About a week ago, I went on a lovely walk with my parents, and here are the pictures.
How I love the beach!
As I am looking more at ripples in the sand, I am seeing them everywhere now. Below, we are looking at a little area on the beach (the water would be just outside the top of the picture) and we have two different grains sizes of sand, and remnants of wave ripples. And a pothole forming aroud the stone. Fascinating!
This part of the coast is super interesting anyway, there are so many fossils to be found!
And it really shows the force of the sea, nibbling away at these cliffs.
Even though it looks so calm and peaceful!
I also find it fascinating how there are these different lines on the beach with pebbles of different sizes. Probably left there by storms, or other events with higher water levels. But it looks different every time!
Also fascinating: a ship and lighthouse that seem to be hovering in the air above the horizon. Optics are so much fun!
Luckily I had a nice spot from which I could observe what happened next…
…lots of drops. In the ocean. Or oceans in the drops? Who knows. Anyway, after just having done that drop drawing, I couldn’t very well get upset, and I love watching rain on water anyway.
Just look at all the wave rings, and the way drops are catapulted up again only through surface tension!
Here is a (first normal speed, then slow motion) video so you can appreciate it properly, too:
As the rain passed, I found it super impressive to watch the rain showers as they went down elsewhere.
Like over the mouth of Kiel fjord, and I am showing the same spot repeatedly in the following (with more or less the same view, you can use the buoy as point of reference).
I don’t know enough about meteorology to understand what’s going on there, but I can still appreciate the beauty of the rain cloud and how differently things look where it is propagating to (to the right) and where it has already left (to the left).
See how much lower the clouds on the right are, and clearly a different kind of cloud compared to the ones on the left?
At times, it got really dark.
And I watched this one cloud move, continuously raining.
Then there was a dry period of a couple of hours, and when I walked home, it looked like this: Again distinct areas with rain showers.
What I found also really interesting is the swimmer’s wake you see below. There is so much to see in that one picture: The wake, the rain shower in the background, the changing surface roughness from rougher, darker areas, and smoother, lighter areas, and then the areas in the foreground where we can look into the water (see here for why we can do that in some places and not in others)
Same thing as above, only in a different picture…
And again, this time with a really impressive black cloud. And interference pattern in the waves in the foreground.
And now even ring waves that that seagull made…
And as if I hadn’t had enough wave watching in one day, here is a different spot in the afternoon. See the interference pattern as waves get refracted around the bollard?
And, of course, another strong shower came and made us retreat to the inside. But see the rainbow in the picture below? Those are the kind of things that make me really happy! :-)
Sometimes the best wave watching doesn’t happen how you expect it to happen. Look at this jellyfish, bobbing about in the surface of Kiel fjord. Can you spot the circular wave pattern all around where it breaks the surface? I find this so amazing. Would you have thought that you would spot waves that a jellyfish makes?
Btw, there are other places with capillary waves in this picture, too: In several spots you see thin wave crests, parallel to each other, running in front of a larger wave crest. Those are capillary waves, and the cool thing is that the shorter their wavelength, the faster their propagation. Therefore the larger crests seem to be pushing the smaller ones in front of them, bunching them up over time.
Whenever I get out of my house and it looks like this, I am slightly disappointed because it means that the wave watching that morning will not be ideal. I mean, I like colorful sunrises as much as the next person, buuuut…
Today, at least, the fog was kinda interesting, also because there was a large cruise ship driving through.
There was a low layer of fog, but look at what happens as the ship passes through: It lifts up! Visualizing the stream lines around the obstacle. Pretty cool! (And thank you, little police boat, for making at least some waves for me today!)
Even better visible below, but check out the smoke coming from the ship’s chimneys. Do you see how it is propagating forward? Or does it just look like that to me? At least below the fog layer there was pretty much no wind. So what’s going on up there? Anyone care to explain?
When I go wave watching back home in Kiel, I tend to be drawn to other places than this particular one, but sometimes you find gold in the places you least expect it. And then, what is usually a really nice and easy to explain kind of wave — shallow water waves — acts up and becomes difficult. You win some, you lose some…
In these pictures, we see these very weirdly-shaped waves in very shallow water. When the water is shallow enough, waves don’t even have a “proper wave shape” any more, they look more like pool noodles that are being pushed towards the beach, but in a very inefficient, sideways manner.
When the water is shallow enough, the waves also change their behaviour in that usually we can just add two incoming wave fields and get a good idea of what the resulting wave field will look like, but in very shallow water, things become very nonlinear and messy.
Do you see how wave crests seem to start clinging together, resulting in weird X and Y shapes?
Usually we can easily calculate the velocity of shallow water waves just from the water depth, but here in this picture, all kinds of weird and wonderful things are happening and I don’t actually have a clue what’s going on.
A little bit further along, some other surprising wave watching: A wake is running onto the shallow beach.
What i find really interesting here is the one long, straight wave crest that runs all the way across the picture, and then how different the waves look on either side of the draining pipe (actually, I don’t know what’s going into Kiel fjord there, although now I am curious…).
On the left side of the picture, the wave crest hits the shore and that’s the end of waves on that side. On the right side, though, wave crests continue on in shallow water for quite some time before they end up on the shore, and here we see how they get bent by the changing water depth (Remember? Phase velocity of shallow water waves should only depend on water depth, so the deeper the water, the faster the wave). The wave crests get slowed down a lot faster on towards the shallow water on the left than towards the deeper water on the right, thus the right side starts overtaking the left, bending the whole wave crest around.
A week ago already, Frauke and I went on an evening walk in Kiel Holtenau. Beautiful wave watching to be done there as always! Here you see the one side of a ship’s V-shaped wake approaching our vantage point. You can see the individual “feathers” of the wake: Short wave crests, all parallel to each other, but slightly shifted to the side to form a straight line (well, two straight lines to form a V with the ship at its tip, but the other side of the V is not visible on this picture).
And this is what it looks like when the wake has moved past us: Looking on the back of the feathery shapes. The ship that made all these waves has long sailed away.
Wakes are always interesting to watch. But usually, I am showing wakes of ships going straight ahead. So today, I have something cool for you: The wake of a ship doing a 90 degree turn!
And what that does is that the feathery wake that is usually V-shaped now gets deformed!
And this deformation of the wake means that on one side of the wake, the feathery waves that are usually parallel now become fanned open, while on the other side they get bunched together. See?
After the ship had gone a lot further, there were still effects of its wake visible, both of the waves created as well as the turbulent wake that is still visible in a surface roughness that is different from the rest of Kiel fjord, and a little foam.
Fascinating how long such a wake stays visible!
And fascinating that such a small boat — even though it was going a lot faster — does create waves that are a lot higher than the much larger ColorLine does!
If you look at the large ColorLine, you see that there is a large turbulent wake, but (at this speed) hardly any waves created, so hardly a V-shaped wake!
I’m lucky to have great friends like Alice, who was spontaneous enough to go on a mini cruise with me today (for which I was only given tickets when I was already on my way to meet her somewhere else). So we boarded the historic MS Stadt Kiel and the adventure began! (Note the Europe flag? Hope you’ve been voting already when you are reading this, otherwise stop reading and go vote! :-))
I had never been on the MS Stadt Kiel before, even though I’ve seen it many times. It’s lovely inside — historic charm and the smell of marine diesel. What more could you want on a gloomy grey Sunday? And a super nice crew of volunteers who run the ship!
Plus we got to see all my favourite spots, like the light house at Holtenau. You also see the pilot station right behind the light house, that’s where the pretty orange pilot ship lives that you see at least in every other of my blogposts ;-)
And the Kiel Canal locks at Kiel Holtenau; looking at them from Kiel fjord. I usually take my pictures either from the shore on the left close to where you see the tower, or from the bridge that you see in the background.
And then, as you do on historic cruises, there was Swing dancing with a dance crew who was performing for us and then even gave us the opportunity to join in, which, of course, Alice and I did. Unfortunately I wasn’t wearing exactly historical costumes, but hey! It was fun! Thanks, Christian! :-)
For privacy reasons as well as for fairness, I had to give everybody the same face that I am making on the picture ;-)
Yesterday, I took some pretty pictures of a red balloon floating on Kiel fjord, some seagulls swimming close to it, and — of course, most importantly — the seagull’s waves. You see some that they just made where you can still see how they relate to where they are swimming now. But then there are also these large circles from previous movement, and the origin of those we can only guess. As we see from the seagulls’ wakes, they haven’t been swimming in that direction long, and they started out from a resting position. Maybe the large circles are from when they landed? We can only speculate.
I’m showing you the pictures of the seagulls and the ballon because I think they are pretty, but also to have a reference for what “normal” waves look like. “Normal” meaning that they are waves whose restoring force is gravity.
There is, of course, other kinds of waves.
Check out the picture below. It’s super choppy, but do you see parts that look different? It’s an overall choppy day, so it might be a little difficult to see what I am talking about.
Let’s zoom in to see some capillary wave action! Capillary waves are the ones that are restored by surface tension rather than gravity. They are a lot shorter than “normal” waves, wavelengths are only up to less than 2 cm long! And they often appear as several wave crests right behind each other, like below. Short wavelengths travel faster than longer ones, which is why from a main crest, more and more capillary waves emerge which seem to be bunched up moving right in front of the main crest. Pretty cool, I think!
Edit, a couple of minutes after initial publishing this blog post:
I saw a friend use a comic app on Instagram and, of course, went down that rabbit hole. So here is a recap of the pictures as the app sees them below. Do you feel like the waves are easier to see in the comics than in the pictures?
Below, you see the seagulls as they have just started paddling forward, and the large circles are still fairly close to where the seagulls are.
Now the seagulls have swum a little further, but you still see where they initially started out. And you see that the time lag between the two pictures really isn’t that large — the large wave ring hasn’t propagated a lot compared to the balloon (which is also freely drifting, so maybe that’s not the smartest comparison).
But my capillary waves become a little clearer now, I feel: The bunches of parallel wave crests on the right half of the picture that are now drawn in black (while all the choppy stuff is just shared, but not contoured).
What do you think? Are these pictures helping to show what exactly I am talking about, or is it just as confusing as before, only in a different way?