Hypercane
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A hypercane is a hypothetical class of extreme
tropical cyclone A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its locat ...
that could form if sea surface temperatures reached approximately , which is warmer than the warmest ocean temperature ever recorded. Such an increase could be caused by a large
asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
or
comet A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...
impact, a large supervolcanic eruption, a large submarine
flood basalt A flood basalt (or plateau basalt) is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ocean floor with basalt lava. Many flood basalts have been attributed to the onset of a hotspot (geolo ...
, or "incredible"
global warming Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes ...
. There is some speculation that a series of hypercanes resulting from the impact of a large asteroid or comet contributed to the demise of the non-avian
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
s. The hypothesis was created by Kerry Emanuel of MIT, who also coined the term.


Description

In order to form a hypercane, according to Emanuel's hypothetical model, the ocean temperature would have to be at least . A critical difference between a hypercane and present-day hurricanes is that a hypercane would extend into the upper
stratosphere The stratosphere () is the second-lowest layer of the atmosphere of Earth, located above the troposphere and below the mesosphere. The stratosphere is composed of stratified temperature zones, with the warmer layers of air located higher ...
, where as present-day hurricanes extend into only the lower stratosphere. Hypercanes would have wind speeds of over , potentially gusting to , and would also have a central pressure of less than , giving them an enormous lifespan of at least several weeks. The pressure drop, compared to mean sea level pressure, would be the equivalent of being at almost in elevation, a level sufficient to cause altitude sickness. This extreme low pressure could also support massive storm systems roughly the size of North America. For comparison, the largest and most intense storm on record was 1979's Typhoon Tip, with a 1-minute sustained wind speed of and a minimum central pressure of . Such a storm would be nearly eight times more powerful than Hurricane Patricia, the storm with the highest sustained wind speed recorded, which had 1-minute sustained winds of . However, hypercanes may be as small as in size, and they would lose strength quickly after venturing into colder waters. The waters after a hypercane could remain hot enough for weeks, allowing more hypercanes to form. A hypercane's clouds would reach into the
stratosphere The stratosphere () is the second-lowest layer of the atmosphere of Earth, located above the troposphere and below the mesosphere. The stratosphere is composed of stratified temperature zones, with the warmer layers of air located higher ...
. Such an intense storm would also damage the Earth's
ozone layer The ozone layer or ozone shield is a region of Earth's stratosphere that absorption (electromagnetic radiation), absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the a ...
, potentially having devastating consequences for life on Earth. Water molecules in the stratosphere would react with
ozone Ozone () (or trioxygen) is an Inorganic compound, inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , break ...
to accelerate decay into O2 and reduce absorption of ultraviolet light.


Mechanism

A hurricane can be idealized as a Carnot heat engine powered by the temperature difference between the sea and the uppermost layer of the troposphere. As air is drawn in towards the eye it acquires
latent heat Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process—usually a first-order phase transition, like melting or condensation. ...
from evaporating sea-water, which is then released as
sensible heat Sensible heat is heat exchanged by a body or thermodynamic system in which the exchange of heat changes the temperature of the body or system, and some macroscopic variables of the body or system, but leaves unchanged certain other macroscopic vari ...
during the rise inside the eyewall and radiated away at the top of the storm system. The energy input is balanced by energy dissipation in a turbulent
boundary layer In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a Boundary (thermodynamic), bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces ...
close to the surface, which leads to an energy balance equilibrium. In Emanuel's model, if the temperature difference between the sea and the top of the
troposphere The troposphere is the lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the Atmosphere, planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the ...
is too large, there is no solution to the equilibrium equation. As more air is drawn in, the released heat reduces the central pressure further, drawing in more heat in a runaway positive feedback. The actual limit to hypercane intensity depends on other energy dissipation factors that are uncertain: whether inflow ceases to be isothermal, whether shock waves would form in the outflow around the eye, or whether turbulent breakdown of the vortex happens.


See also

* Extraterrestrial cyclone *
Global catastrophic risk A global catastrophic risk or a doomsday scenario is a hypothetical event that could damage human well-being on a global scale, endangering or even destroying modern civilization. Existential risk is a related term limited to events that co ...
* Great Dark Spot *
Great Red Spot The Great Red Spot is a persistent high-pressure area, high-pressure region in the atmosphere of Jupiter, producing an anticyclonic storm that is the largest in the Solar System. It is the most recognizable feature on Jupiter, owing to its red-o ...
* Saffir–Simpson scale *
Tornado A tornado is a violently rotating column of air that is in contact with the surface of Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, although the ...


References

{{Cyclones


External links


Hypercanes: The Next Big Disaster Movie?
– YouTube Tropical cyclone meteorology Weather hazards Doomsday scenarios Geological hazards Future problems Meteorological hypotheses