Tag Archives: Ratzeburg

Morning and evening #wavewatching in Ratzeburg, including sun dogs!

Leave a reply

I’m super excited to be back in Ratzeburg, but before I start on all the new pictures I will be taking over the next couple of days, let’s get some old pictures out of the pipeline, all taken either in the morning when the lake is still calm, or in the evening, when it’s calm again.

I love, for example as shown in the picture above and below, how paddling with my feet dangling from the pier creates this beautiful pattern of waves that radiate for such a long distance over the lake. And I love how we see that there is wind somewhere further out — the surface roughness is higher and the lake appears a darker blue — but that there is an area with very little wind, where we can see the dark reflection of the forest on the shore across the lake.

Looking into the water at a steeper angle, how creepy are those water plants growing there? The water depth is larger than 2.5 meters here and they still almost reach the surface! Did I mention I like my water without any biology in it? ;-)

Depending on the light, it can look even more creepy, like below…

Good things there are other views to be had, too, when you do a tour around the island. Like here, all those waves coming through the narrow inlet and spreading over the calm pond! Such a pretty sight!

Or a different corner of the small pond — so fascinating how there are the different reflections, shadows and insights into the water happening simultaneously!

And the picture below just makes me happy. Doesn’t it evoke feelings of promise and a new day? (Although it must have been taken in the evening if the sun is on that side. But anyway, all that spring green! :-))

Another thing I observed on two evenings in a row: Sun dogs! Can you spot one in the image below?

Or in this one? Below there should even be two sun dogs (but maybe that’s mainly due to my active imagination…)

Wake watching at Ratzeburger Segelschule

1 Reply

The waves that ducks (or ships, or anything else moving through water) make are called “wakes”. And wake watching is so much fun! A wake is pretty much the Mach cone in 2D — waves from the duck can’t propagate faster than the leading edge of the wake. When a wake passes by, that’s the moment you would hear the supersonic boom of an aircraft in the Mach cone analogy. That explains why the wake develops as a feathery V with the duck at its tip. Or several ducks at the tips at several Vs, as in the picture above. How awesome is that?

But wake watching is usually more complicated than just Vs with stuff at their tips. See for example below — two ducks with Vs, two row boats also with Vs, but with the additional eddies where their oars pushed through the water.

See how different the two pairs of wakes look?

Or here, we have wakes again, but they are now occurring on a lake surface that shows more different waves: The half circles that my feet tapping on the water made! And, if you look closely, you can spot algae growing in the lake in the foreground of the picture.

Isn’t it fascinating how you see the algae in the foreground, but the further you look towards the other shore of the lake, the more you see the reflection of the sky or the other shore instead?

That’s due to a phenomenon called “total internal reflection“: For light that hits the interface between two different materials (air and water in this case), there are angles at which it can cross the interface (at steep angles we can look from the air into the water and see the algae), and others where it can’t (at small angles, we cannot look into the water, light gets reflected at the lake’s surface and we see the opposite shore instead). This fascinates me time and time again!

Note how the duck in the image above doesn’t actually have a wake? That’s because it’s swimming too slowly for the wake to develop — it is just radiating ring waves in all directions.

Below, this is kind of a boarder line wake — we can see the V developing, but se also still see the ring waves in the spot where the duck first started swimming.

But of course, wakes are only straight Vs when the ship is driving in a straight line, too, otherwise it will get deformed like below.

And just because I love this picture so much: Here is a wake coming across the lake…

The perfect wave — and why this is not a fake image

Leave a reply

This picture might look fake, but it’s not.

But what about it does scream “fake!”? To me, there are several things:

  • the almost perfect sinusoidal shape of the waves
  • the way how wavelengths and amplitudes decrease with distance
  • the almost complete lack of other waves except for the one dominant field
  • the way we can look into the water and see the jungle beneath the waves

Of course, all of these can be explained:

  • the almost perfect sinusoidal shape of the waves: We are used to seeing waves that have longer troughs and pointier crests. The waves we see here are the wake of a small boat which caused a large disturbance that then propagates over the lake, keeping its shape fairly well.
  • the way how wavelengths and amplitudes decrease with distance: Usually when we see wave heights increasing towards the shore, we would at the same time see wavelengths decreasing since the increasing wave height would be due to the waves running up a slope and being slowed down. In deep water (i.e. water deeper than a wavelength, which is the case here), longer wavelengths propagate faster than shorter ones, therefore longer waves outrun shorter ones. And the leading wave is the actual wake, the largest disturbance, whereas later waves are just oscillations before the surface comes back to rest.
  • the almost complete lack of other waves except for the one dominant field: Usually we would expect to see a bunch of different wavelengths occurring at the same time if we were looking at a wind generated wave field, but in this case we are looking at a dominant wave field created by a boat. There was almost no wind that day; wind waves are just the small ripples perpendicular to the dominant wave field.
  • the way we can look into the water and see the jungle beneath the waves: this is due to a phenomenon called total internal reflection. Spooky, isn’t it?

Here is how the waves developed over time from when the boat passed by until they reached the jetty on which I was sitting:

I really like another way of looking at that wave field, and that is how my camera roll shows them. Which wave picture of all of these is your favourite?

This is my personal favourite:

More than 2/3rds need to be water

Leave a reply

I’m in this weird phase right now: In landscape pictures that I take, I like more than 2/3rds of the total area to be of water. That I like water shouldn’t really come as a surprise to anyone, but this perspective — looking from right above the water level towards the horizon — is new to me and I am totally into it. Maybe because I’m swimming almost every morning these days?

Anyway, here is a bunch of pictures taken in Ratzeburg recently when I helped out in their sailing school (ratzeburger-segelschule.de — totally recommended! Clearly awesome instructors there ;-))

And obviously the first one of the bunch had to deviate from my 2/3rds-water rule…

img_0421

img_0426

img_0428

img_0432

img_0434

img_0437

img_0439

img_0442

img_0443

img_0445

img_0446

img_0447

img_0449

img_0451

img_0453

img_0454

img_0478

img_0479

img_0497

img_0501

img_0507

img_0512

img_0514

img_0525

img_0527

img_0532

img_0496