Tag Archives: wave watching

Same beach, different waves. Why?

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Here is a puzzle for you.

Walking along a beach, first, the waves looked like this: One wave breaking at a time.

That’s the situation you also see in the foreground of the picture below, while in the background, a little further down the beach, something else starts happening.

If we look closely at that situation (shown in the picture below), there are several waves breaking at the same time, one behind the other.

And it isn’t just coincidence, it keeps happening throughout hundreds of pictures I took that windy Sunday. Why is that?

I think (and this theory would be easy enough to test if the water was warmer or if I wasn’t such a sissy) that the slope of the beach is just different on either side of this little jetty or whatever it is. The shallower the slope, the earlier waves of the same wavelength can “feel” the sea floor, or the shorter waves have to be to “feel” the sea floor at the same distance from the water line.

So I think the slope on the left of the jetty is shallower than on the right, making the incoming wave field that is the same on either side (I’m assuming, but give me a good reason for why it shouldn’t be?) behave differently.

Funnily enough, the only reason I ended up on that beach was that I wanted to go watch a cruise ship go through the locks and into the Kiel canal with a friend. And, funnily enough, the ship decided to not go through the Kiel canal, as it did the week before. So we decided that we should go to the beach. Very good decision! :-)

But here is a “before” pic from when I was still thinking I would be writing a blog post about the ship going through the locks. Isn’t the seagull hilarious, posing like that?

Early morning wave watching. Nothing quite like it :-)

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Occasionally working from home is awesome for many reasons, but mainly because I can use the time usually spent on commuting on … wait for it … wave watching. With my cup of coffee so I can warm up my fingers in between taking tons of pictures.

But I just love it. See below how the seagull is making waves where it is swimming, but is surrounded by a much larger circle, too, that it started when it landed on the water?

And especially gorgeous in the morning light: The reflections of sunlit structures on the water. The pier you see above gets distorted into something like this:

And if you look closely, you see the ring waves radiating from where the pylons disturb the water surface as waves go by.

I absolutely love to watch how the much longer waves can cause these ring waves with such a short wave length, and how they are deformed again by the waves that caused them. I can look at this for a long time without getting bored, it is so calming to me! Especially in the early morning light.

But anyway, time to start working. Have a great day everybody!

Sightseeing in Berlin? Any excuse for a #wavewatching trip!

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Berlin is full of interesting history to discover … for example that of ships that have gone past on the Spree! :-D

Let’s start with some easy wave watching. In the picture above, you see a ship and its wake (both parts: the turbulent one where the ship has gone, and the feathery wake that forms the V with the ship at its tip). And you can make out the wake of a ship that has already gone round that bend of the Spree: the turbulent part showing a different surface roughness, and reflected remains of the feathery V on the right shore of the Spree. So far, so good!

Below, you see two turbulent wakes: The one of the ship you still see, and then the one of a ship that went the other way, but already went out of the area captured in the picture.

Berlin Cathedral Church seen from across the Spree

And here is a series where you see the feathery wake reach the side of the Spree…

Bode museum and television tower Berlin

…get reflected there…

…and then meet the reflection of the other side of the V to form a checkerboard pattern! Would you have known what’s going on here if you hadn’t spotted the ship just about to leave the picture, or seen the previous images?

Below is another nice one. What happened here? A ship sat there, waiting, and then started moving again right before I took the picture! This is the beginning of a turbulent wake right here.

Reichstag, home of parlament

And below another nice wake plus reflection.

And here you see another feathery wake, plus the turbulent wake of the same ship on the other side of the Spree.

Reichstag, home of parlament

Similar picture as above, except in a different spot…

German Chanellery in Berlin seen across the Spree

Yes, that’s a pretty good representation of what sightseeing trips with me are like ;-)

You are watching seals? I am watching waves!

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On a recent evening stroll with a friend, the seal basin looked like this:

“Do you think there are any seals in there today?” she asked. “Why yes, of course, don’t you see the waves?” I replied. Because obviously in a basin sheltered by the wind and with no moving parts in it except possibly a seal or three, there is no other mechanism that I could imagine that would create such a wave field. Sometimes I wonder what everybody else is thinking about all the time that I am thinking about waves while they aren’t… Who’s missing out on the cooler thoughts, me or them?

Anyway, we got to do some proper seal watching and wave watching, respectively:

Pretty, isn’t it? the wake of a seal. Pay close attention, I might be testing you on this some time soon ;-)

Wake comparisons: Row boat and motor boat

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I just love this picture: The two boats in the front are going at the same speed (the trainer is driving right next to the person in the row boat over a long distance), yet look at how different the two ships’ wakes look!

The motor boat has this huge, breaking, turbulent wake. Even though it rides so high up in the water, it displaces a lot of water and creates a wake with a large amplitude (how large the amplitude is is visible in the picture below, where some poor people were sitting in row boats when a motor boat sped past. But also here: Look at how cool these feathery waves that constitute the wake look together!).

But then, going back to the original picture (which I am showing again below) — look in contrast at the row boat’s wake. You see the paired eddies where the oars were in the water, and you see a tiny little trail where the body of the ship went. But that’s all. Yet both boats are going at exactly the same speed! Pretty cool, isn’t it? (Also pretty scary how much energy the motor boat is spending on moving water and moving a larger hull and a heavy engine rather than just propulsion when the payload of both boats is more or less the same — one person)

Night swimming… or at least night-time wave watching

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Looking at Kiel fjord in the picture below, it is quite obvious from the shape of the waves that those waves are some ship’s wake.

Why is that obvious? Because the waves a) have a very short wavelength for their height, and b) are also all of the same wavelength. What I mean by that is a) on Kiel fjord, if we see waves that high that are driven by the wind, their wavelength is a lot longer since the waves have been building up over a long distance. For short waves to display such an amplitude, the waves would have to run up a fairly steep slope which I know is not the case in this location (and which would also lead to two or three high crests in the shallowest part of the water, not to as many as far out as we see here). B) we don’t see a spectrum of wavelengths as we would expect in a wind-driven wave field. In fact, the water surface doesn’t display any ripples or other evidence of wind at all.

And what do you see when you look at water at night? :)

Roll waves in the sand dunes? Observing erosion

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On our trip to the west coast yesterday, I observed something really cool: Sand roll waves (I think!) in the sand dunes!

But before I get to that, this is the setting on Sylt. A sandy beach opening up to the North Sea, that is separated from the land by sand dunes which are overgrown with some kind of beach grass.

Yesterday was a windy day as you see from the waves, but neither was the water level very high, nor was the wind anywhere near as strong as it gets here during winter storms, so the erosion happening yesterday is not very strong compared to what it is like during more extreme weather conditions (and the process I am focussing on here is probably one of the least important ones).

In order to prevent erosion of the dunes which protect the inland from storm surges etc, it is crucial that the beach grass growing on the dunes isn’t stepped on by the hundreds of tourists visiting this beach every day (probably thousands during summer). Therefore there are these wooden staircases installed in regular, short intervals to bring people across the dunes without them doing any damage to the vegetation.

Therefore, in most places, the dunes look like this.

In some places, though, there is little or no grass growing on the dunes, so imagine what kind of damage strong winds can do here, let alone a storm surge!

And in one of these open sand areas I observed what I think are roll waves. Do you see what looks like a drag mark a little right of the center in the picture below?

Check it out in the movie below (it zooms in after 5 seconds to show it more clearly) — there is sand surging down this track! To me this looks very similar to roll waves, and I know roll waves have been observed in sediment flows and lots of other places, so why not in the sand of these dunes? What do you think?

Wave watching from a train

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You know how they say that the journey is the destination? That was certainly the case for my spontaneous mini-vacation yesterday (and how awesome is it that my #BestTravelBuddy is up for a cross country trip on a day’s notice?). We went all the way from the east coast to the west coast — which in Germany admittedly isn’t that terribly far — to visit the island Sylt in the North Sea for a day.

Even the train ride itself is spectacular, though, at least if you are as easily excited as we are. Wave watching from the bridge across the Kiel canal in Rendsburg (below): A super neat wake of the ship, showing the turbulent wake as well as the feathery V-shaped wake. And as you can see from the rows of foam on the water that are a sign of Langmuir circulation (more about that here): It was pretty windy, too!

But it got even better when we reached the west coast. This is my kind of train ride!

Below is a view of the dam that connects the island Sylt with the main land, and here again you see how windy it is, and this is in the lee of the island. In the lee of those shallow dams you see that it really doesn’t take long for the surface roughness to increase again.

So are you excited to see the wind-ward side of the island now? I’ll post some wave watching from that side soon, but I first have to wade through literally thousands of pictures to cut it down to a handful. I’m already down to about the 100 best, but now I can’t decide which ones to post, because I like them all…

But here is a picture of the train ride back. Do you notice how there are regions with really low surface roughness on either side of the dam, suggesting that this dam is sheltering the water surface from the wind in two directions? Of course it isn’t — it’s just ebb tide and the smooth surface areas towards the right of the dam are wet sand that look similar to a smooth water surface.

So that’s my wave watching from the train! Excited to go back soon! :-)

A different kind of drop photography today…

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After all the professional drop photography I talked about yesterday, here is some of my own from a walk that I took after the amazing and slightly overwhelming experience of giving the laudation speech at the opening of an art exhibition.

Below, I really liked how the wave rings have such different sizes and amplitudes depending on whether they were made by rain drops or ducks (you might have to click the image to enlarge to see what I am talking about).

And below, I love so much about this picture. The long waves with the very small amplitude that are coming into Kiel fjord from some far-away storm. The short waves and small scale turbulence that is created where wave crests just manage to flood a step on the staircase, but the water then flows off it again during the next wave trough. The small speckles made by rain drops. The fact that it seems to almost be summer again because the beach chairs are back! And, of course, that I caught the splash and the flying drops of the wave.

I read this poem by E.E. Cummings on Saturday that really speaks to me. It ends in

“For whatever we lose (like a you or a me)
it’s always ourselves that we find in the sea”
E.E. Cummings

Intriguing interference pattern of waves

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Do you see those weird traces going away from us, perpendicular to the wave crests, but in parallel to the bright stripes on the sea floor (I talked about those in yesterday’s post), looking almost like waves but not quite? What’s going on there?

Something very cool! :-)

In the gif below, I have drawn in several things. First, in red, the “weird” tracks that we are trying to explain. Then, in green, the crests of two different wave fields that are at a slight angle to each other. I’m first showing one, then the other, then both together. Lastly, I am overlaying the red “tracks”.

So this is what those tracks are: They are the regions where one of the wave fields has a crest and the second one has a trough (i.e. where we are right in the middle between two consecutive crests). What’s happening is destructive interference: The wave crest from one field is canceled out exactly by the wave trough of the other field, so the sea level is in its neutral position. And the wave fields move in such a way that the sea level stays in a neutral position along these lines over time, which looks really cool:

Some more pics, just because they are pretty and I like how they also show total internal reflection :-)

And don’t you just love the play of light on the sea floor?

And even though these weird neutral sea level stripes are parallel to the bright stripes on the sea floor, I don’t think that the latter one is caused by the first. Or are they? Wave lengths seem very different to me, but on the other hand what are those stripes on the sea floor if they aren’t related to the neutral stripes in the surface??? Help me out here! :-)