1. Integrated Science
Unit 9, Chapter 27

2. Unit Nine: Energy in the Earth System
Chapter 27 Weather and Climate
27.1 Earth's Heating and Cooling
27.2 Global Winds and Currents
27.3 Weather Patterns
27.4 Storms
27.5 Weather and Climate

3. Chapter 27 Learning Goals
Learn how Earth’s rotation, Earth’s axial tilt, and distance from the equator cause variations in the heating and cooling of Earth.
Learn how the heating of Earth’s surface and atmosphere by the sun causes convection cycles in the atmosphere and oceans, producing winds and ocean currents.
Learn about tools meteorologists use to predict weather, and how to read a weather map.
Make and test your own weather instrument.
Model a Doppler radar system.
Learn about the physical features that interact to form the climate of each of six important land biomes.

4. Chapter 27 Vocabulary Terms
air mass
El Niño-Southern Oscillation
biome
cold front
Coriolis effect
cumuliform cloud
desert
grassland
gyres
isobars
jet stream
latitude
longitude
prevailing westerlies
polar easterlies
temperate forest
stratiform cloud
stratocumulus cloud
taiga
temperature inversion
trade winds
tropical rainforest
tundra
warm front

5. 27.1 Variations in Earth's Heating and Cooling
Key Question:
What causes seasons?
*Read text section 27.1 AFTER Investigation 27.1

6. 27.1 Heating and Cooling Earth
Satellite data is used to map patterns of heating and cooling.
The National Oceanic and Atmospheric Administration (or NOAA) uses infrared photography to map how much heat is reflected or emitted from different areas of Earth each day.

7. 27.1 Latitude Latitude lines measure distance from the equator.
These lines run parallel to the equator and are labeled in degrees north or degrees south.

8. 27.1 Longitude
Longitude lines run vertically from the north pole to the south pole.
The line that runs through Greenwich, England, is labeled 0 degrees longitude and is called the prime meridian.
Lines east of the prime meridian are numbered from 1 to 179 degrees east, while lines west of the prime meridian are numbered from 1 to 179 degrees west.
The 0- and 180-degree lines are not labeled east or west.

9. 27.1 Temperature and Latitude
Earth’s temperature varies with latitude.
At higher latitudes, solar radiation is less intense.
The same thing happens to the sun’s energy when it reaches the south pole at an angle.

10. 27.1 Temperature and Rotation
As Earth rotates, the portion of the globe facing the sun warms as it absorbs more solar radiation than it emits.
Earth constantly emits some of the absorbed energy as infrared radiation.
This emission of heat cools the dark side of the planet.

12. 27.2 Global Winds and Ocean Currents
Thermals are small convection currents in the atmosphere.
While thermals form on a local level, there are also giant convection currents in the atmosphere.
These form as a result of the temperature difference between the equator and the poles.

13. 27.2 Coriolis Effect
Bending of air currents is called the Coriolis effect, after the French engineer mathematician Gaspard Gustave de Coriolis ( ), who first described the phenomenon in 1835.

14. 27.2 Global Winds
There are three important global surface wind patterns in each hemisphere:
trade winds
polar easterlies
prevailing westerlies

16. 27.2 Ocean Currents
Global wind patterns and Earth’s rotation cause surface ocean currents to move in large circular patterns called gyres.

17. 27.2 Global Winds and Ocean Currents
Key Question:
How do temperature and salinity cause ocean layering?
*Read text section 27.2 BEFORE Investigation 27.2

18. 27.3 Weather Patterns
Three important factors that shape the weather in a given region are:
temperature
pressure
water
A sling psychrometer can measure water in the air.

19. 27.3 Phase changes of water
Water in the atmosphere exists in all three states of matter.
High in the troposphere, there are ice crystals.
Tiny water droplets, much too small to see, are suspended throughout the troposphere virtually all the time.
Other water molecules in the atmosphere are truly in the gas state, separate from all other molecules.

20. 27.3 Cloud formation Different conditions cause different clouds.
Cumuliform clouds form when convection causes rising pockets of air in the atmosphere.
Cumuliform clouds include:
cirrocumulus
altocumulus
cumulus
cumulonimbus

21. 27.3 Cloud formation Different conditions cause different clouds.
Stratiform clouds form when a large mass of stable air gradually rises, expands, and cools.
Stratiform clouds include:
cirrostratus
altostratus
nimbostratus

22. 27.3 Cloud formation
Sometimes a cloud formation combines aspects of both cumuliform and stratiform clouds.
We call these clouds stratocumulus clouds.

23. 27.3 Cloud formation
Cirrus clouds are thin lines of ice crystals high in the sky, above 6,000 meters.
They are just a thin streak of white across a blue sky.

24. 27.3 Precipitation
A raindrop begins to form when water molecules condense on a speck of dust.
At first it is round, but when it is large enough that it begins to fall, air resistance causes the underside of the drop to flatten, so that it looks more like a hamburger bun.
As it grows larger, it looks more like an upside down bowl with a thick rim.
If it hasn’t hit the ground by this point, it will break up into smaller droplets and the process repeats itself.

25. 27.3 Air masses and fronts
An air mass is a large body of air with consistent temperature and moisture characteristics throughout.
Changing atmospheric conditions and global wind currents eventually cause these air masses to move.

26. 27.3 Low and high pressure areas
When a cold front moves into a region and warm air is forced upward, an area of low pressure is created near Earth’s surface at the boundary between the two air masses.
A center of high pressure tends to be found where a stable cold air mass has settled in a region.
Isobars show areas with the same atmospheric pressure on map.

27. 27.3 Weather Patterns Key Question:
How can we measure water content in the atmosphere?
*Read text section BEFORE Investigation 27.3

28. 27.4 Storms
Thunderstorms arise when air near the ground is strongly warmed and rises high into the troposphere.
As the air rises, it cools and condenses, forming a towering cumulonimbus cloud.
Eventually some of the cloud droplets become large enough to fall as rain.
a storm cell

29. 27.4 Hurricanes
Several conditions must be present for a rotating system to become a hurricane:
wind speeds of at least 74 miles an hour.
warm ocean water must be at least 46 meters deep.
the air must be warm and moist to a point at least 5,500 meters above sea level.
a tropical cyclone

30. 27.4 Tornadoes
A tornado, like a hurricane, is a system of rotating winds around a low pressure center.
An average tornado is tiny, compared with the average diameter of a hurricane.
However, the wind speeds of a tornado are much greater than those of a hurricane.
A tornado’s wind speed can reach 400 kilometers per hour.
a tornado

32. 27.4 Storms Key Question: How does Doppler radar work?
*Read text section 27.4 BEFORE Investigation 27.4

33. 27.5 Weather and Climate
Climate is defined as the long-term average of a region’s weather.
Climate depends on many factors:
latitude
precipitation
elevation
topography
distance from large bodies of water

34. 27.5 Weather and Climate
Scientists divide the planet into climate regions called biomes.
An example of a biome is desert.

36. 27.5 Biomes Key Question: How do zoos model climates?
*Read text section 27.5 BEFORE Investigation 27.5