Micro-Spherical Rain vs Flat Land and Fictional Sky

Sometimes it’s the little things… like virga and mist…

This article on WUWT per Willis and his adventure has an interesting comment in it.


Willis had mused about virga in his article:

I got to thinking about “virga” on this trip. Virga is rain that falls from clouds but evaporates before it hits the surface. I saw lots of it, and I wonder how much of it is captured by the climate models. In fact, how much of it is captured by observations? How would you even measure it when it doesn’t hit the ground? Gotta love the settled science …

I’ve had the joy of standing in virga that was making my face damp, but not my toes… Marvelous stuff. Typically raindrops that have evaporated to the point of being nearly nothing, and then it is nothing. Like cotton candy of the air.

Yet what it represents is a huge movement of heat from where it evaporated, to where it condensed, and then it is back to cycle again… How many times does that water cycle in that small part of our spherical heat pipe Earth? Nobody knows. And I do mean nobody. It isn’t measured, and as pointed out, nobody knows how to measure it. Often in the distance you will see what is clearly a thunderhead, dumping rain streaks, that end 1/2 way to the ground. Not even virga, it evaporates too high up, to cycle again.

I’ve commented about the potential for rain to act as a counter flow stripper scavenging CO2 from the air. This works due to the enormous surface area of droplets. Any Chem.E. or Mech.E. can tell you all about it.

The commenter, David Dibbell , had a different view of the droplets, and a very interesting one. I’m quoting his posting here in full, as it is worth reading twice…

Willis, thanks for your interesting and insightful posts, and may you have safe journeys. Your mention of virga prompts me to put here as a comment a post I composed a couple months ago on social media. I know it’s a bit long. It astounds me how so many otherwise capable folks – scientists or otherwise – can buy into such an obvious (to me) misconception about how the atmosphere works. I address the global warming issue as an old-school mechanical engineer who started with a slide rule.
I was in Mr. Heinrich’s geometry class in high school. Great teacher. So does geometry matter? Is it reliable?
Can geometry help us examine the “global warming” hypothesis? Let’s illustrate with a geometry exercise. It’s a long post, but please read on if you are curious and wish to consider this question from an alternative viewpoint.

About one meter (40 inches) of precipitation falls per year, averaged over the globe. This is one cubic meter of volume per square meter of surface. Raindrops are 2.5 millimeters in diameter, more or less. From geometry, one calculates that the surface area of all the raindrops in one cubic meter of water is about 2400 square meters. Hold that thought.

The global warming claim is that the lower atmosphere will heat up as concentrations of carbon dioxide and other “greenhouse gases” increase, absorbing more of the heat emitted upward by the earth’s surface. Then the warmed atmosphere emits more heat back downward, warming the surface. That’s the hypothesis. The geometry of this claim is one square meter looking up from the surface, one square meter projected downward from the atmosphere, as heat is radiated upward and downward.

But wait. The atmosphere does not actually work like that. The radiative emission and absorption of heat is in every direction from every location, not just up and down. In our illustration, as raindrops fall from cooler conditions higher up through warmer conditions down low, a huge surface area is exposed to the atmosphere for heat to be exchanged. Over a year’s time, this is 2400 square meters, on average, per square meter of earth’s surface! This geometric advantage applies to all forms of heat exchange between raindrops and the lower atmosphere: radiative, direct contact, and evaporation. The heat transfer happens rapidly as raindrops experience a stiff breeze as they fall by gravity. So just as the oceans and land surfaces are cooled by evaporation, convection, and radiative emission, so also is the lower atmosphere itself cooled, even more intensively as this geometry exercise about raindrops illustrates.

So what will an increasing concentration of carbon dioxide do? Logically, it will simply increase the effectiveness of the radiative part of the heat transfer between raindrops and the atmosphere. But will it change the temperature of the atmosphere? This is not plausible, as the fixed properties of water such as vapor pressure and latent heat of evaporation already exert such complete control over the temperature resulting from this intense interchange. Furthermore, if carbon dioxide increases the radiative effect downward near the surface, then logically the radiative effect is increased outward to space higher up where condensation occurs. Water vapor is recycled back up to condense again and form raindrops to fall back down to the surface, easily counteracting any tendency of “greenhouse gases” to change the resulting temperature down low. This happens without even implying any net change in rainfall reaching the surface. The atmosphere determines for itself how much of each raindrop makes it to the surface. We only measure the remainder. We don’t measure what doesn’t reach the surface, therefore it cannot have been modeled accurately enough for computers to tell us anything useful about it. But we can grasp what must be happening as we observe the rainfall and apply the geometry and the properties of water to this question.

So here’s the bottom line of this illustration: Some say “Dangerous carbon pollution!” “Climate catastrophe!”. But in reality, the atmosphere knows exactly what to do to control its own temperature, and will do it reliably using water as the vehicle with an overwhelming advantage in surface area. Geometry rules! Thank you Mr. Heinrich.

In highschool, my Geometry Teacher sat at an overhead projector, with large acetate films, and spent the day putting on a film, and then explaining how to create, recreate, or use what was on it. My memory hoard of Geometry is neat black and white type and a mix of red, green, and blue fine point markers explaining or using it… We each had a protractor, ruler (that he insisted on calling a ‘straight edge’), compass and pencil. That, and a bit of paper, was all we used.

Starting with two dots and a line, we proceeded to derive all of the Geometry that fit into one class year. Other students found it dull and drifted. I loved it. So much, from nearly nothing. It taught me the discipline of orderly thought (No, you can NOT just assume… NO, you can NOT use anything outside what has already been proven. NO, what you THINK you KNOW is not enough…) along with a love of minimalism. To this day I strive for the most understanding from the minimum possible assumption set. (In assumptions there is error… another learning… or at least uncertainty… another learning, or…)

At the end of the year I appreciated the 3? thousand years of thought that had been gifted to me and the purity of soul that pursued it.

So that above quote touched my inner core of reason. So simple, so few assumptions, so clearly stated. Tiny things in large numbers have gigantic surface areas. What chance does one square meter of surface stand against 2400 sq. m. of rain? (Or the 10s of thousands of m^2 of mist…)

Then there are clouds… same issue on steroids.

It is that which causes me to think this is worth preserving…

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About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
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17 Responses to Micro-Spherical Rain vs Flat Land and Fictional Sky

  1. E.M.Smith says:

    This follow on comment is also interesting:
    May 8, 2016 at 8:54 pm Edit

    One observation about virga that is interesting to me is the heat transfer. The condensation of virga constitutes the release of heat of vaporization as radiation at whatever altitude the cloud deck happens to be. At the same time, the virga, which by definition is not reaching the ground, then takes in an equal amount of heat in order for it to “revert” to vapor. That vapor would then head skyward once more, acting as a conveyor of heat energy from lower altitudes to higher altitudes.Willis has repeatedly underscored this. His photos underline the underscore. The small tropical storm systems are conveyors that carry heat upward. While a fraction of that heat roughly proportionate to the angular area of sky versus the angular area of land and sea at the altitude of condensation may once more “warm” the solid and liquid portions of the planet, more will head for space and will not return. As David makes the point, it is simple geometry.

  2. richard ilfeld says:

    Catastrophic Anthropogenic Global Warming which has somehow morphed into ‘carbon pollution’ in the references of the slimy left, is much like non-Euclidian geometry. It might be fun to imagine a world where parallel lines eventually intersect, but not of much use if your task is to build a railroad.

  3. Chazz says:

    No protractors allowed in Mr. Dye’s Euclidean geometry class.

  4. E.M.Smith says:


    IIRC, it was Mr. McDowell for us… strange that I’ve not thought of him for 40? years? yet still the name arises. ..

    He did say that was possible, but we could use the protractor to facilitate more rapid learning; but we really ought to think about how to avoid using it… This was farm country with near zero “academic orientation” in the general population, so he ‘cut us some slack’ but with an admonishment… You could tell he was mildly bothered at the impurity of it … And, frankly, all I remeber us using it for was to measure constructed angle to see the sizes and relationships..

  5. Larry Ledwick says:

    One of the lessons of storm chasing is how dramatically water evaporation can change heat distribution and local conditions. I have vivid memories of sitting in a car in bright sunlight sweltering in brilliant sun. Air dead still and skies clear and blue and then over just an hour or two watching water turn that scene upside down. First small puffs of white cloud form. At first you don’t notice but there is a continuous dance of energy and form taking place right before your eyes. Those wispy puffs of vapor and micro droplets are really in slow constant motion, and if you watch closely at the edges you can see the condensation happen on the hot moist areas of the cloud and the evaporation occur at the warm dry areas of the cloud. What looks to the casual glance to be a soft puff of cloud is a powerful cooling engine, moving heat from warm moist to cooler dry areas of the atmosphere.

    Over time that little puff slowly grows and begins to form a solid cumulus which slowly bubbles, it grows for a while than deflates over and over like a coffee pot starting to “perc”. The action is so slow most don’t even notice it unless you watch over time. Each time it bubbles up it moves so much heat it kills the local convection and then collapses until the system recharges. Like a pot coming to a boil it gradually gets bigger (and other similar clouds form nearby). You then see the top of that cloud bumping into the top of the local convective layer and fighting to get through the convective cap. It tries over and over as the hot stifling day wears on. Air at the ground still as death, sweat running down your neck, you are trying to find a way to sit in the car so you are mostly out of the direct sun because it is burning hot on your skin.

    Then the magic begins. One of those little bubbling clouds by random chance gets a bit bigger than most. Maybe it is located over a darker south facing slope on the ground which is just a bit warmer than the rest, and it builds and instead of stalling and collapsing, it pushes up hard against the convective cap then with a silent bang it breaks through the cap and before your eyes you see a giant materialize! Suddenly the cloud mass is boiling and growing so fast vertically you have to slowly tilt your head back to watch the top of the cloud rocket up at 200+ mph.

    Now you have stepped out of the car and the air which was dead calm begins to stir, first you notice a slight warm breeze at your back as you face the cloud then soon it is a steady hot moist breeze, then a wind. You are in the inflow as warm moist air from miles around begins to slide faster and faster toward that convective tower. Like a giant vacuum cleaner it sucks in warm moist air over square miles of terrain. The warm moist air reaches the updraft and makes a sharp turn to the vertical and as it crosses the boundary where conditions allow, condensation of its moisture load it explodes upward as latent heat of condensation warms the air.

    And you stand there in awe at the enormous amount of energy being released to lift thousand of tons of liquid water at over 200 miles an hour to an altitude of 30 – 40 – 50 – 60 thousand foot altitude.
    Then the heat engine really turns on as some of that water begins to condense to rain and the rain shaft forms on the back side. Now you have a complete circulation (and heat engine) which is moving billions of BTUs of energy and millions of tons of water from ground level to the top of the troposphere.

    As that rain descends it cools the air around it and also physically drags it downward as the drops descend. That down burst of air which in a matter of minutes has dropped 30-40 deg F in temperature plunges toward the ground and then like a waterfall crashes into the ground and washes outward in all directions.

    You see the gust front coming and then like a freight train thundering by, it rolls over you and suddenly you are immersed in a strong cold wet wind full of ice cold raindrops where just minutes before it was sweltering hot and dead still.

    You cannot experience that sequence of events repeatedly with out having a real “Come to Jesus” moment about the power of water to move energy in our atmosphere. The sheer numbers involve are mind numbing if you stop to think about it.

    In a matter of 10 – 15 minutes multiple cubic miles of atmosphere have been suddenly cooled by 20 – 30 deg F or more if there is hail. And billions of tons of water and air have been moved tens of miles.

  6. Larry Ledwick says:

    All climatologists/modelers should be required to witness first hand the birth of a super cell thunder storm and this dance of convection. You can’t do that without having great respect for the power of water vapor and convection.

  7. Glenn999 says:

    Larry Ledwick
    I absolutely loved your description of the clouds forming, the rain drops and the winds. You should write some more; very compelling. Perhaps a new way of writing science books to capture the imagination of kids.
    Thanks for that

  8. p.g.sharrow says:

    @Larry; very graphic description of those pretty little puffy clouds turning into snarling monstrous Anvil-heads. To really experience them you must be in a slow light plane attempting to sneak past their advancing front to the safety of a tie-down at the airfield beyond. Can’t fly over them, far too high. Can’t fly under them as they will suck you into their maelstrom and their bases have Rocks in them. So you must thread the narrowing canyons between them with diminished ground speed as the winds that helped spawn them impedes your progress…pg

    When I just became a teen my parents took us on a tour of California in the early spring. It was snowing in the Mohave Desert as we progressed into Death Valley. Snowing too hard to visit Scotty’s Castle, we camped in the bottom of the valley. Mother made us bologna sandwiches for lunch, You know 1950s balloon bread, mayo and 2 slices of “meat” stuff. I eat fast, but the second half of that sandwich was drying faster! It was snowing down to 2,000ft, raining hard to sea level and then a thin strata of fog/cloud as the rain evaporated and we were in the DRY and warm at -200 feet 8-0.

    @EMSmith; Often we can look to the west of our northern California foothill home and watch the advancing rain clouds as they dump their burden of rain over the Sacramento Valley, Verga, never reaching the parched fields below, while if they fly over our heads we get cool damp air and showers at our 2,000ft elevation. Gods great air-conditioner at work, pumping energy from the surface to the Troposphere by the refrigerant action of H2O…pg

  9. Larry Ledwick says:

    Just a simple observation from the storm chasing experience (by the way thanks for the kind words folks!). In this part of the country when conditions are right for large scale convection, it will take summer sun about 6 hours of heating to reach favorable conditions (8 AM til 2 PM). A large thunderstorm can reverse that day of heating in about 15 minutes in the area it builds sustained convection. So as a back of the envelope estimate, large scale convection is somewhere in the neighborhood of 24x more effective at cooling the atmosphere and the earth’s surface than mid day summer sun is at heating it.

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  11. cdquarles says:

    Oh, not only that. You can smell the ozone in that gust front if you’re in a part of the country where there are lots of vegetation, especially pine. It has been 44 years now since my grandfather passed and before he did, he took me out into the wilds of Coosa County where some relatives lived. He had me working with him to fix their house and do some gardening, though they had more land and it was closer to farming. I watched a thundershower build out there. Eventually that shower moved in and washed out some of the HHH. I still remember smelling the ozone (rain’s a comin’) in the gust front.

  12. gareth says:

    “Over a year’s time, this is 2400 square meters, on average, per square meter of earth’s surface!”

    I think that there is a fallacy here but can’t pin it down exactly:

    The statement above has units of 1/time i.e. frequency (sq m / sq m / year).

    He’s trying to use it in relation to heat exchange, which has units of watts/sq m (joules /sq m /second).

    I can’t see where the two fit together.

    Also, if you recast his 2400 sq m / sq m / year as 76 sq mm / sq m /second (the same time base as watts) you can see that the number is actually not so large…

    Anyone with a clearer brain?

  13. Dai Davies says:

    Interesting post – thanks – I missed the original.
    Larry’s response is a great read.
    I did a quick BoE estimate a while back for global annual energy.
    It’s ‘missing heat’ level.

    A rough calculation of thunderstorm energy:
    Typical energy per storm = 1×10^15 Joules (source http://en.wikipedia.org/wiki/Thunder_storms#Energy)
    Storms per year = 6,657,600 storms/y (source http://www.bbc.co.uk/news/science-environment-12991483)
    Energy per year = 1×10^15 x 6,657,600 = 6.7×10^21 Joules/y
    Ocean heat content change = 6.3×10^21 Joules/y (ROAS4 OHC, average over 2000-2004 rise)

  14. John F. Hultquist says:

    To really experience them you must be in a slow light plane attempting to sneak past their advancing front …

    I think I’ll pass on that.
    Actually, I was on an Eastern Airlines flight [maybe a DC-8] that made some twists and turns to get around towering storms in the US Midwest. I think we were over Nebraska.

    I see a lot of this. The Cascades of Washington State average about 5-6,000 feet but I live close to the Columbia River near the center of the State where the elevation drops to under 1,000 feet. Seeing virga in this, so called, rain shadow region is common.

  15. Annie says:

    I’ve really enjoyed this article and the comments, especially that longer one by Larry Lerwick. Thank you.

  16. Annie says:

    Ledwick…..predictive text snuck in when I wasn’t looking; sorry!

  17. E.M.Smith says:


    The “fallacy” (really more of an overstatement-of-facts) is that the sq m of land exists and is radiating 100% of the time. The 2400 m^2 of droplet surface only exist in fractional parts and only on those days when precipitation is falling. So if you had an average m falling, but as 5 cm at a time / day, that would be 100 cm height / 5 cm /event = 20 events. So only on 20 days would those droplets be in place, and as 2400/ 20 m^2 each day = 120 m drops vs 1 m land… significantly different ratio, eh? And then only on 20 of 365 days… on average.

    So it overstates the effect, IMHO.

    The effect is still very much there, but vastly different on windward Oahu (400 inches rain / year on the mountain) vs Death Valley (near zero).

    But then again there are all those millions of clouds unaccounted at all in the budget, and the endless virga all over the globe, cycling and never measured…. so maybe that overstatement isn’t so bad after all. A look at the global cloud marble of Earth from space shows it more or less constantly covered in cloud somewhere. Tropics in particular. IMHO the actual “downrating’ ought to be about 50% on average. But that doesn’t account for the virga drops…

    Hope that helps ;-)

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