The ACE MECHANISM 
"Hurricane Katrina produced more energy than all the power stations on Earth combined" (news article)
- Heat
- Basic Physics
- 100% Relative Humidity
- Adiabatic Heating and Lapse Rates in Cyclones
- The Tropopause, Above and Below
- Hot Towers
- Microbursts
- Two Mechanisms for Cyclone Genesis
- How Sublimation contributes to a Paradox
Heat
The temperature gradient that initially drives a storm is miniscule when compared to the temperatures used in industrial power production. For efficiency, industry strives for a 1000 degrees or more to drive it's generators but the largest storm commonly works on no more than 20oC-30oC . How is this so? To top
Basic Physics.
According to Boyle's Law, as free-flowing air is heated within the atmosphere, it's volume expands by a small amount. (ie ~1/270th/ per degree centigrade.) Thus, an increase in air temperature of 27oC will cause the volume of the air to increase by10%. This modest expansion is enough to make the air lighter and then rise by convection.
However, when water expands to vapour, it expands by a factor of 1700. Whilst water and water vapour make up only a small percentage of air they are by far the most significant mechanism in driving what we call our weather.
The main ingredient in driving the increasing wind speed and the intensity of any storm is condensation which can occur with an almost instantaneously drop in atmospheric pressure should a vortex be initiated. To top
In a desert, the dry air will heat rapidly in the morning and the volume of the air may increase by 20% over the period of an hour as the tempersture goes from 0oC-50oC. And at night, as it cools, the process is reversed. However, the presence of water vapour changes the whole process, slowing the heating proces and generally keeping temperatures more even. However, with high temperaturs and a high moisture content, the situation can change dramatically.
More vapour increases the air's volume and makes it lighter. As the air rises the air will cool and relative humidity increases, making the air increasingly unstable until, at 100% humididty, even the smallest disturbance can potentially trigger the so-called 'Butterfly Effect', the vortex phenomenon that can trigger a storm.
When the air is super-saturated, the smallest vortex will trigger a 'positive feedback mechanism' that can turn all the available vapour into condensate or liquid water. This collapse can flow through the whole air mass within seconds turning vapour into condensate. On a hot and humid afternoon the air's volume could potentially reduce by 40% within minutes once the trigger is effected. To top
100% Relative Humidity
As the temperature of the air drops, relative humidity rises until the dew point is reached. At that point, the volumetric collapse of vapour to liquid condensate will potentially cause an inflow that may ultimately trigger a storm. The storm may be an isolated event but it can also develop along a frontal system as a Cool Change
As a Cool Change becomes established, relative humidity rises and as more vapour condenses, a positive feedback cycle becomes established that will continue until all the available moisture is drawn in and condensed. In just minutes, in coastal cities like Sydney and Melbourne, a cool change will typically whip up high winds and cause air temperatures to plummet by as much as 20oC in a matter of minutes. The heavy rain that commonly accompanying these events can cause significant local flooding. To top
Adiabatic Heating and Lapse Rates in Cyclones
As air rises it expands and the adiabatic process of pressure reduction with height allows the air to cool. As it descends, air pressure increases and the process acts in reverse. These effects vary very significantly depending on the vapour content of the air. The Lapse Rate of Dry Air (DALR) is a constant 9.8oC/1000m (ie for all intents and purposes,10oC/km) and applies mainly to air in or drawn down from the Stratosphere. In stark contrast, the Wet Air Lapse Rate (WALR) of 6.5oC/km* applies to most of the air in the temperate regions within the lower atmosphere or Troposphere. the region mostly affected by weather. [*The WALR.is technically a variable but in reality and for various reasons varies very little across a wide humidity range]
Any event that causes dry air to be drawn down from the Stratosphere will heat at the DALR (ie 10oC/1000m) which is far higher than the WALR normally associated with the air of the tropopause though which it will pass. Should the eye of a cyclone cause an incursion of dry air from the Stratosphere into the lower regions of the atmosphere it will potentially have a quite dramatic effect, adding vast amounts of heat to the wet air through which it passes. Indeed, the author believes this is precisely how a cyclone gains much of its power.
Air drawn down from just below the Tropopause (at say 10,000m) will heat as it descends at the WALR ( 6.5oC/km) by 65oC. However, dry air from the Stratosphere just above will heat 50% faster (ie by 100oC), . Although mixing and radiation could be expected to mitigate the extremes, the heat gained adiabatically within the heart of an IRV nevertheless becomes a major potential contributor to cyclonic weather systems. Potentially adding gigawatts to the energy potential of this unique type of storm, cyclones are clearly a major player in reducing global warming. To top
The Tropopause, Above and Below
At the Tropopause the temperature remains a constant -56oC. In both directions, both above and below this imaginary demarcation line, the temperature gradually increases. Below the Tropopause, in the lower atmosphere (ie the Troposphere), the atmosphere is dynamic. And, until the recent discovery of Hot Towers, the atmosphere above the Tropopause was always considered essentially inactive or static. To top
Hot Towers
Whilst the water to ice phase-change also involves a significant energy exchange and the possible release of electrical discharges, it involves only a negligibly small change in volume. However, ice particles can trigger massive condensation and they thus play a significant role in the development of major storms. Dumps of icy cold air from so-called 'Hot Towers' (see sidebar 4) are of particular relevance in cyclone genesis. To top
Microbursts
Commercial aircraft have been brought down on a number of occasions by the occurrence of a microburst from a major storm cell. Strong and impressively powerful downdrafts of cold air from the base of a thunderstorm can rob an aircraft of lift. The danger is especially critical as it comes in to land. It is thought that microbursts occurring over the sea, possibly as a result of a Hot Tower, are strongly linked to cyclone genesis.
Two Mechanisms for Cyclone Genesis
The eye of a cyclone is an inverted ring vortex (ie an externally-driven IRV). The IRV requires a very specific trigger mechanism to get started and is normally only seen in a cyclone's eye within an encirdling ring of conventional storms.
1. The recently identified 'Hot Towers', seen (by satellite thermal imaging cameras) just prior to cyclone formation would seem to provide the most likely mechanism for cyclone genesis. As the Hot Tower looses its upward momentum and collapses back below the Troposphere, the (now frozen) vapour particles and hail may gain sufficient momentum to trigger a microburst and the formation of an inverted ring vortex (IRV).
2..An alternative mechanism could possibly be provided by the known process of vortex decay that occurs when a conventional NRV is tilted for more than a few seconds. Such tilting would almost certainly occur if an NRV should collide with the tilted base of a Tropical Depression and could equally well result in ice and frigid air being dumped into the sea.
It would seem entirely possible that either or both mechanisms in unison could contribute to cyclone genesis. To top
How Sublimation contributes to a Paradox
In the overall global circulation of the atmosphere (and in arctic storms) the sublimation of ice directly to vapour is a major factor but can largely be ignored in the context of the basic research. However, it may be of consideratble significance in the longer term if global warming melts the (north) polar ice sheet.
Air flowing northward from the south pole is affected by gravity to flow down from the high antarctic plateau. Air flowing south from the North pole is floating on the sea and is thus not flowing downhill and circulation toward the equator occurs less strongly, simply to replace the warm air lifting in storms at low latitudes. The circulation in the two hemispheres is thus clearly quite different.
In so-called 'normal' conditions the cold, dry air at the arctic will still pick up some moisture from the ice and over time this will generate storms, as occur in the Antarctic. However, the situation can be expected to change significantly if global warming melts the polar ice at the North Pole each summer.
With open water, the volume of vapour released is 20x greater than when the sea is frozen and will inevitably generate far more snow than is considered the norm. Ergo, Global warming in the Northern Hemisphere creates more open water in summer and (apparently paradoxically), open water in the summer could potentially create a Northern Hemisphere Ice Age. By the obvious and quite simple mechanism, blizzards in the Fall generate vastly more snow than would have occurred had the sea been frozen over all year.
That an Ice Age could be a result of Global Warming may seem paradoxical but is easily understood within what is already known about the circulation globally within each hemisphere.
The various weather events of storm, cyclone, tornado and waterspout are all triggered by quite different basic phenomena and I saw learning how to make each one as basic to developing the methods to control, harness and utilise the power they each are able to develop. In the event, it involved two quite different basic techniques and a range of possible approaches, depending upon the specific application.