I'm sure we've been over this before but what's the difference between ground swell and long period swell?
Isn't that apples to oranges? It would be ground swell vs wind swell or short period vs long period. Ground swell tending to have a longer period and wind swell tending to have shorter periods. No?
on swellinfo, the term "ground swell", isn't used... We use short, medium, long, extra long to describe the periods of the swell. The term "ground swell" is used for longer period swells, because the swell energy has much greater interaction with the ocean bottom. Meaning the wave energy travels to much greater depths, and the ocean bottom will be more influential in transforming the wave energy through the shoaling and refraction processes. The wave energy is felt at the ground. I dont really like the term "ground swell", because it is usually thrown around by people in the wrong context. And, really, it isn't very descriptive, because all swells interact with the ocean bottom, it is just that as the swell period increases, the wave energy will interact with the ocean bottom at an increasing rate -> meaning the waves will interact with the ocean bottom at greater depths and further off the shoreline. On the east coast, you will here people talking about ground swells, when it is a wave period of 10 seconds, while on the west coast they would consider this a very short period. hope that helps.
oops! i guess i was wrong, we do throw the ground swell term in the mix... I need to setup a look up table to show how the different period swells are defined on Swellinfo.
A groundswell by definition is any swell energy that propogates from a windfield. On the east coast we typically get short period ground swells after a front moves thorough (i.e. 5 ft @ 8 seconds). I agree with the Administrator, anything more than 10-11 seconds is usually a longer period ground swell. 3 @ 10 seconds is much better than 3 @ 4 seconds. The closer the swell height is to the period the closer you are to the wind field which translates into less energy unloaded on the beach.!
What does Wiley Bascom have to say about this? <<because all swells interact with the ocean bottom>> So you're saying that a 1' swell makes contact with the bottom in the Baltimore Canyon?
Think a second about the ultimate in ground swells -- a tsunami -- 1 ft @60 sec or whatever the number is -- mucho power and push. Probably should be defined as a long period wave.
your logic suggests that in order to touch the bottom, we would need a 100ft swell... lol im letting you slide with this one md only cause knowing your knowledge of the ocean i think you are f-ing with us
no, thats not what I'm saying.... The waves that we surf, eventually all feel the bottom. This is what creates a breaking wave as the wave energy interacts with the bottom, the wave becomes unstable and topples over.
the swell height does not show far the wave energy travels in depth. It is actually only a factor of the wavelength (or wave period). Depth(ft) = Period*Period * 2.56ft , where period is in seconds. 10 sec period => 256 ft 12 sec period => 369 ft. 14 sec period => 502 ft. 16 sec period => 655 ft. 18 sec period => 829 ft. 20 sec period => 1024 ft The continental shelf has depth of approx 460 ft. What happens is the swell traveling at the top of the surface, creates an orbital motion in the water molecules that has the diameter of the wavelength. And, due to friction, this orbital motion interacts with the water below the wave... The bigger the swell, the bigger the orbital motion, and the further in depth the wave energy travels. I wish I had an illustration to show here, but its is some textbook that I dont feel like scanning at 2:30am.
ok, lets rephrase that... All breaking waves interact with the ocean bottom - the waves we surf. Its just a matter at what depth.
Thank you for posting that. I read that a long time ago along with other facts and info about how waves interact with the ocean floor. Anyway, that stuff is really interesting to learn about and I would link what e-book or whatever it was but it has been such a long time, i have no idea what it was called or where i found it.
