The Power Behind Hurricanes and Tornadoes
Posted by Jeff Id on February 2, 2010
For a long time I’ve wanted to do a post on some work by Dr. Anastassia Makarieva who has in my opinion explained the driving mechanisms behind hurricanes and tornadoes. Now I’m not an expert, but as an aeronautical engineer the equations were familiar so the paper read easily. As I understand it, the mechanism she describes was previously unknown and this work is starting to gain some acceptance. If she’s right, and I think she is, the work explains far more than just hurricanes and tornadoes though, it also explains a missing driver of winds on earth as well as planets throughout the solar system – condensation.
Now we’ve all been taught, warm air rises and cold air falls, to create updrafts, wind, tornadoes and this kind of thing (Carnot heat engines). Anastassia’s work demonstrates problems with the Carnot model and then looks at the forces created when a moist air column experiences condensation. The condensation itself removes water from the gas phase resulting in a pressure drop. This pressure drop powers the column of rising air in the walls of hurricanes and tornadoes. It’s really an exciting development, but as a climate outsider it seems hit you in the head obvious. Who knew this hadn’t already been figured out? Anyway, the work is very interesting and an entertaining read.
There are all kinds of things which happen when water condenses. When water condenses on a surface it creates heat on that surface. This makes sense because the molecules are closer together.
Let’s talk about that for a minute. What is temperature after all? I bet many of the readers here haven’t conceptualized what something as common as hot or cold is. I was born with an ugly obsession to need to know how everything works. Sometimes I think I should have written every article on “how it works”, except that there are a lot of people like me hanging around this blog.
Temperature is basically an amalgam of the both the number and velocity of the impact of individual particles on other particles. Think about that. It is important. The number and velocity of individual impacts. All vibrations of weird shaped molecules are taken into account, spinning, linear velocity and really about everything. In making that statement I expect someone will challenge, but the point is the concept, not the introduction of effects which create confusion.
Let’s use a sealed canister of pure gold as a surface of atoms, I like gold, it’s heavy, dense, doesn’t corrode and sounds like money. Now say the gold is 72degF temperature – room temp. Now say we have an equal temperature of hydrogen gas inside the gold can. Our gas is funny gas, normal hydrogen is H2 (two little atoms together shaped like a barbell) but ours is H1. Since the atomic weight of hydrogen is far lower than gold and the density of a gas is also far lower than a solid, an equal temperature means a couple of things:
First, our special H1 hydrogen’s spin typically would have little thermal component. In our H1 gas, it’s a single proton and electron pair. So spinning it would be entirely differnet than say an elongated octane molecule with 8 monster 6 proton carbon atoms whipping around on a powerful stiff chain with 18 hydrogen atoms stuck all around.
Second, in order to balance the vibration velocity and impact number of the surface of the gold atoms, the hydrogen gas must, on average, receive a total energy equal to that which it expends while impacting the surface of the gold.
Let’s assume temporarily that the gold atoms were perfectly stationary (absolute zero temp), after impact a fraction of a hydrogen atom’s velocity would be transferred to the gold creating a non zero temp and the hydrogen would slow down cooling off. There are some simple equations which govern this but they don’t matter to the concept.
The second law of thermodynamics is written in a variety of ways. I like this one from Wiki which recognizes the particulate nature of temperature.
Heat generally cannot flow spontaneously from a material at lower temperature to a material at higher temperature.
Now gold in a solid is like a pile of ball bearings connected by springs. The atoms at non-zero temperature have velocity, stretching the springs between them which eventually launches them back into position. The result is incessant vibration. If the gold is the same temperature as the hydrogen, the gold’s spin, vibration and mass result in an equal transfer of velocity, spin and vibration to the hydrogen gas.
That’s it. The second law of thermo.
The point of all this is twofold; First, light particles have to hit at a much faster velocity than heavy particles of the same temperature, and second, to explain what temperature is in general.
Now that we’ve figured that out.
Let’s consider for a moment about what happens when you cram a pile of hydrogen atoms whipping around a container into a smaller container? For a moment assume the reduction in volume happens instantly. I’m not talking about a metal hammer slamming into molecules at lightspeed but rather some kind of transporter beam that instantly places all the molecules with their original velocity, spin and vibration in a smaller space.
We know the velocity of each atom didn’t increase but all but moments later, the number of impacts per unit volume inside our container have gone up. Also the number of impacts to the surface of the container per unit area has risen. The net result is a higher temperature.
Ok, so now we know higher temperatures occur when hydrogen gas particles are crammed closer together, it’s reasonably easy to expand the concept to bigger molecules. These molecules can be thousands of protons and atoms large, they bend and twist like perfect springs bouncing around and whipping in impossible complexity, yet the constant is the impacts per second, the mass of the particles and the velocity of impact. If you’ve followed this far, the second law of thermodynamics should now be hit you in the head obvious.
Of course warm temperature (average velocity and mass) transfers to cold.
So back to hurricanes, what happens when you take a bunch of H2O water gas and Vander Waals forces condense it into a liquid?
Now assume further that these microscopic drops consist of a few million water molecules. What will the average velocity of the total mass of the droplet be? Will it shoot off to the left or right at the speed of sound like an individual gas atom or will the sheer number of molecules take over and average to zero.
Zero is the answer.
Zero net velocity.
Did you know there is no such thing as suction? There isn’t, a suction is a negative pressure differential between surfaces, but the question we need to answer is the same as the one for temperature above
‘what is pressure?’
Pressure, very similarly to temperature, yet slightly different is the transfer of momentum of an impacting particle to another particle. What keeps a balloon expanded is a balance of the number and velocity of internal impacts against the stretchyness of the ballon and the number and velocity of impacts on the outside of the balloon.
More impacts per second, higher mass per impact or higher velocity per impact and the balloon is larger. Gawd it’s simple when you think of it like that isn’t it?
Now the payoff.
Say you have a column of 100% moist air right at the edge of condensation which experiences just enough pressure
change to cause a shift from gas to liquid. All of a sudden, water molecules bouncing around at the speed of sound with an equal temperature to the surrounding air, become stationary drops with a slightly warmer temperature.
Less collisions per second, there are no water molecules per second as velocity has dropped to zero for those.
Lowered pressure – big time.
Surrounding gas still having air with moisture falls, suddenly drier and lower pressure condensed air pushes past the droplets which still rise through the column of dry air now racing past in an upward direction.
What a concept. Here’s how Anastassia’s paper describes it:
Hurricanes and tornadoes could be compared to an explosion reversed and prolonged
in time. In the ordinary explosion potential energy concentrated in the explosion
center is released in a burst, making local air pressure rise sharply and causing
dynamic air 5 movement in the direction away from the explosion center. Conversely,
condensation of saturated water vapor within the column of ascending air in hurricanes
and tornadoes leads to a sharp drop of local air pressure. This further enhances the
ascending motion of yet accelerating air masses, as well as the compensating radial
fluxes of moist air incoming to the area where the process of condensation is most
10 intensive. Water vapor contained in the incoming air undergoes condensation in the
same area; this sustains the pressure difference between the hurricane center and
its environment. Hurricane could also be compared to a black hole, which sucks the
surrounding air into the center, where it partially “annihilates” due to condensation of
water vapor and its disappearance from the gas phase. Thus, hurricane is an “anti15
explosion”. While in explosion the gas phase appears from either liquid or solid phase,
in hurricanes and tornadoes, conversely, the gas phase of water vapor partially disappears
from air due to condensation.
Unlike in explosion, the velocity of air masses in hurricanes and tornadoes is significantly
lower than the velocity of thermal molecular motion. In consequence, all air
20 volumes are in thermodynamic equilibrium, so that air pressure, temperature and density
within the hurricane conform to equilibrium thermodynamics. The driving force of
all hurricane processes is a rapid release, as in compressed spring, of potential energy
previously accumulated in the form of saturated water vapor in the atmospheric column
during a prolonged period of water vapor evaporation under the action of the absorbed
25 solar radiation. Since the power of the practically instantaneous energy release in
the hurricane greatly exceeds the power of energy exchange with the environment, all
hurricane processes can be described as adiabatic. The outlined approach predicts
that high wind velocities can develop anywhere in the atmosphere (over land as well
as over the ocean), where absolute humidity is high and the process of condensation
is spatially non-homogeneous. It thus provides a unifying theoretical framework for
understanding both hurricanes and tornadoes.
For the technical readers, of which there are many, the link to the paper is here.
The whole thing is amazingly interesting to me. There is a second paper at her site too, on the same topic, which for those who enjoy math is even more entertaining. I’ll let you guys find it though, at least until I decide to have some more fun.