A retrospective, Climate Audit and the late Prof. Kreiss

Posted: July 8, 2016 by tchannon in Forecasting, general circulation, Maths, Obituary

Tim writes,

Published 27th February 2016 Climate Audit published a small article in honour of Kreiss to do with atmospheric modelling, the hydrostatic balance… or not.

Comments follow from Names. I think the comments are worthy of a read and decode by Talkshop readers who have an interest in this kind of topic.

Gerry Browning: In Memory of Professor Heinz Kreiss

Gerry Browning writes:

The Correct System of Equations for Climate and Weather Models

The CA article is old, do not comment as though current.


Post by Tim

  1. ren says:

    Hydrostatic equilibrium is a fact, and the tropopause lifted and descends depending on the pressure.

  2. Gerald Browning says:

    The large scale motions of the atmosphere are in approximate hydrostatic balance. However the primitive equations that assume exact hydrostatic balance are not the system that accurately describes the large scale motions of the atmosphere to first order. In fact they are mathematically ill posed for both the initial value and initial/boundary value problems. I recommend looking at the following link to see how bad the primitive equations are and how numerical trickery is being used to uncouple the noise caused by Richardson’s equation from the large scale geopotential.


  3. tchannon says:

    IIRC this harks back to Essex’s seminal papers which are essentially about tending to something exact but never is exact, always an approximation. This kind of thing is unstable.

    A long time ago I dabbled with real world modelling / prediction / etc. as part of doing things. When practical computers arrived I had a lot to learn. This very much included finding out the hard way on what is rational.

    The upshot of this is not knowing the detail of or having experience of what these youngsters are doing with their climatic or weather toys but I don’t need to know, won’t work for rather obvious reasons they don’t get.

  4. Gerald Browning says:

    The correct system that describes the large scale atmospheric equations to first order of accuracy
    is well posed for both the initial value and initial/boundary value problems as is the multiscale hyperbolic system introduced by Browning and Kreiss (2002). The multiscale system has also been proved to accurately describe the large scale and mesoscale atmospheric motions. This cannot be done for the hydrostatic system.


  5. Roger Clague says:

     Browning says;

    hydrostatic balance, i.e., balance between the vertical pressure gradient and gravitational force,

    There is no hydrostatic balance

    The vertical pressure gradient of the atmosphere does not produce a force.
    The horizontal pressure gradients produce wind. That is air moves to try to equalize pressure
    Vertically the pressure gradient, the lapse rate, is stable.. There are not large vertical movements of air, wind, trying to to equalize vertical pressure differences.
    There is no vertical pressure gradient force

    Also the atmosphere does not cause downward gravitational force. This is proved by the zero reading on a force meter placed on a solid flat horizontal surface.

    No vertical upward pressure gradient force
    No downward gravitational force
    Therefore no hydrostatic balance

  6. Roger Clague says:

    ren says:
    July 8, 2016 at 4:51 pm
    Hydrostatic equilibrium is a fact, and the tropopause lifted and descends depending on the pressure
    Please explain how “the tropopause lifted and descends depending on the pressure” is evidence for hydrostatic equilibrium