Download Physical Oceanography

Physical Oceanography (2010)
Problem 9: due October 27 (Wednesday), 2010
Surface Gravity Waves
(9a) You are fishing in a small boat in the ocean. You notice that your boat is
going up and down with the ocean sea surface, that the time between successive
crests is about 12 seconds, and that the crests appear to be moving by your boat at
about 10 m/sec. Assuming that your boat is at a fixed horizontal location, and that
shallow water theory applies, estimate the wavelength of the surface gravity waves
and the depth of the ocean at your location. Is shallow water theory a good
approximation at this location (yes or no, and why)?
(9b) You are in the middle of the ocean observing the surface wave field. At noon,
you notice the arrival of a group of gravity waves with a frequency of 0.1 Hz. The
next day at noon, the wave groups have a dominant frequency of 0.2 Hz. What is
the wavelength of the gravity waves in each of these groups? If these wave groups
were both generated by the same meteorological disturbance, estimate the distance
of this disturbance from your observing location.