## How Far Away Is A Lightning?

Next time you’re stuck in a thunderstorm, try this easy way to calculate how far away you are from lightning strikes.

Just count the number of seconds that pass between a flash of lightning and the crack of thunder that follows it, then divide that number by five.

The resulting number will tell you how many miles away you are from where lightning just struck.

Five seconds, for example, indicates the lightning struck 1 mile away, and a 10-second gap means the lightning was 2 miles away.

This technique is called the “flash-to-bang” method, and it can keep you safe during rainy summer weather.

The National Weather Service recommends taking cover if the time between the lightning flash and the rumble of thunder is 30 seconds or less, which indicates the lightning is about 6 miles away or closer.

This method is based on the fact that light travels much faster than sound through the atmosphere: Light travels at 186,291 miles per second (299,800 km/s), whereas the speed of sound is only about 1,088 feet per second (332 meters per second), depending on air temperature.

For metric-system conversions, follow this method: Sound travels at about 340 m/s, so multiply the number of seconds you counted by 340, and you’ll know how many meters away lightning struck.

A three-second count, then, would place the lightning strike about 1,020 m away, or roughly 1 km.

Pass it on: Popular Science

## Reading Past Climates From Ice Cores

Professor Thomas Stocker of the University of Bern in Switzerland is one of the principal investigators of EPICA (European Programme for Ice Coring in Antarctica.)

Stocker explains that EPICA, a joint ESF- European Commission (EC) effort funded by the Commission and 10 national agencies, has put Europe in a leading position in ice core research, in which specially designed drilling technology is used to obtain continuous ice sequences 3.8 thousands of metres in length.

A series of EPICA papers in journals such as Nature and Science are evidence of its world importance. The principle behind ice coring is straightforward.

Snow falls in Greenland and the Antarctic, but conditions there are too cold for it to melt. In most places it will eventually be carried away by glacial movement, but it is possible to find areas where the snow has piled up for hundreds of thousands of years, turning to ice as the weight of later snowfall builds up on top.

Drilling out a core of such ice reveals the past in a neat sequence of millennia. Better still, the ice contains information about the past.

It includes trapped air bubbles that can be analysed to reveal the composition of the ancient atmosphere. Layers of ash reveal ancient volcanic eruptions.

And the ratio of different isotopes of oxygen in the ice is a virtual thermometer that tells us past temperatures. The more of the lighter isotope, oxygen 16, there is, the colder it was.

Stocker says: “Ice-drilling is an area in which Europe has taken a decisive technological and scientific lead in the past decade. We now have a continuous record of 800,000 years of climate history, thanks to EPICA and other European initiatives.

These ice cores directly illuminate current climate debates. As Stocker points out, air bubbles allow us to measure how much methane and carbon dioxide there was in the air when the snow fell.

These — especially carbon dioxide — are the principal greenhouse gases in the Earth’s atmosphere. It is clear that they are now at their most abundant for hundreds of thousands of years.

By contrast, the most-used direct measurements of atmospheric carbon dioxide, made on Hawaii, only date back to 1958. So as Stocker says: “EPICA results form a cornerstone of the current climate debate.

While these cores still have plenty to tell us, Stocker and his colleagues are in little doubt about the overall message.

They think that climate “forcing” by greenhouse gases is a very real phenomenon: in other words, that rising greenhouse gas concentrations drive the Earth’s temperature upwards in a very direct way.

So the ice cores now deposited in cold “stores” around the world have a clear message for us all.

Pass it on: Popular Science

## Why You Really Can Smell Approaching Storms

Most people can detect the distinctive fresh, earthy aroma of an approaching rainstorm, but now scientists have worked out why.

Researchers using high-speed cameras have found that drops of water release clouds of tiny particles when they hit surfaces like soil and leaves.

Their study showed that a raindrop hitting an uneven surface, they trap bubbles of air that shoot upwards and burst from the top of the water droplet like fizz in a champagne glass.

These tiny bubbles carry minute amounts of aromatic particles of oil and dust from the surface that can then be blown for miles by gusts of wind ahead of rain storms.

This, the scientists say, explains why it is possible to smell a rainstorm long before it arrives, even when it has been dry for several days.

The effect, known as Petrichor, is often most pronounced during the summer, accompanying the first rain after a long dry smell when more dust and oils have accumulated on plants and on the ground.

The new research, which was conducted by scientists at the Massachusetts Institute of Technology, found that different types of rainfall could alter the smell.

The scientists found that light showers and moderate seemed to trigger more aerosols compared with heavy rain that might accompany thunderstorms.

They also found that the type of soil could also influence how many aerosols were released and was particularly pronounced on clay or sandy soil.

Dr Youngsoo Joung, one of the scientists at MIT’s department of engineering who conducted the research, said the findings could also help to explain how some soil-based bacteria can spread disease.

He said: “Until now, people didn’t know that aerosols could be generated from raindrops on soil.

“When moderate or light rain hits sandy or clay soils, you can observe lots of aerosols, because sandy clay has medium wetting properties.

“Heavy rain (which has a high) impact speed, means there’s not enough time to make bubbles inside the droplet.

“This finding should be a good reference for future work, illuminating microbes and chemicals existing inside soil and other natural materials, and how they can be delivered in the environment, and possibly to humans.

“To prevent transmission of microorganisms from nature to humans, we need to know the exact mechanism. In this work, we provide one possible way of transmission.”

Scientists in Australia were the first to coin the word ‘petrichor‘ for the smell of approaching rain and characterized it as the release of plant oils along with a compound called geosmin, which is produced by soil-dwelling bacteria.

However, the new research is the first to explain the mechanism that causes these compounds to become airborne.

Pass it on: Popular Science

## The Deadly Combination Of Heat And Humidity

The most deadly weather-related disasters aren’t necessarily caused by floods, droughts or hurricanes. They can be caused by heat waves, like the sweltering blanket that’s taken over 2,500 lives in India in recent weeks.

Temperatures broke 118 degrees in parts of the country. The death toll is still being tallied, and many heat-related deaths will be recognized only after the fact.

Yet it’s already the deadliest heat wave to hit India since at least 1998 and, by some accounts, the fourth- or fifth-deadliest worldwide since 1900.

These heat waves will only become more common as the planet continues to warm.

They don’t just affect tropical, developing countries; they’re a threat throughout the world. The July 1995 heat wave in the Midwest caused over 700 deaths in Chicago.

The August 2003 heat wave in western Europe led to about 45,000 deaths. The July-August 2010 heat wave in western Russia killed about 54,000 people.

But as anyone who’s spent a summer in the eastern United States knows, it’s not just the heat; it’s also the humidity. Together, they can be lethal, even if the heat doesn’t seem quite so extreme.

Scientists measure the combination using a metric known as wet-bulb temperature. It’s called that because it can be measured with a thermometer wrapped in a wet cloth, distinguishing it from the commonly reported dry-bulb temperature, measured in open air.

Wet-bulb temperature can also be calculated from relative humidity, surface pressure and air temperature.

But this fate is not yet locked in. Moderate reductions in emissions of heat-trapping gases sufficient to stop global emissions growth by 2040 and bring emissions down to half their current levels by the 2070s.

This can avoid those paralyzing extremes and limit the expected late-century experience of the average American to about 18 dangerously humid days a year.

And strong reductions — bringing global emissions to zero by the 2080s — can cap the growth of humidity extremes by the midcentury.

Climate change is increasing the risks to our health, our economy and our environment.

Communities need to prepare. But as world leaders get ready for the United Nations climate change conference in Paris this December, it’s also important to recognize that shifting to carbon-free energy will reduce the risks we will face from extreme heat and humidity.

As India’s tragic heat wave shows, these risks cannot be ignored.

Pass it on: Popular Science

## Just Another Day on Aerosol Earth

Take a deep breath. Even if the air looks clear, it is nearly certain that you will inhale millions of solid particles and liquid droplets.

These ubiquitous specks of matter are known as aerosols, and they can be found in the air over oceans, deserts, mountains, forests, ice, and every ecosystem in between.

If you have ever watched smoke billowing from a wildfire, ash erupting from a volcano, or dust blowing in the wind, you have seen aerosols.

Satellites like Terra, Aqua, Aura, and Suomi NPP “see” them as well, though they offer a completely different perspective from hundreds of kilometers above Earth’s surface.

A version of a NASA model called the Goddard Earth Observing System Forward Processing (GEOS FP) offers a similarly expansive view of the mishmash of particles that dance and swirl through the atmosphere.

The visualization above highlights GEOS FP model output for aerosols on August 23, 2018.

On that day, huge plumes of smoke drifted over North America and Africa, three different tropical cyclones churned in the Pacific Ocean, and large clouds of dust blew over deserts in Africa and Asia.

The storms are visible within giant swirls of sea salt aerosol (blue), which winds loft into the air as part of sea spray.

Black carbon particles (red) are among the particles emitted by fires; vehicle and factory emissions are another common source.

Particles the model classified as dust are shown in purple. The visualization includes a layer of night light data collected by the day-night band of the Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP that shows the locations of towns and cities.

Note: the aerosol in the visualization is not a direct representation of satellite data.

The GEOS FP model, like all weather and climate models, used mathematical equations that represent physical processes to calculate what was happening in the atmosphere on August 23.

Measurements of physical properties, like temperature, moisture, aerosols, and winds, are routinely folded into the model to better simulate real-world conditions.

Some of the events that appear in the visualization were causing pretty serious problems on the ground.

Last August 23, Hawaiians braced for torrential rains and potentially serious floods and mudslides as Hurricane Lane approached.

Meanwhile, twin tropical cyclones—Soulik and Cimaron—were on the verge of lashing South Korea and Japan.

The smoke plume over central Africa is a seasonal occurrence and mainly the product of farmers lighting numerous small fires to maintain crop and grazing lands.

Most of the smoke over North America came from large wildfires burning in Canada and the United States.

Pass it on:  Popular Science

## Hurricane Lane Threatens Hawaii

Hawaii residents and visitors are bracing for Hurricane Lane as the now Category 4 storm continues on its path toward the Pacific state.

Hurricanes are rare in Hawaii, but Lane is expected to bring heavy rain and flooding, dangerous surf and strong winds as it continues to churn toward the islands.

### Where is Lane now?

Lane is approximately 275 miles south of Kailua-Kona, Hawaii, the Central Pacific Hurricane Center said in an 8 p.m. ET advisory Wednesday. It is about 400 miles south-southeast of Honolulu, Hawaii.

With maximum sustained winds of 150 mph, Lane is moving west-northwest at approximately 8 mph, as of Wednesday evening.

### What is the saffir-simpson hurricane wind scale?

Lane is expected to weaken, Dean said. But Lane still could be a strong hurricane off the Kona Coast of the Big Island Thursday, and still could be at hurricane strength near Maui County or Oahu Friday — areas that are not accustomed to hurricane conditions, she said.

Lane is currently a Category 4 hurricane.

### What else should I know about the hurricane?

A hurricane warning is in effect for Hawaii and Maui counties as well as some smaller islands.

A hurricane watch has been issued for Oahu and Kauai as well as some smaller islands.

Pass it on: Popular Science

## Green Flash: Sunset Phenomenon

A green flash, which occurs more commonly at sunset but can also occur at sunrise is a phenomenon in which part of the sun can be observed suddenly and briefly changing color.

It usually lasts only a second or two which is why it is referred a flash as the sun changes from red or orange at sunset, for example.

The green flash is viewable because refraction bends the light of the sun. The atmosphere acts as a weak prism, which separates light into various colors.

When the sun’s disk is fully visible above the horizon, the different colors of light rays overlap to an extent where each individual color can’t be seen by the naked eye.

As the sun sinks into the Pacific, its last light seems to glow green. This “green flash,” caused by light refracting in the atmosphere, is rarely seen.

But Nigella Hillgarth, the director of the Birch Aquarium at the Scripps Institution of Oceanography in San Diego, got lucky one night.

I often work late and have developed the habit of taking photos of the incredible sunsets over the Pacific from the Aquarium,” Hillgarth said.

One evening, I was snapping away and caught the green flash as it appeared. I was hoping for a green flash, but was very excited when one actually happened and I caught it!

When the sun starts to dip below the horizon the colors of the spectrum disappear one at a time, starting with those with the longest wavelengths to those with the shortest. At sunrise, the process is reversed, and a green flash may occur as the top of the sun peeks above the horizon.

It is a primarily a green flash because more green light gets through and therefore is more clearly seen.

Sometimes, when the air is especially clear, enough of the blue or violet light rays make it through the atmosphere, causing a blue flash to be visible. However, green is the most common hue reported and captured in photos.

Most green flashes fall into two categories: inferior mirage flashes and mock mirage flashes.

Inferior mirage flashes, which accounts for about two-thirds of all green flash sightings, are oval and flat and occur close to sea level and when the surface is warmer than the air above.

Mock mirage flashes occur higher up in the sky and when conditions on the surface are colder than the air above. The flashes appear to be thin, pointy strips being sliced from the sun.

Pass it on: Popular Science

## The Weirdest Weather Events of 2018 So Far

We’ve already seen our share of winter storms, severe weather, cold outbreaks, flooding and droughts so far in 2018. But there are some weather events every year that are downright strange, and this year is no exception.

The events we consider strange are weather phenomena happening repeatedly in one place, in a place where you wouldn’t think they would occur or during an unusual time of year.

Some are phenomena you may not find in a Weather 101 textbook.

### Freezing Rain in Florida

Just after New Year’s Day, Winter Storm Grayson blanketed Tallahassee, Florida, with its first measurable snow since 1989, and the first January such occurrence, there, in records dating to 1885.

That’s eye-catching enough.  What was even more bizarre was seeing an ice accumulation map involving the Sunshine State.

Up to a quarter inch of ice accumulation was measured in Lake City, and light icing on elevated surfaces was reported as far south as Levy County.

### A Horseshoe Cloud

While the nor’easter parade was hammering the East Coast, a bizarre cloud was captured in video over Nevada in early March.

As meteorologist Jonathan Belles explained, this rare horseshoe vortex is fleeting, lasting only minutes, when a relatively flat cloud moves over a column of rising air, which also gives the cloud some spin.

### A State Record Hailstone

Alabama’s notorious history of severe weather, particularly tornadoes, is well documented.  On March 19, however, it was a hailstone that captured meteorologists’ attention.

One softball-size hailstone near Cullman, Alabama, was found to set a new state record, more than 5 inches in diameter.

Pass it on: Popular Science

## Watch Lightning Seen From Space

Astronauts were treated to a striking sight when they spotted a lightning storm from space.

These stunning images caught an electrical storm in full flow almost 250 miles above the earth while the space men were orbiting at 17,895 mph in the International Space Station.

The pictures show the swirling clouds and multiple lightning strikes as the eye of the storm moves across land, thought to be Iran.

The flashes were spotted by the European Space Agency’s Nightpod camera, which astronauts set up to take crystal-clear images which have only now been released after being taken in 2012.

Despite the distance from the planet and the speed involved, the high-tech camera is specially adapted to keep the pictures in focus to avoid blurring.

Pass it on: Popular Science

## What If The Moon Disappeared Tomorrow?

Ah, yes, the moon. To it, over it, shooting for it. Blue, green. Pies, faces, shines, lighting. And I haven’t even gotten to all the Luna-based concepts. Earth’s moon plays a significant role in our culture, language and thoughts.

But does it … you know … matter? If it disappeared in the blink of an eye tomorrow (and for discussion’s sake let’s assume it does so nonviolently), would we even notice? Would we even care?

Well, it depends ….

## Do you like tides?

Gravity — at least the Newtonian kind — is pretty straightforward: The closer you are to something, the stronger its pull of gravity.

So stuff that’s closer to the moon gets a stronger gravitational tug, and stuff that’s farther away gets a weaker one. Easy-peasey.

When looking at the effects of the moon on the Earth, you can essentially boil it down to three parts: The Earth itself, the ocean-close-to-the-moon and the ocean-far-from-the-moon.

On any given day, the ocean closest to the moon gets a bonus gravitational pull, so it rises up slightly, reaching out in watery embrace to what it can never reach.

And since the ocean is so big, all the water from one horizon pushes up against water from the other, resulting in a fantastic tidal bulge.

OK, tide on one side of our planet, done. But what about the other?

The solid rocky bits of the Earth are closer to the moon than the ocean on the far side, so the Earth too gets a little more snuggly with the moon, leaving the far-side ocean behind.

Result? Tides on the far side. From the perspective of someone standing on Earth, it looks like that ocean is rising up, but really it just doesn’t get to join the party. And there you have it: two tides on opposite sides of the Earth.

If the moon disappeared, we wouldn’t be totally out of tidal luck; the sun also stretches and squeezes the Earth, so our surfing opportunities wouldn’t be completely eliminated.

## Do you like 24 hours in a day?

The Earth used to spin on its axis faster than it does today. As in, way faster. After the hypothetical giant impact that led to the formation of the moon, the Earth’s day was as short as 6 hours. How did it get to a leisurely 24?

That’s right, it was the moon! The moon makes some pretty nice tides, but the Earth is also spinning on its axis. That spinning physically drags the tidal bulges around the planet.

So instead of the tides appearing directly beneath the moon, they’re slightly ahead of it, orbitally speaking.

So you’ve got a big lump of extra ocean water in a place where it’s not supposed to be. Since gravity is a two-way street, that lump pulls on the moon.

Like tugging a reluctant dog on a leash, that tidal bulge yanks on the moon bit by bit, accelerating it into ever-higher orbits.

By the way, the moon is slowly getting farther away from Earth.

And that energy to accelerate the moon has to come from somewhere, and that somewhere is the Earth itself: Day by day, millennium by millennium, the Earth slows down, converting its rotational energy into the moon’s orbital energy.

If you took away the moon, itꞌs not like this process would reverse, but it wouldn’t keep going. That might or might not be a good thing, depending on how much you like the length of your workday.

## Do you like seasons?

The Earth’s axis is tilted, and that tilt can change with time. No biggie, all the planets do it; it’s fun. But what’snot fun is when the tilt changes rapidly.

What would happen if Antarctica pointed straight at the sun for 24 hours a day, plunging North America and Europe into permanent darkness?

And then a few hundred thousand years later it flipped over? We take the long-term regularity of our seasons for granted, and we might have the moon to thank for it.

Those kinds of crazy wild swings in the axial tilt are due to resonances, or unlucky interactions with distant objects in the solar system.

For instance, letꞌs say that one day in its orbit the Earth’s axis just happens to point away from the sun, and Jupiter is hanging out in that direction at the same time.

And let’s say that happens again … and again … and again. Every time Earth’s axis and Jupiter line up, it gets a super-tiny gravitational pull. At first it’s nothing.

But over millions of years it can add up. Before you know it, the accumulation of tugs has flipped the Earth over like a pancake.

What might stabilize this is the moon: it’s really, really big, and orbits us pretty fast. All that angular momentum prevents the other planets from playing any axial shenanigans.

Or not. The moon may actually be hurting us in the long term, since it’s slowing us down, which makes us more susceptible to the intrigues of the outer planets.

But that’s a billion-year problem anyway, and if the moon disappeared tomorrow, our seasons would still be seasonal for a really long time.

So, besides the tides, would we notice a disappeared moon? Well, yes, because it’s really big and bright, and there’d be nothing to howl at anymore. But would it affect us? Not really. So as for the moon … I’m over it!