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 _______ currents (hint: type of heat transfer: warm air rising,cools and falls back down)

Convection is the transfer of ______, usually in _______ or liquids.

After the atmosphere is warmed by radiation and conduction, heat is transferred throughout the atmosphere by convection. * warmed air has _____ space between molecules, it ’s _____ dense & rises *Cooled air is more dense & tends to sink *In general, air near the equator ______ & air near the poles ______

The Coriolis effect-wind patterns because of earth’s rotation

Take a look at this!

Notice the band of clouds around the equator ? This is the ITCZ zone a.k.a ________________ _____________ __________

Why do you think there is this band of clouds near the equator?

Did you figure it out? Warm, moist air in the topics _____ Cold air holds ____ moisture than warm air As moist warm air _____, it condenses and forms ________!

The Wind Highways The Coriolis effect causes air & water to be deflected to the right or____________ north of the equator, and _____________south of the equator. This creates global weather highways of wind.

The Westerlies Because of our latitude, most of our weather comes from the ____ Looking at the weather map, what type of weather might we expect? ________ What type of weather might we expect in a few days? _________

short review 1.Transfer of heat in liquids or gases is called _____. 2. _____ air is dense and tends to sink. 3. Band of clouds found around the equator______ 4. Cold air holds _____ moisture than warm air 5. The Coriolis effect causes the air and water to be deflected to the _____ of the equator

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?

Look at the weather map Notice that there are ___ ’ s(blue) and L ’ s (red) on the map blue lines w/ spikes red lines w/ 1/2 circles

High Pressure Areas When cooler air sinks & is warmed, the air can hold ___ moisture. This usually means _____ skies Winds tend to move clockwise around high ______ ___

Low Pressure Areas When warm air rises & is cooled, the air can not hold as much ______. Often, these areas are associated w/ _________ (hint: rain snow sleet or hail) & stormy weather Winds tend to move _______ _____around a low_______ _______.

If you see a big blue ___on the weather map over your area, you can expect______ weather

See a big red L in your area, there will probably be______ weather

These highs and lows move more or less along the jet stream and brings changes in our weather

Fronts & Air Masses ____ _____is a large body of air whose __________ & ________ are fairly similar at a given altitude _____ are boundaries separating different air masses There are _____ different air masses that affect the United States

The Air Masses cP( continental polar) : ___, dry stable cT( continental tropical) : hot, ____, stable air aloft, unstable at surface mP( maritime polar) : cool, ____, unstable mT( maritime tropical) : ____, ____, unstable

Map shows air mass source regions and there paths

Ok, now we see the difference in the air masses * look at the different fronts & their impact on weather Can you see the four different types of fronts on the map?

Warm Fronts * warm front is warm air displacing cool air diagram *Shallow leading edge warm air must “ overrun ” cold air *These are usually _____ moving

Cold Fronts _____ air advances into region of ____ air Intensity of precipitation greater, but short lived Clearing conditions after front passes Usually approaches from W or NW

Stationary Fronts Surface positions of the front do not move Often a region of clouds

Occluded Fronts Cold front overtakes warm front Often found close to the low pressure center

Ready for a little quiz? You ’ ll need a sheet of paper Write your answers as we go Here we go!

1. Winds in a low pressure system move _____ around the low

2. Name type of front found close to point

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

4. Give the name of the air mass/front that would have the following characteristics: cool, moist, unstable

5. That important weather word that refers to the transfer of heat (hint: rises and falls)

6. In general, air near the equator tend to_____. ( rise or fall )

7. What causes air & water to be deflected to the right… north of the equator?

8. Which of the weather highways usually controls 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?

11. Band of clouds found around the equator______

12. The Coriolis effect causes the air and water to be deflected to the _____ of the equator