Prince William Sound Field Experiment

why care about waves in the sound?

All mariners can appreciate the value of accurate wave measurements, and especially accurate wave forecasts. Accurately forecasting waves could help prevent future disasters. It could also help researchers determine the importance of waves in sediment transfer, and especially how the movement of sediments affects marine life around the Sound.

wave forecasting
in the sound

swan model wave heights

Go to AOOS Wave data

Also available from AOOS:


Forecasts: Waves

principal investigator:
vijay panchang, texas a&m university

In December of 2004, Hurricane Ivan hit the northern shores of the Gulf of Mexico, creating waves as tall as 16 meters (about 48 feet). The waves carried oil pipes as far as two miles from their original locations and caused massive mudslides along the shore. "My preliminary data suggests that this was nothing less than a 10,000 year event in the Gulf of Mexico," said Vijay Panchang, head of the Department of Maritime Systems Engineering at Texas A&M University.

In the Gulf of Alaska, waves have been measured at almost 17 meters -- the tallest waves ever measured by NDBC buoys.

sailing in large waves, by frank gerryWave simulations in the Gulf of Alaska currently generate relatively coarse-scale forecasts that are of little value at the fine (small) scale of Prince William Sound.

 

The SWAN Model

Using SWAN (Simulating WAves in the Nearshore) modeling, Panchang and colleagues have been forecasting waves around the country up to 48 hours in advance based on measurements from NDBC buoys. Placing this modeling system in the Sound allows for forecasts that are accurate to within 500 meters.

The SWAN model was developed in Holland and is being used in more than 50 countries to predict wave heights in nearshore and inland waters. It has been used to accurately predict waves in the Gulf of Maine for nearly two years.

How SWAN Works

SWAN simulates the following physical phenomena:

  • Wave propagation in time and space, shoaling, refraction due to current and depth, frequency shifting due to currents and nonstationary depth
  • Wave generation by wind
  • Nonlinear wave-wave interactions (quadruplets and triads)
  • Whitecapping, bottom friction, and depth-induced breaking
  • Blocking of waves by current

The SWAN model uses data collected from the three NDBC buoys for validation in the Sound, as well as data from the Cape Suckling and Cape Cleare buoys to validate Gulf of Alaska waves. The model runs every 12 hours to track and predict wave heights. In addition, new technology is being developed by the research group at Texas A&M University that will allow for real-time wave forecasts that are nearly exact for up to six hours at a time. Once it is fully developed, this technology can easily be added to the SWAN modeling system.

Validating Model Results in the Field

Researchers use satellite and in-situ wave observations for validation of model results and satellite wind and wave observations for data assimilation to enhance model results. Besides traditional data assimilation schemes, they will explore techniques of artificial intelligence to incorporate satellite measurements into wave model results.

In the summer of 2005, NDBC buoys tracked waves in the Sound with maximum wave heights of six to seven meters during peak wave periods. The results demonstrated the model's ability to predict such events with reasonable accuracy.

Plans for 2009

Scope of work of Wave Modeling Group for field experiment through August 2009:

  1. Incorporate new bathymetry in our modeling scheme.
  2. Incorporate RAMS windfields in our modeling scheme.
  3. Help identify locations for buoys for 2009 experiment.
  4. Analyze data from buoys.
  5. Perform simulations for the field experiment
  6. Assess quality of simulation (e.g. error as a function of lead time).
  7. Provide model calculated wave velocity estimates for possible use with GNOME, the oil spill trajectory model used by NOAA emergency responders during an oil spill.

Photo: Frank Gerry