Introduction to Physical Oceanography
Homework Set 9
Due 28 November 2007

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

This assignment takes you to the NOAA Wavewatch web site for ocean wave forecasts operated by the NOAA Marine Modelling and Analysis Branch. Use the information from the site to answer the following questions. Note you may need to use Internet Explorer, although I have no problems accessing the site with Firefox on a Mac.

1. Where in the North Atlantic Ocean are the waves the largest? Click on center pull down menu box (It says-Info Page) and select North Atlantic from global then click on the right pull-down menu box and select wave heights.
   • Print out and save the map.
   • What is the significant wave height and period of the largest waves?
   • What is the direction of the largest waves?
     
2. What are the maximum winds in the vicinity of the maximum waves? Click on the right pull-down menu box and select wind speeds.
   • Wind speed and direction?
   • What is the approximate fetch of the winds producing the maximum waves?
     
3. Using the Pierson-Moskowitz ocean wave spectrum and derived quantities given in Section 16.4 of the class notes and the information from the first two questions above:
   • What is the significant wave height you expect from the winds from question two that produced the biggest waves?
   • What is the period of the waves at the peak of the Pierson-Moskowitz spectrum for these wind speeds?
   • How do the calculated values of wave height and period compare with the same values from the latest model run from NOAA?
   • Is the Pierson-Moskowitz formulas useful for estimating the waves produced by storm winds in this case?
   • Were the assumptions used to derive the Pierson-Moskowitz spectrum violated in this case?
     
4. Now, lets look at the accuracy of the NOAA wave forecasts.
   • Click on the top left box and select the oldest model run (it is probably 18 to 24 hours old). Under that box, select the forecast that should give the present waves. Plot the forecast wave map.
   • Print out and compare this forecast map with the map you printed for question one above. Make sure the map of forecast waves is for the same time as the map of the actual waves.
   • How good is the forecast?
     
5. What wave model was used to produce the wave forecasts from the WaveWatch III model?
   • What is the input for the model?
   • Describe briefly how the model works.

Revised on: 16 November, 2007