Wednesday, February 21, 2018
4:00 pm

Environmental Science and Engineering Seminar

Long Range Propagation of Ocean Swell
William Young, Professor, Physical Oceanography, Scripps Institution of Oceanography, University of California, San Diego

The global propagation of ocean surface waves is a happy example in which a linear theory (almost) explains ocean observations. I'll review the history of this problem, starting with early  work on wave prediction in World War II. The most conspicuous failure in the classic work  is  that  wave sources inferred by great-circle backtracking are often as much as 1000 kilometers away from the storms reported on weather maps; several sources seem to  fall on the Antarctic continent. We have reproduced these old observations  using modern recordings of swell from deep-water pitch and roll buoys and  find  that  modern inferences of generation sites are most often in excellent agreement with the location of large storms on weather  maps of the Southern Ocean. There are, however,  a few puzzling  failures of great-circle backtracking e.g., in one case,  the direct  great-circle route is blocked by the Tuamoto Islands and the inferred source falls on New Zealand. I'll explain the frequent  mirages in the old observations, and the occasional mirages in the modern observations,  as resulting from  refraction of ocean surface waves by currents.

Contact Kathy Bravo kbravo@gps.caltech.edu at 626-395-8724
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