Category Weather & Climate


          The damage caused to crops by large hailstones has prompted many attempts to prevent hail forming. Techniques similar to those used in cloud seeding have been tried, aiming to turn hailstones into rain, but this does not seem to work. In the early 20th century, people tried using “anti-hail guns”. These would fire huge amounts of debris into the clouds in an attempt to break up the hailstones. They were tried many times, unsuccessfully, in the vineyards of France.

          A Hail cannon is a shock wave generator claimed to disrupt the formation of hailstones in the atmosphere.

          These devices frequently engender conflict between farmers and neighbors when used, because they are repeatedly fired every 1 to 10 seconds while a storm is approaching and until it has passed through the area, yet there is no scientific evidence for their effectiveness.

          In the French wine-growing regions, church-bells were traditionally rung in the face of oncoming storms and later replaced by firing rockets or cannons.

          A mixture of acetylene and oxygen is ignited in the lower chamber of the machine. As the resulting blast passes through the neck and into the cone, it develops into a shock wave. This shock wave then travels at the speed of sound through the cloud formations above, a disturbance which manufacturers claim disrupts the growth phase of hailstones.

          Manufacturers claim that what would otherwise have fallen as hailstones then falls as slush or rain. It is said to be critical that the machine is running during the approach of the storm in order to affect the developing hailstones, although all manufacturers unanimously agree that the area of effect of their device is only 100 to 200 square meters directly above.

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          The next generation of lightning conductor could be a type of laser gun. A laser beam fired from the ground into a storm cloud could charge the air molecules along the way, creating a path for the lightning bolt to follow. Once the lightning is set on a direct path, its charge can be neutralized. It is thought that such a device could be used to steer lightning away from exposed structures such as power lines.

          Thousands of lightning bolts strike the Earth’s surface roughly every couple of seconds, but despite their ubiquity, this phenomena is somewhat poorly understood. Lightning is also unpredictable. While humans have been placing lightning rods for centuries to increase the probability of striking in a certain fixed point, its path cannot be controlled. That may be true in nature, but in the confinement of a lab of the INRS Energie Materiaux Telecommunications research centre (Varennes, QC, Canada), scientists have defied this common knowledge and used lasers to coax lighting to follow a predefined path.

          Lighting is one of the most powerful forces found in nature (if one single lightning strike was harnessed, the energy would power an entire home for a whole week), but at its core we can say that lightning is nothing but a discharge of static electricity. What we know from static electricity is that these discharges are caused by separation of charges into positive and negative ions.  Over time more of one charge builds until its natural attraction to the opposite charge causes it to migrate in an electrical discharge. In the case of lightning, the charge is built up in water.

          So, when you discharge static electricity between two tiny electrodes that’s basically a mini lightning strike – a couple of million volts short of the real deal discharged in thunder clouds. Electric arcs are used for all kinds of applications, from things as simple as ignition in a vehicle, to pollution control, to micromachining. Now, if you could also control the path of electric arc, then a slew of other potential applications could open up.

          One first baby step was made by the team at Advanced Laser Light Source facility, INRS. Their experiment was based on the self-healing properties of certain laser beams. When a laser beam is obstructed by an object, it can sometimes reconstruct its intensity once past the object. Using various laser shapes, like Airy beams and Bessel beams, the researchers guided electrical discharges and effectively controlled the path of mini lightning bolts, as described in Science advances.

          “Our fascination with lightning and electric arcs aside, this scientific discovery holds out significant potential and opens up new fields of research,” said Yves Begin, vice dean of research and academic affairs  at INRS. “This spectacular proof of concept, which was conducted over a distance of a few centimetres, required the high-power lasers, state-of-the-art facilities, and extraordinary research environment that our professors helped to create at INRS. Being able to work in such cutting-edge labs enables our students and postdoctoral fellows to embark on the path of scientific discovery even while still in school.”

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          Scientists believe that it may be possible to “kill” a tornado. Space satellites could be used to fire beams of microwave energy towards the base of a thunderstorm. The theory is that this would heat up the cool downdraft of air that helps create the tornado, effectively knocking it out. This sounds very much like science fiction, and many scientists claim that it could never work.

          The most intense tornadoes emerge from what are called supercell thunderstorms. For such a storm to form, you first “need the ingredients for a regular thunderstorm,” says Brooks. Those ingredients include warm moisture near the surface and relatively cold, dry air above. “The warm air will be buoyant, and like a hot-air balloon it will rise,” says Brooks.

          A supercell requires more: winds that increase in strength and change direction with height. “Then the updraft tends to rotate, and that makes a supercell,” explains Brooks. The supercell churns high in the air and, in about 30 percent of cases; it leads to the formation of a tornado below it. This happens when air descending from the supercell causes rotation near the ground.

          Even then, “we still don’t know why some thunderstorms create tornadoes while others don’t,” tornado-chaser Tim Samaras said in early 2013. Samaras was a scientist and National Geographic grantee who was killed by a twister on May 31, 2013, in El Reno, Oklahoma.

          Brooks says scientists believe strong changes in winds in the first kilometer of the atmosphere and high relative humidity are important for the formation of tornadoes. He adds that there also needs to be a downdraft in just the right part of the storm.

          Tornado formation also requires a “Goldilocks” situation, in which air must be cold but not too cold. It should be a few degrees more frigid than surrounding air, Brooks says.

          He adds, “We don’t understand how tornadoes die: Eventually the air gets too cold and it chokes off the inflow of new air into the storm, but we don’t know the details.”

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          Hurricanes are probably the most destructive of all extreme weather events — a category 5 hurricane is thought to contain the same amount of energy as all the world’s power plants combined. The ability to reduce this power would be a huge benefit. American scientists are looking at ways of cutting off a hurricane’s energy source by using cooking oil. The theory is that aircraft would be used to spray a thin layer of oil over the surface of the ocean. This would help prevent water evaporating into the atmosphere — the process that provides a hurricane with its heat and energy. This would work with any kind of oil, but vegetable oil is considered to be the most environmentally friendly substance. It is thought that using a process similar to cloud seeding could also be used to tame a hurricane by “cooling it down”.

          Tropical storms have the power to cause massive destruction and widespread loss of human life, as was demonstrated by last year’s deadly Atlantic hurricane season, which caused hundreds of deaths and $280 billion worth of damage. And as the world warms, scientists think these devastating events will only become more frequent and extreme.

          While this idea may seem a little farfetched, Norwegian scientists from SINTEF, the largest independent research organization in Scandinavia, say they have a feasible solution that involves, of all things, blowing cold air bubbles into the sea.

          Hurricanes are generated in the tropics when masses of cold and hot air collide with one another. But crucially, the sea surface temperature must be more than 79.7 degrees Fahrenheit, or 26.5 degrees Celsius, for a storm to form.

          “Climate change is causing sea surface temperatures to increase,” said Grim Eidnes, a senior research scientist at SINTEF Ocean, in a statement. “The critical temperature threshold at which evaporation is sufficient to promote the development of hurricanes is 26.5 degrees Celsius. In the case of hurricanes Harvey, Irma and Maria that occurred in the Gulf of Mexico in the period August to September 2017, sea surface temperatures were measured at 32 degrees Celsius [89.6 degrees Farenheit].”

          So, if there were a way to cool the surface temperature to below the magic 79.7 degrees Fahrenheit mark, then, in theory, humans could stop hurricanes.

          Various radical solutions have already been proposed to tackle this problem. One suggestion involved towing icebergs from the Arctic into the Gulf of Mexico. Another proposal suggested the use of seeding clouds with salt to make them whiter and therefore more reflective, which would block heat from the sun and reduce sea surface temperatures. Scientists have even tried to use aircraft to release dry ice near hurricanes, in an attempt to increase precipitation, which would release some of their destructive energy.

          However, none of these proposals or ideas have been much of a success, according to Eidnes. Now, the SINTEF researchers are developing a relatively simple method, known as a “bubble curtain,” which may prove to be more successful.

          The bubble curtain method involves placing perforated pipes below the water before pumping bubbles of compressed air through them. The idea is that the bubbles will rise, taking cold water with them that will cool the surface.

          The sintef team say that, ideally, the pipes should be placed between 100 and 150 meters below the surface to ensure that the water being carried to the surface is cold enough.

          “By bringing this water to the surface using the bubble curtains, the surface temperature will fall to below 26.5 degrees Celsius, thus cutting off the hurricane’s energy supply,” Eidnes said. “This method will allow us quite simply to prevent hurricanes from achieving life-threatening intensities.”

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          Cloud seeding is a scientific process that makes clouds produce rain and snow. It works by sending tiny particles of silver iodide, or other substances such as dry ice or liquid propane, into rain-bearing clouds, usually by aircraft. These substances stimulate the production of rain by providing something for water droplets to freeze on to — scientists call them ice nuclei. Once enough of the droplets take hold, they become heavy enough to fall to the ground. Cloud seeding cannot produce clouds — it can only make existing clouds produce rain.

          Cloud seeding is a type of weather modification that aims to change the amount or type of precipitation that falls from clouds by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud. The usual intent is to increase precipitation (rain or snow), but hail and fog suppression are also widely practised in airports where harsh weather conditions are experienced. Cloud seeding also occurs due to ice nucleators in nature, most of which are bacterial in origin.

          The most common chemicals used for cloud seeding include silver iodide, potassium iodide and dry ice (solid carbon dioxide). Liquid propane, which expands into a gas, has also been used. This can produce ice crystals at higher temperatures than silver iodide. After promising research, the use of hygroscopic materials, such as table salt, is becoming more popular.

          In mid-altitude clouds, the usual seeding strategy has been based on the fact that the equilibrium vapor pressure is lower over ice than over water. The formation of ice particles in supercooled clouds allows those particles to grow at the expense of liquid droplets. If sufficient growth takes place, the particles become heavy enough to fall as precipitation from clouds that otherwise would produce no precipitation. This process is known as “static” seeding.

          Seeding of warm-season or tropical cumulonimbus (convective) clouds seeks to exploit the latent heat released by freezing. This strategy of “dynamic” seeding assumes that the additional latent heat adds buoyancy, strengthens updrafts, ensures more low-level convergence, and ultimately causes rapid growth of properly selected clouds.

          Cloud seeding chemicals may be dispersed by aircraft or by dispersion devices located on the ground (generators or canisters fired from anti-aircraft guns or rockets). For release by aircraft, silver iodide flares are ignited and dispersed as an aircraft flies through the inflow of a cloud. When released by devices on the ground, the fine particles are carried downwind and upward by air currents after release.

          An electronic mechanism was tested in 2010, when infrared laser pulses were directed to the air above Berlin by researchers from the University of Geneva. The experimenters posited that the pulses would encourage atmospheric sulfur dioxide and nitrogen dioxide to form particles that would then act as seeds.

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          In the USA, 2 February is an important date for traditional weather forecasting. On this day, it is said that a groundhog emerges from hibernation to check on the weather. If it is sunny on that day, the groundhog will see its shadow and return to its burrow in the belief that the weather will be cold for the following six weeks. A cloudy day (and no shadow) will keep the groundhog above ground in anticipation of fine weather. The tradition originates in Europe, where 2 February, known as Candlemas, marks the point halfway between the winter solstice and the spring equinox.

          On this day in 1887, Groundhog Day, featuring a rodent meteorologist, is celebrated for the first time at Gobbler’s Knob in Punxsutawney, Pennsylvania. According to tradition, if a groundhog comes out of its hole on this day and sees its shadow, it gets scared and runs back into its burrow, predicting six more weeks of winter weather; no shadow means an early spring.

          Groundhog Day has its roots in the ancient Christian tradition of Candlemas, when clergy would bless and distribute candles needed for winter. The candles represented how long and cold the winter would be. Germans expanded on this concept by selecting an animal–the hedgehog–as a means of predicting weather. Once they came to America, German settlers in Pennsylvania continued the tradition, although they switched from hedgehogs to groundhogs, which were plentiful in the Keystone State.

          Groundhogs, also called woodchucks and whose scientific name is Marmota monax, typically weigh 12 to 15 pounds and live six to eight years. They eat vegetables and fruits, whistle when they’re frightened or looking for a mate (they’re sometimes called whistle pigs) and can climb trees and swim.

          They go into hibernation in the late fall; during this time, their body temperatures drop significantly, their heartbeats slow from 80 to five beats per minute and they can lose 30 percent of their body fat. In February, male groundhogs emerge from their burrows to look for a mate (not to predict the weather) before going underground again. They come out of hibernation for good in March.

          They go into hibernation in the late fall; during this time, their body temperatures drop significantly, their heartbeats slow from 80 to five beats per minute and they can lose 30 percent of their body fat. In February, male groundhogs emerge from their burrows to look for a mate (not to predict the weather) before going underground again. They come out of hibernation for good in March.

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