Met Office fakes the Foehn effect

Posted: October 24, 2018 by tallbloke in atmosphere, general circulation, Incompetence, MET office, Thermodynamics, weather, wind

Descending air in the atmosphere rises in temperature as it is adiabatically compressed in the pressure gradient created by gravity acting on atmospheric mass. This has been known for centuries. However, the MET Office has decided to do away with this fundamental fact of physics in a short video it has produced.

Even their own website page on the Foehn effect (now safely screenshotted and web-cited) tells us:

“ foehn air… becomes warmer and drier on the leeside after it is compressed with descent due to the increase in pressure towards the surface.”

So why would the MET Office miss out one of the principle causes of the Foehn Effect in its info-video they tweeted out? Is it that the MET Office is staffed by people who don’t understand the basic thermodynamics of meteorology these days?

Or could it be they don’t like Ned Nikolov and Karl Zeller’s discovery that adiabatic heating in the pressure gradient is the cause of the ‘greenhouse effect’ rather than trace gases like water vapour and carbon dioxide.

I made an info-graphic  by modifying the NASA energy budget to show how adiabatic compression heating is an important factor missed off by climate scientists in their models. They don’t account for the way descended air heated by adiabatic compression will impede the surface-air conduction rate by lowering the temperature differential.


It looks like the propaganda war to deny this critical omission has started. I wonder if the MET Office webpage containing the vital information about the Foehn effect will get edited. Perhaps not now I’ve web-cited it and documented this attempt to erase the gravito-thermal effect of convection.


  1. tallbloke says:

  2. Phoenix44 says:

    I am confused by this. If IR radiation is not important, then why are the Poles very cold in winter? Just the lack of direct warming?

  3. Ned Nikolov says:

    There seems to be really no legitimate excuse for the Met Office to misrepresent so egregiously the fundamental pressure-heating mechanism of Foehn winds (called Chinooks in North America:

    As Roger suggested in the above post, I think the Met Office probably got wind of our discovery about the thermodynamic (non-radiative) nature of the so-called “atmospheric Greenhouse effect”, and is now actively trying to avoid any mentioning of adiabatic heating caused by increasing pressure… Their explanation for the warmth of foehn winds is simply ridiculous! In their video, they state that the absence of clouds on the leeward side of the mountain allows more solar energy to reach the ground and the turbulence of the descending air somehow causes further heating!!??

  4. Ned Nikolov says:

    Phoenix44, the Earth surface is not warmed globally and regionally by the downward IR radiation, but by the shortwave solar radiation, which the true external source of energy to the Earth system. The Poles receive much less solar radiation than lower latitude and especially than the Equator. Thus, they are the coldest regions on our spherical planet…

  5. oldbrew says:

    This was still on the internet recently…

    It’s on the Talkshop now.

    PS the Wikipedia entry on Foehn has much the same wording as the MetO site.

    But they call it ‘Isentropic draw-down (the draw-down of warmer, drier air from aloft)’.

  6. Pablo says:

    As I understand it, in a stable atmosphere there is an increase in potential temperature with height of 3ºc/km due to presence of water vapour.The air being 3ºc/km warmer than it should be for its height though still colder with altitude by 6.8ºc/km.
    How much of this is down to latent heat released by condensation or the ability of water vapour to radiate energy to warm the air above and so cool the air below is up for discussion.
    Turbulent mixing will restore this thermal imbalance to the gravitational adiabatic dry lapse rate of 9.8ºc/km and thus raise the surface temperature without any additional energy. This happens every morning within the boundary layer as turbulence
    starts mixing potentially warmer air from above with the colder below.
    If dry air blows over a mountain range without any turbulent mixing of air with a higher potential temperature from above it would increase temperature at the same rate on the descent as the ascent.

  7. Pablo says:

    …it would increase temperature at the same rate on the descent as… it cooled on… the ascent.!

  8. cognog2 says:

    Lenticular clouds that you see static on top of mountains are a good example of what is happening here. In fact although the cloud appears static the wind is still passing through it. Adiabatic de- compression on the windward side decreases the temperature and causes condensation. Hence the cloud. On the lee side the opposite occurs and the cloud disappears. Meanwhile the wind passes on.

    The prime interest here is that it is gravity which ultimately determines the temperature albeit in conjunction with the properties of water where phase change takes place at constant temperature and generates buoyancy which transports the Latent Heat upwards in opposition to the adiabatic compression factor.

    CO2 and Radiation are irrelevant here; for it is purely a matter of where the enthalpy lies. Temperature or Latent Heat. Take your pick.

  9. oldbrew says:

    Foehn chart for the Alps [see website for actual chart]

    The forecasted pressure gradient (unit hectopascal, hPa) between Bolzano in northern Italy and Innsbruck in Austria shows the strength of foehn winds over the Alps. If we have a positive pressure gradient, that means the surface pressure in Innsbruck is lower than in Bolzano, south foehn comes up in the Austrian Alps (wind from south). The intensity of foehn winds increases with larger pressure gradients.

    Empirically we need at least a pressure gradient of 4 hPa for the breakthrough of foehn winds in most alpine valleys and at least 8 hPa for the breakthrough in the adjacent lowland.

    The forecast is based on model output statistics (MOS) by Meteomedia and is updated every hour.
    – – –
    That’s the entire entry for the above website, under that title.

    Here’s the entry for Vienna:
    The west wind in the Vienna region is canalised along the Danube in Upper Austria and overflows the Vienna Woods. The strength can be estimated by considering the difference of the air pressure between the Inn-area in Oberösterreich and the Burgenland. Statistical evaluation shows that the difference of the air pressure has to be at least 4 hectopascal, to have strong winds in a large area.

  10. oldbrew says:

    In a nutshell…

    Foehn Winds That Produced Large Temperature Differences near the Southern Appalachian Mountains
    David M. Gaffin
    National Weather Service, Morristown, Tennessee

    1. Introduction
    Foehn winds are commonly observed in the lee of large mountain ranges and are typically associated with large temperature increases and relative humidity decreases due to adiabatic compression of the descending wind.
    – – –
    Changes in temperature caused by the expansion (cooling) or compression (warming) of a body of air as it rises or descends in the atmosphere, with no exchange of heat with the surrounding air.

  11. John P says:

    seems pretty clear to me what they think? from the 50 second mark to 1 minute and 10 seconds

  12. tallbloke says:

    Good Spot John P!

  13. tallbloke says:

    Stephen: N & Z don’t explain it in their paper because it’s not their job to be explaining well known meteorological effects to atmospheric scientists!

  14. Rog,

    I haven’t seen a source anywhere else that describes how the mechanism of adiabatic convection translates into a higher than S-B temperature prediction for the entire surface area of a rotating planet. It doesn’t seem to be well known to anyone otherwise the radiative theory would never had been so broadly accepted and if it had been I wouldn’t have needed to create such a description.

  15. oldbrew says:

    Weather Warning
    Issued by the Met Office
    YELLOW WARNING OF SNOW for ‘Central, Tayside & Fife’, ‘Grampian’, ‘Highlands & Eilean Siar’

    Updated 26 October at 1043 BST

    Valid from 2000 BST on Fri 26 October to 1100 BST on Sat 27 October

    Hail, sleet and snow showers will leave surfaces prone to patchy ice, together with slushy snow over some upland routes.

    – Probably ice on some untreated roads, pavements and cycle paths, making accidents and injuries more likely

    – Some roads and railways likely to be affected with longer journey times

    [From BBC weather warnings]
    – – –
    ‘Hothouse Earth’ gone AWOL.

  16. ren says:

    Stratospheric intrusions in the winter bring very cold air from the north.
    The level of the tropopause is lowered.

  17. ren says:

    Along with the dry air, Stratospheric Intrusions bring high amounts of ozone into the tropospheric column and possibly near the surface.

  18. Ned Nikolov says:

    Apparently the Met Office understands pretty well the adiabatic (pressure-induced) heating as explained in this video about the mechanism of “Sudden Stratospheric Warming” by Adam Scaife, the Head of Seconal to Decadal Forecasting:

    Note what he says at 1:00 min “So, there is no heating going on as such, but you are compressing the air and, therefore warming it, and temperature can rise by as much as 50 degrees in just a few days

    Our research has shown that the entire Atmospheric Thermal Effect (a.k.a. “Greenhouse Effect”) on any planet and moon (including Earth) is a form of compression heating. Hence, it is independent of atmospheric composition!

    Click to access New-Insights-on-the-Physical-Nature-of-the-Atmospheric-Greenhouse-Effect-Deduced-from-an-Empirical-Planetary-Temperature-Model.pdf

  19. “Our research has shown that the entire Atmospheric Thermal Effect (a.k.a. “Greenhouse Effect”) on any planet and moon (including Earth) is a form of compression heating. Hence, it is independent of atmospheric composition!”


    I have been saying that for years and have created a clear description of the mechanism involving conduction and convective overturning.

    The point is that convective overturning of gases cannot be prevented above an unevenly heated surface beneath an atmosphere. The concept of an isothermal atmosphere as proposed by Roy Spencer and others is physically impossible because such overturning involves conversion of KE (heat) to PE (not heat) in rising columns and the reverse in falling columns.

    Such overturning obviously represents a slower rate of energy transfer than radiative transmission so the process of overturning introduces a slowdown in the rate of radiative energy transfer through the system and surface temperature must rise above the purely radiative S-B prediction.

    An ‘additional’ energy store is needed at the surface to sustain continuing convective overturning in addition to sustain radiation escaping to space at the same rate as radiation comes in from space.

    The reason that density serves as a good proxy for the amount of temperature rise is because greater density increases the efficiency of conduction between surface and atmospheric gases.
    The presence of the lapse rate slope provides a marker in the vertical plane which shows the changing effect with density of conductive efficiency relative to radiative efficiency.

    As one descends along the lapse rate slope the thermal effect of conduction gradually increases relative to that of radiation with a consequent rise in temperature.

    An atmosphere reaches long term hydrostatic equilibrium when radiation and conduction are perfectly balanced on average and any imbalances are then neutralised by convective adjustments.

    That is the real cause of the greenhouse effect and it is nothing to do with radiative gases.

  20. John P says:

    A late response but interesting and relevant to NED i believe. This from the Met office. How to form a cloud in a bottle. A continual reference to pressure and temperature