Category Weather & Climate

          Napoleon Bonaparte was one of the finest military leaders in history. His clever tactics brought a series of victories that allowed him to rule over large parts of Europe over 200 years ago. However, it was the weather that was to prove instrumental in his downfall. He invaded Russia in the summer of 1812 and captured Moscow, following the Russians deeper into the country. By November, a lack of supplies forced Napoleon and his army to retreat, and the extremely harsh winter killed many thousands of troops as they returned to France.

          In the year 1812, the infamous Napoleon assembled the largest army Europe had ever seen, more than 600 000 men strong. His plan was to march into Russia, and his last concern was the approaching winter chills. Napoleon confidently captured Moscow; his soldiers pillaged the city, stealing jewels, furs, and war prizes. However, it was too soon to be celebrating – since Napoleon had failed to consider how very cold Russia can be. As Napoleon’s army marched away with their prizes, temperatures dropped to minus 40 degrees Celsius. Many soldiers died of frostbite and starvation, and in one 24-hour period 50 000 horses died from the cold – leaving men to struggle on foot through the icy environment. Even with their stolen furs to wrap themselves up in – of the 600 000 men who marched into Russia, only 150 000 limped home. This was the beginning of the end for Napoleon’s empire, and heralded the emergence of Russia as a power in Europe.

Picture Credit : Google

          Throughout history, the weather has had a major influence on the outcome of certain events. Adverse weather conditions have helped decide the outcome of battles and military campaigns, while over longer periods of time, climate change is thought to have brought about the end of some civilizations and the beginning of others.

          While searching for some topic of interest to bumble on about in this blog, I remembered an article I read ages ago that left an impression. Maybe the weather is something that most of us at CSAG think about on a daily basis (I hope), but it is interesting to hear how the weather has helped shaped history – and thus the societal world we live in.  As will be discussed shortly, the weather can be a huge deciding point in what happens when, and it is interesting to hear about events that may or may not have happened because of weather conditions (and I’m not talking about a picnic at Kirstenbosch event).

          On the 6th August 1945 it was a fine summer day in Hiroshima. At 7:09am a weather reconnaissance plane passed overhead and radioed back: “Cloud cover less than three-tenths. Advice: bomb primary.” Thus, the sky was clear enough to drop the first nuclear weapon used in war. The lack of cloud cover sealed Hiroshima’s fate, and spared the back-up target. Even more dramatic was the effect of cloud cover on Kokura. On the 8th August 1945, the second nuclear weapon was loaded into a B-29, however the skies were overcast over the primary target, Kokura. Instead, the bomb was released over the backup target: Nagasaki.

          In the 13th century, Kublai Khan, leader of the Mongol Empire, set his sights on the conquest of Japan, but was defeated by not one, but two monsoons. Shinto priests, who believed the storms were the result of prayer, called them kamikaze or “divine wind.”

Picture Credit : Google

          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.

Picture Credit : Google

          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.”

Picture Credit : Google

          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.”

Picture Credit : Google

          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.

Picture Credit : Google

          The Appearance of blossom on trees is traditionally said to mark the beginning of spring and the end of winter. Trees do only come into bloom in mild weather, but as anyone who lives in a temperate part of the world knows, cold weather will often return after the blossom appears! The dates on which blossom appears have been recorded in some weather records for many years, which helps to show what the weather was like in the past.

          The cherry blossoms will be blooming again soon around the Tidal Basin in Washington, D.C., as they have every year since Japan shipped its arboreal gift of more than 3,000 cherry trees to the United States in 1912. And for this year, anyway, climate change won’t have much effect on the timing.

          The projected peak days for 2019 are right around the historic average of the past several decades, according to the park service. The agency determined the projected dates after analyzing a variety of data, including winter temperatures and the forecast for March, according to NPS acting superintendent Jeffrey Rein bold. He said that the development of the blossoms will depend on variable weather conditions.

          Experts at the park service and elsewhere say that local conditions of daylight and heat are the main factors that determine the blooming time in temperate ecosystems. However, they say that although bloom times can vary from year to year because of those local conditions, the long-term trends clearly show the impact of climate change on the trees in Washington, D.C., and elsewhere.

Picture Credit : Google

          Pine Cones make one of the best natural weather indicators. The scales of a pine cone open out when the weather is dry and close up when the air is humid — a good sign that rain is coming. The natural state of the cone is closed — the scales are shrivelling up when it is dry. When the air is moist, the cone becomes flexible again and returns to its regular shape.

          There are two main types of superstitions tying plants and animals to weather forecasting: Those that imply that the flora and fauna “know” what the coming season (typically winter), will bring, and those that rely on the physics, chemistry and biology of living things responding to changing conditions. The former generally don’t hold up — plants and animals react to their past or present environments, they don’t predict the future — but there’s definitely hope for the latter.

          For example, some say that a profusion of pine cones in fall means a cold winter to follow. This one’s a bust: Actually, pine trees can take three years to fully grow cones, and varying their cone production from year to year helps them throw off predators. However, you can use pine cones to predict weather in another way: watching as they open or close.

          Pine cones are the procreative parts of pine trees. Male versions produce pollen, and pollenated female forms yield seeds. Under dry conditions, the outer parts of the cones’ scales dry more than the inner parts, causing the cone to open. This is good news for the tree, since dry, calm weather provide a better environment for seed dispersal. In wet weather, the scales absorb moisture and swell shut, shielding the seeds until better days roll around.

Picture Credit : Google