Hypercane

Template:Short description Template:Use mdy dates A hypercane is a hypothetical class of extreme tropical cyclone that could form if sea surface temperatures reached approximately Template:Convert, which is Template:Convert warmer than the warmest ocean temperature ever recorded.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Such an increase could be caused by a large asteroid or comet impact, a large supervolcanic eruption, a large submarine flood basalt, or "incredible" global warming.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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 dinosaurs.<ref name="extinction" /> The hypothesis was created by Kerry Emanuel of MIT, who also coined the term.<ref>Template:Cite magazine</ref><ref name="MIT">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="extinction">Template:Cite journal</ref>

Description

File:Typhoonsizes.svg

The relative sizes of Typhoon Tip, Cyclone Tracy, and the Contiguous United States. While hypercanes can be smaller than Cyclone Tracy, the largest hypercanes could even exceed Typhoon Tip in size.

In order to form a hypercane, according to Emanuel's hypothetical model, the ocean temperature would have to be at least Template:Convert. A critical difference between a hypercane and present-day hurricanes is that a hypercane would extend into the upper stratosphere, where as present-day hurricanes extend into only the lower stratosphere.<ref>Template:Cite interview</ref>Template:Full citation needed

Hypercanes would have wind speeds of over Template:Convert, potentially gusting to Template:Cvt,<ref name="600 mph winds">Template:Cite news</ref> and would also have a central pressure of less than Template:Convert, giving them an enormous lifespan of at least several weeks.<ref name="MIT" /> The pressure drop, compared to mean sea level pressure, would be the equivalent of being at almost Template:Convert in elevation,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> a level sufficient to cause altitude sickness.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> This extreme low pressure could also support massive storm systems roughly the size of North America.<ref name="MIT" /><ref name="end life">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> For comparison, the largest and most intense storm on record was 1979's Typhoon Tip, with a 1-minute sustained wind speed of Template:Cvt and a minimum central pressure of Template:Cvt. 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 Template:Convert.<ref>Template:Cite interview</ref>Template:Full citation needed However, hypercanes may be as small as Template:Cvt in size, and they would lose strength quickly after venturing into colder waters.<ref name="600 mph winds"/>

The waters after a hypercane could remain hot enough for weeks, allowing more hypercanes to form. A hypercane's clouds would reach Template:Convert into the stratosphere. Such an intense storm would also damage the Earth's ozone layer, potentially having devastating consequences for life on Earth.<ref name="MIT" />Template:Failed verification Water molecules in the stratosphere would react with ozone to accelerate decay into O₂ and reduce absorption of ultraviolet light.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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 from evaporating sea-water, which is then released as sensible heat 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 close to the surface, which leads to an energy balance equilibrium. Template:Citation needed

In Emanuel's model, if the temperature difference between the sea and the top of the troposphere 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.<ref name="extinction" /><ref>Template:Cite journal</ref>

See also

• Extraterrestrial cyclone
• Global catastrophic risk
• Great Dark Spot
• Great Red Spot
• Saffir–Simpson scale
• Tornado

External links

• Hypercanes: The Next Big Disaster Movie? – YouTube