Tag Archives: weather

Storm in a computer

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Decorative painting of a stormy seascapeAs part of my undergraduate course on thermodynamics [see ‘Change in focus’ on October 5th, 2022) and in my MOOC on Thermodynamics in Everyday Life [See ‘Engaging learners on-line‘ on May 25th, 2016], I used to ask students to read Chapter 1 ‘The Storm in the Computer’ from Philosophy and Simulation: The Emergence of Synthetic Reason by Manuel Delanda.  It is a mind-stretching read and I recommended that students read it at least twice in order to appreciate its messages.  To support their learning, I provided them with a précis of the chapter that is reproduced below in a slightly modified form.

At the start of the chapter, the simplest emergent properties, such as the temperature and pressure of a body of water in a container, are discussed [see ‘Emergent properties’ on September 16th, 2015].  These properties are described as emergent because they are not the property of a single component of the system, that is individual water molecules but are features of the system as a whole.  They arise from an objective averaging process for the billions of molecules of water in the container.  The discussion is extended to two bodies of water, one hot and one cold brought into contact within one another.  An average temperature will emerge with a redistribution of molecules to create a less ordered state.  The spontaneous flow of energy, as temperature differences cancel themselves, is identified as an important driver or capability, especially when the hot body is continually refreshed by a fire, for instance.  Engineers harness energy gradients or differences and the resultant energy flow to do useful work, for instance in turbines.

However, Delanda does not deviate to discuss how engineers exploit energy gradients.  Instead he identifies the spontaneous flow of molecules, as they self-organise across an energy gradient, as the driver of circulatory flows in the oceans and atmosphere, known as convection cells.  Five to eight convections cells can merge in the atmosphere to form a thunderstorm.  In thunderstorms, when the rising water vapour becomes rain, the phase transition from vapour to liquid releases latent heat or energy that helps sustain the storm system.  At the same time, gradients in electrical charge between the upper and lower sections of the storm generate lightening.

Delanda highlights that emergent properties can be established by elucidating the mechanisms that produce them at one scale and these emergent properties can become the components of a phenomenon at a much larger scale.  This allows scientists and engineers to construct models that take for granted the existence of emergent properties at one scale to explain behaviour at another, which is called ‘mechanism-independence’.  For example, it is unnecessary to model molecular movement to predict heat transfer.  These ideas allow simulations to replicate behaviour at the system level without the need for high-fidelity representations at all scales.  The art of modelling is the ability to decide what changes do, and what changes do not, make a difference, i.e., what to include and exclude.

Source:

Manuel Delanda Philosophy and Simulation: The Emergence of Synthetic Reason, Continuum, London, 2011.

Image: Painting by Sarah Evans owned by the author.

Certainty is unattainable and near-certainty unaffordable

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The economists John Kay and Mervyn King assert in their book ‘Radical Uncertainty – decision-making beyond numbers‘ that ‘economic forecasting is necessarily harder than weather forecasting’ because the world of economics is non-stationary whereas the weather is governed by unchanging laws of nature. Kay and King observe that both central banks and meteorological offices have ‘to convey inescapable uncertainty to people who crave unavailable certainty’. In other words, the necessary assumptions and idealisations combined with the inaccuracies of the input data of both economic and meteorological models produce inevitable uncertainty in the predictions. However, people seeking to make decisions based on the predictions want certainty because it is very difficult to make choices when faced with uncertainty – it raises our psychological entropy [see ‘Psychological entropy increased by ineffective leaders‘ on February 10th, 2021].  Engineers face similar difficulties providing systems with inescapable uncertainties to people desiring unavailable certainty in terms of the reliability.  The second law of thermodynamics ensures that perfection is unattainable [see ‘Impossible perfection‘ on June 5th, 2013] and there will always be flaws of some description present in a system [see ‘Scattering electrons reveal dislocations in material structure‘ on November 11th, 2020].  Of course, we can expend more resources to eliminate flaws and increase the reliability of a system but the second law will always limit our success. Consequently, to finish where I started with a quote from Kay and King, ‘certainty is unattainable and the price of near-certainty unaffordable’ in both economics and engineering.

More violent storms

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I made a mistake last week by initially publishing two posts.  My apologies for confusing you or tantalising you with the prospect of going bungee jumping and then postponing the trip.  We’ll go bungee jumping next week.  I postponed it because it’s a preview of the new MOOC on ‘Understanding Super Structures‘ that I am writing and there was a delay in publishing the registration page for the MOOC.

When I posted my comment about postponing the bungee jump due to rain, I didn’t realize that, the following day Liverpool would be battered by Storm Doris, with 90 miles per hour winds that closed the Port of Liverpool.  As I sat writing week 4 of the new MOOC, the wind was swirling around our house causing the windows to rattle; and, on the top storey of our narrow but tall house, you could feel the house moving in the gusts of wind.  Across the street, people visiting Liverpool Cathedral were hanging onto the railings as they made their way to the entrance, and the trees were being bent over to an angle that made you think there would be a loud cracking and splintering of wood at any moment.  Fortunately, the storm was short-lived in Liverpool and moved on to wreak havoc inland.  Bungee jumping would have been very hazardous!

The number of violent storms appears to be increasing and the graphic shows the number of storms in the Atlantic basin since 1850.  Although there is a lot of scatter in the data, there is a clear concentration in the last couple of decades of years with fifteen of more named storms, which suggests there has been more energy in the weather systems in recent years.  The primary source of this energy is the temperature of the oceans and atmosphere.  There is a good account of the development of storms cells in Manuel Delanda’s book ‘Philosophy and Simulation: The Emergence of Synthetic Reason‘, see chapter 1 – The Storm in the Computer, which is available via Google Preview.

The increased frequency of high-energy storm systems is a very apparent manifestation of climate change that is having an impact on many people.  Yet, some governments refuse to even consider the possibility that our climate is changing and that they need to lead our society in discussing and planning strategies to mitigate the impacts.  It reminds me of the saying, attributed to Henri Poincare: ‘To doubt everything, or, to believe everything, are two equally convenient solutions; both dispense with the necessity of reflection.’