Activity: Investigating Wind and Water

Summary: Students explore the relationship between wind speed, wind direction and water displacement levels using charts, images and data.

You Need:

 

Guide to Great Lakes Coastal Forecasting System (GLCFS) Images

coastal forcasting system
Wind and water level data are available from Great Lakes CoastWatch, via the Great Lakes Observing System (GLOS).

See: Great Lakes Coastal Forecasting System; Images of Great Lakes water levels and winds produced by the National Oceanic and Atmospheric Administration, Great Lakes Environmental Research Laboratory.

There are three types of images available:

  • Nowcast – Updates every three hours from current time to throughout the previous 48 hours. Nowcasts are generally posted at about 2:25 a.m., 8:25 a.m., 2:25 p.m. and 8:25 p.m., Eastern Standard Time (EST).
  • Forecast – Updates every three hours, from 3 to 60 hours from current time. Forecasts are generally posted by 10:15 a.m. and 10:15 p.m.
  • Animations – The previous 48 hours of data are available. Files are in an FLC format.

 

Interpreting Great Lakes Coastal Forecasting System (GLCFS) Images

The following information will help you decipher the forecasting system data:

  • Color ramps – Colors represent water displacement in feet.
  • Time – Image time is recorded in Greenwich mean time (GMT), however, images displaying winds also include EST.
  • Wind – Wind direction and speed is represented by symbols called wind barbs. The barbs on the symbols point in the direction from which the wind is blowing. The number of barbs and barb length indicate wind speed. Each short barb represents 5 knots, each long barb represents 10 knots. See: Wind barb image

 

Procedure

Investigate the relationship between wind direction and water displacement using GLCFS images. Refer to Lesson 1: Figures.ppt.

Investigating Lake Michigan

Part 1

Water levels, Lake Michigan (color ramp). See: Slide 1, Nov 27 – 7:00 a.m.

  • Point out features of image; date/time, color ramp, etc. Note: GLCFS images illustrate changes in water depth as water displacement.
  • Ask students to identify water displacement in Lake Michigan and Green Bay.
  • Examine average water level.
  • Ask students to predict wind direction in Green Bay.

Part 2

Wind direction, Lake Michigan (wind barbs). See: Slide 2, Nov 27 – 7:00 a.m.

  • Examine the features of the image like wind barbs (observed vs. analyzed) and color ramps.
  • Does the wind direction match students’ predictions? Note: Wind is from the west, and water seems to be displaced from the west-southwest.

Part 3

Wind direction, Lake Michigan (water displacement). See: Slide 3, Nov 27 – 5:00 and 6:00 a.m.

  • Investigate the delay between wind and its effects on water displacement.
  • Discuss the delay between the wind and water displacement.
  • Investigate the impacts of basin size, basin depth and fetch on water displacement, using GLCFS images (Slides 4-5).

Part 4

Water levels, Green Bay. See: Slide 4, Nov 28, 12:00 a.m.

  • Ask students to predict wind direction in Green Bay.
  • Displacement depth is much greater in southwestern Green Bay than in northeastern Green Bay or northern Lake Michigan. Why? Hint: size and shape of basins, fetch, etc.

Part 5

Wind direction, Green Bay. See: Slide 5, Nov 27, 10:00 p.m. and Nov 28 – 1:00 a.m.

  • Compare the relationship between wind speed and direction and water displacement in slides 4-5 and slides 1-3 (water displacement is greater in Green Bay even with weaker winds than in Lake Michigan, which is likely due to the size and shape of the basins, fetch.

Part 6

Forecasts vs. Nowcasts, Lake Michigan See: Slides 6-7, Nov 27 and 28

  • Slide 4 was a Forecast.
  • How did the water levels and winds differ from the Forecast? Note: There was not as much water displacement as predicted, as winds were more variable.
  • Discuss how variable winds may impact water levels.

 

Investigating Lake Erie

Part 1

  • Ask students to predict wind direction and speed in Lake Erie on Nov. 27 – 3 p.m.
    • See: Slide 8.
  • Compare predictions with wind direction and speed.
    • See: Slide 9, Nov. 27, 2:00 p.m. and 3:00 p.m., westerly winds from 30-40+ knots.
  • Ask students to predict wind direction and speed in Lake Erie on Nov. 28, 7:00 a.m.
    • See: Slide 10.
  • Compare predictions with wind direction and speed.
    • See: Slide 11, Nov. 28, 7:00 a.m., south, southwesterly, southeasterly, northwesterly winds, approximately 10 knots.
  • Why was displacement depth greater on November 27 than on November 28? Discuss how wind direction impacts water displacement in slides 8 and 10.
  • Remind students that wind speed and direction are not the only factors influencing water movement in the Great Lakes.

Part 2

Lake Erie Seiche (Slides 12-15)

  • Graph: Water levels at Gibraltar, MI station 9044020, Detroit River, Sept 28-Oct 1, 2005.
    • See: Slide 12.
  • Photograph of water levels, Lake Erie Metropark, Sept 29, 2005 – 9:36 a.m.
    • See: Slide 13.
  • Photograph of water levels, Lake Erie Metropark, Sept 30, 2005 – 12:18 p.m.
    • See: Slide 14.
  • Graph (finer scale) – Water levels, Gibraltar, Mich. graph shows decreasing oscillations during a seiche.
    • See: Slide 15.

 

For All Great Lakes

In small groups:

Create groups of three to four students. Select one Great Lake per group.

  • Groups use Great Lakes Coastal Forecasting System (GLCFS) images to examine their lake and use data sheet to predict likely seiche locations (based on basin shape, fetch, etc.).
  • Groups share their predictions with the class and defend predictions using GLCFS images as evidence.