The physics of clouds

From the University of California – Santa Barbara

cloud streets

Cloud streets — long rows of cumulus clouds oriented parallel to the direction of the wind — are an everyday example of natural turbulent convection. Credit: MODIS Rapid Response Team at NASA GSFC

A UCSB physicist’s experimental results disprove long-held ideas about turbulence

In 1941, Russian physicist Andrey Kolmogorov developed a theory of turbulence that has served as the basic foundation for our understanding of this important naturally occurring phenomenon.

Turbulence occurs when fluid flow is characterized by chaotic physical changes. Kolmogorov’s theory has been interpreted to imply that transitions from one state of turbulence to another must be a smooth evolution because very intense fluctuations that are part of the process itself would smooth out anything sharp.

Now, however, a new experiment conducted by physicists at UC Santa Barbara disproves this interpretation of Kolmogorov’s theory. Their results appear this week in the journal Physical Review Letters.

“In our paper we offer experimental evidence that these transitions are indeed sharp,” said Guenter Ahlers, a professor in UCSB’s Department of Physics. “We have been enlightened by these data and they have shown us that the interpretation of Kolmogorov was incorrect. To a physicist that is a very important step forward.”

Ahlers and his postdoctoral co-workers Ping Wei and Stephan Weiss study turbulent convection, which plays a major role in numerous natural and industrial processes. Turbulent convection results when a contained fluid is heated from below and cooled from above. As the temperature differential increases, the convective flow becomes so vigorous that the velocity field becomes turbulent.

Using a cylindrical rotating system built by Ahlers’ team, the researchers heated the fluid from the bottom so it expanded and became less dense than the liquid at the top. Earth’s gravity caused the liquids to change positions with each other, which in turn created turbulence. Then the scientists added rotation.

“When you rotate, you get new forces acting, including the Coriolis Force — a product of the Earth’s rotation as well as of rotation in the laboratory — which spins the liquid into little vortices or tornadoes,” explained Ahlers.

“So the system is full of little tornadoes near the heating plate and also near the top — only there, they are cold tornadoes,” Ahlers added. “At first, these tornadoes are not connected because they are relatively short. But as you rotate the cylinder faster and faster, the tornadoes extend and eventually form columns over this whole system. When that happens, physicists say that the symmetry of the system changes.”

The next step for Ahlers and his team was to measure the heat transport — the exchange of thermal energy — which is expressed by the Nusselt number. Wilhelm Nusselt was a German engineer in the early 1900s who measured the heat transport through double window panes.

“If you look at the Nusselt number, it has these breaks, which indicates that the heat transport does not change smoothly as the rotation rate is increased,” Ahlers said. “By the way, Lev Landau told us that a long time ago. And while Landau wasn’t talking about turbulent systems, his arguments can be directly carried over to the turbulence state.”

Ahlers was referring to another Russian physicist, and a Nobel laureate, who theorized that when the symmetry of a system changes, the change must be sharp. It cannot be smooth because a system has only two states: disordered or ordered and there is nothing in between.

“The trouble is that people in turbulence never thought about Landau because he was in a completely different field and the information doesn’t get carried across because there’s just too much of it,” Ahlers added. “But I worked in the field of critical phenomena for many, many years and know Landau’s work very well. Then I changed to studying turbulence, and when this issue popped up, it was obvious to me what was going on.”

In the paper, the researchers use cloud streets — long rows of cumulus clouds oriented parallel to the direction of the wind — as an everyday example of natural turbulent convection. These flat-bottomed, fluffy-topped clouds are formed when cold air blows over warmer waters and a warmer air layer (temperature inversion) rests over the top of both.

As the comparatively warm water gives up heat and moisture to the cold air above, columns of heated air called thermals naturally rise through the atmosphere. When the rising thermals hit the warm air layer, they roll over and loop back on themselves, creating parallel cylinders of rotating air that act similarly to the fluid in Ahlers’ cylindrical rotating system. While the process sounds smooth, Ahlers’ latest experiment proves that it is anything but.

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117 thoughts on “The physics of clouds

  1. “If you look at the Nusselt number, it has these breaks, which indicates that the heat transport does not change smoothly as the rotation rate is increased,”
    By extension, Is this an explanation for the common eye wall collapse and a new eye-wall forming in the most intense tropical cyclones?

    • So the system is full of little tornadoes near the heating plate and also near the top — only there, they are cold tornadoes,” Ahlers added. “At first, these tornadoes are not connected because they are relatively short. But as you rotate the cylinder faster and faster, the tornadoes extend and eventually form columns over this whole system.

      From hurricanescience.org:
      http://www.hurricanescience.org/images/hss/HurricaneCrossSectionwithWinds2.jpg
      The winds in a hurricane/TC follow the isobar lines, with conservation of angular momentum and tightening pressure gradients.
      http://www.hurricanescience.org/images/hss/HurricaneIsabel12Sept2003.jpg
      figure legend: Defense Meteorological Satellite Program (DMSP) image of Hurricane Isabel at 1315 UTC 12 Sep 2003. The “starfish’ pattern in the eye is caused by the presence of six mesovortices – one near the eye center and five surrounding it. Image credit: University of Wisconsin-Madison, Space Science Engineering Center, Cooperative Institute for Meteorological Satellite Studies (CIMSS).

      “Eyewall replacement cycles can have very serious consequences, especially when they occur just before landfall. At great cost to life and property, Hurricane Andrew (1992) unexpectedly strengthened to a Category 5 hurricane while making landfall in southeastern Florida immediately following an eyewall replacement cycle. In addition to large and rapid intensity swings, eyewall replacement cycles usually cause hurricanes to grow larger. This occurred as Hurricane Katrina moved through the Gulf of Mexico, resulting in a much larger and more dangerous storm threatening New Orleans. During landfall, larger hurricanes do more wind damage, but they are also accompanied by greater storm surge and wave heights due to increased wind fetch. When multiple eyewall replacement cycles occur, the hurricane can continue to grow larger with each cycle. Hurricane Igor (2010) went through multiple cycles and became one of the larger Atlantic hurricanes on record, causing significant waves and rip currents along the U.S. east coast, even while staying far out to sea.”
      source: hurricanescience.org

      • Emphasis should be noted on the ” In addition to large and rapid intensity swings, eyewall replacement cycles usually cause hurricanes to grow larger.”
        And “rolling overand looping back on itself is beginning of the outer wall organization. The cycle completes and the hurricane grows stronger (dissipating more energy).
        The abrupt energy transitions allow for reorganization and thus more work on the system.

  2. It is most gratifying to see untainted science at work. The climate is far too important a subject to understand to let it wallow in it’s current political morass. Now is the time to continue the discovery process. When our levels of understanding are far greater than they are now, we can reflect on and determine any appropriate actions…

  3. Very nice. The formation of thunder heads and downdrafts and all that convective weather is in the same boat. You can watch it happen in the summer south.
    I saw a few clouds form up into rows, then the rows form into groups. With some spin it could have made tornados or cyclones. Clouds are a key missing bit.

    • When I was a boy growing up on the prairie, I first noticed that thunderheads collapsed in the evening when the Sun was low in the sky and a cool breeze soon followed the collapse. That air was cool, because the thunderheads had transferred the heat many miles higher into the atmosphere (didn’t understand “why” at the time, though.)

      • The big ones that bust through the Tropopause and dump their heat into the stratosphere help to directly cool the planet. There’s nothing quite like the rain water-cooled, cleansed, and ionized fresh air of a summer thunderstorm after it has passed by.
        Even the ones that don’t make it, still indirectly cool the sun-warmed oceans (since that is Earth’s climate heat reservoir) by being part of the hydrological cycle.

  4. Makes sense. I have seen water heating and then boiling in a beaker on a hotplate. Convection to a certain point then that breaks down to bubbles from the bottom. This would indicate that there is a sharp transition from liquid to vapour state in isolated areas. The beaker of water never gradually moves from liquid to vapour.
    My observations when I was younger and working in a laboratory. They didn’t have the internet then and I didn’t spend my time going on reddit or looking at pictures of cats. I tended to look at the world around me and try to puzzle things out.

    • Alex , is this what you refer to?
      “Ahlers was referring to another Russian physicist, and a Nobel laureate, who theorized that when the symmetry of a system changes, the change must be sharp. It cannot be smooth because a system has only two states: disordered or ordered and there is nothing in between.”
      I am having a hard time understanding that there is no “boundary” area, to me there has to be a transformation even if it is at the minute particle levels IE electrons etc. Where am I going wrong? thanks any referrals I’d be happy to follow.

  5. Hilarious – assigning some kind of “constant” to cyclone and storm activity is nonsense. The rate of transport of heat through the atmosphere is subject to abrupt changes. Back to the drawing board muddlers!

    • Websites like wuwt fail to recognize that you can have all the wonderful arguments you wish but when the influence comes through the schools and classrooms of a nation then it is just killing time here in this forum and little else .
      In the late 17th century they lunged at a conclusion using newly invented accurate clocks and stellar circumpolar motion where the tethered the rotation of the planet directly to the daily return of a star to a fixed point and came up with the notion that 24 hour days and rotations fall out of step – something which is continued even to this day –
      “During one orbit around the Sun, Earth rotates about its own axis 366.26 times” Wikipedia
      http://en.wikipedia.org/wiki/Earth
      The rise and fall of temperatures within each 24 hour cycle should draw attention to the fact that such a notion is impossible for how else to account to temperature fluctuations and how we experience them –
      http://prairieecosystems.pbworks.com/f/1179343887/crerar%20temperature%20variation.jpg
      Common sense is all about dynamical knowledge, at least in this climate matter, and I have seen precious little of common sense over the years here or anywhere else.

      • I’m sorry, But I don’t understand what you are talking about. Your point (which may be valid) is a little obscure

      • Why would having a fractional day in a year be disproven by 24 hour days? That just doesn’t make sense.
        If the calendar has the wrong length of year, then the solar year and calendar year would drift. It wouldn’t drift on a daily basis. Look at the pre-Renaissance calendar, you would find the result. The Roman months were wrong by a few days, so the calendar year drifted apart from the solar year, and it wasn’t until the Calendar Reforms initiated around the time of Copernicus that the calendar was brought back to alignment with the sun.

      • First, there are, apparently no websites like WUWT (note awards, visits, eclectic subject matter) and second, your understanding of what WUWT ‘understands’ seems and odd criticism. If you are providing understanding with what you say (and it isn’t crystal clear that your are), then, automatically WUWT (readers), too, ‘understand’ and indeed, you were attracted to this site to provide understanding.
        Now what understanding have you brought to us from on high? It was a discovery for you that there is one extra rotation per year of the earth viewed from the sun? Surely you are not suggesting that the day and night we experience on reference earth needs correction – it automatically comes with the territory. When the sun ‘goes down’ we start to cool, ‘comes up’ we start to warm. The earth doesn’t care where it is in its orbit for determining these phenomena. Of course, I may have misunderstood your point entirely which would be your fault.

      • For the puzzled, Gkell1 is blathering on about the difference between a solar day and a sidereal day, although he really doesn’t understand the difference himself.
        For the earth to rotate one full revolution with respect to the distant stars, so that a given star would be in the same place in the sky the next night, takes about 23 hours and 56 minutes. This is known as a “sidereal day”. But during this period, the earth has moved almost one degree in its annual orbit around the sun, so it takes an additional 4 minutes or so until the sun is in the same place in the sky as in the previous day.
        This 24-hour period is known as the “solar day”, and for 99.99% of all purposes, it is the important one to deal with, so it is completely appropriate that our clocks are tied to the solar, and not the sidereal, day.
        However, for a physicist, there are some reasons to need to know the difference. One of our early space flights landed very far from the target, because the target calculations mistakenly used a solar day instead of a sidereal day to compute the speed of rotation of the earth.

      • There are a lot of people out there trying to propose predictions as facts using the vehicle of ‘climate change’ but they are doing so in an era where they assign the wrong number of rotations within the confines of an orbital circuit and that I find incredible . Look at the mistake based on the ‘solar vs sidereal’ fiction again in case you all missed it the first time –
        “During one orbit around the Sun, Earth rotates about its own axis 366.26 times” Wikipedia
        The parent observation is that the planet turns 1461 times within the confines of 4 orbital circuits which reduces to 365 1/4 rotations per circuit or in the human timekeeping format of 3 years of 365 rotations and 1 year of 366 rotations hence they merge to a close approximation at February 29th which represents both 24 hours of rotation and 24 hours of orbital motion.
        With nobody around to investigate the references used for timekeeping and the historical development, all that remains is the late 17th century mistake which proposes a hideous ideology of more rotations than days within an orbital circuit.

      • Well Curt, the idea was to bypass the central Sun as a fixed reference for rotation and use the average 24 hour day in order to determine the circumpolar return of a star to the same position 3 minutes 56 seconds earlier. They then allowed this 3 minute 56 second difference to accumulate and ended up with this notion that there is one more rotation than there are 24 hour days within an orbital circuit.
        The thing about is that the average 24 hour day is only valid within the 365/366 rotation format which includes February 29th so the observation and the circumpolar conclusion is invalid and meaningless.
        Go back to the temperature graph and you will discover there are 7 rotations in 7 days, a thousand rotations in a thousand 24 hour days or any other number you care consider. They created a train wreck in the late 17th century via the Ra/Dec framework which allows observers to predict astronomical events like eclipses and transits within the calendar scaffolding and it is this ‘predictions’ notion that has got humanity into a whole lot of trouble.
        In truth this all needs a thorough investigation and not snivelling acquiescence .

      • Gary Pearse ,
        +1
        His point is that it is impossible for the Earth to rotate 366.26 times around its axis over one orbit around the sun.
        His proof is that the temperature goes up and down every day.
        Furthermore, you can experience these fluctuations in temperature! QED

      • Curt wrote “For the puzzled, Gkell1 is blathering on about the difference between a solar day and a sidereal day, although he really doesn’t understand the difference himself.” Curt was being nice.
        So tell me, Gkell1, does the moon rotate on its axis? Please be sure to reconcile your answer with the fact that, from the earth, we only ever see one side of the moon.
        The sun rises and sets 365.26 times in a year. The earth rotates on its axis 366.26 times in a year. If you are unaware of those facts, or of the reason for the difference, you are uninformed. If you deny those facts, you are ignorant.

      • I am going to park all this even though it really needs to be sorted out. There is no point in blaming Wikipedia for a horrible ideology which is firmly implanted from one generation to the next through classrooms –
        ” It is a fact not generally known that,owing to the difference between solar and sidereal time,the Earth rotates upon its axis once more often than there are days in the year” NASA /Harvard
        http://adsabs.harvard.edu/full/1904PA…..12..649B
        When you all look at the graph where the temperatures rises as a location swings back into solar radiation and falls as it turns into darkness ,this is a property of one rotation. The evolution of frost/ice at a local level based on a turning Earth is founded on this principle whereas the evolution of Arctic sea ice is due to another rotation but this time writ large as a component of the orbital motion of the Earth.
        In truth, axial precession as a perspective needs to be modified to take account of the annual evolution of Arctic sea ice and this is how this fuss of ‘climate change’ is obliterated by introducing explanations people can understand . Remember now, although titled ‘axial precession’, the polar day/night cycle relies on the surface rotation of the entire planet to the central Sun and,in respect to the circle of illumination, the North/South poles will look like this –
        http://upload.wikimedia.org/wikipedia/commons/4/43/Earth_precession.svg
        Thanks to the moderator for not shutting me out.

      • To Mike M
        Before there was ‘climate change’ there was the controversy of the ‘moon’s rotation’ in the 19th century.
        http://books.google.ie/books?id=MfU3AAAAMAAJ&pg=PA27&dq#v=onepage&q&f=false
        There is a thread about ‘Earthrise’ but the truth the photo is taken from an orbiting spacecraft because common sense determines that it can’t be other than from spacecraft that the Earth comes into view.
        Some ideas grab hold of a certain personality every now and again,the idea of a spinning moon being one of them but the idea of more rotations than days is equally mindnumbing if not more so when so much discussion centers around rising and falling temperatures in this forum.
        The principles where timekeeping and the motions of the Earth mesh are exceptionally old but currently they all meet at February 29th and the seamless progression of days and rotations in respect to orbital circuits. You all should try to work these things out instead of trying to bait someone who just isn’t interested.
        Spinning moon indeed !.

  6. The science isn’t settled. And there’s the benefit of multidisciplinary experience. So nice that they’re citing experimental evidence.

  7. Could also explain the power within ‘Clear air turbulence’ (CAT) which can damage aircraft…..

    • Actually, the damage comes from abrupt changes in lift and/or when there is a lift differential between the left and right wings when entering and exiting drafts. When entirely enclosed within a draft the aircraft moves with it.

  8. The phenomenon may start as purely convective, but conditions in the boundary layer involve the release of latent heat, at which point chaotic flow seems to maximize, as any seasoned air traveler can tell you. It would seem logical that the release of latent heat in the boundary layer is connected to the moment of symmetry breaking within the system.

  9. Interesting, though the experiment with water still misses important variables when trying to model the atmosphere. This being the difference in “fluid” density or pressure from bottom to top. Then there is the the fact that engery transfer from the sun is occurring directly in the atmosphere as well as from conduction and convection from the surface. Truly a chaotic system and one humanity is a long way from properly understanding.

    • @wickedwenchfan March 12, 2015 at 12:29 am

      Interesting, though the experiment with water still misses important variables when trying to model the atmosphere.

      I agree with the above.
      Quoting article, to wit:

      Turbulent convection results when a contained fluid is heated from below and cooled from above.

      A contained fluid in a beaker or flask is in fact, a “semi-closed” environment …. wherein there are different “forces” acting upon the fluid, ….. whereas the atmosphere is an “open” environment which is not subject to the aforesaid “forces”.
      Thus, me thinks the researchers need to “re-think” their experiment.

      • However, isn’t the principal of carbon dioxide acting as a greenhouse gas from a “contained system” experiment by Aarhenius?

      • However, isn’t the principal of carbon dioxide acting as a greenhouse gas from a “contained system” experiment by Aarhenius?

        Indeed.
        And no-one has replicated any of those experiments in the open atmosphere. The models cannot deal with the uncontained atmosphere so deal with everything as instantaneous addition of CO2 to a ‘slab’ (i.e. contained) atmosphere. But then [when] does reality have to come into climate ‘science’,
        There are other issues with the experiment posted. Liquids have little expansion compared to gases when heated so there may be far more rapid changes due to convection. Also regardless of heat, addition of water vapor lowers the density of a volume of atmosphere as the H2O molecule is lighter than N2 or O2 and of course condensation removes those molecules from the gas laws. So the liquid model although useful is not an accurate representation of clouds or of their convection.

    • To the contrary, WWF, to study a system of the atmosphere’s complexity, you have to isolate the individual parts as best you can. It’s not completely applicable because it’s necessarily simplified. In short, it’s not a bug, it’s a feature that enables us to make direct observations of this isolated function. Otherwise, we’d never get anything completed.

  10. Using a cylindrical rotating system built by Ahlers’ team, the researchers heated the fluid from the bottom so it expanded and became less dense than the liquid at the top. Earth’s gravity caused the liquids to change positions with each other, which in turn created turbulence. Then the scientists added rotation.
    ==============
    It;s called a Taylor-Couette system –
    http://en.wikipedia.org/wiki/Taylor%E2%80%93Couette_flow
    You can see one in action demonstrating the same sharp transition to turbulence in this awesome video from 1989 (starting around 26:15):

    You also see zonal (Taylor Vortex Flow) and meridional (Wavy Vortex Flow) patterns emerge in the system–just like we see in our atmosphere.
    That’s something you don’t see in GCMs.

    • I haven’t read the paper, but I didn’t interpret this as a Taylor-Couette cell. Rather like a big cylindrical dish that mimics looking down on one hemisphere of the earth from above the pole. As a Taylor-Couette I have trouble visualizing how the Coriolis acceleration plays much of a role.

    • I’m reluctant to rely on a human’s perception of chaos versus order. In the rotating fluid example, we see chaos begin at a precise point, but a hawk watching the same turbulence might continue to see orderly patterns. Our pattern recognition is hard wired.

    • Using wikipedia for a source again. Instead, find the original source, look it up and actually read it to see if it makes sense. Best to avoid wikipedia in the first place.

  11. A lot of calculation required to include this new information into the climate models. Bigger computers will be needed for sure.

    • Also the cell size will have to be reduced. You just won’t see this phenomena on a 100kmX100km grid!

    • For air (kinematic viscosity = 1.42*10^-5, typical velocity = 10 m/s, model length scale = 1mm), the Reynolds number would be Re = 704, still high but getting close to the non-turbulent scale. i.e. our models would need to be at least 100km / .001m = 10^8 times smaller in length scale than existing climate models. Three spatial dimensions are being modeled and, by the CFL principle, the time scale would need to be similarly reduced and so, for 4 dimensions, a computer would need to be 10^32 times more powerful than existing state-of-the-art computers.
      According to Moore’s Law computer power doubles every 2 years. 10^32 = 2^106 approximately. Hence at the present rate of computer power growth, it will take at least 212 years before such modeling can reasonably be attempted. It seems unlikely that Moore’s-law-growth will continue exponentially for this length of time.
      Modeling climate by means of deterministic numerical models is like trying to work out thermodynamics by tracking the paths of individual molecules. Nevertheless modeling thermodynamics did ultimately prove possible using statistical mechanics. By analogy only stochastic models are ever likely to be successful in describing climate.

  12. Don’t overlook the huge difference between the thermal effect of turbulence in liquids (or solids that have liquid characteristics) as comparted to that in gases.
    As per the Gas Laws expansion of gases results in cooling as kinetic energy converts to potential energy and the reverse on contraction. That does not apply to liquids because their inter molecular bonds are so much stronger such that there is little expansion or contraction within the turbulent flow.
    Any work done by gases rising up against gravity (expanding in the process) or descending with gravity (contracting in the process) is by definition adiabatic (no new energy added or removed) so that the cooling on ascent is caused by conversion of KE to PE and warming on descent is caused by conversion of PE to KE.
    It is that thermal effect of descent (heating) that is omitted in the global energy budgets which leads to the need to balance the energy budget by incorrectly proposing extra downward radiation from GHGs.
    The heating on descent does not warm the surface directly but instead dissipates clouds to allow more solar radiation to reach the surface and then inhibits convection because the warmed air coming down from above blocks warmed air rising from the surface by reducing the lapse rate slope.
    That leads to the surface becoming warmer than expected from the S-B equation.
    Averaged over the Earth as a whole that warming effect nets out to an additional 33C at the surface.
    As a result of atmospheric mass and not as a result of GHGs.

    • The truth of my comment is illustrated in the photograph provided.
      Each cell of cumulus cloud is a package of air in which water vapour has condensed out as a result of convective uplift leading to expansion and cooling (KE replaced by PE) to a temperature below the dew point and each clear cell between the cumulus clouds is a package of air in which cloud condensate cannot form because of convective descent leading to contraction and warming which keeps the temperature above the dew point.
      Each cumulus cloud is a package of air at fractionally lower pressure (rising air) than the fractionally higher pressure in the spaces between cumulus clouds (falling air) .
      That picture contains a miniature representation of the large scale convective cells (both low and high pressure) around the Earth which give rise to our permanent climate zones. Those convective cells would exist even if we had no water vapour or clouds (or GHGs of any kind).
      Beneath each clear cell more sunlight can reach the surface which then warms above S-B because convection is inhibited beneath those descending cells.
      There is an inversion present above the cumulus clouds which prevents even more convection. That inhibiting of convective uplift leads to the surface beneath those clouds also becoming warmer than S-B.
      The radiative fluxes that are present are then a consequence and not a cause of the vertical thermal profile in the troposphere created by the work being done by convection with gravity (descent) and against gravity (uplift). That vertical thermal profile is the lapse rate and is caused by conversion of KE to PE within gases suspended within a gravitational field as per the Gas Laws.
      A knowledge of cloud physics leads inevitably to a proper appreciation of the mass induced greenhouse effect.

    • Stephen
      There are similarities between liquids and gases, they are both fluids. Some characteristics are quite close and some are far apart (as you described). It’s still useful to run some experiments for visual reasons. It opens the door for further investigation.

    • Stephen Wilde
      “The heating on descent does not warm the surface directly but instead dissipates clouds to allow more solar radiation to reach the surface and then inhibits convection because the warmed air coming down from above blocks warmed air rising from the surface by reducing the lapse rate slope.”
      I get that but surely anything that is warmer than something else will lose heat (at least some) to that. i would guess in this case that the amount of heat swap from warm air to water or land is swamped by direct solar radiation, or is that heat all converted into moisture absorption? However, air passing over land or sea that is different in temperature is what drives our weather as the air either picks up heat and/or moisture or losses it.
      One other observation. I did not realise that you could get cloud streets over water, although the picture clearly shows this. I am aware of cloud streets over land which seems to be a product of thermic days (cold unstable air over warm ground) and wind speed. The ‘streets’ are not over the thermal sources as they are never that organised on the ground. The wind seems to organise and collect all the rising thermals into single long lines. But wind spead is critical. Also I was not aware that you can get thermals over water, so are these streets much the same as over land but the organisation of general heat and moisture rising of the lakes and not specific thermals? From a gliding perspective over water journeys require lots of height from the start as thermals are not expected over water.

      • Usage of terms is important here. The ‘heating’ is as a consequence of having more molecules in the volume with kinetic energy than in the same volume higher up at a lower pressure. Therefore, ‘temperature’ increases because the number of molecules with kinetic energy increases. This is not heat that can be radiated to the surface it is kinetic energy that can pass on sensible heat by collision with surface molecules.
        Radiation cannot be from non-radiative gases but it can come from CO2 which is a radiative gas. Therefore, after collisions with N2 and O2 the CO2 molecule may gain sufficient energy to radiate IR and some of the radiated IR photons will reach the ground. This loss of energy will cool the atmosphere. Similarly, condensing water vapor will radiate latent heat and some fraction of this will reach the ground. Neither of these effects are due to AGW hypothesis that the surface emits IR which is then ‘trapped’ by CO2 and radiated back down.

    • Stephen Wilde
      “The heating on descent does not warm the surface directly but instead dissipates clouds to allow more solar radiation to reach the surface and then inhibits convection because the warmed air coming down from above blocks warmed air rising from the surface by reducing the lapse rate slope.”
      I get that but surely anything that is warmer than something else will lose heat (at least some) to that. i would guess in this case that the amount of heat swap from warm air to water or land is swamped by direct solar radiation, or is that heat all converted into moisture absorption? However, air passing over land or sea that is different in temperature is what drives our weather as the air either picks up heat and/or moisture or losses it.
      One other observation. I did not realise that you could get cloud streets over water, although the picture clearly shows this. I am aware of cloud streets over land which seems to be a product of thermic days (cold unstable air over warm ground) and wind speed. The ‘streets’ are not over the thermal sources as they are never that organised on the ground. The wind seems to organise and collect all the rising thermals into single long lines. But wind speed is critical. Also I was not aware that you can get thermals over water, so are these streets much the same as over land but the organisation of general heat and moisture rising off the lakes and not from specific thermals? From a gliding perspective over water journeys require lots of height from the start as thermals are not expected over water.

      • To Mod. Apologies. Please remove previous (first) post from me as thought I could modify and correct typos etc.. My mistake.

      • Stephen Skinner,
        Some heat does transfer directly from warm air to the surface below but because the specific heat of air is so much less than the specific heat of the surface the amount is too small to consider.
        The true warming effect of adiabatically warmed descending air is via dissipation of clouds and suppression of convection.
        Evaporation plays a role in making it much easier for surface energy to be transported upward and radiated directly to space from within the atmosphere.
        Convective overturning then needs to work less hard to maintain the mass induced thermal equilibrium with space.
        AGW theory proposes that DWIR from GHGs heats the surface and creates more convection not less.
        They miss the point that if energy radiates to space from within the atmosphere then less energy returns to the surface in adiabatic descent than was taken up in adiabatic ascent. Convective overturning slows down.
        That reduction in thermal energy returning towards the surface in adiabatic descent then offsets the potentially warming radiative effect on surface temperature from GHGs.
        The net thermal effect from GHGs being zero.

      • Stephen Wilde March 12, 2015 at 7:50 am
        “AGW theory proposes that DWIR from GHGs heats the surface and creates more convection not less.
        They miss the point that if energy radiates to space from within the atmosphere then less energy returns to the surface in adiabatic descent than was taken up in adiabatic ascent. Convective overturning slows down.”
        IMHO I agree with you. I think there is this fixation with feedbacks particularly a warm atmosphere radiating heat back to the surface, but that almost seems a bit like perpetual motion. I don’t see how that surface evaporation of moisture and subsequent heat loss upwards can be radiated back down. It seems like a one way ticket especially as the atmospheric temperature only ever drops as it goes up (barring temp inversions). However, a temperature inversion where warm air sits over cold air would be a good example for AGW as the warm layer should radiate heat down and warm the surface and dissipate the inversion. But that’s not what happens and if it does it is surely swamped by larger forces such as surface heating from the sun and weather fronts.

      • @ Stephen Skinner March 12, 2015 at 9:56 am

        However, a temperature inversion where warm air sits over cold air would be a good example for AGW as the warm layer should radiate heat down and warm the surface and dissipate the inversion

        Good point, …. but, …. in actuality, …. shouldn’t the warm layer radiate heat down and warm the cold layer underneath it, ……. that is, iffen one is a believer in/of the CAGW “junk science”?

  13. “The trouble is that people in turbulence never thought about Landau because he was in a completely different field and the information doesn’t get carried across because there’s just too much of it,” Ahlers added. “But I worked in the field of critical phenomena for many, many years and know Landau’s work very well. Then I changed to studying turbulence, and when this issue popped up, it was obvious to me what was going on.”

    This needs to be repeated every day in every science classroom in the world.
    As the level of knowledge has grown, more and more science specialties have popped up. And the different specialties tend to be very insular. Hence what might be common knowledge to a organic chemist might be virtually unknown by evolutionary biologists, yet the chemisty knowledge could have a profound impact in the science behind a situation in evolutionary biology.
    And as all the readers here have seen again and again, climate scientists tend to know little about statistics. Often leading to very poor ‘sciencetific’ conclusions.

    • @ ddpalmer March 12, 2015 at 3:53 am

      Hence what might be common knowledge to a organic chemist might be virtually unknown by evolutionary biologists, yet the chemisty knowledge could have a profound impact in the science behind a situation in evolutionary biology.

      Right you are, it needs to be repeated every day in every science classroom in the world as well as hereon WUWT.
      I, myself, have encountered this situation many times in Internet “forum” discussions about CAGW as well as other worldly events of all “kinds n’ sizes n’ colors”.
      One such issue in particular is the “factual claim” that the bi-yearly increase/decrease (avg 6 ppm) in atmospheric CO2 is a direct result of the summer “greening” of plant biomass in the Northern Hemisphere … and the winter “rotting” of plant biomass in the Northern Hemisphere, ….. which is utterly bogus simply because the claimants of said “fact” do not understand and/or refuse to acknowledge the biology associated with the biomass ingassing and/or outgassing of CO2.
      The summer “greening” of plant biomass in the Northern Hemisphere has been inprogress now for the past month and a half and is progressing slowly northward as we speak …. but it will be another two (2) months before the atmospheric CO2 stops increasing …. and begins its bi-yearly decrease.

      • Sam,
        I’ve previously mentioned that the timing is not right for the annual CO2 variance to be due to northern hemisphere biosphere changes.
        The timing is much better for sun induced ocean outgassing because the peak is when the southern oceans are at their warmest in March and the trough when they are at their coldest in September.
        In contrast, the northern hemisphere biomass growth slows down from June onwards whilst the plants shift to supporting seed or fruit growth so the trough should be in June and the peak in December if it were a biomass issue.

      • Steven,
        I have been preaching that very same thing for the past 10+ years … but it seems most everyone wants to avert their eyes and their mind to what is obvious scientific fact that is supported by “tons of data”, ….. pun intended.
        As per the Keeling Curve graph and/or the Mauna Loa Record, the bi-yearly “cycling” of atmospheric CO2 has been “steady & consistent” for the past 57 years …. with the “high” and ”low” point of CO2 ppm …. never varying much more than 7 to 10 days following the Fall Equinox (9-23) … and in mid-May following the Spring Equinox (3-20).
        See my added notations on this copy of the Keeling Curve graph, to wit:
        http://i1019.photobucket.com/albums/af315/SamC_40/keelingcurve.gif

  14. I did some work with CFD software some years back, involving liquids flow, and it was well understood that modelling turbulence was very difficult for various reasons not the least of which is that turbulence occurs at smaller scales than large field steady (notionally inviscid) flow. Much fines meshes are requires as I understand it and thus calculation time goes through the roof. I also came across the false silution problem arising from a mesh that is too coarse to reasonably ‘model’ the rate of change of some phenomenon in the fluid. I have long thought this is the reason the models are so poor compared to the historical record ( even one using such ‘adjusted’ temperature data).
    That said if the CAGW loons incorporate this new turbulent behaviour mechanism into their models what is the bet they will still shout CAGW even if their results just better model the historical record.

    • They can’t include it. Their current mesh is 100kmX100km. To capture this effect the mesh could be no larger than about 1mX1m (and that may be too large). The computational impact of the mesh change by itself means ten orders of magnitude more calculations for each time step. Add to that the equations required to model the heat flow implications of turbulence and I am sure you can add on another couple of orders of magnitude. So basically what I am saying is if it takes 6 months to do a 2 century reconstruction now, it will take 5 million years just based on mesh size. Maybe some of it can be parallel processed with even larger computers, but you are still looking at either a 10 order of magnitude faster (or more parallel) computer or a totally impossible computational problem.
      It may be even worse than I just typed because of the interconnectedness and the fact that I have neglected the resolution in the 3rd dimension which also needs to be no larger than 1m. (I don’t know how big the cell heights are at present.) Each cell has an effect on and is affected by all its neighbors. Turbulent energy flow is in many different directions.
      This means that whatever model we use, however complex we make it, will never be more than a gross estimation of the order of magnitude of reality.

      • According to UCAR, the number of stacked atmospheric cells in the CMIP5 archive ranges from 20 to 30, and most XY grids are about 2.5 degrees lat/lon, or about 280 km at the equator. The finest resolution is about 1.1 degree, or 110 km at the equator.

      • Owen in GA March 12, 2015 at 5:57 am
        Also reality is not constructed out of a theoretical mesh or boxes or whatever framework makes it easier to measure.
        Perhaps related but:
        “Not everything that can be counted counts, and not everything that counts can be counted.” Albert Einstein
        I think the modelling is an heroic attempt to count something before it is fully understood and maybe not measurable ever using meshes or grids or some other artificial construct that is totally removed from reality.

    • Reply to M Seward ==> Computational Fluid Dynamics is what is used to try to solve the linearized, simplified versions of the dynamic formulas of fluid flow. Correct? All the while knowing very well that the actual formulas, the actual equations, for dynamic fluid flows, when all scales are considered, are nonlinear (and basically, practically unsolvable). None of that means that the subject is without tremendous values in applicable fields where even approximate solutions are very useful.
      The mesh size problem is part of the attempt to get around the basic nonlinearity of the subject.
      When trying to test the fluid flow (air) around and past a new fuselage for a new airplane, one tries the CFD program on the proposed design and if all is well, makes a very precise physical model and puts in in a wind tunnel to see if the CFD results hold up — no one would build an airplane, no less try to fly it, without the air tunnel step, because they know the CFD program is only an approximation of what is actually a nonlinear system.
      Do I have this approximately right?

      • Also though the scaling of the model is subject to the same non-linearities, to be really accurate you need a full scale model which is why so much money is put into very large wind tunnels. The largest in the world is 80×120 feet one at NASA Ames.

  15. Very cool commentary concerning clouds and turbulence.
    Just wanted to note that the presumed reason why this paper was pointed out was that the heat transport differences mean effects of clouds is even harder to model than the present failing models fail to do.

  16. I may be way out of line, but I thought we knew about sudden transitions in fluid dynamics. Laminar flow, transition zone (standing waves) then turbulent flow.
    Interesting article. I shall have to reread in the morning.
    Maybe I missed the point a bit, but I thought we knew a bit about this already but simply didn’t apply it.
    http://iopscience.iop.org/1742-6596/14/1/020
    http://www.chemeurope.com/en/encyclopedia/Hydraulic_jump.html
    http://en.wikipedia.org/wiki/Laminar-turbulent_transition
    The Physicists among you have likely perused this list, but some of the topics are interesting. There IS good, interesting research being done. Interesting in real science, how many indeterminate factors are reviewed.
    http://www.fields.utoronto.ca/programs/scientific/11-12/CAIMS_SCMAI/csfd.html

    • Physicists are generally layabouts who live inside their heads. If they really want to be useful in this matter they should look at other rotating planets where exposed fluid compositions exist where those planets (even the Sun displays this feature) display an uneven rotational gradient between Equatorial and Polar latitudes otherwise known as differential rotation.
      Had they any sense they would have applied this uneven rotational gradient to the Earth rotating fluid interior and looked for clues on the surface crust in terms of the evolution of the Mid Atlantic Ridge,the symmetrical generation of crust either side of the Ridge and the wonderful ‘S’ shape that splits at the Earth’s Equator –
      http://upload.wikimedia.org/wikipedia/commons/b/b2/Mid-atlantic_ridge_map.png
      Interpretative science is lost as an art presently amid the overblown hoopla of trying to pass predictions off as fact.

    • > I thought we knew about sudden transitions in fluid dynamics.
      That was my first thought, I was always fascinated by plumes of cigarette smoke or water spreading out in the kitchen sink. I think the addition of rotation may be adding a lot to the behavior and that may not have been applied before.

    • Wayne Delbeke March 12, 2015 at 4:19 am
      I think many things are understood already but the sheer volume of accumulated knowledge and the need to justify a job or research grant means the wheel will keep being reinvented and maybe not as good as the first time.
      I saw a fascinating programme on Greenland some 30 years ago where modern scientific criminal forensics were used to determine what happened to the Early Vikings there. They looked at seeds, pollen, plants and other indicators of conditions in the layers of soil around that period. The conclusion was that conditions deteriorated in a short time making living there untenable, and untenable meant very cold. I have seen no reference made to this important work which I would expect modern studies to do.

  17. “It cannot be smooth because a system has only two states: disordered or ordered and there is nothing in between.”
    Holy crap, I can’t believe that an entire field bought into this notion, that’s like saying “If you push something hard enough it will fall over!” (thanks to P. Bergman)…

  18. Finally, experimental meteorology opens our eyes to the inherent chaos in non-equilibrium fluid dynamics, proving that the atmosphere is inherently non-deterministic. The Cartesian determinism necessary for the digitizing of the General Circulation Models is shown to be a fatally flawed oversimplification, and incorrigible.

  19. “The trouble is that people in turbulence never thought about Landau because he was in a completely different field and the information doesn’t get carried across because there’s just too much of it,” Ahlers added. “But I worked in the field of critical phenomena for many, many years and know Landau’s work very well. Then I changed to studying turbulence, and when this issue popped up, it was obvious to me what was going on.”

    This is a great example of why we need more generalists and fewer specialists.

  20. I love this subject. I spent a lot of time programming simulations of 3-phase boundary-less viscous flow in my graduate work circa 1980’s. It is fascinating to me. I was aware of the sharp transition between laminar low to turbulence but never considered transitions within the turbulent field. It was never in my scope. Very neat.

  21. In the paper, the researchers use cloud streets — long rows of cumulus clouds oriented parallel to the direction of the wind

    Great choice of photos.
    I generally see them off the Atlantic coast during local TV weather segments. Sometimes we get them over land, like today. Mostly clear to the west, snow clouds to the east, banding obvious on radar. I was a bit surprised that we had a trace of snow this morning until I checked the radar and then looked east.

  22. WRT to the photo, Note the discrete turbulent streams, yet each turbulent streams form a laminar-esque stream lines SW across lake superior. The lines themselves are locally turbulent, yet they’re orderly in the macro scale. I think that is interesting.

  23. We have great difficulty in modeling the shower curtain effect, yet people think they can micro-model the entire atmosphere?

    • I blame the PC and EXCEL, (or similar software). When I was in school we started with passe ideas, like internal and external validity and reliability. Now it seems like every idiot with some data shoots a best-fit line through it, then guesses at an interpretation. If you think it’s bad in the physical sciences you would be absolutely stunned by some of the garbage that’s happening in the social-pseudo-sciences

      • The social-pseudo-sciences – where they have to arbitrarily attach numbers to “feelings” and such? Yeah. I shake my head at their bozo efforts to join real science and gain street cred.
        But at the same time, when I see a straight-line fit in climate, I wanna scream. Like temperatures don’t go up AND down – and have to get to a zero-slope point (catastrophe) in the turn-around. And there goes the straight line… Any person who projects the temps to go up and up and up, forever – whatever they are smoking, I don’t want none of it. They actually think it is NEVER going to flatten out? (Like the hiatus, for example?)

  24. Can someone supply a link to the original paper? I haven’t been able to find it at Physical Review Letters.
    Thanks!

  25. Science is in the business of constantly proving itself wrong. That’s why the term “settled science ” is idiotic. Example above rolling with a theory for 74 years that was incorrect. For once someone needs to admit the area of climate is in its infancy.

  26. Glider pilots have long enjoyed the benefits of cloud streets: glider gas we call them. Nice that they can also fuel new discoveries in turbulent behavior.

  27. I’m a bit confused.
    In what world did people think the “transitions from one state of turbulence to another must be a smooth evolution”?
    I thought the transitions were characterized by critical numbers — points — … not critical ranges.
    And what do the authors mean by “smooth” vs “sharp”? What is the metric here?
    Plus, it doesn’t it sound like their little tornado formations made abrupt appearances; it sounds like they emerged smoothly.
    And with respect to: “If you look at the Nusselt number, it has these breaks, which indicates that the heat transport does not change smoothly as the rotation rate is increased…”
    How do you have ‘sharp’ changes in heat transport?
    Don’t get me wrong. I love the topic, the big names mentioned, and the notion of new insight. I guess I just need to read the actual paper.

  28. Well, Kolmogorov did a lot of things, and in the annals of math and science his contributions are major, whereas I doubt we, who don’t work in this field of mega turbulence, will hear much about these researchers beyond UCSB press releases. I’m not slagging the researchers achievements – I just think the article is a little strident in claiming they have proven Kolmogorov wrong. He developed math and theory describing weak turbulence, and to say it was applicable to all atmospheric phenomena is a little … disingenuous? There is a tendency by some to use Kolmogorov theory beyond the scales intended, but that’s not Kolmogorov’s fault. In the field of path turbulence measurement we have a saying for when we see odd stuff – “that’s definitely non-Kolmogorov!”

  29. In 1941, Russian physicist Andrey Kolmogorov developed a theory of turbulence

    Kolmogorov was a mathematician, one among the greatest. Not a physicist.
    His mathematical theory of (weak) turbulence is flawless, the blame belongs to those who applied it to physical phenomena for which not all preconditions of applicability were met.

    • I too was surprised when I read of Kolmogorov being described as a physicist. Definitely a mathlete, and a studly one at that.
      At the moment I have between my two typing hands a copy of his “Elements of the Theory of Functions and Functional Analysis.” It’s sooooo purdy. (It actually makes me feel like I know something.)
      Landau was no slouch either. As an undergraduate I had the pleasure of using Landau and Lifshitz’s Course on Theoretical Physics, Vol 1, Mechanics. I still enjoy picking it up and marveling at their demonstration of the Principle of Least Action of Ink and Paper.
      No one can accuse those two of abusing trees, that’s for sure.

    • Kolmogorov did most of his (brilliant) work before there were any computers, so naturally, most of his work is theoretical. Most non-linear problems do not have neat analytic solutions. Even motion of the planets is almost impossible to calculate exactly without the aid of a computer, even though you can write down all the equations.

      • Indeed. One can argue that during the Cold War, the Soviet Union did not have a vast pool of filthy capitalist $$$ to support state-of-the-art computers needed to solve non-linear problems, so out of necessity it produced great theoretical mathematicians, such as our Kolmogorov.

  30. Like several others here, I am puzzled by the claim: “Kolmogorov’s theory has been interpreted to imply that transitions from one state of turbulence to another must be a smooth evolution”. That may be true spatially, but I don’t think it is true temporally; as conditions change uniformly in a confined system, transitions from one flow regime to another can be quite abrupt. That is what the authors found. I don’t see how that disproves anything about Komogorov or how it tells us anything about the atmosphere.

    • Does it not seem that the authors are trying to surreptitiously siphon off brand equity by associating their paper with greats like Kolomogorov and Landau?
      (What’s next? Peppering their paper with photons?)

      • Directly contradicting Kolomogorov seems to have been necessary, since that is the main thrust of their results.
        Maybe I m wrong about that, but that is what I see…

  31. I met Guenter Ahlers many years ago and would be greatly surprised if he’s got any significant part of this wrong.

  32. You too can learn from experiment
    Get yourself a glass coffee cup with a cylindrical shape — fill it to within a cm of top with coffee or an equivalent water-based dark colored liquid
    Heat the coffee to just short of boiling in a microwave or pour it directly from a coffee brewing device
    Let it sit for a few minutes to lose any gross motion associated with pouring
    Get your self some cream or similar solution / suspension slightly less dense than water and cool it to below room temperature
    Carefully pour some of the cream on top of the coffee — stand back and watch
    Fabulous as when the experiment completes — you can drink it
    Enjoy the science of turbulence — no algebra required

  33. Folks, the idea that transitions occur between heat transfer regimes has been understood for many years. Just read the wikipedia article on natural convection.
    “As the Rayleigh number is increased even further above the value where convection cells first appear, the system may undergo other bifurcations, and other more complex patterns, such as spirals, may begin to appear.”

  34. I am wondering if the warm and cold tornadoes they talk about are in any way part of the formation of actual tornadoes, in which vortices up high and on the ground join up and become more organized and more powerful – in making the jump from one state to the next. And the spinning system in which they occur is a direct analog for their rotating cylinder.

  35. I have one problem with the rotating cylinder aspect of this. The solid wall of the cylinder introduces shear and other forces that I don’t think exist in the real world atmosphere – forces that in themselves may be creating the tornadoes or reducing them or magnifying them.

    • I’ve worked with fluids and walls and boundary layers, and I know that things happen there that aren’t happening out in the more free regions of the flow, things that people had to learn about the hard way…

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