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  • Hurricanes. Typhoons. Cyclones.

  • They are creatures of tropical seas, sweeping up heat laden waters, converting it to wind,

  • rain, and waves.

  • Why do a rare few evolve into colossal monsters that leave in their wake a trail of destruction,

  • death, and despair?

  • Do we now face a rising tide of Super Hurricanes and Typhoons?

  • For millennia, we saw the oceans as mysterious wellsprings of natureÕs power.

  • Capable of rising up and engulfing us.

  • In William ShakespeareÕs drama, The Tempest, a shipÕs crew faces a sudden maelstrom, as

  • dramatized in the 2010 Julie Taymor film. Unknown to the crew, the storm was conjured

  • by a would be ruler turned sorcerer.

  • The story is said to have been inspired by a storm that sent the English flagship Sea Venture

  • onto Bermuda shoals in the year 1609.

  • ItÕs now one of many shipwrecks that litter tropical sea bottoms.

  • So too, the history books are filled with stories of cities and towns caught off guard

  • by the sudden onrush of a tropical storm.

  • Among the worst, Galveston, Texas, September 1900.

  • With swells beginning to rise on September 7th, officials issued a hurricane warning.

  • A ship at sea estimated the winds in the approaching storm at 100 miles, or 160 kilometers, per

  • hour.

  • As powerful as the storm was, little was known about it, including where it would hit and

  • how bad it would be.

  • By 5:00 PM, hurricane force winds began to pound the beaches of Galveston.

  • By the time the hurricane came ashore that evening, its winds had risen to 217 kilometers

  • per hourÉ a category four on todayÕs five-point Saffir-Simpson scale.

  • In what is still to this day the deadliest natural disaster in American history, 8,000

  • lives, 20% of the islandÕs population, were lost.

  • The city of Galveston was reduced to rubble by wind-driven waves and tides, called storm

  • surge, that rose to over 5 meters.

  • Hurricanes, also called cyclones or typhoons, are giant rotating storms that feed on solar

  • heat captured by tropical oceans.

  • A rare few, like the one that hit Galveston, go beyond the norm, to marshal the extreme

  • power of the seas.

  • In 1969, weather satellites showed hurricane Camille bearing down on the Mississippi coast.

  • ItÕs now six-thirty pm in Biloxi, Mississippi and the hurricane is really beginning to be

  • felt here. As you can see the palm trees are blowing, the rain is beginning to increase,

  • and the sea is beginning to churn in the Gulf. It promises to be a long, long night in Biloxi.

  • The storm intensified suddenly as it hit land with category five winds of over 300 kilometers

  • per hour, and a storm surge that reached 8 meters high.

  • Camille wrecked the coastline and drowned 143.

  • Sweeping inland, it brought floods to the mountains of Virginia that killed another

  • 113.

  • Ironically, just as Camille headed for landfall, scientists flew out to Hurricane Debbie to

  • perform the last in a series of experiments designed to bend back NatureÕs power.

  • The idea of the project, called Stormfury, was to load up an airplane with silver iodide

  • crystals.

  • Flying around the periphery of a storm, they would spread the crystals around in hopes

  • of stimulating new cloud formation, and in so doing steal the energy flowing into the

  • eye.

  • The idea was never proven to work.

  • We now see hurricanes, typhoons, and cyclones as the product of climate systems on a much

  • larger scale, water and wind, oceans and land.

  • They are fueled by heat from the sun, captured and stored in the upper layer of tropical

  • oceans.

  • The deeper and warmer this upper layer becomes, the stronger and longer lasting a hurricane

  • can be.

  • In the Atlantic ocean, they often begin their lives over mountains in East Africa.

  • As the wind sweeps over them, an area of low pressure forms. It tavels across the Sahara

  • Desert, then moves out over the warm Atlantic.

  • There, it can spawn thunderstorms over a broad region.

  • As the low gradually comes under the influence of the EarthÕs rotation, called the coriolis

  • force, it begins to spin.

  • As the storm intensifies, the pressure in its center continues to drop, forming whatÕs

  • known as the eye.

  • It acts like a partial vacuum, causing winds at the sea surface to spiral inward toward

  • it.

  • These in-spiraling winds evaporate moisture from the warm ocean surface. As they near

  • the eye, they veer upward, producing clouds and rain.

  • Much of this air moves outward at the top of the storm, like a chimney. Some flows back

  • down into the center, causing the eye to dry out and become clear.

  • The path a hurricane takes, and the intensity it reaches, are determined by its interaction

  • with global weather systems and ocean currents.

  • In most cases, they form in vast ocean areas along the equator, pushed along by equatorial

  • wind currents.

  • At higher latitudes, to the north and south, east-bound winds circle the globe.

  • Where they converge in the tropics, the flow shifts to the west, forming the trade winds

  • and a band of precipitation called the Intertropical Convergence Zone.

  • Stretching all around the Earth, this is the breeding ground for countless thunderstorms

  • and larger tropical storms.

  • The moisture they stir up often flows toward the poles, drawn by great spiraling weather

  • systems to the north and south.

  • When the tropics flare up, a fleet of satellites monitors the activity and sends down a wealth

  • of data about the state of the oceans and the atmosphere.

  • Meteorologists tap into a network of buoys and ship reports to monitor ocean temperatures,

  • wind, and wave heights, on the hunt for conditions that favor hurricane development.

  • From all this data, meteorologists have improved their ability to forecast the twists and turns

  • of a hurricaneÕs path.

  • As a result, few are caught by surprise, from shipping companies to coastal businesses,

  • local and state governments, and the public at large.

  • And yet the challenge of protecting life and property is only getting worse.

  • Lately, scientists have been computing the risks, and running the probabilities, of a

  • terrible growing conflict between humans and nature.

  • Quite simply, more and more people are moving to coastlines around the world, drawn by a

  • combination of jobs and lifestyle.

  • In the United States, for example, 39% of the population lives in coastal counties.

  • A Columbia University report takes a global look at this trend by identifying major disaster

  • hot spots.

  • Bangladesh. The Philippines. The east coast of China. The east coast of North America.

  • To make matters worse, the oceans have gotten steadily warmer over the last few decades,

  • adding potency to the hurricaneÕs fuel.

  • Sea levels are expected to rise by as much as a meter by the end of the century, increasing

  • the risks of storm surge.

  • As more people pack the coastlines, man and nature are in the midst of an excrutiating

  • head-on collision.

  • Hurricane Ike slammed into Galveston in 2008. The cost in 2010 dollars: 28 billion.

  • Andrew hit Miami in 1992. 45 billion.

  • Sandy swept into New Jersey in 2012. 60 billion.

  • Katrina in New Orleans: 106 billion.

  • Not to mention the loss of thousands of lives.

  • To help communities prepare, hurricane scientists are working to improve their ability to predict

  • changes in a stormÕs intensity: to find out whether it will fizzle, bringing only wind

  • and high surf, or become a destructive monster.

  • As large as a hurricane is, its behavior is subject to subtle shifts in wind and ocean

  • currents, the presence of land masses, and the interaction of all the clouds and water

  • molecules and even dust within it.

  • Scientists are zeroing in on a few key diagnostics.

  • One of these is the warmth of the ocean out ahead of the storm, the fuel that feeds a

  • hurricane.

  • Because hurricanes draw water up from the deep, a warm and thick surface layer is crucial

  • for the storm to reach high intensity.

  • When hurricane Katrina entered the Gulf of Mexico in 2005, it encountered a wide and

  • deep tongue of exceptionally warm water that originates in the Caribbean, called the loop

  • current.

  • As Katrina moved over this current, its winds picked up speed, reaching 281 kilometers per

  • hour, category five status.

  • A series of individual storms literally exploded close to the eye, visible in this sequence

  • of satellite images.

  • This often happens when the eye of the storm, the central region, contracts, getting smaller.

  • As the storm spins up, the winds moving around the eye accelerate.

  • Eddies, or vortices, begin to develop.

  • These whirling winds evaporate large volumes of moisture from the ocean surface. That feeds

  • the clouds, and causes them to shoot to high altitudes.

  • Because these clouds can be spotted from satellites, they are a sign that things are heating up.

  • These are photographs of the central, clear eye of Hurricane Katrina, taken by researchers

  • who flew into it.

  • From this vantage point, a hurricane is a beautiful architecture of the skies, built

  • from clouds that have erupted from the sea like bombs.

  • Their rise coincided with a fierce battle that had begun to develop deep within the

  • storm.

  • In this satellite image, a microwave beam was used to slice through Katrina at the point

  • of maximum intensity. Storms were rising all around the hurricane.

  • In radar images since the 1980s, scientists have seen that even as a tight, clear eyewall

  • forms, conditions can be so favorable for hurricane development that a second eyewall

  • forms around it.

  • That steals some of the inflowing air and causes the inner eyewall to fade away. The

  • outer eye then contracts, forming a new inner eye.

  • Through this process, strong hurricanes can go through cycles of weakening and intensifying.

  • You can see it happening in Katrina as it moved across the Gulf of Mexico. In this radar

  • image, Katrina was rated a category five, as winds raced around its relatively small

  • eye.

  • While the central eyewall remained intact, storm development on the periphery began to

  • sap its energy.

  • Entering cooler waters along the coast, it ramped down to a category 3.

  • Even then, wind driven waves breached levies that had been built to protect New Orleans,

  • and flooded the city.

  • But not all destructive storms fit this mold. Hurricane Sandy was a rare late October storm

  • rated category 1 as it moved up the Atlantic seaboard.

  • Forecasters predicted that Sandy would be blocked by a high pressure system moving across

  • Canada, then drawn to land in New Jersey by a storm moving up from the South.

  • Based on that guidance, the HMS Bounty, a replica of the famous ship built for a Marlon

  • Brando movie in 1960, sailed to the east. The captain hoped to go around the storm,

  • then to head south.

  • Instead, the ship sailed into the storm.

  • Responding to calls for help, the coast guard flew out into the storm to attempt a rescue.

  • Crew members had jumped into the sea to escape the sinking ship.

  • All but one were found and brought back to shore.

  • As Sandy moved up the coast, it passed over the unusually warm waters of the Gulf Stream.

  • That caused it to intensify to a more dangerous category 2 storm.

  • A hurricane hunter aircraft from Keesler Air Force Base in Mississippi flew in to poinpoint

  • its center, to help determine where exactly it would make landfall and when.

  • The crew did this in part by flying down to get a look at the movement of waves and wind at

  • the surface.

  • They dropped sensors to measure wind speeds all the way down to the ocean.

  • Turning into colder coastal waters, Sandy lost strength as it came ashore at night in

  • New Jersey.

  • But because it ran ashore at high tide, during a full moon, Sandy delivered storm surge levels

  • of about 4 meters, almost as high as Katrina.

  • As accurate as the forecasts had been, they could not have prevented the catastrophic

  • damage that the region sustained.

  • Community and government leaders have since proposed ambitious plans to mitigate the damage

  • from future super storms, from building on stilts to sealing off subway and train tunnels,

  • and even leveling flood prone communities.

  • Whether or not future sea levels rise, or storms become stronger, coastal population

  • growth around the world ensures an ongoing stream of mega disasters.

  • The latest, a typhoon called Haiyan, rose up for all to see in the Western Pacific Ocean.

  • With no land masses to disrupt it, or cool currents to sap its strength, Haiyan reached

  • supertyphoon status.

  • At landfall, surface wind estimates ranged from 200 to 300 kilometers per hour.

  • Hitting a densely populated region in the Philippines, the storm displaced some 4.3

  • million, killed at least 6 thousand, destroyed crops, infrastructure, and half a million

  • homes.

  • The tools scientists are now using to study and predict the rise and fall of tropical

  • storms are more accurate than ever: rainfall rates, convective towers, the battle of the

  • eyewalls, and more.

  • They are learning how these factors evolve within the context of changing storm environments

  • and a changing global climate.

  • Devastating storms no longer seem to come from nowhere.

  • At the same time, when a super hurricane and super typhoon forms, the stakes are steadily rising.

  • For with each new storm season, we crowd ever closer to the shores.

  • And brace ourselves against the gale winds and rising tides of a planet in motion.

Hurricanes. Typhoons. Cyclones.

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スーパーハリケーンと台風 (Super Hurricanes and Typhoons)

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    realvip に公開 2021 年 01 月 14 日
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