference Our frame of reference = Northern

hemisphere = winds curve to the RIGHT In Southern hemisphere, winds curve to

the LEFT. Earth rotates counterclockwise when

viewed from above the north pole. Rotation makes stuff happen.

Global Winds (Ideal, pg 541)Global Winds (Ideal, pg 541)

Polar cell = Air moving South

warms and rises

Hadley cell = air moving North cools and sinks

Notice ALL arrows! What happens to them?

Coriolis effectCoriolis effect

Ball is rolled straight across the merry-go-round.

Due to the spin, ball does not go where it is aimed, but goes to the person next to them.

Ball is rolled straight across the merry-go-round.

Due to the spin, ball does not go where it is aimed, but goes to the person next to them.

QuickTime™ and aVideo decompressor

are needed to see this picture.

Global Winds & CoriolisGlobal Winds & Coriolis

To see Coriolis effect, “stand” at the TAIL of the arrow and “look” towards the HEAD of the arrow.

To see Coriolis effect, “stand” at the TAIL of the arrow and “look” towards the HEAD of the arrow.

Put the pieces togetherPut the pieces together

We’ve got the pieces, PUZZLE time!

Mid-latitude cyclones. These things are why we get cold and rain with a low pressure system.

Let’s start with Definitions. . .

We’ve got the pieces, PUZZLE time!

Mid-latitude cyclones. These things are why we get cold and rain with a low pressure system.

Let’s start with Definitions. . .

Cyclones, AnticyclonesCyclones, Anticyclones

Cyclones = areas of low pressure at the surface Counterclockwise winds Air moving inward at the surface =

convergence

Anticyclones = Areas of high pressure at the surface Clockwise winds Air moving outward at the surface =

divergence

Cyclones = areas of low pressure at the surface Counterclockwise winds Air moving inward at the surface =

convergence

Anticyclones = Areas of high pressure at the surface Clockwise winds Air moving outward at the surface =

divergence

Air will move from high pressure areas to low.

L960

980*Air moving down in a high pressure area can’t make clouds because it is warming up! Bigger cup!

windH1012

1008

L

•Coriolis effect causes wind to curve to the right.

L

•We will see these on weather maps. Instead of arrows, there will be front lines. (Air masses don’t mix.)

•Fronts curve due to friction at the surface. Like playing crack the whip!

•Warm front = Sunday driver, “moseying” along. Gives high clouds & slow, lasting rain. Slides over the cold air and cools slowly.

LWarm Air

Here

Coldest Air Here

Cold Air Here

•Cold front = Road rage. Gives thunderstorms and severe weather. Shoves under the warm air and cools it quickly.

LWarm Air

Here

Coldest Air Here

Cold Air Here

So What?So What?

Question 1: Why does a high pressure system seem to go with clear warm days if high pressure goes with cool air?

Answer: Air moving downward can’t make clouds, because it is warming up as it sinks. Warmer air increases it’s capacity. (Cup cannot overflow)

That’s why it is sunny with a high system!

Question 1: Why does a high pressure system seem to go with clear warm days if high pressure goes with cool air?

Answer: Air moving downward can’t make clouds, because it is warming up as it sinks. Warmer air increases it’s capacity. (Cup cannot overflow)

That’s why it is sunny with a high system!

And?And?

Question 2: So, if warm air means less pressure, then why do we get colder rainy days with a low pressure system?

Air rushing into a low pressure area creates fronts.

Cold fronts associated with low systems push warm, wet air up where it is cooled quickly to make clouds and rain.

Question 2: So, if warm air means less pressure, then why do we get colder rainy days with a low pressure system?

Air rushing into a low pressure area creates fronts.

Cold fronts associated with low systems push warm, wet air up where it is cooled quickly to make clouds and rain.

High pressure system on the right!

High pressure system on the right!

•Cold air sinking toward Earth will warm up. This will increase the capacity to hold water.•Makes it SUNNY!•Low pressure system on the left!•Warm air rising will cool down. This decreases the capacity to hold water.•Makes it CLOUDY!

HL

This represents a

front line!

Convergence & Divergence

Convergence & Divergence

Air rushing into a low (convergence) will increase the pressure and weaken the Low.

Same for the High! Have to have balance above, in the

atmosphere, to maintain the high or low pressure system.

Divergence (moving air away) has to be maintained above in order for a low to continue at the surface.

Air rushing into a low (convergence) will increase the pressure and weaken the Low.

Same for the High! Have to have balance above, in the

atmosphere, to maintain the high or low pressure system.

Divergence (moving air away) has to be maintained above in order for a low to continue at the surface.

Convergence & Divergence

Convergence & Divergence

LH

Divergence

Divergence

Convergence

Convergence

Recipe for a snow stormRecipe for a snow storm