Study Guide Unit 12 Weather
OVERVIEW: This unit addresses the interaction of atmospheric conditions and the effects of these on
weather.
Students will understand how the distribution of land and oceans affects weather.
Demonstrate that land and water absorb and lose heat at different rates and explain the resulting
effects on weather patterns.
Relate unequal heating of land and water surfaces to form large global wind systems and weather
events such as tornados and thunderstorms.
Relate how moisture evaporating from the oceans affects the weather patterns and weather
events such as hurricanes.
QUESTIONS
#1 How does the sun interact with the earth to produce weather?
#2 How does an ocean affect the weather of adjacent land?
#3 What happens to water after it evaporates from the oceans and land?
#4 How does the sun’s energy cause winds and hurricanes?
WEATHER
1. Climate is temperature measured over a long period of time while weather is temperature measured at
one precise moment.
2. Our atmosphere absorbs the radiation from the sun, heating the earth.
3. Weather describes the atmospheric conditions at a specific place at a specific point in time.
4. Climate is the average pattern for weather over a period of months, years, decades, or longer in a
specific place.
5. Weather is the effect of the conditions of the atmosphere at a particular time and place.
6. Earth has a layered atmosphere, and weather takes place in the troposphere layer.
7. The properties of the atmosphere, such as pressure and temperature, change as elevation changes.
8. The difference in heating of the Earth's surface produces weather patterns.
9. The sun is the major source of energy for events on the surface of the earth including wind, ocean
currents, and waves.
10. A person who studies the atmosphere and forecasting the weather is a meteorologist.
11. Meteorologists use many weather instruments.
Barometer measures Air Pressure.
Thermometer measures Temperature/Heat.
Anemometer measures Wind Speed.
Wind Socks and Wind Vanes measures wind direction.
Psychrometer measures Relative Humidity.
Hygrometer measures Humidity.
12. High pressure is a condition of the atmosphere in which the air pressure is above average.
13. Low pressure is a condition of the atmosphere in which the air pressure is below average.
HUMIDITY & WATER VAPOR
14. Humidity and relative humidity are related but different.
15. Humidity is the amount of moisture in the air.
16. Relative humidity is the amount of moisture in the air compared with the maximum amount of
moisture the air can hold at a given temperature.
17. Air is saturated when the rates of evaporation and condensation are equal.
18. Air cannot hold any more water when it is saturated.
19. The dew point is the temperature at which air with a given amount of water vapor reaches
saturation.
20. Water will condense on objects when it reaches its dew point. Dew and frost are examples of this.
21. The relative humidity is 100% at the dew point.
22. Air’s ability to hold water increases as the temperature increase.
23. A rain shadow is an area on one side of a mountain that does not receive much rain. Wind usually
blows from the ocean inland. The wind from the ocean carries a lot of water and it falls as precipitation
on the ocean side of the mountain. The rain shadow is on the other side of the mountain.
AIR MASSES
24. Warm air holds more water vapor than cold air.
25. Land heats up and cools down faster than water. As warm air rises, cooler air moves down, creating
convection currents.
26. Unequal heating of land and water forms wind systems and weather events. Wind is caused by
differences in air pressure, going from an area of high pressure to lower pressure.
27. Land heats up and cools down faster than water. During the day, land heats faster than a body of
water, so the air above the land becomes warmer. The warm air expands and creates a low-pressure
system. The cooler air above the body of water blows inland and under the warm air.
28. At night, the land cools faster than the water so the air above the water rises since it is warmer. The
cooler air over the land blows toward the water. These are called sea breezes.
29. An air mass is a large body of air that has the same moisture and temperature.
A warm air mass is called a Tropical air mass.
A cold air mass is called a Polar air mass.
A dry air mass is called a Continental air mass.
A wet air mass coming from the ocean is called Maritime air mass
A cold dry air mass is called Polar Continental air mass.
A cold wet air mass is called Polar Maritime air mass.
A warm dry air mass is called Tropical Continental air mass.
A warm wet air mass is called Tropical Maritime air mass.
30. Isobars indicate air pressure on a weather map.
FRONTS & CLOUDS
31. An air mass is a large body of air that has the same moisture and temperature throughout.
32. A front is the boundary that forms where two different air masses meet.
33. A front that forms when a warm air mass is trapped between cold air masses and forced to rise is
called an occluded front.
34. A cold front occurs when a cold air mass meets and displaces a warm air mass.
35. When a warm front and cold front collide, the cold front forces the warm air up. The warm air
cools so it cannot hold as much water so it begins to rain.
36. A cold front causes heavy rain because a cold air mass pushes a warm air mass higher. As the warm
air mass rises it cools, it cannot hold as much water. When the air rises, the water vapor in the air
condenses and the water becomes heavier and falls to the ground as precipitation.
37. All clouds are water molecules that condensed from water vapor.
38. Clouds can form very close to the surface of the earth as fog.
39. Fog is simply a low stratus cloud.
40. Rain clouds form when water droplets condense from water vapor in the atmosphere.
41. Nimbus means Precipitation, Rain.
42. Cirro means Thin, feathery, wispy cloud that is very high and no rain is expected.
43. Alto means medium altitude.
44. Strato means Spread Out, forms layers.
45. Puffy white clouds with flat bottoms are called cumulus.
46. Thin feathery clouds made of mostly ice are called cirrus.
47. Large thunderhead clouds that produce precipitation are called Cumulonimbus clouds.
SEVERE WEATHER
48. Thunderstorms and tornadoes occur because of sudden changes in air pressure or as a fast moving
cold front hits a slow moving warm front.
49. Large thunderstorms and tornadoes occur most frequently in the spring and summer. The ground is
warming and warm air masses move north from Mexico, while cold air masses move south from
Canada.
50. Tornadoes are a destructive vortex of violently rotating winds having the appearance of a funnelshaped cloud and advancing beneath a large storm system.
51. A severe storm that forms as a rapidly rotating funnel cloud is called a tornado.
52. A hurricane is a large tropical storm system with high-powered circular winds.
53. Lightning is as hot as the surface of the sun.
54. When clouds collide they either lose or gain electrons. This difference in electrons causes an
electron imbalance. When the electrons flow together to balance the electron inequality, lightning
occurs.
55. Hail is formed by a rising current of warm air forces water drops to rise. When the water droplets
reach colder, higher altitude they freeze. The frozen rain droplets fall to the ground as hail.
56. Hurricanes are the largest of storm systems.
57. The storm surge of a hurricane causes the most deaths during the storm.
58. Tornadoes have the highest wind speed of all storms systems.
59. Events, such as volcanic eruptions and clear cutting of trees in the rainforest, can have global effects
on weather patterns.
VOCABULARY
weather describes the atmospheric conditions at a specific place at a specific point in time.
climate is the average pattern for weather over a period of months, years, decades, or longer in a specific
place.
isobars – symbols on a weather map that indicate air pressure
weather front – the boundary that forms between two different air masses
air mass – a large body of air that has the same moisture and temperature
humidity – the amount of moisture in the air
relative humidity – the amount of moisture in the air compared with the maximum about of moisture the
air can hold.
dew point – the temperature of the air when the air becomes saturated
saturation – air is saturated when the air cannot hold any more water
meteorologist - a person that studies the atmosphere and forecasting the weather
tornadoes – a destructive vortex of violently rotating winds having the appearance of a funnel-shaped
cloud and advancing beneath a large storm system
hurricanes – a large tropical storm system with high-powered circular winds
high pressure - a condition of the atmosphere in which the pressure is above average
low pressure – a condition of the atmosphere in which the pressure is below average
rain shadow - A rain shadow is an area on one side of a mountain that does not receive much rain.