Given that Hurricanes apparently serve no useful purpose and bring great harm and destruction to human life and property, given that the number of powerful and dangerous hurricanes is on the rise, no thanks to global warming, what can be done to stop them or to reduce their intensity? What is the state of the art in hurricane mitigation?
Over the past century, there have been a number of ideas and techniques that have been proposed and analyzed to stop, weaken or prevent dangerous hurricanes. It is a daunting task, given the astronomical amount of energy contained in a typical hurricane; no large scale successful experiment has been conducted yet.
What is a Hurricane?
A hurricane (aka a tropical cyclone) is a rapidly rotating storm system with a low-pressure center, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain. The storm is known as a hurricane in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon in the northwestern Pacific Ocean, and a cyclone in the south Pacific or Indian Ocean.
Tropical cyclones typically form over large bodies of relatively warm water. They are triggered by tropical atmospheric disturbances and pressure differences. Earth’s Coriolis effect causes winds to blow towards the low pressure center and create a circulation. The cyclone is fueled by the evaporation of warm water from the ocean surface, which rises and ultimately recondenses into clouds and rain, thereby releasing heat. As air flows inwards towards the low pressure center of the storm, the conservation of angular momentum principle causes the rotating winds to achieve higher and higher speeds. Often, cool dry air moves downwards in the eye of the storm. Hurricane winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
In the Northern hemisphere, the "right side of the storm" relative to the storm's forward motion is where the strongest winds are found because the propagation of the hurricane also contributes to its winds.
See en.wikipedia.org/… for more information on tropical cyclones
Scientists estimate that a tropical cyclone releases heat energy at the rate of 50 to 200 exajoules (1018 J) per day; this rate of energy release is equivalent to 70 times the world energy consumption of humans and 200 times the worldwide electrical generating capacity, or to exploding a 10-megaton nuclear bomb every 20 minutes.
Hurricane Tracks and Distribution
The following map from NASA shows the tracks of all tropical cyclones during the 1985-2005 time period. The Pacific Ocean west of the International Date Line sees more tropical cyclones than any other basin, while there is almost no activity in the Atlantic Ocean south of the Equator. Tropical cyclones do not form around the equator.
A large number of Atlantic hurricanes originate near the Cape Verde islands, off the west coast of Africa and are know as the “Cape Verde hurricanes.” These hurricanes form from a tropical wave that has passed over or near the Cape Verde islands after exiting the coast of West Africa. Hurricanes Dean (2007), Ivan (2004), Floyd (1999) Hugo (1989), Fran (1996), Isabelle (2003) are examples of Cape Verde hurricanes.
Hurricane Taming Techniques
Various techniques proposed over the years to prevent or weaken hurricanes include —
- Seeding hurricane clouds with silver iodide, to cause freezing and disruption of the inner structure of the hurricane
- Nuclear bombs
- Pumping surface warm water to the bottom of the ocean
- Spreading substances to prevent evaporation
- Changing the radiational balance in the hurricane environment by absorption of sunlight with carbon black
- Lasers — to precipitate rain (similar to seeding) and trigger lightning
- Sonic booms
- Dropping water absorbing substances
- Dropping ice into the hurricane
- Cooling the ocean with cryogenic material or icebergs
- Wind turbines
- Ocean thermal energy conversion (for power generation)
See www.popsci.com/… for a good summary.
Project Stormfury was a U.S. Government program between 1962 and 1983, where NOAA and its predecessor tried to weaken hurricanes by seeding them with silver iodide. During the STORMFURY years scientists seeded clouds in Hurricanes Esther (1961), Beulah (1963), Debbie (1969), and Ginger (1971). The experiments took place over the open Atlantic far from land.
It was hypothesized that the silver iodide would cause supercooled water in the storm to freeze, thereby disrupting the inner structure of the hurricane. However, it was later shown that this hypothesis was incorrect. It was determined that most hurricanes do not contain enough supercooled water for cloud seeding to be effective. Additionally, researchers found that unseeded hurricanes often undergo the same structural changes that were expected from seeded hurricanes.
The Salter Sink
The "Salter Sink" is a design invented around 2009 by professor Stephen Salter, Bill Gates and Nathan Myhrvold (formerly Chief Technology Officer at Microsoft, then co-founder of Intellectual Ventures) .
Stephen Salter, an emeritus professor of engineering design at the University of Edinburgh, proposed a method for mixing deep cold water and warm surface water of the ocean. The design consists of a floating ring structure 100 meters in diameter, which could be constructed out of used tires. The inner part of the ring would support a tube made of a flexible thin material 100 meters in diameter and 200 meters in length, hanging down towards the bottom of the ocean. Wave motion would slosh surface water into the ring, from where it would naturally sink to the bottom of the tube. Salter's design was relatively simple, inexpensive and required no explicit energy source. However, its operation is slow (note that it does not pump cold water to the ocean surface, it only transports some of the top surface warm water to the bottom) and would require a large number of these rings to be deployed during the hurricane season. See www.scientificamerican.com/... for more details.
Salter and and others surmised that the process might even increase the biological productivity of the seas, because it would mix nutrient-rich, deep water with warm, relatively nutrient-poor surface water. The ecological consequences of such large scale geo-engineering and the responses of biological systems to it are complex matters that require further study.
Bringing deep ocean waters to the surface may also lead to significant transfer of CO2 from the deep waters to the atmosphere, as cold deep water under high pressure contains a higher concentration of CO2.
The text for the main patent can be found here www.google.com/…; there are four more at www.google.com/.… The power source shown in the diagram below is for electronics used for monitoring and communications.
In 2001, the Dyn-O-Mat Company patented a water-absorbing substance called Dyn-O-Gel, which they claimed could be used to weaken a hurricane. The company actually tested it on live clouds and storms in the Caribbean. The small particles are able to absorb water up to several thousand times their own weight and create a heavy gel, and the clouds and thunderstorms tested actually did seem to disappear.
From www.prh.noaa.gov/… -
One of the biggest problems is, however, that it would take a LOT of the stuff to even hope to have an impact. 2 cm of rain falling over 1 square kilometer of surface deposits 20,000 metric tons of water. At the 2000-to-one ratio, each square km would require 10 tons of goop. If we take the eye to be 20 km in diameter surrounded by a 20 km thick eyewall, that's 3,769.91 square kilometers, requiring 37,699.1 tons of "Dyn-O-Gel". A C-5A heavy-lift transport airplane can carry a 100 ton payload. So that treating the eyewall would require 377 sorties. A typical average reflectivity in the eyewall is about 40 dB(Z), which works out to 1.3 cm/hr rain rate. Thus to keep the eyewall doped up, you'd need to deliver this much "Dyn-O-Gel" every hour-and-a-half or so. If you crank the reflectivity up to 43 dB(Z) you need to do it every hour. (If the eyewall is only 10 km thick, you can get by with 157 sorties every hour-and-a-half at the lower reflectivity.)
One of the popular solutions that occurs to most lay people is to drop a nuclear bomb into a hurricane and destroy it. Simple.
From www.aoml.noaa.gov/... —
The main difficulty with using explosives to modify hurricanes is the amount of energy required. A fully developed hurricane can release heat energy at a rate of 5 to 20x1013 watts and converts less than 10% of the heat into the mechanical energy of the wind. The heat release is equivalent to a 10-megaton nuclear bomb exploding every 20 minutes. According to the 1993 World Almanac, the entire human race used energy at a rate of 1013 watts in 1990, a rate less than 20% of the power of a hurricane.
In addition, an explosive, even a nuclear explosive, produces a shock wave, or pulse of high pressure, that propagates away from the site of the explosion somewhat faster than the speed of sound. Such an event doesn't raise the barometric pressure after the shock has passed because barometric pressure in the atmosphere reflects the weight of the air above the ground. For normal atmospheric pressure, there are about ten metric tons (1000 kilograms per ton) of air bearing down on each square meter of surface. In the strongest hurricanes there are nine. To change a Category 5 hurricane into a Category 2 hurricane you would have to add about a half ton of air for each square meter inside the eye, or a total of a bit more than half a billion (500,000,000) tons for a 20 km radius eye. It's difficult to envision a practical way of moving that much air around.
Apart from the fact that this might not even alter the storm, this approach neglects the problem that the released radioactive fallout would fairly quickly move with the tradewinds to affect land areas and cause devastating environmental problems.
This method proposed by University of Akron at Ohio professor Arkadii Leonov and his colleagues uses supersonic jet aircraft to fly in concentric circles around the eye of the hurricane. The jets would generate a sonic boom that would disrupt the upward flow of warm air that creates the hurricane. www.popsci.com/...
In their patent application, Leonov's team claimed that because sonic booms spread out as they travel away from an aircraft, you might only need a small number of jets to stop a hurricane. They wrote: "Two F-4 jet fighters flying at approximately Mach 1.5 are sufficient to suppress, mitigate and/or destroy a typical sized hurricane/typhoon."
The folks at NOAA were not too impressed, not to mention the minuscule power of a couple of F-14s compared with 1013 Watts of a hurricane. Also, the shock wave is like a very intense sound wave that passes through the storm without affecting it much. Nuclear bombs, although much more energetic, have the same issue.
Arrays of Offshore Wind Turbines
Mark Jacobson, a professor of civil and environmental engineering at Stanford University showed using computer simulations that 78,000 large wind turbines spread across 35,000 square kilometers of ocean outside of New Orleans would have cut Hurricane Katrina’s category 3 winds at landfall by 129 to 158 kilometers per hour (80 to 98 miles per hour) and reduced the storm surge by 79 percent. The same collection of turbines offshore of New York City would have dropped Hurricane Sandy’s winds by 125 to 140 kph and the surge by up to 34 percent. www.scientificamerican.com/...
Prof. Jacobson states — “The turbines pay for themselves through the revenue from generating electricity. The storm surge and wind protection are free - a bonus.”
Now that’s an interesting idea with benefits all around!
Other Geo-Engineering Techniques
There are number of geo-engineering proposals targeted not at hurricanes specifically, but aimed at the broader goal of combating global warming. From en.wikipedia.org/… -
Techniques that reduce solar heat absorption include —
- Surface-based: for example, using pale-colored roofing materials, attempting to change the oceans' brightness, or growing high-albedo crops.
- Troposphere-based: for example, marine cloud brightening, which would spray fine sea water to whiten clouds and thus increase cloud reflectivity.
- Upper atmosphere-based: creating reflective aerosols, such as stratospheric sulfate aerosols, specifically designed self-levitating aerosols, or other substances.
- Space-based: space sunshade—obstructing solar radiation with space-based mirrors, dust, etc.
Carbon dioxide removal techniques include —
Ocean cooling techniques —
Irma is shaping up to be one of the most powerful hurricanes in history. There are plenty of diaries here at DK with up-to-date information and resources on Irma.
Irma is a Cape Verde hurricane; Irma originated off the coast of West Africa.
Here is an IR image of Irma from the VIIRS instrument of the NASA-NOAA Suomi NPP satellite.
More images and animations at rammb.cira.colostate.edu/…
Interactive real-time imagery in multiple bands from the GOES-16 satellite at rammb-slider.cira.colostate.edu/...
Preventing or weakening hurricanes seems to be a technologically hard problem.
The long-term solution might be simply to prevent or reduce the effects of global warming by reducing our carbon footprint, phasing out fossil fuels, using green energy sources and improving energy efficiency.
But meanwhile, more research, funding and creative ideas are needed to prevent the hundreds of billions of dollars of damage caused by these monster hurricanes.
What do you think? Are you aware of other promising techniques?What are your insights on how we might tackle this gargantuan problem?
- Myths about hurricanes — www.prh.noaa.gov/…
- Tropical cyclone — en.wikipedia.org/…
- Hurricane info — www.hurricanescience.org/…
- Weather modification en.wikipedia.org/…
- Climate engineering — en.wikipedia.org/...
- Assessing A New Approach to Tropical Cyclone Modification by Hygroscopic Smoke — www.wmo.int/…
- Why Can’t We Stop A Hurricane Before It Hits Us? www.popsci.com/…
- Hurricane Forcing: Can Tropical Cyclones Be Stopped? — www.scientificamerican.com/…
- How to stop a hurricane (good luck, by the way) — blogs.scientificamerican.com/…
- The Man Who Wanted to Nuke a Hurricane — warisboring.com/…
- Can Hurricanes Be Tamed? Scientists Propose Novel Cloud-Seeding Method — insideclimatenews.org/…
Taming hurricanes with arrays of offshore wind turbines — www.nature.com/...
In the poll below, I intentionally did not list phasing out fossil fuels as an option — that’s too easy a choice and the right one for the long term.