December 18, 2014 07:36 UTC

Science & Technology

Let It Snow, Let it Snow, Let It Snow!

Read, listen and learn English with this story. Double-click on any word to find the definition in the Merriam-Webster Learner's Dictionary.

The Science of Snow
The Science of Snow

Multimedia

Play or download an MP3 of this story
From VOA Learning English, this is SCIENCE IN THE NEWS, in Special English. I’m Bob Doughty.
 
And I’m Faith Lapidus. Today, we will tell you about a winter storm that brought heavy snowfall to the Middle East. And we will tell you everything you ever wanted to know about snow.

Snowfall is common in many areas during the winter. But snow recently fell in some places where it is rarely seen. The eastern Mediterranean received what has been called its worst winter storm in 20 years in early January. Weather experts say the storm produced as much snow and rainfall as the average precipitation totals for all winter long.
 
The storm affected life in many cities, from Gaza to Istanbul. It also worsened the suffering of hundreds of thousands of Syrian refugees and the one million other Syrians displaced from their homes by almost two years of conflict.
 
As much as 15 centimeters of snow fell in cities like Jerusalem, Ramallah, Amman and Damascus. As much as 30 centimeters of snow covered rural areas of Jordan and northern Israel. Officials there closed public transportation, schools, and government offices because of the snow. Many businesses did not open because their workers could not get to work.
 
But the news was not all bad. Some people enjoyed the snowfall. Israeli President Shimon Peres went outside and placed a hat on a snowman.
 
“It is so rare, so beautiful, so unifying. Whatever happens in Jerusalem is a blessing. This time it’s a blessing in white.”
 
Snow is a subject of great interest to weather experts. They sometimes have difficulty estimating where, when or how much snow will fall. One reason is that heavy amounts of snow fall in surprisingly small areas. Another reason is that a small change in temperature can mean the difference between snow and rain.
 
Just what is snow, anyway? Snow is a form of frozen water. It contains groups of ice particles called snow crystals. These crystals grow from water droplets in cold clouds. They usually grow around dust particles.
 
All snow crystals have six sides, but they grow in different shapes. The shape depends mainly on the temperature and water levels in the air.
 
Snow crystals grow in one of two designs: plate-like and columnar. Plate-like crystals are flat. They form when the air temperature is about 15 degrees below zero Celsius. Columnar snow crystals look like sticks of ice. They form when the temperature is about five degrees below zero.

The shape of a snow crystal may change from one form to another as the crystal passes through levels of air with different temperatures. When melting snow-crystals or raindrops fall through very cold air, they freeze to form small particles of ice, called sleet. Groups of frozen water-droplets are called snow pellets. Under some conditions, these particles may grow larger and form solid pieces of ice, or hail. Hail can be dangerous to people, animals and property.
 
When snow crystals stick together, they produce snowflakes. Snowflakes come in different sizes. As many as 100 crystals may join to form a snowflake larger than two and one-half centimeters. Under some conditions, snowflakes can form that are five centimeters across. Usually, this requires near-freezing temperatures, light winds and changing conditions in Earth’s atmosphere. 
Snow contains much less water than rain. About two and one-half centimeters of rain has as much water as 15 centimeters of wet snow. About 76 centimeters of dry snow equals the water in two and one-half centimeters of rain.
 
Much of the water the world uses comes from snow. Melting snow provides water for rivers, power stations and crops. Mountain snow provides up to 75 percent of all surface water supplies in the western United States.
 
Snowfall helps to protect plants and some wild animals from winter weather. Fresh snow is made largely of air trapped among the snow crystals. Because the air has trouble moving, the movement of heat is limited.
 
Snow also influences the movement of sound waves. When there is fresh snow on the ground, the surface of the snow absorbs, or takes in, sound waves. However, snow can become hard and flat as it grows older or if there have been strong winds. Then, the snow’s surface will help to send back sound waves. Under these conditions, sounds may seem clearer and may travel farther.
 
Generally, snow and ice appear white. This is because the light we see from the sun is white. Most natural materials take in some sunlight. This gives them their color. However, when light travels from air to snow, some light is sent back, or reflected. Snow crystals have many surfaces to reflect sunlight. Yet the snow does take in a little sunlight. It is this light that gives snow its white appearance. 
 
Sometimes, snow or ice may appear to be blue. The blue light is the product of a long path through the snow or ice. Think of snow or ice as a filter. A filter is designed to reject some substances, while permitting others to pass through. In the case of snow, light makes it through if the snow is only a centimeter thick. If it is a meter or more thick, however, blue light often can be seen.
 
Snow falls in the Earth’s extreme North and South throughout the year. However, the heaviest snowfalls have been reported in the mountains of other areas during winter. These areas include the Alps in Italy and Switzerland, the coastal mountains of western Canada, and the Sierra Nevada and Rocky Mountains in the United States. Snow is even known to fall near the Equator, but only on the highest mountains.
 
Each year, the continental United States has an average of 105 snowstorms. An average storm produces snow for two to five days. 
Almost every part of the United States has received snowfall at one time or another. Even parts of southern Florida have reported a few snowflakes.
 
The national record for snowfall in a single season was set in the winter of 1998 to 1999. Two thousand eight hundred ninety-five centimeters of snow fell at the Mount Baker Ski area in the northwestern state of Washington. 
 
People in many areas have little or no natural snowfall, but they still want to see snow. So scientists have come up with a solution. In 1936, a physicist from Japan produced the first man-made snow in a laboratory. Then, during the 1940s, American scientists developed methods for making snow in other areas. Clouds with extremely cool water are mixed with man-made ice crystals, such as silver iodide and metaldehyde crystals. Sometimes, dry ice particles or liquid propane are used. Today, machines are used to produce limited amounts of snow for ski areas when not enough natural snow has fallen. 
 
Snow may be beautiful, but it can be deadly. It is responsible for the deaths of hundreds of people in the United States every year. Many people die in traffic accidents on roads that are covered with snow or ice. Others die from being out in the cold, or from heart attacks caused by too much physical activity. 
 
You may not be able to avoid living in areas where it snows often. However, you can avoid becoming a victim of a snowstorm. Most people are told to stay in their homes until the storm has passed. When removing large amounts of snow, they should stop and rest often. Difficult physical activity during snow removal can cause a heart attack, especially among older adults. 
 
It is always a good idea to keep a lot of supplies in the home, even before winter begins. These supplies include food, medicine, clean water and extra power supplies.
 
Some drivers have become trapped in their vehicles during a snowstorm. If this happens, people should remain in or near their car unless they see some kind of help. They should get out and clear space around the vehicle’s exhaust pipe to prevent the possibility of carbon monoxide poisoning.
 
Drivers should tie a bright-colored object to the top of their car to increase the chance of rescue. Inside the car, they should open a window a little for fresh air and turn on the engine for ten or fifteen minutes every hour for heat.
 
People living in areas where winter storms are likely should carry emergency supplies in their vehicle. These include food, emergency medical supplies and extra clothing to stay warm and dry. People in these areas should always be prepared for winter emergencies. Snow can be beautiful, but it can also be dangerous.
This forum has been closed.
Comments
     
There are no comments in this forum. Be first and add one

Learn with The News

  • A screenshot from Cuban television shows President Raul Castro addressing the country, in Havana, Dec. 17, 2014.

    Audio US, Cuba Normalize Relations

    After the release of Alan Gross from prison, U.S. and Cuba announce policy changes that end more than 50 years of diplomatic isolation that began in the Cold War. Also in the news, India joins Pakistan in mourning after Tuesday's Taliban attack. And Sony Pictures cancels release of "The Interview." More

  • Audio How Much of You Does Facebook Own?

    If you use Facebook, your friends may have posted an update recently saying Facebook is not permitted to violate their privacy. But how much of your data -- things you post -- does Facebook legally own? Experts say Facebook's terms of service agreement clearly says they own most of what you post. More

  • India schoolgirls offer prayers for victims killed in a Taliban attack on a Pakistan military-run school, in Mumbai, India, Dec. 17, 2014.

    Audio India Joins Pakistan in Mourning Murdered Students

    India and Pakistan have long disagreed about many issues. But on Wednesday, Indian lawmakers and students lowered their heads and observed two minutes of silence in memory of 132 Pakistani children. The children died on Tuesday in an attack on their school in the city of Peshawar. More

  • Liberal Democratic Party (LDP) Secretary-General Sadakazu Tanigaki, center left, gestures next to Japan's Prime Minister Shinzo Abe, center right, as they pose during an election night event at the LDP headquarters in Tokyo, Dec. 14, 2014.

    Video Shinzo Abe's Victory Likely Raises Conflict with Neighbors

    Japan’s Prime Minister Shinzo Abe and his allies easily won a two-thirds majority in Parliament on Sunday. Mr. Abe’s win will permit him to continue economic reforms. At the same time, he can also pursue policies likely to increase tensions with Japan’s neighbors. More

  • Texas Execution

    Audio In US, Support for Death Penalty Is Strong

    Public opinion surveys show 60 percent of Americans want judges and juries to be able to sentence criminals to death. But the same studies show that many Americans have concerns about the justice system and the way executions are carried out. | As It Is More

Featured Stories

  • Lee Surrenders to Grant at Appomatox

    Audio Southern General Robert E. Lee Surrenders at Appomattox

    General Robert E. Lee’s military skill and intelligence helped extend the war between the states. But even his skill could not save the South from the industrial power of the North and its mighty armies -- armies that were better-fed and better-equipped. On Sunday, August 9, Lee surrendered. More

  • Uganda Playground for Disabled Children

    Audio Helping Uganda’s Disabled Children Play

    You may think that all children have freedom to play. But for children who look differently from others or have physical disabilities, the idea of play can seem far away. An organization in Uganda is seeking to change that. Read on to learn words needed to talk about this sometimes difficult topic. More

  • A microneedle used to inject glaucoma medications into the eye is shown next to a liquid drop from a conventional eye dropper. (Georgia Tech Photo: Gary Meek

    Audio Tiny Needles Treat Eye Disease

    Glaucoma is the second leading cause of blindness around the world. In the United States, more than two million people suffer from the disease. Now, researchers are developing very small needles that may offer a more effective and painless treatment for glaucoma and other eye diseases. More

  • The National Museum of Organized Crime and Law Enforcement in Las Vegas

    Audio Mob Museum Tells About the Mafia in America

    The U.S. government has long used public money to fight organized crime. Now, public money is also paying for a museum in Las Vegas to tell about "The Mob,” and not everyone is happy about that. But some say it helps the local economy by bringing people to a part of Las Vegas that few visit. More

  • Big Hero

    Video Filmmakers Create New Technology for 'Big Hero 6'

    Directors Don Hall and Chris Williams wanted the film to be based on some real science, to make it believable. 'We don’t have any super-powered people in this movie. It’s all super technology.' The film was just nominated for a 2014 Golden Globe award for best animated film. More

Practice Your Writing

Confessions of an English Learner BlogConfessions of an English Learner Blog

Tell us About Our Programs