Subject: Precipitation on the Earth
Objectives:
Students will:
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understand definicions of absolut and relative humidity;
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explain connection between relative humidity and air temperature;
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lern how to recognize different types of clouds;
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understand processes of formation rainfall;
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indicate regions with highest precipitation;
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lern how to explain high precipitation in certain locations.
Time: 1 hour.
Material required:
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computer and projector;
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Microsoft Power Point program;
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Map of World;
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Map of global distribution of precipitation.
Suggested Procedure
Opening:
Explain two definitions: absolut humidity (the amount of water vapour in grams held in 1
cubic of air) and relative humidity (the water – vapour pressure in the given valume of air
compared to the saturation vapour pressure and is expressed as a percentage).
Review with students how wind, air pressure and air temperature depends on each other.
Wind
higher temperature
low pressure
lower temperature
high pressure
Development:
Explain conditions needed for precipitation formation. The amount of water vapour depends
on air temperature and pressure (when air temperature is lower, then relative humidity
increase). The condensation process in the atmosphere leads to cloud formation.
Use computer and projector to present types of clouds.
Presentation contains of classifications of cloud, photographs and test.
Presentation contains two classifications, which identifies clouds by appearance (basic types
of clouds include: heaped clouds, layer clouds, feathery clouds) and height of clouds base
(high-level clouds, mid-level clouds, low-level clouds and vertical clouds).
Students observe photographs and lern how to recognize basic types of clouds.
Students do three tasks to improve their knowledge about clouds:
Task 1. Put the given names of clouds in the charts.
Task 2. Match the definition to the clouds types.
Task 3. Look at the photos and give the name of clouds.
After every task students can check the answers.
At the end of presentation show other phenomena as “halo” irisation and mirage.
Drow the simple sketch and explain the processes of formation frontal, convectional and
orographic rainfall (the main reason of clouds formation is fast upward air movement):
convectional rainfall
orographic rainfall
frontal rainfall
Next, ask students where these three types of rainfall occur. Students indicate the areas with
highest precipitation on maps and give explenation of these phenomena.
Closing:
Remind students that we can observe various types of clouds above our heads but mainly low
– level clouds bring rain or snow.
Remind students that climatic conditions on the Earth are diverse. Point out three locations
with highest precipitation: the equatorial zone, monsoon area and mid – latitudes.
Suggested student assessment:
1. Answering for three questions about clouds.
2. Have students prepare a short answer to the question: Give the names of two regions
with highest precipitation and give explenation of it.
Try this at home:
Students can do daily observation of clouds and other phenomena. They can also take photos
and describe them.
Agata Łazarz