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Physical Oceanography
Combined Homework and Laboratory Set 3
Due 10 February 2004

Late work will cost 15 points per week or part of a week it is late.


The purpose of this homework is to help you become familiar with satellite measurements of ocean winds. To learn more about the wind-measuring systems read sections 4.4 and 4.5 of the textbook.

The NOAA Marine Observing System web site distributes ocean-surface wind maps made from ERS-2, QuikScat, and SSM/I satellite data. But, the power supply on the ERS-2 instrument failed more than a year ago, and there are no recent maps from ERS-2.

  1. QuikScat: QuikScat is a radar in space that measures radar reflections from the sea surface. Data from the instrument are used to calculate ocean surface wind speed and direction.
    • Look at the QuikScat data page. At the bottom of the page is a map of the most recent 22 hours of winds. Are all areas of the ocean observed in the last 22 hours? What is seen, what is not?
    • What is an ascending pass? A descending pass?
    • Download and print out the image of ascending-pass winds. Circle the area with the maximum winds. What is the latitude, longitude, date, and time where maximum winds were measured?
    • Click on the region of maximum winds.
      • What is the maximum wind on the plot?
      • Where is the maximum located?
    • Go the the QuikScat Web page. What is the swath for this instrument? What percent of the ocean is viewed every day?

  2. Special Sensor Microwave/Imager: The Special Sensor Microwave/Imager SSM/I is an instrument carried on satellites operated by the Defense Meteorological Satellite Program DMSP. Data from the instrument are used to calculate ocean-surface wind speed.
    • Go the the SSM/I Global Page. At the bottom of the page is a map of the most recent 22 hours of winds. Are all areas of the ocean observed in the last 22 hours?
      • What is seen, what is not?
      • Is then coverage similar to QuikScat or different?
    • Download and print out the image of ascending-pass winds. Circle the area with the maximum winds. What is the latitude, longitude, date, and time where maximum winds were measured?
      • What is the maximum wind on the plot?
      • Where is the maximum located?
    • Using information from the Special Sensor Microwave/Imager. and Defense Meteorological Satellite Program web pages:
      • What is the swath width of the sensor?
      • How far back in time are data from SSM/I available?

  3. Real-Time Data: Suppose you need real-time winds from the Gulf of Mexico. Go to the Marine Observing System pages for MPC Forecast Area For SSM/I.
    • Go to the Atlantic Basin Northern or Atlantic Basin Tropics (both include the eastern Gulf of Mexico).
    • At what times are data available over the past 24 hours for the eastern gulf? You need to click on images for the different times to find which have data for the gulf.

  4. Alternate QuikScat Data: QuikScat data are also available from Remote Sensing Systems at the QuikScat Web Page. Remote Sensing Systems and NOAA process QuikScat winds differently. Does the different processing make much difference in storms? Let's find out for one case.
    • Click on the daily map, and print the image. How does this map compare with the QuikScat map from NOAA that you printed out earlier? Are the times the same?
    • Click on the region map in the area with the maximum winds you determined from NOAA. When the map displays, does it show the same maximum winds and in the same location as the NOAA map?
    • Click on link to the Pre-Rendered Data Images to get monthly maps. Get the map for July 2002. Print the map. Then compare with figure 4.4 in the textbook. Circle areas on the map that are different, and describe the differences.

  5. Regional Ocean Model: You are asked to run a local ocean circulation model of Galveston Bay and local offshore waters. The model has 6-hour time steps, it is run every day, and it needs present values of winds over the area. What wind data set will you use, and why? Please state what data sets you considered, and why one is better than the others for this problem.

Revised on: 5 September, 2004

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