Science 6‎ > ‎

Chapter 11

Weather and Climate

Mr Zingy is a meteorologist and spends much of his time measuring air studying weather, air temperature, air pressure, wind direction, humidity and precipitation to report on the evening news.  How would life change if Mr Zingy quit his job one day with no one to replace him?

Lesson 1:  Weather

Weather is the atmospheric conditions, along with short term changes, of a certain place at a certain time.

Air temperature is the measure of the average kinetic energy of air molecules.

Air pressure is the pressure that a column of air exerts on the air below it.

Wind direction is the direction from which the wind is coming.

Humidity is the amount of water vapor per volume of air and is measured in grams of water per cubic meter of air.

The amount of water vapor present in the air compared to the maximum amount of water vapor the air can hold at a temperature before becoming saturated is the relative humidity.  Eg., relative humidity of 50%

The temperature at which air becomes fully saturated with water vapor and condensation forms is the dew point.

When water, in liquid or solid form, falls from the atmosphere it is called precipitation.

Lesson 2:  The Water Cycle

To understand how the water cycle works, read the text below and listen to the song from the video.  Then type up the song.  Finally, answer the questions at the end of the video.

Heat from the Sun causes water on Earth to change into gas.  Warm air rises.  Water that evaporates from lakes, streams, and oceans enters Earth's atmosphere as water vapor.  As the air masses rise, the air expands and cools down.  When the air cools down, the water vapor changes from a gas back into a liquid, a process called condensation.  As the water vapor condenses, water droplets form.  These water droplets than form clouds.  When the droplets become larger and heavier, precipitation falls from the clouds to Earth's surface.

YouTube Video

!)  Why does air rise?
2)  Why does it cool down?
3)  Why do clouds form?
4)  Why does it rain?

Lesson 3:  How cold and warm fronts produce clouds and rain

You are planning a trip to Asia and Africa.  You need to work out what clothes to take.  The only information you have on the weather from satellite images is the following:
  • In Jakarta, cold air mass will move towards warmer air.
  • In Nairobi, warm air will move towards colder air.
Q1:  What is the weather you should expect in Jakarta?  What clothes should you pack?
Q2:  What is the weather you should expect in Nairobi?  What clothes should you wear?

Notes from the textbook:

Notes from the Video:

Task Helper 1:  Useful points from the textbook
  • An air mass is a body of air that has consistent features, such as temperature and relative humidity. 
  • The boundary between two air masses of different density, moisture, and temperature is called a front.  A cold front occurs when a colder air mass moves towards warmer air.  The cold air pushes the warm air up into the atmosphere.  The warm air cools as it rises and water vapor condenses.  Clouds form and precipitation begins to form, often giving rise to severe storms.
  • A warm front forms when lighter, warmer air moves over heavier, colder air.  Clouds form as the water in warm air condenses.  A warm front usually results in steady rain for several days.

Task Helper 2:  Helpful video

YouTube Video

Lesson 4: How Earth's shape determines intensity of solar radiation
  • Jenny lives on the northern hemisphere of planet earth while Vijay lives on the southern hemisphere
  • Earth is tilted on its axis
  • Jenny gets more solar radiation in the northern hemisphere in June
  • Vijay gets more solar radiation in the southern hemisphere in January

YouTube Video

1)  Why does Jenny get more powerful sunshine in June?
2)  Why does Vijay get more powerful sunshine in January?
3)  When is it summer for Jenny?
4)  When is it winter for Jenny?
5)  When is it summer for Vijay?
6)  When is it winter for Vijay?

Lesson 5: Floods and Droughts
  • There is a drought in Nono's country in East Africa
  • A drought is a period of time when precipitation is much lower than normal or absent
  • In Bangladesh, Salima's family has been hit by a flood
  • Floods occur when water enters an area faster than it can be taken away by rivers and lakes or absorbed by the ground
  • Floods can also be caused by snow melting quickly
  • A flash flood takes place suddenly
  • Construction of buildings, parking lots and other structures decrease the amount of vegetation and soil that can absorb water
1)  Why is there a drought in Nono's country?
2)  In Salimah's village in Bangladesh, snow melted very quickly this summer.  Could this have caused the flood?  How?
3)  Salimah's neighbors are blaming the new Japanese car company in the neighborhood for making it difficult to deal with the flood.  Could they be right?  Explain how.

Lesson 6: The Weather in California

Why fog forms on the coast

Main points:
  • Warm air mass accumulates off the shore
  • Wind transports it to the coast
  • Moist air crosses over the cold water in the California Current
  • Warm air cools and condenses to become fog

John lives on the Pacific coast in California.  On many days, John sees that the coast has a thick layer of fog over it.  Explain why.  Use the following sequence in your description:
  • Sun warms up land and water
  • Warm air
  • Cold air
  • Condensation

B)  Rain Shadows

Main points:
  • An area of low rainfall on the lee side, or downwind slope, of a mountain is called a rain shadow
1)  Jane lives on the green side of the mountain.  Explain why her side is green.
2)  Amelia lives on the dry side of the mountain known as the rain shadow.  Why is it so dry there?

C)  Sea Breeze and Land Breeze

Main points:
A wind that blows from the sea to the land is called a sea breeze
A wind that blows from the land to the sea is called a land breeze


Explain why does John get a cool breeze during the day?  Explain in a paragraph.

D)  Valley Breeze and Mountain Breeze

Main points:
  • Valley breezes blow upward from the valley along the mountain slopes.
  • Mountain breezes flow down from mountains.

  • Why does Sally get a warm valley breeze during the day?
  • Why does she get a cool mountain breeze at night?
E) Santa Ana Winds

Main points:
  • In southern California, winds that blow from the east or northeast and continue toward the coast are called Santa Ana winds. 
  • They start out as cools winds
  • Flows towards coastal areas through canyons and mountain passes
  • It is forced downslope by the high pressure system behind it
  • The air that started is now very dry and warm
  • They can dry out vegetation and increase the risk of fire
Imagine yourself as the Santa Ana Wind.  In the first person describe your journey from being a cool wind to a dry, speedy one that sweeps into LA and sets fire to dry land.