GB2436197A

GB2436197A - Neutralisation of strong winds

Info

Publication number: GB2436197A
Application number: GB0605087A
Authority: GB
Inventors: Stephen Tew; Henrik Hess-Petersen
Original assignee: GEN APPLIC FOR SPECIAL MATERIA
Current assignee: GEN APPLIC FOR SPECIAL MATERIA
Priority date: 2006-03-14
Filing date: 2006-03-14
Publication date: 2007-09-19
Also published as: GB0605087D0; WO2007105014A1

Abstract

Any Aerogel placed inside a hurricane to help neutralise it, by absorbing the water.

Description

NEUTRALISATION OF STRONG WINDS

Field of the Invention

The present invention relates to the neutralisation of strong winds. In particular, the invention relates to the neutralisation of hurricane-force winds (also known as "big winds") and the prevention of hurricane formation.

Background to the Invention

Big winds (Hurricanes, typhoons), are well known, and are severe storms that form under certain conditions. Big winds for example gather heat and energy through contact with warm waters. Evaporation from the water increases their power. Big winds rotate in a counter-clockwise direction around an "eye." Big winds generally have winds at least 74 miles per hour. When they come onto land, the heavy rain, strong winds and heavy waves can damage buildings, trees and cars.

Big winds are part of a family of weather systems known as "tropical cyclones".

A hurricane begins its life as a disorganized storm system which forms over warm, tropical waters in the Atlantic. When the storm system becomes more organized, it is classified as a "tropical depression," and given a number by the National Hurricane Centre. If the winds in a tropical depression grow in intensity to 40mph, it is re-classified as a "tropical storm," and it receives a name. When the winds in the storm reach 75mph (1 2okph), the storm is upgraded to a hurricane. The winds of a hurricane are structured around a central "eye", which is an area that is free of clouds and relatively calm. Around this "eye" area, storm clouds wrap in a counter-clockwise motion. This "eyewall" of clouds, wind and rain, is the most destructive part of the storm. In fact, it is the eyewall that creates the eye, since the rapidly spinning clouds in the wall reduce the pressure in the eye and suck out any clouds that may be there.

Big winds are classified into five categories, based on their wind speeds and potential to cause damage.

* Category One --Winds 74-95 miles per hour * Category Two --Winds 96-110 miles per hour * Category Three --Winds 111-130 miles per hour * Category Four--Winds 13 1-155 miles per hour * Category Five --Winds greater than 155 miles per hour These big winds cause massive destruction, even death.

Hurricane Andrew, the most expensive natural disaster in United States history, caused $26.5 billion worth of damage, it cut a path through the north-western Bahamas, the southern Florida peninsula and south-central Louisiana. The category 5 hurricane came ashore on August 24, 1992, near Homestead, Florida, resulting in 15 deaths. As many as 250,000 people were left temporarily homeless. More than 700,000 insurance claims were filed relating to Andrew.

One known method to weaken big winds is the dropping of silver iodide -a substance that serves as effective ice nuclei -into the rain bands of the storms.

The dropping or seeding targeted convective clouds just outside the hurricane's eyewall in an attempt to form a new ring of clouds that, it was hoped, would compete with the natural circulation of the storm and weaken it. The idea was that the silver iodide would enhance the thunderstorms of a rain band by causing the supercooled water to freeze, thus liberating the latent heat of fusion and helping a rain band to grow at the expense of the eyewall. With a weakened convergence to the eyewall, the strong inner core winds would also weaken quite a bit. For cloud seeding to be successful, the clouds must contain sufficient supercooled water (water that has remained liquid at temperatures below the freezing point, 0 C/32 F) Another method used involves the use of "Dyn-O-Gel". This is a special powder (produced by Dyn-O-Mat) that absorbs large amounts of moisture and then becomes a gooey gel. It has been proposed to drop large amounts of the substance into the clouds of a hurricane to dissipate some of the clouds thus helping to weaken or destroy the hurricane. This is described in more detail in US 6,315,213.

One possible way that "Dyn-O-Gel" could weaken a hurricane has been tried out. An effect was seen but it was small (l mis). The argument was that the gel would make raindrops lumpy (i.e., non-aerodynamic), they would fall more slowly and increase condensate loading, thus weakening the eyewall updraft. If, by contrast, one increases the fall speed of the hydrometeors, the storm strengthens (again by only -P1 mis). In the numerical experiments "decrease" meant reduce the fall velocity to half the real value, and "increase" meant double the real value. The foregoing effect is larger than anything one could hope to produce in the real atmosphere.

One of the biggest problems is, that it would take a lot of the Dyn-O-Gel to even hope to have an impact. 2 cm of rain falling over 1 square kilometre of surface deposits 20,000 tonnes of water. At the 2000-to-one ratio that "Dyn-O-Gel" advertise, each square km would require 10 tonnes of material. If we take the eye to be 20 km in diameter surrounded by a 20km thick eyewall, that's 3,769.91 square kilometres, requiring 37,699.1 tonnes of "Dyn-O-Gel". A C-5A heavy-lift transport airplane can carry a 100 tonne 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 cmlhr 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.).

Summary of the Invention

It is the object of this invention to either slow down a big wind or stop the big wind and overcome the problems seen by Dyn-O-Gel and other methods.

I

It is known that a big wind over land will begin to weaken rapidly -not because of friction -but because the storm lacks the moisture and heat sources that the ocean provided. This depletion of moisture and heat hurts the big winds ability to produce thunderstorms near the storm centre. Without this convection, the storm rapidly fills.

The lack of moisture is due to dust particles that are picked up from the ground. These attach to the water, causing rain to form. As the moisture dissipates as rain, the wind loses strength and eventually slows down or stops.

In accordance with one aspect of the present invention there is provided a method for seeding a rain cloud, comprising: introducing a material having a high surface area mass ratio into the cloud.

In accordance with another aspect of the present invention there is provided a method of reducing the force of a storm, comprising introducing a material having a high surface area: mass ratio into the path of the storm. The material should absorb water, and will therefore need to be highly porous.

A preferred material is that known as "aerogel". Aerogel is a silica amorphous material, a desiccant and it has an extremely large surface area per unit mass. The surface area is about 600 m2/g.

The aerogel is dropped into the big wind as early as possible, preferably by the use of a reinforced aeroplane (although it will be appreciated that other methods of introducing the aerogel are possible). Because the Aerogel is a desiccant it will absorb water, but as it has an extremely large surface area it will create a massive amount of rain due to the large mass of the individual particles absorbing water.

In more detail, aerogel comprises interconnected strands of silica. Aerogels are very interesting materials due to their extremely low density, low index of refraction, and reasonably high light transmission properties. The density can be less than 1% of that of ordinary glass, with aerogels still exhibiting glass-like transparency and high monolithicity. Cabot Corporation (USA) manufacture and distribute an aerogel material under the trade mark NanogelTM. Explained simply, the aerogel production process consists of a sol-gel process followed by a supercritical drying of the gel. The product is a transparent, highly porous, inorganic material in which the solid part is quartz. 1)

Claims

CLAIMS: 1. A method of seeding a rain cloud, comprising introducing a

material having a high surface area: mass ratio into the cloud.

2. A method of reducing the force of a storm, comprising introducing a material having a high surface area: mass ratio into the path of the storm.

3. A method as claimed in claim 2, wherein the material absorbs water.

4. A method of reducing the force of a storm, comprising introducing a highly porous, low density material into the path of the storm.

5. A method as claimed in claim 2, 3 or 4, wherein the material stimulates the formation of rain.

6. A method as claimed in any preceding claim, wherein the material is aerogel.

7. A method as claimed in any preceding claim, comprising releasing the material from an aeroplane.

8. A method of reducing the force of a storm, comprising introducing aerogel into the path of the storm.

9. A system for neutralising the force of a storm, comprising: a material having a high surface area: mass ratio; and a delivery mechanism for introducing the material into the path of the storm.

10. A system as claimed in claim 9, wherein the material is aerogel.

11. A system as claimed in claim 9 or 10, wherein the delivery mechanism includes an aeroplane.