Summer Swell/Weather Predictability

I think you are thinking more along the lines of momentum and force than kinetic energy.

For example...

The weight of a cubic meter of water at 80 degrees F is about 6 kg less than at 33 degrees F. You are saying that the momentum of that extra 6 kg could impart more force on impact.

I'll buy that theoretically. But there are so many other factors involved that I can't believe that they could be isolated enough to measure that difference.

6 kg = about 13 lbs. Assuming the area of a head high wave that impacts the surfer has about 20 cubic meters of water behind it that would be about 260 extra pounds. Now determine the speed of travel at impact and find the force. So yeah if you had two identical waves with about 40 degree F difference in temperature, sure you might notice the difference in force.

 

...Nope

That's only qualitative. I'm requesting quantitative measurement.

 

heaviness in surfing is pretty subjective. Waves with more energy (longer wave periods) generally create waves breaking with more power. In my eyes, a heavy wave would be the more hollow wave as compared to the weak crumbling wave.

 

I agree, but I was looking for a more tangible answer. It's kind of a rhetorical question, because I know that it is purely subjective, but if you were to approach it from a scientific perspective, how would you measure the "heaviest" wave in the world?

For example...

1. The impact force
2. How much weight it can push
3. Velocity
4. Water mass of the wave


I've surfed waist high 20+ second waves that have kicked my arse, and overhead short period waves that barely tickled... So, if face size isn't the measure... what is? LBcrew suggested temperature effects the "heaviness". I'm sure that period does as well. Maybe if you can't measure how "heavy" a wave is, then you can only extrapolate a proportionality to the wave attributes that effect heaviness.

 

Technically, a colder water temperature does in fact create a more "dense" wave, but not necessarily heavier. We're talking molecules though, so unless its almost frozen you really aren't going to notice much more pressure on you. Like Swellinfo said, an ice cube would be a good example. The molecules in a solid piece of ice are obviously more tightly compact than water, so as temperature decreases, density increases.

 

I haven't seen it brought up, but doesn't bottom contour have a lot to do with wave shape, and therefore, heaviness? I would think on the east coast a reason you see heavier waves in the winter might have something to do with how the sand bars have been re-arranged from all the hurricanes and n'oreasters. Surely it can't just be that the water is cold. One of the heaviest waves out there is in tropical water:

 

given equal swell height, period, and direction, wave bottom contour has everything to do with the shape of the wave. The swell direction, magnitude, and frequency are obviously contributing factors to how any given swell will behave when it interacts with the ocean bottom.

 

colder water is actually less dense... That is why an ice cube floats to the top of a glass of water. I wasn't thinking correctly when I first responded.

 

That is false.


Water in it's solid form (ice) is less dense than water in it's liquid form (water) at the same temperature due to the bonds of the crystaline structure. The bonds in the crystal latice structure actually force a greater space between molecules than when water is in the liquid form.

Water becomes more dense as it cools due to less movement of the molecules, but less dense once it crystalizes.

 

That's at the molecular level. I don't think that's what Sniffer was referring to, which was, I think, the kinetic energy of the wave... not the molecules of water that make it up.

 

Exactly right, and well said.

 

Ok, that sounds reasonable... That is what I thought originally that colder water was more dense... Got confused for a bit there. Thanks for clearing that up!

 

I have come to the conclusion that I'm not smart enough for this thread...

 

That makes more sense.

So then that's (mv^2)/2 = mass times velocity squared divided by 2.

Only problem is... what is the mass of the wave?

We know the mass of the wave will increase will increasing density (since volume is constant), so we can infer that the kinetic energy of the wave will increase with increasing density (decreasing temperature).

But, I still don't see how anyone can isolate all the variables that effect the kinetic energy to prove that colder water causes greater erosion or makes a "heavier" wave. Velocity and volume are not going to be constant. Its an assumption that increased mass is significant enough to increase erosion. How do they prove that the area studied is not subject to higher wave periods, etc.

So theoretically it holds water (pardon the pun) but in practice I don't think it can be proven.

 

thank you, I knew my last year in AP Chemistry wasn't just a joke

 

This was a long time ago... but I took a Geomorpholgy course at the University of Michigan, and this topic was part of that course. It's a phenomenon that's been studied at length, and tested in wave tanks, where they drive a pin into a substrate and measure the amount of pin material that gets exposed after a period of time. I don't have any sources, but that was the gist of it. I think the guru was a geomorpholgist named Bloom.

 

are you kidding? its way easier to predict summer waves than winter....summer is flat the whole time

 

Yeah I don't think I phrased that correctly. You're right that ice floats because it's less dense, but I was trying to point out that the colder the water gets, the more dense it is. This remains true until it turns into ice, allowing it to float.

 

Warmer water actually has more kinetic energy on a molecular level. Temperature is defined by the particles kinetic energy, so more energy translates to higher temperature. But in the end I don't think water temperature really affects the wave's "energy" because it's on such a small scale.