On September 10th, 2017 we learned about

How hurricanes batter the ocean’s waters while over the open sea

The wind, rain and storm surge of a hurricane can be incredibly destructive to those of us on shore, and the processes that build them are no less disruptive to the oceans that build them. We often hear reports about the “warm waters” that fuel hurricanes, but when a storm draws on that energy, it will churn  the ocean in the process, changing conditions as deep under the water. The water that doesn’t get sucked up into a cloud is left with different temperatures, depths and salinity, all of which can take weeks to years to truly restore everything to normal.

Stirring up the depths of the seas

Normally, ocean water is slightly layered according to salinity, or salt concentrations, and temperature. Colder, saltier water goes down, while fresher, warmer water sits closer to the surface. When the storm comes along, it stirs all this up like a meteorological egg-beater, creating a more uniform mix of water as it goes. By drawing warmer air and water into the air, and pulling cold water up from the depths, the wake the hurricane leaves behind is significantly colder than the ocean around it, to the point that the “cold wake” of a storm can be detected well after the hurricane has passed by.

The are numerous lasting effects of these changes in temperature and salinity. Marine animals generally expect a degree of stability in their environments, and changes in water temperature can be dangerous to many species that can’t flee the area. The upside of this is that the colder water brought to the surface has less energy to fuel the storm, and so in some cases this process can actually reduce the hurricane’s strength.

Tossed by turbulence

Beyond changes in bringing cold water up, hurricanes trigger a lot of lateral movement as well. Currents and turbulence underwater can slam things around, almost like a marine version of the winds we experience on land. Oil pipelines have been broken, sunken ships moved and sand resettled, even close to 1,000 feet below the water’s surface. Some animals will just get shoved around in all this, but sedentary marine life, like corals, can take a beating during a hurricane, suffering from both impacts with other objects as well as being choked by fine particulate stirred up by the water.

Sucking water to build a storm surge

Finally, there’s some significant “mixing” with the air above the water too. High winds and strong currents help whip the water up into waves and sprayed water, sometimes to the point where the boundary between “air” and “water” gets pretty blurred. Quite importantly, the center of hurricane is actually a place with very low air pressure, meaning there’s less air molecules to push down against the water. In a full vacuum, this can lead to water essentially boiling away into vapor, and while that’s not exactly what’s in a hurricane, there’s certainly a bit of a void to be filled.

With air being pushed away from the eye of the storm, the most abundant material to fill that space is even more water. The combination of currents, wind and low air pressure essentially shoves more and more water from elsewhere in the ocean into a big bulge of water under the hurricane. In big storms, this can lead to dramatic situations where water has been drawn away from shorelines, draining beach fronts and bays. As with the other processes that build a hurricane, this can disrupt marine life, leaving creatures like manatees beached when the water evacuates from underneath them.

The water isn’t technically being sucked by the storm, of course, but is instead rushing to the point of lower air pressure creating what’s known as a storm surge. When conditions change and the eye of the hurricane begins releasing more of this water, the surge can come rushing back to shores very quickly, often exceeding normal sea level by over ten feet. As fascinating as it may be to walk the ocean floor for a few minutes, you can’t be sure when the surge will return, and it can certainly rush inland with enough force to damage roads, buildings and of knock you off your feet.

Altogether, hurricanes reshape the oceans as much as they do life on land. We don’t have to the same reference points when watching the ocean, but it’s still pretty clear that these storms effectively upend normal water flow, even before that water starts getting dumped on the land.

Source: What Happens Underwater During a Hurricane? by Brian McNoldy, Rosenstiel School of Marine & Atmospheric Science

On August 22nd, 2017 we learned about

Meteorological simulations suggest small amounts of snowfall each night on Mars

In 2008, the Phoenix lander spotted some unexpected weather on Mars. On a planet noted for red rocks and swirling dust storms, the lander caught a glimpse of dark clouds and bits of falling ice crystals blowing through the air. New data and detailed simulations are suggesting that that flurry wasn’t actually all that rare. The Red Planet likely gets a touch of snowfall each night thanks to some very cold winds, although not enough that the Curiosity rover will ever need a snowplow or snow chains.

The snow seen in 2008 was thought to be a bit of an outlier at first. There’s lots of evidence that Mars once had more liquid water on its surface, and that a fair amount of that water circulated in the skies as rain and snow. However, the latest data from the Mars Global Surveyor and Mars Reconnaissance Orbiter suggest that some snow may fall every night, because there’s still enough ice in the atmosphere waiting to be blown to the ground.

Nippy at night

Mars’ thinner atmosphere loses a lot of heat at night, causing clouds to drop rather quickly. Any warmer air on the planet’s surface would rise up, and the competing activity would make for some strong winds, possibly blowing around 22 miles per hour. These gusts would then collect and blast ice crystals from the upper atmosphere down to the ground as microbursts, like miniature blizzards in the dark.

New data is not showing any kind of accumulation of snow pack, which isn’t surprising. While there are apparently just enough ice crystals in the Martian atmosphere to make a microburst, most of them seem to sublimate before they hit the ground. This doesn’t mean that this weather report isn’t significant to mission planners though. Even if future spacecraft or astronauts don’t need to worry about serious snowfall, the nightly gusts of wind that blow the ice around may be strong enough to warrant special consideration to avoid damaged equipment or complicated landings.

Source: We Have First-Ever Evidence That Mars Gets Intense Snowstorms in The Dead of Night by Peter Dockrill, Science Alert

On July 4th, 2017 we learned about

Martian water may have flowed thanks to intermittent infusions of methane

In their ongoing quest to understand Martian water, scientists are now suggesting that the Red Planet was once heated by a planetary Dutch Oven. Many geological features on Mars suggest that water once flowed over much of its surface, but scientists are at a bit of a loss to pinpoint how that would have worked with the planet’s thin atmosphere. As far as we can tell, heat from the Sun should have been lost too quickly to warm up the planet’s water, prompting investigations into alternative climate models. One promising possibility may be periodic bursts of methane erupting from the bowels of Mars surface, creating temporary insulation to let the planet warm up.

If this model can be verified, it matches up with existing evidence of shifting temperatures quite well. With all the channels and signs of erosion spread across Mars, it seems that the place was once quite wet, even sporting enough water to support tsunamis. But while there’s little doubt about the existence of these past rivers, lakes and oceans, the timing has never made sense. Dates estimated from impact craters indicate that the water was somehow flowing after most of Mar’s atmosphere had already been lost to space thanks to influences like solar wind. Intermittent puffs of methane can then fill in that hole, providing warmth for these periods when water flowed while never replacing a stabilized atmosphere.

Other models for methane

Mars isn’t burping up a lot of methane today, but there is some precedent for this idea. Saturn’s moon Titan is currently socked in with methane in it’s atmosphere, and the gas helps create a greenhouse effect that traps solar energy close to the moon’s surface. Similarly, Earth’s methane supply does the same thing, working alongside other gases like carbon dioxide to hold onto heat from the sun. Further data is being gathered by the MAVEN spacecraft, and we may see a more detailed model for exactly how warm methane could have made Mars in it’s more liquid-friendly days, billions of years ago.

Source: Bursts of Methane May Have Prepped Ancient Mars for Life by Irene Klotz, Seeker

On March 29th, 2017 we learned about

The strangely unshifting sands and sparkling seas of Saturn’s moon, Titan

In 2005, the Cassini spacecraft launched the Huygens probe on a one-way trip to Saturn’s largest moon, Titan. For over two hours, the probe flew through Titan’s dense atmosphere of nitrogen and methane, finding a landscape of rocky, icy terrain with signs that liquids had once flowed over its surface. Since then, continued study of Titan’s atmosphere and surface has found a variety of weird phenomena, from burping lakes to electrically-charged sand dunes.

Gulping gases

Titan’s atmosphere is thicker than Earths, with large amounts of nitrogen acting like a heat shield for the moon’s surface. Rather than capture heat the way carbon dioxide does on Earth, Titan’s atmosphere reflects a lot of sunlight back into space, keeping the surface around -290º Fahrenheit. There is some variation in temperature though thanks to movement of clouds around the moon, which is key to the weird bubbling seen in the lakes of liquid methane, ethane or other organic compounds.

When temperatures drop due to cloud cover and raining methane, the lakes, rivers and small seas, mostly clustered near the poles, can absorb a lot of atmospheric nitrogen. When things clear up, the liquid methane warms enough to shake things up, and the nitrogen molecules congeal into bubbles of gas that rise to the surface, like a giant, stinky soda fizzing up. In some cases the bubbles congeal in huge bubbles that get compared to temporary islands, which then pop like a huge eruption, belching the nitrogen back into the atmosphere.

Electrostatic sand

The drier parts of Titan have their own quirks as well. Sand dunes almost 300 feet high have been found that are somehow shaped in defiance of the prevailing winds. Somehow the sand appears to be shaped by westerly winds, even though they usually blow in from the east. They’re not especially strong winds at the surface, but scientists have been trying to figure out why they weren’t shaping the sand dunes since 2005.

Scientists from Georgia Tech have started looking into whether the issue with the dunes isn’t Titan’s weather, but found in the sand itself. The sand isn’t the silicon dioxide most commonly found on Earth, but is instead likely bits of water ice coated in the various hydrocarbons that make up Titan’s atmosphere, like the aforementioned methane and ethane. While the Huygens probe did gather lots of data for us, it wasn’t ready to answer this question, and so researchers have been experimenting with forms of Titanesque sand here on Earth.

The key to their hypothesis is the alien sand’s electric charge. Putting synthesized sand in a pressurized, rotating cylinder, they looked at how the surface conditions of Titan might cause sand to build up a static charge. They found that their simulated sand did indeed clump thanks to static electricity, not unlike the way a charged balloon can stick to a wall.  So smaller winds probably rub the sand together, helping it charge it with electrostatic stickiness. Only larger, less common winds are then strong enough to really blow the dunes down.

Source: NASA/JPL Scientists Think Titan's Towering Dunes Are Made of Unyielding Electric Sand by Peter Dockrill, Science Alert

On April 24th, 2016 we learned about

Lightning bolts are born from friction, ice and ash

My kids’ first concept of lightning was an ancient one. As depicted in Fantasia, lighting was the result of a bored Zeus, asking the mythical blacksmith Hephaestus for forged bolts of electricity to throw at terrified, reveling satyrs and unicorns. The takeaway was that lighting was something to be feared, because not only was it capable of blowing a tree to cinders, but it likely being targeted right at you. It’s certainly more dramatic than the bits of ice bumping into each other you find in real clouds, but maybe those don’t match Beethoven too well.

Ice-crystal currents

The ice in question is a mix of tiny crystals and slightly larger pellets. These particles get tossed around in the wind at speeds up to 100 miles-per-hour, with positively-charged crystals moving up, rubbing past ice pellets with negative charges on their way down. Like rubbing socks on a carpet, this contact can build up an electrical charge, leading to a spark, but you would only notice it if enough ice is discharging at once. That’s not a big problem for a good storm cloud though, as even a modest storm might have around 11,000 tons of ice to toss around, which is good to produce mega-volt discharges three times as hot as the surface of the sun.

Volcanic voltage

Ice particles aren’t the only way to get lightning though. When a volcano erupts, it spews tons of debris and ash into the sky, sometimes reaching as high as 12 miles up into the stratosphere. This is actually high enough to get ice crystals and the associated lightning, but the ash lower to the ground can also do the job. Just like the ice crystals, bits of ash being blown against each other can build up an electrical charge. The resulting lighting is more likely to hit the ground, as well as look completely awesome over spewing magma. Maybe even enough to warrant some Beethoven.

Source: Electric Ice by Dr. Tony Phillips, NASA Science News

On February 18th, 2016 we learned about

Forming snowflakes when it’s not freezing cold

My first grader recently asked if snow angels were real. Not real in the sense of divine flying creatures, but if people ever flopped down in the snow, waving their arms and legs as she’d seen in books and movies. While I’ll attribute this to her being a native of California, it may be a question on more kids’ minds in the future as the United States sees more rain and less snow during the winter. As average temperatures rise, getting to the perfect conditions for a beautiful snowfall may be less common. You might assume that “perfect” means “freezing,” but it’s not actually that simple.

How critical is the cold?

There are actually a couple of temperatures that need to be right for a good snow. The first issue is the temperature up around the clouds, which does indeed need to somewhere at or below freezing. It really can’t be too cold for snow, although colder air isn’t as good at holding moisture, which would leave too little water to freeze into snowflakes. This is why some parts of Antarctica can be very cold but with very little snowfall, since they’re just too dry for any real precipitation.

Cold air close to the ground is also a sure win, but snow can survive slightly warmer conditions as it falls. As they warm slightly, the outer layer of melting water on the ice crystal will trigger evaporation cooling in the air around it, as the newly warmed water had to draw its heat from somewhere. That cooled air then adds less heat to the remaining snowflake, slowing the melting process. This allows a wetter flake to make it to the ground when ambient temperatures are above freezing, even as high as 41° Fahrenheit.

Warmer under the snow

The snow that does accumulate on the ground will often melt slightly, then refreeze if temperatures drop again to form an outer crust. Subsequent snowfalls add more and more layers of snow, which can help keep itself cold while sitting on the not-quite-frozen earth. With sufficient coverage, the snow is actually insulating for creatures living in the ground below, particularly against any sudden drops in the surface temperatures. Rather than see all their warmth get wicked away in a big blizzard as the ground freezes, a blanket of snow will keep temperatures constant for subterranean animals like porcupines or willow ptarmigans. Animals living above ground also benefit, because a layer of snow will keep the ground from hardening, allowing them to forage for food more easily.

It’s also quite pretty, and of course, more conducive to sledding and snow angels.

Source: How Snow Forms, National Snow and Ice Data Center

On January 27th, 2016 we learned about

The Moon’s pull on the atmosphere creates a tiny bit more precipitation

As the Moon orbits the Earth, it exerts gravitational forces strong enough to move the less-solid bits around, leading to movements of material that rise and fall on a daily basis. While this concept most famously applies to the daily tides in our oceans, water isn’t the only substance to be pulled and collected in response to the Moon. The atmosphere, being a gas, is pulled by the Moon as well, but for the most part, we don’t notice it the way we do something more visible, like a waterline at the beach. Analysis of 15 years of data, however, has found that the tidal influence on the atmosphere appear to be strong enough to change the weather. At least a little bit.

It seems obvious that the gases in our atmosphere would moved significantly by the Moon’s gravity, since water, as a colder, heavier substance moves an average of 21 inches per tidal cycle, depending on the local terrain. But the movement of the planet’s air turns out to be almost imperceptible. The one hypothesized effect was that movement in the atmosphere would have to be changing air pressure as well, which can lead to shifts in the weather. This was first purposed in 1969, but the effect is so small that were no good data sources to test with. It wasn’t until the launching of weather satellites decades later that scientists could really look for measurable, Moon-induced shifts in the weather. After looking at 15 years of data, with eight measurements a day, the hypothesis has been supported, although even the researchers working the project stress that a rising Moon isn’t reason to bring an umbrella to the beach.

Rising moon, falling temperatures

The logic behind the Moon’s influence is based on how air pressure and temperature relate to humidity. As the Moon’s gravity gathers more air beneath it in an atmospheric ‘high tide,’ the more densely collected air has a higher air pressure and temperature. This air can then hold more water vapor in the sky, lowering the chances of rain. At low-tide, the opposite takes place. The thinner layer of air has lower air pressure and temperatures, and is therefore unable to support as much water vapor. That vapor is more likely to condense and fall as rain, leading to the one micrometer change in rainfall that was able to be attributed to the Moon.

A meteorological drop in the ocean

The essentially imperceptible effect on the weather isn’t because tidal forces are weak. Tidal forces obviously move the oceans a great deal, greatly impacting the plants and animals that live there, particularly along the shore. The issue is that the change in weather is an indirect effect of the tides, and is subject to a variety of influences, like other temperature and weather conditions, not to mention other tidal forces, like those coming from the Sun. With this many variables pushing, pulling and moving the air, the Moon’s influence is basically washed out.

Source: Atmospheric tides alter rainfall rate by Thomas Sumner, Science News

On December 23rd, 2015 we learned about

The farmer who found and photographed the shapes of snow

The person who sparked the idea that “no two snowflakes are alike” was not a trained meteorologist or physicist, but a farmer. This doesn’t mean that Wilson Alwyn Bentley wasn’t a researcher, as much of his life was spent studying and carefully documenting the nature of snow crystals, plus hypothesizing about what influenced their size and shape. His work was eventually reviewed and published, not only providing insight into how snow works, but also showing that a degree isn’t strictly necessary to work as a scientist.

At age 15, Bentley’s father gave him a microscope, which he used to view snowflakes in his native Vermont. He sketched what he could, but in 1885 his father bought him a camera, enabling the twenty-year-old to take the world’s first photomicrograph of a snow crystal. This required some technical invention on Bentley’s part, using a variety of tools from pre-cooled slides to turkey feathers to maneuver the delicate snowflakes into position for a photo. Over the years, Bentley refined his technique, even going as far as altering the contrast of images by hand after they were exposed.

Aside from mastering photographic techniques, Bentley also made some analysis based on his observations. He found connections between ambient temperatures and the shape of the ice crystal. These findings were eventually confirmed and published, but not for 30 years after Bentley’s initial work.

Further work and recognition

In the mean time, Bentley did find some notoriety for his photos. They were published in various magazines and newspapers, and earned the farmer the nickname “Snowflake Bentley.” During the summers, he also turned his attention to other meteorological phenomena, namely rain. As with the snow, Bentley found that raindrop size was also influenced by the air’s temperature, as well as the altitude of the storm clouds.

Bentley continued photographing snow until he died in 1931. While his work grew more sophisticated, he always used the same camera he started with as a young man.

Source: Keith Heidorn by The Snowflake Man of Vermont, Public Domain Review

On December 21st, 2015 we learned about

Shedding light on the solstice’s stake in the start of winter

In addition to counting down to Christmas, my first grader has been diligently reminding us about when winter really starts. She’s aware of the solstice, but there’s some understandable confusion about why the start of winter means more sunshine, not less. All this is understandable, because by many counts the season and the daylight are related, but different, things.

Winter by orbit

The solstice on the 21st of December marks the when the North Pole is the farthest it can get from the Sun. Since or planet’s axis is tilted around 23º, the northern hemisphere and southern hemispheres don’t get equal exposure to the Sun. Depending where we are in our yearly orbit, the north or the south is going to be getting more or less sunlight. The December solstice is the North’s day of minimal sunlight, spending more time pointed away from the Sun’s light (and of course, it’s the South’s longest day.) Since more direct sunlight brings warmth, darker days means colder temperatures, and thus our tipped planet gets to enjoy seasonal weather.

Winter by weather

The importance of the tipped axis and sun exposure in seasons would then seem to support the idea of December 21st being the First Day of Winter, since… well, obviously it’s a big deal! It’s got to be something, right? From a meteorological perspective, it’s actually a bit late in the year to be the start of cold weather in the Northern Hemisphere. Since meteorologists look at winter as the months with the coldest average temperatures, they usually mark the start of winter with December 1st, extending until the start of March. This fits closer to our daily experience in many places, since winter weather often turns up well before the last week of the year.

Winter by daylight

There’s another metric to consider when measuring the onset of winter, which nicely combines the above ideas. The solstice marks the shortest day of the year in the Northern Hemisphere, but it’s also a turning point when the days start getting longer (for the most part). If winter is the measure of the shortest days of the year, the solstice suddenly becomes the apex of the season, falling right in the middle. Historically, this has been a popular way to measure the year, with many cultures marking winter as the darker days after the Fall equinox, up until the Spring equinox, both of which are equally light and dark.

Using light to measure the seasons seems to have fallen out of favor thanks to artificial lighting. What had once forced major, if cyclical, changes in lifestyle can now be nearly ignored. At least until you’re the one out shoveling the driveway in the dark.

Source: Don’t Believe the Hype: Winter Does Not Begin Tonight by Amos Zeeberg, Nautilus

On October 4th, 2015 we learned about

How wildlife holds out during a hurricane

One of the problems with natural disasters like a hurricane is that they can turn any and all of your surroundings into a potential threat. Even a home can be stripped, shaken and flooded, transforming it from a haven to a hazard. This is true for animals as well as humans. Even though a fish or a rabbit isn’t worried about something like their windows breaking, they still face many of the same dangers humans do, from the destruction of their homes to a lack of accessible food once the storm is over.

Out at sea, fish don’t worry about their home being “broken” per se, but that doesn’t mean they’re out of danger when a hurricane comes to their patch of ocean. The strong winds of a storm and disrupted currents can mix and move warm and cold water, leaving fish in an environment they’re ill suited to until things settle. These strong currents and winds can also move the animals entirely, leaving them beached in a worst case scenario. In shallower areas, the violent waves and swirling debris can also destroy coral, leaving ecosystems in disarray for years.

On land, the question becomes flooding. Animals in surviving trees have a decent chance of using the tree as shelter, assuming the winds don’t destroy the tree. Riding the storm out along the ground is harder. Burrowing animals are especially at risk from flooding and falling debris. Once things dry out, the winds often disrupt food chains, stripping plants of valued seeds, fruits and leaves that would have normally been an herbivore’s lunch.

Some silver linings

A hurricane doesn’t have to be the end of the world though. Sharks seem to sense shifts in barometric pressure, and have been known to vacate regions where a hurricane is approaching. Some animals caught in storms can ride them out, and have even been transported huge distances on natural rafts, only to do quite well in their new environment. Animals who remain at the site of the hurricane may face a temporary loss of food sources, but similar to the regrowth after a forest fire, new plants can often take advantage of freshly cleared land, inviting larger and larger species to return.

Source: What happens to animals in a hurricane? by Sarah Zielinski, Wild Things