Upload
aubree-asquith
View
229
Download
7
Tags:
Embed Size (px)
Citation preview
Why Do We Have Why Do We Have Weather?Weather?
WHY DO WE HAVE THE WHY DO WE HAVE THE WEATHER ?WEATHER ?
Just think about it!Just think about it! Why is there wind? Why does it blow Why is there wind? Why does it blow
from one direction one day and from one direction one day and another the next?another the next?
Why is it rainy one day and dry the Why is it rainy one day and dry the next?next?
How come it’s cold in the winter?How come it’s cold in the winter? How can we have hail in the summer?How can we have hail in the summer? What causes snow and freezing rain?What causes snow and freezing rain?
If we were to pick one term to help If we were to pick one term to help explain why we have weather, what explain why we have weather, what do you think would be a good word?do you think would be a good word?
You might pick heat or sun….but You might pick heat or sun….but another good choice would beanother good choice would be
ConvectionConvection
Convection is the transfer of Convection is the transfer of heat,heat,
usually in gases or liquids.usually in gases or liquids.
After the atmosphere is warmed by radiation After the atmosphere is warmed by radiation and conduction, the heat is transferred and conduction, the heat is transferred
throughout the atmosphere by convection.throughout the atmosphere by convection. Since warmed air has Since warmed air has
more space between more space between the molecules, it’s less the molecules, it’s less dense and risesdense and rises
Cooled air is more Cooled air is more dense and tends to sinkdense and tends to sink
In general, air near the In general, air near the equator tends to rise equator tends to rise and air near the poles and air near the poles tends to sinktends to sink
Take a look at this!Take a look at this!
Why do you think there is this Why do you think there is this band of clouds near the band of clouds near the
equator?equator?
Did you figure it out?Did you figure it out?
Warm, moist air in the topics risesWarm, moist air in the topics rises Cold air can hold less moisture than Cold air can hold less moisture than
warm airwarm air As the moist air rises, it condenses and As the moist air rises, it condenses and
forms clouds!forms clouds!
More on this laterMore on this later
Hadley CellsHadley Cells
Caused by convection Caused by convection currents.currents.– Warm air near the Warm air near the
equator risesequator rises– Cold air near the poles Cold air near the poles
sinkssinks
Consequences of Rotation: the Coriolis Consequences of Rotation: the Coriolis EffectEffect
The Weather HighwaysThe Weather Highways
The rotation of the The rotation of the earth creates the earth creates the Coriolis effect.Coriolis effect.
The Coriolis effect The Coriolis effect causes the air and causes the air and water to be water to be deflected to the deflected to the West.West.
This creates global This creates global weather highways.weather highways.
The Prevailing WesterliesThe Prevailing Westerlies
Because of our latitude, Because of our latitude, most of our weather most of our weather comes from the westcomes from the west
Looking at the weather Looking at the weather map, what type of map, what type of weather might we weather might we expect?expect?
Combining Hadley Cells, the Coriolis Effect, and Prevailing Westerlies
gives you... Tradewinds:
Where do you think
they got their name?
Who were these winds
particularly important to?
Let’s break for a short reviewLet’s break for a short review
1.1. Transfer of heat in liquids or Transfer of heat in liquids or gases_____gases_____
2.2. _____ air is dense and tends to sink._____ air is dense and tends to sink.3.3. Cold air holds _____ moisture than Cold air holds _____ moisture than
warm airwarm air4.4. The Coriolis effect causes the air and The Coriolis effect causes the air and
water to be deflected to the _____ of water to be deflected to the _____ of the equatorthe equator
How did you do?How did you do?
1.1. CONVECTIONCONVECTION
2. 2. COLDCOLD
3. 3. LESSLESS
4. 4. RIGHTRIGHT
Now What?Now What?
Ok, so we know that the weather Ok, so we know that the weather moves around on these highways and moves around on these highways and that warm air rises and cold air sinks.that warm air rises and cold air sinks.
But why is it sunny one day, and rainy But why is it sunny one day, and rainy the next?the next?
Let’s take another look at the Let’s take another look at the weather mapweather map
Notice that there Notice that there are are HH’s and ’s and LL’s on ’s on the mapthe map
There are also blue There are also blue lines with spikes lines with spikes and red lines with and red lines with half circleshalf circles
Let’s take a closer Let’s take a closer look!look!
High Pressure AreasHigh Pressure Areas When cooler air When cooler air
sinks and is sinks and is warmed, the air can warmed, the air can hold more moisturehold more moisture
This usually means This usually means sunny and clear sunny and clear skies skies
Winds tend to move Winds tend to move clockwise around a clockwise around a highhigh
Low Pressure AreasLow Pressure Areas When warm air rises and is When warm air rises and is
cooled, the air can not hold cooled, the air can not hold as much moistureas much moisture
Often, these areas are Often, these areas are associated with associated with precipitation and stormy precipitation and stormy weatherweather
Tornadoes and hurricanes can Tornadoes and hurricanes can produce very low pressure produce very low pressure readings.readings.
Fronts and Air MassesFronts and Air Masses
An air mass is a large body of air An air mass is a large body of air whose temperature and moisture are whose temperature and moisture are
fairly similar at a given altitudefairly similar at a given altitude Fronts are boundaries separating Fronts are boundaries separating
different air massesdifferent air masses
There are four different air masses There are four different air masses that affect the United Statesthat affect the United States
The Air MassesThe Air Masses
cPcP( continental polar) : cold, dry stable( continental polar) : cold, dry stable cTcT( continental tropical) : hot, dry, ( continental tropical) : hot, dry,
stable air aloft, unstable at the surfacestable air aloft, unstable at the surface mPmP( maritime polar) : cool, moist, ( maritime polar) : cool, moist,
unstableunstable mTmT( maritime tropical) : warm, moist, ( maritime tropical) : warm, moist,
unstableunstable
This map shows the air mass This map shows the air mass source regions and there pathssource regions and there paths
Ok, now we see the difference Ok, now we see the difference in the air massesin the air masses
Let’s look at the different fronts and their impact on Let’s look at the different fronts and their impact on weatherweather
Can you see the four different types of fronts on the Can you see the four different types of fronts on the map?map?
Cold Fronts
Cold air pushes under a warm air mass. Warm air rises quickly=narrow bands of violent storms form
This is the symbol for a cold front
Warm Front
Warm air slides over departing cold air- large bands of precipitation form
This is the symbol on a map for a warm front
Occluded Front
2 air masses merge and force warm air between them to rise quickly. Strong winds and heavy precipitation will occur
This is the weather map symbol for an occluded front
Stationary Front
Warm or cold front stops moving. Light wind and precipitation may occur across the front boundary
This is the weather map symbol for a stationary front
Ready for a little quiz?Ready for a little quiz?You’ll need a sheet of paperYou’ll need a sheet of paper
Write your answers as we Write your answers as we gogo
Here we go!Here we go!
1.1. Winds in a low Winds in a low
pressure pressure system move system move _____ around _____ around the lowthe low LL
2.2. What type of What type of
front can be front can be found close to found close to point point D D ??
3.3. Which of these Which of these
fronts would fronts would you expect to you expect to have greater have greater precipitation, precipitation, but be short but be short lived as the lived as the front passes?front passes?
4.4. Give the name Give the name
of the air mass of the air mass that would that would have the have the following following characteristics:characteristics:
cool, moist, cool, moist, unstableunstable
5.5.That important weather word That important weather word that refers to the transfer of that refers to the transfer of
heatheat
6.6.In general, air near the equator In general, air near the equator
tends to_____ ( rise or fall )tends to_____ ( rise or fall )
7.7.
It causes air and water to be It causes air and water to be deflected to the right north deflected to the right north
of the equatorof the equator
8.8.Which of the weather highways Which of the weather highways
usuallyusuallycontrols our weather controls our weather
9.9.
Warm air holds ( more or less ) Warm air holds ( more or less ) moisture than cold airmoisture than cold air
10.10. If there is a bigIf there is a big
HH on the on the weather map weather map
where you live, where you live, would you would you
expect fair or expect fair or stormy weatherstormy weather
HH
How did you do?How did you do?
Let’s check the answers!Let’s check the answers!
AnswersAnswers
1. 1. Counterclockwise Counterclockwise 8. 8. WesterliesWesterlies
2. 2. Cold Cold 9. 9. MoreMore
3. 3. Cold Cold 10. 10. FairFair
4. 4. Maritime polar (mP)Maritime polar (mP)
5. 5. ConvectionConvection
6. 6. RiseRise
7. 7. CoriolisCoriolis