atmospheric physics

An opportunity to become a cafe-scientist

coffee, Timberyard, wooden tray

A great place to sit and do some citizen science: Timberyard, Seven Dials has plenty of seats outside.

There are many things to be gained from putting down your smart phone when you enter a café. Firstly, there is the opportunity to fully experience the coffee. The sounds as it is made, the smell, the taste, even the feel of the coffee. Then there is the opportunity for people watching; their behaviour as they order their coffees or have their meetings or try to alleviate boredom while playing with their smartphones. Of course, there is also the opportunity to look at the history of the café and its surroundings, to think about a café-physics review or just slow down and notice things. There’s always something interesting going on.

If you are lucky enough though to be in Athens, Barcelona, Belgrade, Berlin, Copenhagen, London, Manchester, Milan or Rome there is now even more reason to put down that phone while you savour your coffee. By doing so, you could be helping scientists with a few questions that they have about atmospheric pollutants. If you are not in one of those cities, you miss out this time, but you may want to keep reading because if enough people get involved now, perhaps next time the iSPEX-EU project may come near you.

contrail, sunset

What sort of aerosols and pollutants are floating in the atmosphere above your head at this moment?

The question is, what are the atmospheric pollutants that are in the air near where you are now? Perhaps you are in a café on a main road and the answer seems obvious, it is those cars and buses that keep passing by. But there are in fact many forms of atmospheric aerosols or particles and they range in size from a few nanometers to tens of microns (which, in terms of coffee grind is from much smaller than the smallest Turkish coffee to approximately the size of a small particle in an espresso grind). Is it really so clear that where you are, in the centre of that big city, is that polluted? If on the other hand you are on the coast in Barcelona, just how salty is that salty sea air? The iSPEX-EU project allows you to measure it and find out.

These particles of dust, salt and soot etc. can have  an effect on human and animal health, so clearly we want to know more about their distribution and their prevalence. But there are also, more subtle reasons why we may want to know about them. They may have an effect on global warming and they are certainly needed in order for clouds to form, (though as yet we still do not fully understand this process). We need more data about what aerosols are around and where they are to start to know what questions to ask (let alone answer) about health, the climate and cloud formation. Yes, we have satellite measurements and pollution data at specific locations, but what people are missing is that local information. What are you actually breathing? When you look up at the blue sky, what pollutants (or other type of aerosol) are you looking through? Can we get enough data to know how the air quality varies between the cafés of Hackney and those of Hammersmith?

Skylark Wandsworth

Another ideal cafe for iSPEX-EU measurements, great coffee and a lovely outdoor seating area at Skylark cafe, Wandsworth Common

To get this data the scientists involved in iSPEX-EU need people, many people. People who are willing to spend 5 minutes turning their iPhone (sadly it is an iPhone-only project) into a pollution detector. The more people that they can get measuring, the more data that they will be able to obtain. All you need is an app from the App-store and a (free) device that fits over your iPhone camera which you can pick up from somewhere local to you. Then, you just take a seat outside the café on a lovely blue sky day between now and the 15th October, aim your phone at the sky and take a series of photographs which are shared back with the scientists coordinating the project. If you are curious to know how your air quality compares with that in another participating city, you can check the live map to see how the measurements are going across Europe.

The device works by looking at the colour spectrum as well as the polarisation of the light reaching the camera as a function of angle. This information gives tell-tale clues as to the size of the aerosols as well as their prevalence. There is a lot more information on the website of the iSPEX-EU project and so I would recommend that if you do want to know more, you click their link here. In the meantime, why not sign up with iSPEX-EU, take a seat outside in that café and enjoy a great coffee knowing that, as you do so, you are contributing to our understanding of atmospheric science.

If you do decide to participate, please let me know of any great locations that you find, both for the coffee and the measurements, or share your pollution measurements with me in the comments section. I look forward to seeing some great data on the live map.

To get involved with the iSPEX project, you can follow the link here.


Dynamical similarity

Science involves designing experiments to test theories. I do not want to get distracted here by how a theory is defined or the precise ways in which a theory is tested by experiment. The point of this week’s Daily Grind is to look at the role of experiments in physics, where they can be used, where it is more difficult to use experiments to test hypotheses and, how this can be connected with coffee. Some physics can be relatively easily tested by observation or experiment: we can for example take photographs of distant no-longer-planets to test theories about the evolution of the solar system or measure the viscosity of a liquid as we add something to it. Yet there are some areas of physics where it is not immediately obvious how you would test any theory that you develop. One such area is atmospheric physics where the limitations of living on one planet with one atmosphere where many different things all happen at once, could potentially be a bit of a problem for doing experiments on the theories of atmospheric physics.

Fortunately, there is a way in which atmospheric physicists can test their theories with experiment and, perhaps unsurprisingly for the Daily Grind, that way involves a cup of coffee (or tea). The route out is called “dynamical similarity” and it is a consequence of the fact that the same mathematics describes much of that which happens in a cup of tea as it does the atmosphere. It is true that a tea cup is a lot smaller than the atmosphere but a vortex in a tea cup is the same as a vortex in the atmosphere even if one is only a centimetre across while the other has a core size of many kilometres. The mathematics will be the same. This allows people to test hypotheses formed about the atmosphere in an environment that they can control and repeat.

A vortex in the atmosphere

… is a vortex.
(Typhoon Nangka, Image Credit: NASA image courtesy Jeff Schmaltz, LANCE/EOSDIS MODIS Rapid Response Team at NASA GSFC. Caption by Kathryn Hansen)

A couple of months ago, I wrote an article in Physics World about the connections between coffee and physics. Shortly after it came out, I got an email from Paul Williams alerting me to an article that he had written in the journal Weather called “Storm in a tea cup“. It turns out that the subject of his research had been to study the impact on the weather of the interaction of two types of atmospheric waves: Rossby Waves and Inertia-gravity waves. The method that he had used to test this was, if not quite a tea cup, a bucket which he could rotate. Rossby waves and inertia-gravity waves are both present in the atmosphere and can be induced, albeit on a smaller scale, in a bucket. He was using the concept of dynamical similarity to explore what happens in our atmosphere. And the experiment was important. Before his experiments, it had been thought that the effect of the interaction of these two sorts of waves was minimal. His experiments revealed that this may not be the case, the inertia-gravity waves can significantly affect the Rossby waves. Given that Rossby waves are responsible for cold/warm fronts and weather phenomena in mid-latitude regions of the world (such as the UK) his results, and his cup of tea, were potentially very important.

I’m always very happy to hear about what others are doing with science in a tea cup or a coffee mug. Please share any thoughts in the comments section below.

Paul Williams “Storm in a tea cup” can be found in Weather, 59, (4), p.96 (2004) 

With apologies to Gertrude Stein.