Gravity waves influence weather and climate

In fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the ocean, which gives rise to wind waves. –source

From GOETHE UNIVERSITY FRANKFURT

FRANKFURT. Gravity waves form in the atmosphere as a result of destabilizing processes, for example at weather fronts, during storms or when air masses stroke over mountain ranges. They can occasionally be seen in the sky as bands of cloud. For weather forecast and climate models, however, they are mostly “invisible” due to their short wavelength. The effects of gravity waves can only be taken into consideration by including additional special components in the models. The “MS-GWaves” research unit funded by the German Research Foundation and led by Goethe University Frankfurt has meanwhile further developed such parameterizations and will test them in the second funding period.

Although gravity waves have comparatively short wavelengths of between just a few hundred metres and several hundred kilometres, at times they influence the transport of water vapour as well as large-scale winds and temperature distributions to a considerable degree. This effect is strongest in the upper layers of the atmosphere. These, in turn, have such a strong effect on the lower layers too that a realistic modelling of weather and climate in the atmosphere is impossible without giving due consideration to gravity waves. Gravity waves also play a significant role for air traffic in predicting turbulence and are an important factor in weather extremes, such as heavy rain or storms.

Gravity waves form in the atmosphere as a result of destabilizing processes, for example at weather fronts, during storms or when air masses stroke over mountain ranges. They can occasionally be seen in the sky as bands of cloud. For weather forecast and climate models, however, they are mostly ‘invisible’ due to their short wavelength. CREDIT Gerd Baumgarten

In the first funding period, the ten research institutes participating in the project documented in detail the formation of gravity waves in one of the largest measuring campaigns ever undertaken, using radar, high-performance lasers, rockets and research planes as well as through laboratory tests. They also refined the hypothesis on the formation and dispersion of gravity waves to such an extent that their development can now be reproduced much more reliably in high-resolution numerical models too.

In a further step, the research unit led by Professor Ulrich Achatz of the Department of Atmospheric and Environmental Sciences at Goethe University Frankfurt has used these findings to improve parameterizations, which serve to describe the influence of gravity waves, in weather and climate models with typically coarser resolution. They have refined the weather and climate model ICON used by Germany’s National Meteorological Service (DWD) and the Max Planck Institute for Meteorology. The new model, UA-ICON, allows more precise predictions for the upper atmosphere and can be operated with different resolutions, so that gravity waves can either be simulated in it for test purposes or must be parameterized in the operational mode. The advanced parameterizations are now being integrated in this model and tested in the second funding period.

The project will also focus on impacts on weather prediction and climate modelling. An important aspect in this context is a better description of the interaction between gravity waves and ice clouds (cirrus), undertaken in cooperation with the University of Mainz. It could well be that this plays an important role for the climate.

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44 thoughts on “Gravity waves influence weather and climate

  1. Gravity waves are of many types, and those called Planetary waves are a type of Rossby waves produced mainly at mid-latitudes in the Northern Hemisphere from the interaction of the atmosphere with orographic ranges. They are extremely important in the mediation of the solar variability and Quasi-Biennial Oscillation effect on climate. During solar minima during the NH winter, when the QBO is in east phase, Planetary waves are deflected and break against the polar vortex and the polar night jet producing sudden tropospheric warming events and destabilizing the polar vortex. The result is that masses of cold dense air that are maintained by the low pressure associated to the polar vortex in the Arctic drift southward producing very cold winters and blocking conditions in the NH winter.

    Thus among many things, gravity waves mediate the climate response to solar variability.

    Climate models do poorly the stratosphere, and do not include the middle and upper atmosphere, so they can’t deal with the climate variability associated to their phenomena that is wrongly attributed to… you guessed it, anthropogenic effects.

      • Oh, yeah?

        Show it. You won’t because you know you’ll be laughed off the board by your scientific betters.

        Why do you even make such obviously ridiculously false assertions?

      • Right. So good that out of 31 CMIP-5 models, only 5 have a (quite poor) spontaneous QBO, while 25 do not include any sort of QBO which is the most prominent stratospheric phenomenon.

        Table 1 of:
        Mitchell, D. M., et al. “Solar signals in CMIP‐5 simulations: the stratospheric pathway.” Quarterly Journal of the Royal Meteorological Society 141.691 (2015): 2390-2403.
        http://onlinelibrary.wiley.com/doi/10.1002/qj.2530/full

        Your concept of quite good appears to be typical for a climate modeler.

      • “quite good” is equivalent to Zeke Hausfather’s “quite well” to describe climate models’ reproduction of recent rates of warming. Quite well can also be called quite poorly, it’s a half filled glass. It is a totally unqualified, unscientific expression of appreciation which tells up more about the speaker’s innate bias than it does about the performance of models.

  2. Yet another thing left out of CMIP5, which for coarse climate model purposes will have to be parameterized, which will yet again drag in the attribution problem, which is why models run hot (see guest post of same name for details). They should have realized by now the basic problem is insoluble, and no amount of additional bandaids is going to help.

      • Yes, the system is too complex to be modelled, this fundamental reality was pointed out years ago by Dr Christopher Essex. Adding another bunch of fiddle factors only increases the likelihood of producing an apparently good fit to the data which does not match the physical mechanisms of the real world and which had ZERO reliability for predicting future change.

        We are all familiar with these gravity waves which strongly resemble the ripples in sand on the beach during a receding tide. All fascinating stuff.

        What would be more relevant to climate is the effect that aircraft contrails have on climate and this happens at the same level in the atmosphere under similar conditions. Currently we don’t seem to even know the net effect of contrails : whether they are net warming or net cooling.

        This is certainly one level of the atmosphere which could merit better understanding of cloud formation and the effect of those clouds.

    • In other words, the coarse model mesh problem, i.e. where tha actual physical mechanism operates at a scale far smaller than the mesh grid of the so called ‘models’, is solved by a ‘fudge factor’. Do these IPCC turkeys appreciate that coarse meshes can readily converge to false ‘solutions’ driven not so much by the underlying maths but by the mesh geometry and the iterative solution mechanisc? I think they do but that would really be “An Inconvenient Trusth” wouldn’t it?

    • I know that the mackerel sky phenomenon is caused by atmospheric waves, but don’t know if those are gravity waves or not. I suspect so, however.

      • I’ve seen them in various parts of the world, including the northern US, but not that often. I’d like to see them more. You’re lucky.

      • Don’t think they are gravity waves. Gravity has been shown to propagate at the speed of light. At the speed of light, a wavelength of 1 km infers a frequency of 300 Khz and a period of 3.3 us which seems unlikely for moving matter in clouds. It could be a VLF sonic effect, where sound is about a million times slower, so a 1 km period wave infers a frequency of about 0.3 Hz and a period of 3.3 seconds, which seems more reasonable …

      • CO2,

        You too are confusing gravity waves with gravitational waves. Despite the similarity in names, they are totally different phenomena. Atmospheric gravity waves, or the same thing in other fluid dynamic situations, are density waves. Einsteinian gravitational waves are a completely different animal altogether. Their medium is the space-time continuum, not an atmosphere, ocean, or even assemblages of solar systems in a spiral arm of a galaxy.

      • Sixto,
        What you’re talking about is related to pressure and density waves propagating at the speed of sound and has absolutely nothing to do with propagating gravity. While the moving matter of air and clouds does have a gravitational wave signature, the magnitude is far, far to small to be measured or noticed, directly or indirectly. Gravitational waves and gravity waves for all intents and purposes refers to the same thing which is the dynamic behavior of the force of gravity consequential to varying or propagating mass. Using gravity combined with waves in the name of this phenomenon is absolutely wrong and this misappropriation of terms happens far too often.

        Science should be precise and misapplying terms only adds confusion and wiggle room for supporting bogus claims. This is like so much else in climate science where terms with a precise meaning and implications are bastardized and reused to refer to something different while retaining the same implications. Feedback, forcing and sensitivity are other examples of terms subverted to retain their implications while those implications are either impossible or otherwise irrelevant to how the climate actually behaves.

  3. A falling leaf in Amazon can later create a hurricane in Maine. Now we need money for gravity waves modelling.

  4. These waves must occur at a boundary layer. The boundary is usually a density jump between two abutting layers. Creating these waves requires significant amounts of energy. Often the Froude number is used to determine correlations between wave energy creation from flow velocities. Furthermore surface waves can be compounded by superimposing other gravity induced waves from adjacent density layers.
    This can be readily observed by watching the ocean surface on a mildly breezy day. Rows of “ruffled water” will appear between smoother stretches. The smooth stretches are peaks of subsurface higher density halocline layer waves cresting up to the surface boundary with the air. The higher density water is less effected by the breeze and will not “ruffle” as easily as the lower density surface waters.
    I might suspect that atmospheric clouds will behave similarly with the lower density regions collecting the clouds.

    • “These waves must occur at a boundary layer.”
      Not really. You need a gravitational density gradient. A converging flow has to be able to build up potential energy, which can then be converted to kinetic energy when the flow diverges again. That happens, and is included in the Navier-Stokes equations of the GCMs. What this report leaves out is what effects the gravity waves have on weather and climate. The answer is, not much. They can’t shift much energy, or anything else, over long distances.
      Sea waves are an analogy. In open sea, they just make things bob up and down. Something floating won’t be carried anywhere else by waves alone. They do have effects at the shore, oil platforms etc. The weaker analogy in the atmosphere are mountain ranges, where you can see some odd effects. But there isn’t much effect on weather, let alone climate. The ups and downs can make cloud patterns, and even maybe trigger a bit of rainfall.

      • What this report leaves out is what effects the gravity waves have on weather and climate. The answer is, not much.

        Not true. Lindzen and Holton proposed and was later demonstrated that gravity waves are responsible for the existence of the QBO, and the QBO is one of the stratospheric phenomena that most affects climate.

        Gravity waves transport momentum and energy from the troposphere to the stratosphere and higher. From the polar vortex to the sudden stratospheric warming events, and the strength of the polar night jet, they are all affected by gravity waves.

      • Javier,
        “Lindzen and Holton proposed and was later demonstrated that gravity waves are responsible”
        Not exactly. Ordinary gravity waves have much higher frequency. Here, from their 1972 update, is their description:

        “Forced by waves… propagating upwards”. But if you want to argue that that is still gravity, then, because of its low frequency, it is well resolved by GCM’s, which could represent them for QBO even back in 1996.

      • They can’t shift much energy, or anything else, over long distances.

        That is not the point Nick. It is not about transporting energy, it is the effect these clouds have on the energy budget. Stratospheric clouds reflect and diffuse sunlight. They also have an impact of outward flow of LWIR.

        While the ripples are very in pretty, I don’t think the waves themselves are very important. It is the critical conditions at the boundary of two air masses which determine the extent of cloud formation which matters. In trying to model the waves they will primarily be confronted with modelling these conditions and assessing their impact.

        When they have mastered that they should be able to model the effect of contrails from commercial aircraft which IMO will be far more significant than the presence of natural ripples.

        There are many days in mid-latitude regions where contrails provoke a significant percentage of the sky to be covered with cirrus cloud which would not otherwise have formed , or may have formed much later in the day. No one has assessed the impact of contrails and thus the TRUE impact of commercial aviation. Despite all the wailing about CO2 , it may actually have a cooling effect.

      • Don’t get interesting on me, Nick.

        https://en.wikipedia.org/wiki/Quasi-biennial_oscillation

        “The precise nature of the waves responsible for this effect was heavily debated; in recent years, however, gravity waves have come to be seen as a major contributor and the QBO is now simulated in a growing number of climate models. [3] [4] [5]”

        3. Takahashi, M. (1996). “Simulation of the stratospheric Quasi-Biennial Oscillation using a general circulation model”. Geophys. Res. Lett. 23 (6): 661–4. Bibcode:1996GeoRL..23..661T. doi:10.1029/95GL03413.

        4. Scaife, A.A.; Butchart, N.; Warner, C.D.; Stainforth, D.; Norton, W.; Austin, J. (2000). “Realistic quasi-biennial oscillations in a simulation of the global climate”. Geophys. Res. Lett. 27 (21): 3481–4. Bibcode:2000GeoRL..27.3481S. doi:10.1029/2000GL011625.

        5. Giorgetta, M.; Manzini, E.; Roeckner, E. (2002). “Forcing of the quasi-biennial oscillation from a broad spectrum of atmospheric waves”. Geophys. Res. Lett. 29 (8): 861–4. Bibcode:2002GeoRL..29.1245G. doi:10.1029/2002GL014756.

  5. A more complete analysis would refer to the boundaries between air parcels of differing densities in relation to which the effects within a convecting atmosphere are infinite on every scale. Weather fronts are just one example of such a boundary. Another is the boundary between the different atmospheric layers such as troposphere and stratosphere. Yet another is the boundary between a cloud and the surrounding clear air.
    Such effects are the mechanism whereby convection neutralises radiative imbalances so that the hydrostatic equilibrium of an atmosphere can be maintained indefinitely at any given level of external insolation.
    If radiative imbalances were ever to disrupt hydrostatic equilibrium then the atmosphere would eventually be lost.
    AGW theory proposes that a new equilibrium is set at a higher surface temperature when GHGs increase but a new equilibrium cannot be set because any such proposed new equilibrium would permanently upset the balance between the upward pressure gradient force and the downward force of gravity. Either the atmosphere would expand indefinitely (if the net effect of GHGs is warming) and be lost to space or it would contract indefinitely (if the net effect of GHGs is cooling) and fall to the ground as a congealed solid.
    The net effect on hydrostatic balance at any given level of insolation by the radiative effects of GHGs must be zero.

  6. Javier said:

    “Thus among many things, gravity waves mediate the climate response to solar variability.”

    Absolutely right.
    Extend the logic to realise that they mediate the climate response to everything that would otherwise serve to disrupt hydrostatic equilibrium.
    So, one can concede that human emissions might affect global air circulation patterns INSTEAD OF changing surface temperatures but due to the vastly greater effects of solar and oceanic variability we could never notice or measure it.

  7. I thought gravity waves were a distortion of space time brought about by the interaction of 2 mega massive bodies of mass.

  8. TSI/(4/3)=4/3*(8g^2)
    4/3pi*r^3=volume of a sphere
    g expressed as g^2 is thermal resistance in units Nm^2 instead of Nm for a force in a point. Nm^2 is equal to watts per square meter.

  9. Oh, here you go.

    grav·i·ty wave (noun) PHYSICS plural noun: gravity waves
    1.another term for gravitational wave.
    2. a wave propagated on a liquid surface or in a fluid through the effects of gravity.

    That should settle the issue, shouldn’t it?

    • IMO it’s better to use the technical term “gravitational wave” to refer to the space-time phenomenon, to avoid confusion with gravity waves in atmospheres or other media.

    • I don’t like the name much either, but it is what it is. I much prefer referring to waves as either transverse waves or compression waves. These are transverse waves.

  10. It seems self evident that in a massive planetary body with a wispy gas atmosphere that the effects of both the static force field of its own gravity and also variations from other celestial objects will both have a significant effect on climate.

    Who else here remembers this comment from (how ironic!), BigWaveDave:

    “Because the import of the consequence of the radial temperature gradient created by pressurizing a spherical body of gas, from the inside only, is that it obviates the need for concern over GHGs”

    What we need to do is to conduct some experiments both in the lab and in the field to look into what gravity is really doing to our own atmosphere. No one can argue with doing well designed repeatable experiments, can they?

    • It is reasonably easy to deduce the effect of gravity on the atmosphere from the gas laws. The effect of moving volumes passing each other was described by Rossby.

    • The Reverend Badger
      September 21, 2017 at 1:38 pm:

      Yes, Rev, and where they have been done (eg Konrad Hartmann, tallblokes blog; Hockey Schtick; Mylar balloon expt, Berthold-Klein etc.), they show zero GHE from any gases. As the Gas Laws insist under the Poisson Relationship…..

      So, we do need more of this, never tried by the climate mafia.

  11. So this phenomenon has always existed? Or has it appeared in our skies with the new cloud types which have been introduced to us during the past decade? Which I think is ridiculous. Are you really scientists?

  12. oscillations driven by fluctuating pressure in air flow once it hits a blocker and is redirected creates waves, I can do this with an air blower and smokey air, it creates waves.

  13. Mackerel sky or herringbone, moving equatorial air running over cooler, showing early collisional vortices with staggered condensation/evaporation effects from uplift I guess?. Sign of strong northerly winds, often rain in 3 days or so here in the south pacific. Those martian shots – awesome. Educational too, remembering that martian air is analogical to our stratosphere or higher. Which also has clouds, IIRC?

  14. But our problem is not with meteorologists, but with climato-political marxists with a sort of Munchausen Syndrome. And their hangers-on like Mosh.

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