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      Orographic Lift

Instructional Objectives
Background Information
Activity
Evaluation
Web Resources



Topic:
The Weather of Denali National Park

Instructional Objectives: Students will:

1. Identify orographic lift through observation of teacher demonstration.

2. Record their observations of orographic lift in student science journals.

3. Draw their observations of orographic lift.

4. Identify orographic lift in the scenes of The Living Edens "Denali."

Background Information:

Orographic lifting occurs when elevated terrain's, such as mountains, act as barriers to the flow of air. As air ascends a mountain slope, adiabatic cooling often generates clouds and precipitation. Some of the rainiest places in the world are located on windward mountain slopes.

In addition to providing the lift to render air unstable, mountains remove additional moisture in other ways. Mountains retard the passage of storm systems. This results in higher precipitation in mountainous regions.

(Source: Lutgens, Frederick K. and Tarbuch, Edward J., The Atmosphere: An Introduction to Meteorology, Fifth Edition, Prentice Hall, Englewood Cliffs, NJ,07632, 1992. p.89)

Activity: Orographic Lift

Time Needed For Activity: One 45 minute period to demonstrate the concept of Orographic Lift.

Target Grade Level: Middle school (Extensions for elementary and secondary found below.)

Materials Needed: TEACHER DEMONSTRATION

  • One large cardboard box (.75-1 meter tall) to represent Mt. Denali
  • One smoke bomb available at party stores (12 for $3)
  • Matches
  • Room with ventilation or outside
  • Small house fan with low speed
  • Student science journals
  • Porcelain dish in which to place smoke bomb
  • Safety glasses for each student
  • Folded cardboard insert as found in glassware boxes to prevent breakage (Use as a baffle/wind tunnel to direct the flow of air of the small fan.)
  • Conduct activity outside on a calm day
    (Extension: A heat source such as a hot plate in front of the base of the box might create enough heat to make smoke (storm front) rise more quickly over the mountain.)

Procedures:

1. Teacher will set up demonstration outside with box, fan about two meters away and smoke bomb in porcelain dish in between fan and box.

2. Teacher will light smoke bomb, turn on fan at low speed to aim smoke
(using wind tunnel/baffle) at box representing Mt. Denali.

3. Students will observe the collection of smoke at the front side of the box and watch smoke rise up to the top of the box to illustrate Orographic Lift.

4. Students will observe and record observations in student science journals.

5. Teacher will dispose of smoke bomb and lead class discussion as to what Orographic Lift looks like.

Evaluation/Alternative Assessment:

Students will present to class what they observed. Students will also draw pictures illustrating what they observed and record observations in their student science journals.

Elementary Extension:

Use cloud charts available from science supply stores to determine types of clouds found in the Denali film. Students may want to draw different kinds of clouds on blue construction paper using white or gray chalk.

Secondary Extension:

Students could work in teams of three to four and research other weather patterns found at Denali. Students will bring the results of the weather research back to class and present their findings.

Web Resources on Orographic Lift:

Lifting of Air Masses
http://www.avalanche.ca/weather/glossaries/advanced/advdefs/lifting.html

Rapid City, South Dakota NOAA Office
http://www.crh.noaa.gov/unr/iwe/1972/Weather/

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