Tag Archives: ice

From Snow to Freezing Rain: Why Winter Precipitation Can Take Several Forms

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The winter season can produce various types of precipitation – rain, freezing rain, sleet, or snow. The form we see at the surface depends on the temperature profile of the lower atmosphere.

All precipitation starts out as snow up in the clouds.  But, as it falls toward the Earth, it can pass through one or more layers of air with different temperatures.  When the snow passes through a thick layer of warm air – above 32°F – it melts into rain.  If the warm air layer extends all the way to the ground, rain will fall at the surface.  However, if there is a thin layer of cold air – below 32°F – near the ground, the rain becomes supercooled and freezes upon impact with anything that has a temperature at or below 32°F.  This is known as freezing rain.  It is one of the most dangerous types of winter precipitation, as it forms a glaze of ice on almost everything it encounters, including roads, tree branches, and power lines.

Sleet is a frozen type precipitation that takes the form of ice-pellets. Passing through a thick layer of sub-freezing air near the surface, liquid raindrops are given enough time to re-freeze before reaching the ground. Sleet often bounces when it hits a surface, but does not stick to anything.  It can, however, accumulate.

Snow is another type of frozen precipitation.  It takes the shape of six-sided ice crystals, often called flakes.  Snow will fall at the surface when the air temperature is below freezing all the way from the cloud-level down to the ground.  In order for the snow to stick and accumulate, surface temperatures must also be at or below freezing.

When two or more of these precipitation types fall during a single storm, it is called a wintry mix.

Precipitation type depends on the temperature profile of the atmosphere. Credit: NOAA

From Snow to Freezing Rain, Winter Precipitation Can Take Several Forms

Posted on by

The winter season can produce various types of precipitation – rain, freezing rain, sleet, or snow. The form we see at the surface depends on the temperature profile of the lower atmosphere.

All precipitation starts out as snow up in the clouds.  But, as it falls toward the Earth, it can pass through one or more layers of air with different temperatures.  When the snow passes through a thick layer of warm air – above 32°F – it melts into rain.  If the warm air layer extends all the way to the ground, rain will fall at the surface.  However, if there is a thin layer of cold air – below 32°F – near the ground, the rain becomes super-cooled and freezes upon impact with anything that has a temperature at or below 32°F.  This is known as freezing rain.  It is one of the most dangerous types of winter precipitation, as it forms a glaze of ice on almost everything it encounters, including roads, tree branches, and power lines.

Sleet is a frozen type precipitation that takes the form of ice-pellets. Passing through a thick layer of sub-freezing air near the surface, liquid raindrops are given enough time to re-freeze before reaching the ground. Sleet often bounces when it hits a surface, but does not stick to anything.  It can, however, accumulate.

Snow is another type of frozen precipitation.  It takes the shape of six-sided ice crystals, often called flakes.  Snow will fall at the surface when the air temperature is below freezing all the way from the cloud-level down to the ground.  In order for the snow to stick and accumulate, surface temperatures must also be at or below freezing.

When two or more of these precipitation types fall during a single storm, it is called a wintry mix.

Precipitation type depends on the temperature profile of the atmosphere. Credit: NOAA

From Snow to Ice, Winter Precipitation Can Take Several Forms

Posted on by

The winter season can produce various types of precipitation – rain, freezing rain, sleet, or snow. It depends on the temperature profile of the lower atmosphere.

All precipitation starts out as snow up in the clouds.  But, as it falls toward the Earth, it can pass through one or more layers of air with different temperatures.  When the snow passes through a thick layer of warm air – above 32°F – it melts into rain.  If the warm air layer extends all the way to the ground, rain will fall at the surface.  However, if there is a thin layer of cold air – below 32°F – near the ground, the rain becomes super-cooled and freezes upon impact with anything that has a temperature at or below 32°F.  This is known as freezing rain.  It is one of the most dangerous types of winter precipitation, as it forms a glaze of ice on almost everything it encounters, including roads, tree branches, and power lines.

Sleet is a frozen type precipitation that takes the form of ice-pellets. Passing through a thick layer of sub-freezing air near the surface, liquid raindrops are given enough time to re-freeze before reaching the ground. Sleet often bounces when it hits a surface, but does not stick to anything.  It can, however, accumulate.

Snow is another type of frozen precipitation.  It takes the shape of six-sided ice crystals, often called flakes.  Snow will fall at the surface when the air temperature is below freezing all the way from the cloud-level down to the ground.  In order for the snow to stick and accumulate, surface temperatures must also be at or below freezing.

When two or more of these precipitation types fall during a single storm, it is called a wintry mix.

Precipitation type depends on the temperature profile of the atmosphere. Credit: NOAA

Art and Climate Change: “In Human Time”

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The inaugural exhibition of The Climate Museum in New York City has brought art and science together in an effort to expand public understanding of climate change. 

“In Human Time” explores the intersections of polar ice, timescales, and human perception. Installed at the Sheila C. Johnson Design Center at the Parsons School of Design (the museum is looking for a permanent home), the exhibit is divided into two parts. The first of which (December 20 – January 15) displayed Zaria Forman’s large-scale image, Whale Bay, Antarctica No. 4. Depicting calved glacial ice grounded in shallow water, it could easily be mistaken for a photograph captured in an instant. However, a time-lapse video alongside the piece reveals it to be a pastel drawing created by hand over many weeks.

Ice Cores. Credit: Peggy Weil

The second part of the exhibition (January 19 – February 11) focuses on the Arctic and highlight’s Peggy Weil’s 88 Cores. This slow-paced video is essentially one continuous pan that takes the viewer nearly two miles down into the Greenland ice sheet and more than 100,000 years back in time. Photographs of ice cores as well as artifacts and media that offer a science context to the Arctic ice accompany the artwork.

“The Climate Museum’s mission,” according to its website, “ is to employ the sciences, art, and design to inspire dialogue and innovation that address the challenges of climate change, moving solutions to the center of our shared public life and catalyzing broad community engagement.”

The exhibition is on view through February 11, 2018, at :
The Arnold and Sheila Aronson Galleries
Sheila C. Johnson Design Center
Parsons School of Design
66 Fifth Avenue, New York City

For more information, visit http://climatemuseum.org/home

“Whale Bay, Antarctica No. 4″, Pastel on Paper, 84″x144”. Credit: Zaria Forman.

Climate Change Indicator: Arctic Sea Ice

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There are a number of key indicators, beyond our rising global temperature, that show Earth’s climate is changing. One of these is Arctic sea ice.

Measured via satellite since the late 1970’s, the extent and thickness of sea ice tend to vary from year to year but both have been in an overall decline for decades. According to NASA, the melt season in the Arctic has increased by 37 days since 1979.

Sea ice extent, the area of ocean with at least 15% sea ice, has a strong seasonal cycle. It typically peaks in March as winter ends and then declines during the summer, reaching a minimum in September. In March 2017, it hit a record low maximum for the third year in a row. The record minimum occurred in September 2012.

According to the National Snow and Ice Data Center, the average age of Arctic sea ice is also changing. Thick multi-year ice – the ice that lasts through at least one melt season – has decreased 11% per decade since the satellite era began. That means there is more first-year ice, which tends to be thin and brittle. This is troublesome because it is more vulnerable to warming temperatures and wave action.

Sea ice is frozen ocean water. It forms, grows, and melts in the ocean. In contrast to land ice (glaciers), it does not contribute to sea level rise. However, as it melts it creates a global warming feedback loop. Ice is lighter in color and reflects more sunlight than dark ocean water. So, as more ocean water is exposed, more of the sun’s energy is absorbed. This drives temperatures up even further and causes more ice to melt.

The Arctic is now warming twice as fast as the rest of the planet – a phenomenon known as “Arctic amplification.”  At this rate, scientists expect the region to be ice-free in summer by the 2030s.

Credit: NSIDC

Ice Thickness Guidelines for Winter Activities

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On Monday night, a group of teenagers fell through the thin ice on a body of water in Central Park known as The Pond. Luckily, all were saved by the quick actions of good samaritans and NYC’s outstanding first responders. That said, this unfortunate incident is a salient reminder about safety issues for all winter activities that take place on the ice.

Winter is usually the time for ice-skating, ice-fishing, cross-country skiing, and snowmobiling. This year, however, unseasonably mild conditions have limited the opportunities for many of these popular pursuits. While there have been a few blasts of cold air, they have not lasted long enough to produce ice that can sustain significant weight. Below are some guidelines on how thick the ice needs to be to support different activities.

It is also important to remember that the thickness of ice can vary dramatically at different locations on the same body of water. Therefore, it is always best to follow the instructions of local officials and posted signs. Moreover, as the old saying goes: “If in doubt, don’t go out!”

Credit: NWS

When to Expect the Final Freeze of Spring

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Most people often associate spring with flowers and mild weather. But as a transitional season, it can also produce some serious cold spells. Wearing shorts one day and a parka the next, you start to wonder when the cold will finally fade away.

The answer to that question largely depends on where you live. Below is a map from NOAA that shows the typical final freeze dates across the continental US. While actual weather conditions vary from year to year, the dates shown are based on climatology – a thirty-year average of temperature data.

Here in New York City, our last spring freeze usually comes in mid-April.

Credit: NOAA

Credit: NOAA

Frigid Weather Turns Ocean Waves to Slush

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How cold has it been in New England recently? Cold enough for ocean waves to partially freeze along the coast of Nantucket Island in Massachusetts.

Photographer Jonathan Nimerfroh captured these unusual slushy waves on February 20th, when the local air temperature reached a high of only 19°F. While freshwater freezes at 32°F, seawater – owing to its salt content – has a lower freezing point of 28.4°F.

To see more images of this uncommon wintry phenomenon, visit the photographer’s website.

Image Credit: Jonathan Nimerfroh

Image Credit: Jonathan Nimerfroh

How Icicles Form

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Icicles are a classic symbol of cold winter weather. In order to form, however, they need a mix of both warm and cold conditions.

These hanging pieces of tapered ice develop when the air temperature is below freezing, but there is enough heat from the sun – or in the case of a building, a  poorly  insulated roof – to thaw some snow. As the melt water runs off the edge of a surface, it re-freezes in the cold air. Starting with only a few water droplets, an icicle can begin to form. Over time, as melt water continues to drip and re-freeze, an icicle gains both layers of thickness and length.

Often seen forming along the edge of roofs, icicles can also be found on tree branches, power lines, and rocks where water seeps out of the ground. The size and shape of an icicle, according to experts at the National Snow and Ice Data Center, depends on a few different factors. These include the shape of the surface on which it forms and the number of different directions from which melt water approaches the growing icicle.

Icicles can range in size from a few inches to tens of feet.

Icicles in the sunshine. Credit: MLE

Icicles in the sunshine. Credit: MLE

The Great Lakes Finally Thaw

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It is now June, the first month of meteorological summer, but it seems winter is only just coming to a close on the Great Lakes.

For the first time since November, according to NOAA, the Great Lakes are ice-free. This marks the latest total thaw on the lakes since record keeping began in the 1970s. Back in March, during one of the coldest winters the region has seen in decades, more than 92% of the Great Lakes were covered by ice. That was the second highest percentage on record.

While a recent string of warm days in the area helped to melt the lingering ice, the U.S. Coast Guard also played a key role. They have reported conducting over 2000 hours of ice-breaking operations throughout this past winter and spring.

Only recently thawed, water temperatures in the lakes are expected to remain rather chilly for most of the summer.

GreatLakes

After a frigid winter, the Great Lakes are finally ice-free. Image Credit: NOAA