April 18, 2013
If you weren’t on the East Coast during Hurricane Sandy, you likely experienced the disaster through electronic means: TV, radio, the internet or phone calls. As people across the country tracked the storm by listening to information broadcast through electromagnetic waves, a different kind of wave, produced by the storm itself, was traveling beneath their feet.
Keith Koper and Oner Sufri, a pair of geologists at the University of Utah, recently determined that the crashing of massive waves against Long Island, New York and New Jersey—as well as waves hitting each other offshore—generated measurable seismic waves across much of the U.S., as far away as Seattle. As Sufri will explain in presenting the team’s preliminary findings today during the Seismological Society of America‘s annual meeting, they analyzed data from a nationwide network of seismometers to track microseisms, faint tremors that spread through the earth as a result of the storm waves’ force.
The team constructed a video (below) of the readings coming from 428 seismometers over the course of a few days before and after the storm hit. Initially, as it traveled up roughly parallel to the East Coast , readings remained relatively stable. Then, “as the storm turned west-northwest,” Sufri said in a press statement, “the seismometers lit up.” Skip to about 40 seconds into the video to see the most dramatic seismic shift as the storm hooks toward shore:
The microseisms shown in the video differ from the waves generated by earthquakes. The latter arrive suddenly, in distinct waves, while the microseisms that resulted from Sandy arrived continuously over time, more like a subtle background vibration. That makes converting these waves to the moment magnitude scale used to measure earthquakes somewhat complicated, but Koper says that if the energy from these microseisms was compressed into a single wave, it would register as a 2 or 3 on the scale, comparable to a minor earthquake that can be felt by a few people but causes no damage to buildings.
The seismic activity peaked when Sandy changed direction, the researchers say, triggering a sudden increase in the number of waves running into each other offshore. These created massive standing waves, which sent significant amounts of pressure into the seafloor bottom, shaking the ground.
It’s not uncommon for events other than earthquakes to generate seismic waves—Hurricane Katrina produced shaking that was felt in California, landslides are known to have distinct seismic signatures and the meteor that crashed in Russia in February produced waves as well. One of the reasons the readings from Sandy scientifically interesting, though, is the potential that this type of analysis could someday be used to track a storm in real-time, as a supplement to satellite data.
That possibility is enabled by the fact that a seismometer detects seismic motion in three directions: vertical (up-and-down shaking) as well as North-South and East-West movement. So, for example, if most of the shaking detected by a seismometer in one location is oriented North-South, it indicates that the source of the seismic energy (in this case, a storm) is located either North or South of the device, rather than East or West.
A nationwide network of seismometers—such as Earthscope, the system that was used for this research and is currently still being expanded—could eventually provide the capacity to pinpoint the center of a storm. “If you have enough seismometers, you can get enough data to get arrows to point at the source,” Koper said.
Satellites, of course, can already locate a hurricane’s eye and limbs. But locating the energetic center of the storm and combining it with satellite observations of the storm’s extent could eventually enable scientists to measure the energy being released by a hurricane in real-time, as the storm evolves. Currently, the Saffir-Simpson scale is used to quantify hurricanes, but there are several criticisms of it—it’s solely based on wind speed, so it overlooks the overall size of a storm and the amount of precipitation in produces. Including the raw seismic energy released by a storm could be a way of improving future hurricane classification schemes.
The prospect of seismometers (instruments typically used to detect earthquakes) being employed to supplement satellites in tracking storms is also interesting because of a recent trend in the exact opposite direction. Last month, a satellite data was used for the first time to detect an earthquake by picking up extremely low pitched sound waves that traveled from the epicenter through outer space. The fields of meteorology and geology, it seems, are quickly coming together, reflecting the real-world interaction between the Earth and the atmosphere that surrounds it.
April 15, 2013
This year, prolonged extreme temperatures and seemingly never-ending snowstorms in the United States forced many inside, seeking shelter from what felt like an unusually long winter. This meant some of us were stuck in bed for a day or two clutching a box of Kleenex and downing cough syrup. That’s because viruses that cause the common cold love enclosed spaces with lots of people—the family room, the office, the gym.
And though spring has arrived, cold-causing microbes haven’t slowed down. More than 200 viruses can trigger a runny nose, sore throat, sneezing and coughing—more than 1 billion cases of the common cold occur in the United States each year. The worst offenders (and the most common), known as human rhinoviruses, are most active in spring, summer and early fall.
While it’s difficult to pinpoint exactly when infected people cease to be contagious, they’re most likely to spread their cold when symptoms are at their worst, explains Dr. Teresa Hauguel of the National Institute of Allergy and Infectious Diseases. However, there’s another window of opportunity to be wary about. “A person can be infected before they actually develop symptoms, so they can be spreading it without even realizing it if they’re around people,” Hauguel writes in an email.
Surprised? Here are five more facts about the common cold.
Cold-causing viruses can be found in all corners of the world. Rhinoviruses (from the Greek word rhin, meaning “nose”) evolved from enteroviruses, which cause minor infections throughout the human body. They have been identified even in remote areas inside the Amazon. But it’s impossible to tell how long humans have been battling colds. Scientists can’t pinpoint when rhinoviruses evolved: they mutate too quickly and don’t leave a footprint behind in preserved human fossils. They could have been infecting
mankindhominids before our species appeared. Or they might have sprung up as small groups of humans moved out of isolation and into agricultural communities, where the pathogen became highly adapted to infecting them.
Cold-causing microbes can survive for up to two days outside of the body. Rhinoviruses, which cause 30 to 50 percent of colds, usually live for three hours on your skin or any touchable surface, but can sometimes survive for up to 48 hours. The list of touchable surfaces is a lengthy one: door knobs, computer keyboards, kitchen counters, elevator buttons, light switches, shopping carts, toilet paper rolls—the things we come in contact with on a regular basis. The number of microbes that can grow on these surfaces varies, but each spot can contain several different types of microbes.
You can calculate how far away to stand from someone who’s sick. When a sick person coughs, sneezes or talks, they expel virus-containing droplets into the air. These respiratory droplets can travel up to six feet to another person. A recent study found that the largest visible distance over which a sneeze travels is 0.6 meters, which is almost two feet. It did so at 4.5 meters per second, about 15 feet per second. A breath travels the same distance but much slower, at 1.4 meters—4.5 feet—per second. Moral of the story: remain six feet from infected people, and move quickly when they gear up to sneeze.
The weather plays a role in when and how we get sick—but not in the way you might think. Humidity levels can help those droplets whiz through the air quicker: the lower the humidity, the more moisture evaporates from the droplet, shrinking it in size so it can stay airborne for larger distances. Cold weather is notoriously dry, which explains why we’re more likely to catch a cold while we huddle up inside when temperatures start sinking. This type of air can dry out the mucus lining in our nasal passages; without this protective barrier that traps microbes before they enter the body, we’re more vulnerable to infection. So we’re weakened by the air we breathe in when it’s chilly out, not the chilly weather itself.
Contrary to popular belief, stocking up on vitamin C won’t help. Linus Pauling, a Nobel Prize-winning chemist, popularized the idea of taking high doses of vitamin C to ward off colds. But when put to the test, this cold remedy doesn’t actually work. If you take at least 0.2 grams of vitamin C every day, you’re not likely to have any fewer colds, but you may have colds that are a day or two shorter. When symptoms start to appear, drizzling packets of Emergen-C into glass after glass of water won’t help either. The vitamin is no more effective than a placebo at reducing how long we suffer from cold symptoms.
April 12, 2013
If you have long hair, you probably don’t need to look up a weather report to get an idea of how much humidity’s in the air: You can simply grab a fistful of hair and see how it feels. Human hair is extremely sensitive to humidity—so much that some hygrometers (devices that indicate humidity) use a hair as the measuring mechanism, because it changes in length based on the amount of moisture in the air.
Straight hair goes wavy. If you have curly hair, humidity turns it frizzy or even curlier. Taming the frizz has become a mega industry, with different hair smoothing serums promising to “transform” and nourish hair “without weighing hair down.” But just why does humidity have this strange effect on human hair?
Hair’s chemical structure, it turns out, makes it unusually susceptible to changes in the amount of hydrogen present in the air, which is directly linked to humidity. Most of a hair’s bulk is made up of bundles of long keratin proteins, represented as the middle layer of black dots tightly packed together in the cross-section at right.
These keratin proteins can be chemically bonded together in two different ways. Molecules on neighboring keratin strands can form a disulfide bond, in which two sulfur atoms are covalently bonded together. This type of bond is permanent—it’s responsible for the hair’s strength—and isn’t affected by the level of humidity in the air.
But the other type of connection that can form between adjacent keratin proteins, a hydrogen bond, is much weaker and temporary, with hydrogen bonds breaking and new ones forming each time your hair gets wet and dries again. (This is the reason why, if your hair dries in one shape, it tends to remain in roughly that same shape over time.)
Hydrogen bonds occur when molecules on neighboring keratin strands each form a weak attraction with the same water molecule, thereby indirectly bonding the two keratin proteins together. Because humid air has much higher numbers of water molecules than dry air, a given strand of hair can form much higher numbers of hydrogen bonds on a humid day. When many such bonds are formed between the keratin proteins in a strand of hair, it causes the hair to fold back on itself at the molecular level at a greater rate.
On the macro level, this means that naturally curly hair as a whole becomes curlier or frizzier due to humidity. As an analogy, imagine the metal coil of a spring. If you straighten and dry your hair, it’ll be like the metal spring, completely straightened out into a rod. But if it’s a humid day, and your hair is prone to curling, water molecules will steadily be absorbed and incorporated into hydrogen bonds, inevitably pulling the metal rod back into a coiled shape.
April 2, 2013
Step outside after the first storm after a dry spell and it invariably hits you: the sweet, fresh, powerfully evocative smell of fresh rain.
If you’ve ever noticed this mysterious scent and wondered what’s responsible for it, you’re not alone.
Back in 1964, a pair of Australian scientists (Isabel Joy Bear and R. G. Thomas) began the scientific study of rain’s aroma in earnest with an article in Nature titled “Nature of Agrillaceous Odor.” In it, they coined the term petrichor to help explain the phenomenon, combining a pair of Greek roots: petra (stone) and ichor (the blood of gods in ancient myth).
In that study and subsequent research, they determined that one of the main causes of this distinctive smell is a blend of oils secreted by some plants during arid periods. When a rainstorm comes after a drought, compounds from the oils—which accumulate over time in dry rocks and soil—are mixed and released into the air. The duo also observed that the oils inhibit seed germination, and speculated that plants produce them to limit competition for scarce water supplies during dry times.
These airborne oils combine with other compounds to produce the smell. In moist, forested areas in particular, a common substance is geosmin, a chemical produced by a soil-dwelling bacteria known as actinomycetes. The bacteria secrete the compound when they produce spores, then the force of rain landing on the ground sends these spores up into the air, and the moist air conveys the chemical into our noses.
“It’s a very pleasant aroma, sort of a musky smell,” soil specialist Bill Ypsilantis told NPR during an interview on the topic. “You’ll also smell that when you are in your garden and you’re turning over your soil.”
Because these bacteria thrive in wet conditions and produce spores during dry spells, the smell of geosmin is often most pronounced when it rains for the first time in a while, because the largest supply of spores has collected in the soil. Studies have revealed that the human nose is extremely sensitive to geosmin in particular—some people can detect it at concentrations as low as 5 parts per trillion. (Coincidentally, it’s also responsible for the distinctively earthy taste in beets.)
Ozone—O3, the molecule made up of three oxygen atoms bonded together—also plays a role in the smell, especially after thunderstorms. A lightning bolt’s electrical charge can split oxygen and nitrogen molecules in the atmosphere, and they often recombine into nitric oxide (NO), which then interacts with other chemicals in the atmosphere to produce ozone. Sometimes, you can even smell ozone in the air (it has a sharp scent reminiscent of chlorine) before a storm arrives because it can be carried over long distances from high altitudes.
But apart from the specific chemicals responsible, there’s also the deeper question of why we find the smell of rain pleasant in the first place. Some scientists have speculated that it’s a product of evolution.
Anthropologist Diana Young of the University of Queensland in Australia, for example, who studied the culture of Western Australia’s Pitjantjatjara people, has observed that they associate the smell of rain with the color green, hinting at the deep-seated link between a season’s first rain and the expectation of growth and associated game animals, both crucial for their diet. She calls this “cultural synesthesia”—the blending of different sensory experiences on a society-wide scale due to evolutionary history.
It’s not a major leap to imagine how other cultures might similarly have positive associations of rain embedded in their collective consciousness—humans around the world, after all, require either plants or animals to eat, and both are more plentiful in rainy times than during drought. If this hypothesis is correct, then the next time you relish the scent of fresh rain, think of it as a cultural imprint, derived from your ancestors.
February 28, 2013
The fascinating idea that a butterfly flapping its wings in Asia can change the path of a hurricane over the Pacific is, alas, probably not accurate. But slight changes in one part of the atmosphere can indeed have disproportionate effects elsewhere, a concept known as the butterfly effect.
Just how slight one of these factors can be—and how incredibly far away their effects can reach—is vividly illustrated by a new finding by an international team of atmospheric scientists and chemists from the U.S. and Israel. As they document in a study published today in Science, dust blown from as far away as the Sahara desert of Africa can seed rain and snow clouds in the Sierra Nevada mountains of California.
The research team, led by Kimberly Prather of the University of California, San Diego, came to the finding after using aircraft to collect atmospheric data over the Sierra Nevada mountains, as well as analyzing precipitation that fell at the Sugar Pine Dam in Northern California. They also retroactively tracked storm masses backward across the Pacific and Asia to pinpoint the origin of the dust they found in the clouds.
Cloud formation depends upon tiny particles such as dust that serve as cloud condensation nuclei or ice nuclei—flecks that act as a surface on which water can condense. Previous studies have found that dust from as far away as the Taklimakan desert in China can be blown around the globe. But temperate deserts such as the Taklimakan and the Gobi are frozen much of the year, while the Sahara never freezes, the researchers noted. Could the Sahara and deserts in the Middle East serve as a significant source of year-round dust which, when lofted high into the atmosphere, seeded storms across the planet?
The answer is yes. Of the six storms the researchers sampled, all showed at least some trace of dust. Then, working backward to determine the origin of each of these air masses and using existing data from previous studies on wind currents across the Pacific, they found strong evidence that the majority of the dust had originated in Africa, the Middle East or Asia and traveled around the globe. Additionally, the observed height of various drafts of dust (as collected by a U.S. Navy program) on the days when the air masses would have moved past the African and Asian regions matched the altitude necessary for the particles to get lifted up into the air currents.
Satellite analysis of the storm masses as they moved across the Pacific also confirmed that they carried dust all the way. As shown in the map above, most came from Northeast China or the Taklimakan, but a sizable amount came from as far as the Middle East or even the Sahara.
Although the butterfly’s role in all this seems to be nonexistent, the study did find that one type of living creature does play a part in cloud formation: bacteria. In recent years, scientists have discovered that bacteria, along with dust, can be lofted up high in the atmosphere and serve as nuclei for cloud formation. In this study, the researchers found that small amounts of bacteria were mixed in with the dust, and likely originated in Asia and Africa as well.
So if you live on the West Coast, the next time you get caught in a rainstorm think of this: Each drop that hits you might contain dust and bacteria that’s traveled halfway around the planet. A close look at something as mundane as our daily weather, it turns out, can open a new window to the complex interconnectedness of our world.