Category Archives: observation

Playing with a thermal imaging camera

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I recently borrowed a thermal imaging camera from work. So much fun!

Below you see a cold sky, warmer trees and two really warm people walking through the park.

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One thing that really surprised me was to see reflections of the warmer trees on the little lake below. Although thinking about it, I am not sure why I should be surprised: If it was a “normal” image and not a thermal image, reflections wouldn’t surprise me at all. So why should thermal radiation behave any different?

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But it messed up my plans quite a bit. I had hoped to maybe be able to see heat being transferred when waves crashed against the sea wall. But a) there were no waves, and b) what did the waves do? Correct: reflect the sky.  Just like they always do…

So this is what we see:

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And this is what the thermal imaging camera sees:

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On a different day you clearly see the warmer clouds:

As well as the apparently much warmer ships.

And looking down from the sea wall:

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And what the camera sees:

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Wind field

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Another boundary layer experience last week: On my way from work I stopped to take pictures of flags that were outside my university’s main building and that very nicely visualised the wind field (as flags tend to do).

If you just look at the flags, they look weird — they wind field was clearly not changing over time, yet the flags were at a weird angle to each other.

And in the next picture you see why: Because the air had to flow around an obstacle, so stream lines were bunching up.

The next morning, I went past there again and stopped to take more pictures, when a colleague of mine stopped next to me, looking a little puzzled that I was taking pictures of our not especially nice main building.

I explained what I was doing, and we got talking about how you see the world with completely new eyes once you have noticed, or have been shown, something tiny. Isn’t that exciting? :-)

On the impact of blogging — or how far does my message mix?

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What is the impact of this blog? And who am I writing it for?

Those are not questions I regularly ask myself. The main reason I started blogging was to organise all the interesting stuff I was collecting for my introduction to oceanography lecture at the University of Bergen in one place, so I would be able to find it when I needed it again. And I wanted to share it with friends who were interested in teaching oceanography or teaching themselves.

Another of the reasons why I blog is that I notice a lot of exciting features in everyday life that relate to oceanography and/or physics, that other people would just walk past and not notice, and that I would like to share the wonder of all those things with others. And noticing all this stuff is so much FUN! The blog “gives me permission” to play, to regularly do weekend trips to weirs or ship lifts or other weird landmarks that I would probably not seek out as often otherwise.

But the other day I was browsing the literature on science blogging in order to come up with recommendations for the design of what is to become the Kiel Science Outreach Campus’ (KiSOC) blog. I came across a paper that resonated with me on so many levels: “Science blogs as boundary layers: Creating and understanding new writer and reader interactions through science blogging” by M-C Shanahan (2011). First, I really liked to see the term “boundary layer” in the title, since it brings to mind exciting fluid mechanics. Then second, I read that the boundary phenomena I was thinking of were really where the term “boundary layer” came from even in this context. And then I realised that I have had “boundary layer” experiences with this blog, too!

So what are those boundary layers about? Well, in fluid mechanics, they are the regions within fluids that interact with “something else” — the boundary of a flow, e.g. a pipe, or a second fluid of different properties.  They are a measure for the region over which temperature or salinity or momentum or any other property is influenced by the boundary. But the same construct can be used for social groups, i.e. in my case oceanographers and non-oceanographers. (You should, btw, totally check out the original article! Her example is even more awesome than mine)

But here is my own boundary layer experience: My sister sent me an email with the subject “double-diffusive mixing” and a picture she had taken! My sister is not an oceanographer, and I wasn’t even aware that she associated the term “double-diffusive mixing” with anything in particular other than me writing my Diplom thesis about it and probably talking about a lot. But that she would recognise it? Blew my mind!

Turns out what she saw is actually convection, but it doesn’t look that dissimilar from salt fingers, and how awesome is it that she notices this stuff and thinks of oceanography?

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Day 1. The remaining pink soap starts making its way up through the refill of clear soap.

Obviously I asked for follow-up pictures:

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Day 2. A lot of the pink soap has reached the top, passing through the clear refill.

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Day 3. All of the “old” pink soap is now on its way up through the clear refill.

And I had another boundary layer experience recently: A sailor on the Norwegian research vessel Håkon Mosby with many many years experience at sea had seen my book and told me that he now looks at waves in a new way. How awesome is that? That’s the biggest compliment my book could get, to teach something new about visual observations of the ocean to someone who looks at the ocean every single day!

Anyway. Reading this article made me think about how happy both those boundary layer experiences made me, and that maybe I should actually start aiming at creating more of those. Maybe not with this blog, that I kinda want to keep as my personal brain dump, but there are so many different ways to interact more with people who would potentially be super interested in oceanography if only they knew about it… I guess there is a reason why I am working the job I am :-)

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Shanahan, M. (2011). Science blogs as boundary layers: Creating and understanding new writer and reader interactions through science blogging Journalism, 12 (7), 903-919 DOI: 10.1177/1464884911412844

More funny waves

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I think I might need to find a new route to walk along the Kiel fjord. When I was walking — in the most beautiful sunshine! — with my friend over the weekend, she pointed out that there are funny waves and it looked like there was water dripping in, and I went without looking “no, there is a step right there that’s causing those“.

You see it in the picture below: Every wave crest washes over the step, and then when it retreats it sends off its own little waves.

It’s a funny thing with professionalized perception. What I notice walking along the Kiel fjord is really highly trained and specialised, I guess. But still a lot of fun! And it makes me really look forward to the excursion that I’ll do later this summer with a couple of high school students where they’ll learn to observe waves my way :-)

Nonlinear effects in shallow water waves

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I recently googled for something related to the shape of waves and came across a photo of a wave that caught my eye, and it took me to a journey that lead to the article “nonlinear shallow ocean wave soliton interactions on flat beaches” by Ablowitz and Baldwin (2012).

What’s discussed in that article is that while many wave interactions can be seen as (more or less) linear, sometimes there are nonlinear effects that can be replicated in a model. So far so not surprising. But I got fascinated because the phenomenon they look at I have seen over and over again and never really paid any attention to it: Wave crests forming X or Y shapes. But looking through my archives, I even had dozens of pictures of this exact phenomenon! (Actually, I didn’t have to look further back than to a beautiful day last November, when I also observed the wavelength dependency of wave-object interactions)

Take for example the picture below: Do you see the H shape in the waves closest to shore? (In the article they would probably call it a more-complex shape, since it’s a double Y shape…)

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Below I’ve drawn into the picture what I mean by H-shape in green, and the typical kind of linear wave interaction in red (all crests just move on without influencing each other except in the spot where they occur at the same time, there they just add to each other):

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Or below, I spot an X-shape:

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And here are several X- and Y-shapes

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And the picture below just to give you an orientation of where you are: Yep, it’s the same spot where we usually observe foam stripes, funny waves, or ice…

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Mark J. Ablowitz, & Douglas E. Baldwin (2012). Nonlinear shallow ocean wave soliton interactions on flat beaches Physical Review E, vol. 86(3), pp. 036305 (2012) arXiv: 1208.2904v1

More foam stripes

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As you might have noticed, I am getting a little obsessed with those foam stripes. Another day, a little more wind, looking up the coast:

And down the coast…

Do you notice the irregularities in the foam stripe in the pictures above? Those are the places where, in much calmer weather, you see the funny waves. I.e. there are steps that disturb the wave pattern and hence the foam stripe.

But remember we saw a foam stripe connecting one going in parallel with the pier to one going parallel to the sea wall? It’s here again:

Its taking a very similar path like it did last time, but this time it joins the one parallel to the sea wall, rather than forming a second stripe parallel to the first one.

And if we continue further down the coast, we see a similar phenomenon (we are now walking towards that edge in the background of the picture below).

Looking back, we see another foam stripe coming from the other edge of the pier, joining the one parallel to the sea wall.

See, this is how they meet at the sea wall?

And, funnily enough, a similar stripe can be seen going through the sailing harbour: Entering it through an opening in the pier and then going across the harbour and out the other end, until it finally joins the stripe at the sea wall.

This stripe finally convinced me: There don’t need to be convergences for the stripes to exist, at least not for those that aren’t running in parallel to the coast. Because I cannot imagine a convergence zone running in such a way through the harbour that is partly sheltered from the wind, has pylons in it, and just has completely different conditions than the open fjord. Or at least the mechanisms forming that convergence zone would have to be very different from those forming the other stripes. So now I am thinking those stripes are just advecting foam from places where it accumulated (in front of the pier) to new places where it accumulates some more.

And finally it just gets stranded on land:

See how nicely the foam stripe is going around the obstacle? :-)

“Coriolis fountain”

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We’ve been thinking about Coriolis deflection a lot recently (see links at the end of this post). But this weekend, at Phaenomenta Flensburg, I came across a so-called “Coriolis fountain”. A fountain that you can put into spin and that then changes shape like so:

Uta, remember we talked about this a couple of years ago? Nice puzzle for anyone interested in fluid dynamics…

Watch the movie and be amazed :-)

Foam stripes mystery — closer to figuring out what’s going on?

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I think I might be getting closer to understanding the foam stripe mystery. Remember how we’ve always observed them going in parallel to the coast?

Yesterday I saw this again, looking up the coast in one direction…

…and down the other direction. I’ve had the hypothesis that they might be somehow related to Langmuir circulation, but in any case there must be some kind of convergence zone there.

But let’s move closer to that pier we see in the background of the picture above. Here we see a foam stripe parallel to the pier, but at a 90 degree angle to the see wall that I am standing on and that has a foam stripe running in parallel, too! And even more curious: at the edge of the pier, the foam strip detaches and runs toward the coast! See?

Looking down the coast again, we see that foam stripe coming in at an angle, and running in parallel to the coastal stripe in the far back.

Looking up the coast from the pier right where it meets the sea wall, we see both foam stripes running in parallel (as we saw in the picture above):

I think what is happening here is that the foam of the foam stripes doesn’t form locally (which was an implicit assumption I had whenever I was staring at the water, trying to observe more wave breaking there than in other places). Instead, foam forms somewhere else (probably pretty much all over the place) and just accumulates in those stripes. That’s actually pretty likely if we think back to the eel grass or leaf stripes: the eel grass and leaves were clearly advected from somewhere else, too. And actually that’s the same with Langmuir circulation, too: stuff just accumulates in convergence zones but isn’t formed there.

So for some reason there is a convergence parallel to the sea wall as well as the pier, and foam just accumulates there. And as for the part of the stripe that detaches from the pier and runs to the coast? It is going more or less downwind. So it’s probably just part of the stripe parallel to the pier that gets advected around the corner and blown toward the coast.

Why does that stripe end up in parallel to the one at the coast rather than joining it? I don’t know yet. But at least now I only need to figure out why there are convergences in some places and I can let go of the obsession with foam formation in the stripe itself :-)

Do you have any idea that might explain those foam stripes? I’d love to hear from you!