Antigravics

Hurricanes

http://www.physorg.com/news115574276.html

>. In a paper published today, Nov. 29, in the "Bulletin of the American Meteorological Society," co-authors Jim Kossin and Dan Vimont caution against only looking at one piece of the puzzle. "Sea surface temperature is a bit overrated," says Kossin, an atmospheric scientist at UW-Madison's Cooperative Institute of Meteorological Satellite Studies. "It's part of a larger pattern."

Kossin and Vimont, a professor in the Department of Atmospheric and Oceanic Sciences, noticed that warmer water is just one part of a larger pattern indicating that the conditions are right for more frequent, stronger hurricanes in the Atlantic.

The atmosphere reacts to ocean conditions and the ocean reacts to the atmospheric situation, creating a distinct circulation pattern known as the Atlantic Meridional Mode (AMM). The AMM unifies the connections among the factors that influence hurricanes such as ocean temperature, characteristics of the wind and moisture in the atmosphere.

Finding that a basin-wide circulation pattern drives Atlantic hurricane activity helps explain evidence of significant differences in long-term hurricane trends among the world's basins.

In a study published last February, Kossin and his co-authors created a more consistent record of hurricane data that accounted for the significant improvement in storm detection that followed the advent of weather satellites. An analysis of this recalibrated data showed that hurricanes have become stronger and more frequent in the Atlantic Ocean over the last two decades. The increasing trend, however, is harder to identify in the world's other oceans.

Kossin and Vimont wanted to determine why long-term trends in the Atlantic looked different from those in other basins, particularly in the Pacific, where the majority of the world's hurricane activity occurs. "The AMM helps us understand why hurricanes in the Atlantic react differently to climate changes than those in the Pacific," Vimont says.

According to Vimont, the other oceanic basins have their own modes of variability. Understanding how factors vary together provides a new framework from which to consider climate change and hurricanes. "Our study broadens the interpretation of the hurricane-climate relationship," Vimont says.

Looking at the larger set of varying conditions provides a more coherent understanding of how climate change affects hurricane activity. In the Atlantic, warmer water indicates that other conditions are also ideal for hurricane development.

However, in the Pacific, a hurricane-friendly environment goes along with cooler ocean temperatures in the area where the storms spend their lives. The inconsistent relationship with sea surface temperature leads Vimont and Kossin to conclude that the connection between hurricane activity and climate variability hinges on more than just changes in ocean temperatures.

"You can never isolate one factor on this planet," Kossin says. "Everything is interrelated."

Depending on the other conditions hurricanes care about, warmer oceans can mean different outcomes. Concentrating on how the atmosphere and the ocean work together helps hurricane researchers see the bigger picture. Because higher sea surface temperatures in the Atlantic act in concert with the AMM, Vimont and Kossin suggest that Atlantic hurricanes will be more sensitive to climate changes than storms in other ocean basins. >>>

Comment
Maybe in the Atlantic it is oil, the oil creating the hot seawater as a distraction.

http://www.physorg.com/news120407801.html

Dust-devils are vortices of wind that form when air rising from a warm surface encounters shear in the above atmosphere. Martian dust devils can attain gargantuan proportions, reaching the size of terrestrial tornadoes with plumes that tower up to 9 kilometers above the surface. Dust-devils play an important role in sustaining the aerosols that make up Mars’ red sky and in cleaning the Martian surface after a dust storm. This observation shows a region near the Martian equator that is a perfect tablet for the scribblings of dust-devils. This region is made up of dark bedrock that is thinly blanketed by bright dust. Dark tracks form when dust-devils scour the surface, exposing the darker substrate. The tracks tend to cluster together, as dust-devils repeatedly form over terrain that has been previously scoured and is consequently darker and warmer than the surrounding surface. Once lofted by a dust-devil, the fine dust can be transported great distances before it settles again onto the surface. Image Credit: NASA/JPL/University of Arizona

>> Mars has an ethereal, tenuous atmosphere with less than one-percent the surface pressure of Earth, which challenges scientists to explain complex, wind-sculpted landforms seen with unprecedented detail in images from NASA's Mars Reconnaissance Orbiter.

One of the main questions has been if winds on present-day Mars are strong enough to form and change geological features, or if wind-constructed formations were made in the past, perhaps when winds speeds and atmospheric pressures were higher.

The eye-opening new views of wind-driven Mars geology come from the University of Arizona's High Resolution Imaging Science Experiment camera (HiRISE). As the orbiter flies at about 3,400 meters per second (7,500 mph) between 250 and 315 kilometers (155 to 196 miles) above the Martian surface, this camera can see features as small as half a meter (20 inches).

"We're seeing what look like smaller sand bedforms on the tops of larger dunes, and, when we zoom in more, a third set of bedforms topping those," said HiRISE co-investigator Nathan Bridges of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "On Earth, small bedforms can form and change on time scales as short as a day."

There are two kinds of "bedforms," or wind-deposited landforms. They can be sand dunes, which are typically larger and have distinct shapes. Or they can be ripples, in which sand is mixed with coarser particles. Ripples are typically smaller and more linear.

HiRISE also shows detail in sediments deposited by winds on the downwind side of rocks. Such "windtails" show which way the most current winds have blown, Bridges said. They have been seen before, but only by rovers and landers, never by an orbiter. Researchers can now use HiRISE images to infer wind directions over the entire planet.

Scientists discovered miles-long, wind-scoured ridges called "yardangs" with the first Mars orbiter, Mariner 9, in the early 1970s. New HiRISE images reveal surface texture and fine-scale features that are giving scientists insight into how yardangs form.

"HiRISE is showing us just how interesting layers in yardangs are," Bridges said. "For example, we see one layer that appears to have rocks in it. You can actually see rocks in the layer, and if you look downslope, you can see rocks that we think have eroded out from that rocky layer above."

New images show that some layers in the yardangs are made of softer materials that have been modified by wind, he added. The soft material could be volcanic ash deposits, or the dried-up remnants of what once were mixtures of ice and dust, or something else. "The fact that we see layers that appear to be rocky and layers that are obviously soft says that the process that formed yardangs is no simple process but a complicated sequence of processes," Bridges said.

"HiRISE keeps showing interesting things about terrains that I expected to be uninteresting," said Alfred McEwen of the University of Arizona Lunar and Planetary Laboratory, HiRISE principal investigator. "I was surprised by the diversity of morphology of the thick dust mantles. Instead of a uniform blanket of smooth dust, there are often intricate patterns due to the action of the wind and perhaps light cementation from atmospheric volatiles."

Paul Geissler of the U.S. Geological Survey, Flagstaff, Ariz., has discovered from HiRISE images that dark streaks coming from Victoria Crater probably consist of streaks of dark sand blown out from the crater onto the surface. Scientists had wondered if wind might have blown away lighter-colored surface material, exposing a darker underlying surface. Geissler is comparing HiRISE images to images taken by NASA's Mars Exploration Rover Opportunity rover at Victoria Crater.

Bridges is lead author and McEwen is a co-author on the paper titled "Windy Mars: A dynamic planet as seen by the HiRISE camera" in Geophysical Research Letters in December.

Source: NASA >>

http://www.nasa.gov/topics/earth/featur ... adoes.html



>> A series of powerful tornadoes ripped through parts of Arkansas, Tennessee, Mississippi, Alabama and Kentucky on Tuesday, Feb. 5, 2008, leaving paths of death and destruction in their wake.

According to news reports, at least 55 fatalities have been attributed to the twisters, making this the deadliest string of tornadoes to hit the nation in almost a quarter of a century.

The tornadoes were spawned from a line of severe thunderstorms that moved eastward across the region. NASA's Tropical Rainfall Measuring Mission satellite captured this unique image of the line of severe storms at 11:08 p.m. Central Daylight Time on February 5.

The fierce storms were fed by warm, moist air from the Gulf of Mexico. La Niña, which brings cooler-than-normal ocean surface temperatures to the eastern part of the Pacific Ocean, may have played a role in the development of these thunderstorms by helping to shift the jet steam, a shift that brought warmer, moister air into the region. >>

http://news.bbc.co.uk/2/hi/science/nature/7347180.stm


The bands appear before and after eclipse "totality"

>> Mysterious bands of shadow which sometimes pass across the ground during an eclipse might be produced by sound pulses, according to a new theory.

"Shadow bands" have been observed travelling across the ground before and after totality - when the Moon completely covers the Sun.

Many attribute these regular light and dark bands to atmospheric turbulence.

But astrophysicist Dr Stuart Eves thinks the phenomenon could be down to something called infrasound.

One astronomer who has studied "shadow bands" was sceptical of the new idea, however. Professor Barrie Jones, from the Open University in Milton Keynes, said that sound travelled too fast to be responsible for the phenomenon.

Prior to the eclipse totality, the bands are usually seen to pass over the ground in the direction in which the eclipse is travelling.

After totality, the bands are often seen spreading at an angle to the path of the eclipse.


If proven, it would be a something of a revelation that eclipses are a sonic as well as an optical phenomenon.

Early theories suggested this effect was due to diffraction of the Sun's rays around the limb of the Moon. But this theory has fallen out of favour.

The theory currently favoured by many astronomers is that the bands result from illumination of the atmosphere by the thin solar crescent a minute or so before and after the eclipse totality.

This means that the light from a distant point can reach a particular place on the ground by a variety of paths, each one is bent in a different way as it passes through the atmosphere.

Thus in some places, the light waves reinforce and the light level is enhanced, whilst in others the waves tend to cancel each other out and the light level is reduced.

When the effects of all the paths taken through the atmosphere are taken together, the result is a ragged banded pattern of light and shade - shadow bands.

The newest idea involves infrasound - sound with a frequency too low to be heard by the human ear.

"As the eclipse shadow moves through the atmosphere, the sudden disappearance of the Sun changes the Earth's temperature," Dr Eves, an astrophysicist who works for Surrey Satellite Technology Limited (SSTL), told BBC News.

This rapid cooling of the air sets up a difference in pressure. The potential energy associated with this pressure difference then escapes as high-intensity infrasound.

Dr Eves says the speed of the Moon's shadow is generally supersonic and likens the phenomenon to the sonic boom of a jet breaking the sound barrier.

But the sound pulses are not generated as single events. Instead, they are created continuously along a "shock front" which moves ahead of the eclipse itself.

This infrasound "front" may create a pattern of peaks and troughs in the atmosphere, which changes the speed and direction of light waves - an effect called refraction - passing through it.

This in turn is responsible for generating the shadow bands seen on the ground.

Dr Eves says the effect could be similar to the way light and dark bands cross a swimming pool when the wind blows on a sunny day.

"None of the [existing] theories seem to take account of the fact that shadow bands change direction," he explained.

But Dr Eves draws a comparison with the waves created when a ship travels through water. If this is correct, then it would explain why shadow bands seen before the eclipse would mostly travel in the direction of the eclipse shadow.

After the eclipse, the shadow bands would travel at angles in the same bay that waves diverge behind a ship.

Barrie Jones, who is director of the physics and astronomy department of the Open University, told BBC News: "I'm not sure how infrasound could generate the bands - it's too fast.

He added: "Infrasonic waves in the atmosphere would move at the speed of sound, which would be something like 400m/s. Shadow bands move at wind speed, so they can be anything from stationary to a few metres per second."

"The [accepted] theory works, there's no need to seek an alternative," said Professor Jones.

Stuart Eves thinks that demonstrating a role for infrasound might explain some other puzzling phenomena associated with eclipses.

For example, long period Foucault pendulums - designed to demonstrate the rotation of the Earth - have been known to swing wildly during eclipses.

Some researchers have proposed that gravitational effects may be responsible.

But Dr Eves thinks the disruption to pendulums may be caused by infrasound pulses causing the ground to vibrate, disrupting the pendulum's rhythm.

In addition, animals, and in particular birds, have been seen to exhibit unusual behaviour. In the case of birds this includes premature roosting and apparent signs of distress or alarm.

Birds have auditory ranges that extend well beyond those of humans, and might be affected by low frequency sound pulses. >>>

http://physorg.com/news131130315.html

>> With the year not even half done, 2008 is already the deadliest tornado year in the United States since 1998 and seems on track to break the U.S. record for the number of twisters in a year, according to the National Weather Service. Also, this year's storms seem to be unusually powerful.

Over the weekend, an extraordinarily powerful twister ripped apart Parkersburg, Iowa, destroying more than 350 homes in the town of about 1,000 residents, said Gov. Chet Culver. At least four people were killed there. Among the buildings destroyed were City Hall, the high school, and the lone grocery store and gas station. Some of those killed were in basements.

The brutal numbers for the U.S. so far this year: at least 110 dead, 30 killer tornadoes and a preliminary count of 1,191 twisters (which, after duplicate sightings are removed, is likely to go down to around 800). The record for the most tornadoes in a year is 1,817 in 2004. In the past 10 years, the average number of tornadoes has been 1,254.

And it's not just more storms. The strongest of those storms - those in the 136-to-200 mph range - have been more prevalent than normal, and lately they seem to be hitting populated areas more, he said. At least 22 tornadoes this year have been in the top part of the new Enhanced Fujita scale, rating a 3 (for "severe") or a 4 ("devastating") on the 1-to-5 scale.

The twister that devastated Parkersburg was a 5 - the first in the U.S. since a tornado nearly obliterated Greensburg, Kan., just over a year ago. The Parkersburg tornado was the strongest to hit Iowa in 32 years.

While tornadoes, like hurricanes, rely on large-scale weather phenomena, the crucial triggers are extremely local weather conditions.

On top of that, tornadoes have a "Goldilocks" issue. To make a tornado, the conditions have to be just right. Too much or too little of one ingredient and there is no tornado. For example, wind shear - when upper and lower winds are at different speeds or coming from different directions - is crucial to create a funnel cloud. Too little and there is no spin. Too much and the tornado falls apart.

And tornadoes form most often in late afternoon, between 5 and 9 p.m., so if a thunderstorm starts up early in the morning, it's far less likely to throw off a tornado, Brooks said. >>

http://news.bbc.co.uk/1/hi/sci/tech/7686530.stm

>> Peeling sticky tape emits X-rays strong enough to scan a human finger, a remarkable experiment has shown.

US researchers used a motorised peeling machine to unwind a roll of Scotch tape at a rate of 3cm per second.

By placing their apparatus in a vacuum, they measured X-rays strong enough to X-ray a human digit, according to a report in Nature journal.

It is well known that unwinding sticky tape produces sparks of light that can be seen in the dark by the naked eye.

This phenomenon, known as "triboluminescence", is produced by the friction generated when two surfaces rub against each other.

The study, by Carlos Camara and Juan Escobar, of the University of California, Los Angeles, USA, provides evidence for the phenomenon, which was first observed more than 50 years ago. >>>

Photographs of rare cloud formations

Mammatus Cloud

These pouch-like clouds seem to be the harbringers of thunderstorms and tornadoes and (in many cases) that’s exactly what they are. They form after long and warm periods and the intensely sheared environment in which Mammatus forms makes them every aviator’s nightmare.

http://www.zmescience.com/7-types-of-ra ... and-videos

known as a Morning Glory cloud can stretch 1,000 kilometers long and occur at altitudes up to two kilometers high. Although similar roll clouds have been seen at specific places across the world, the clouds over Burketown, Queensland Australia occur every spring. These tubes and surrounding air could cause dangerous turbulence for airplanes when clear. They reportedly achieve airspeeds of 60 kilometers per hour over a surface with little discernible wind.
http://www.dailygalaxy.com/my_weblog/20 ... ouds-.html

http://www.physorg.com/news179426300.html

>> Scientists at the Florida Institute of Technology, University of California, Santa Cruz and the University of Florida have estimated that airplane passengers could be exposed to a radiation dose equal to that from 400 chest X-rays if their airplane happens to be near the start of a lightning discharge or related phenomena known as a terrestrial gamma ray flash.

The big unknown: how often — if ever — commercial airliners are exposed to these thunderstorm events, because the bursts of radiation occur only over extremely brief periods and extend just a few hundred feet in the clouds.

"We know that commercial airplanes are typically struck by lightning once or twice a year," said Joe Dwyer, professor of physics and space sciences at Florida Tech. "What we don't know is how often planes happen to be in just the right place or right time to receive a high radiation dose. We believe it is very rare, but more research is needed to answer the question definitively."

The authors did not measure high radiation doses directly with airplanes. Instead, they estimated radiation based on satellite and ground-based observations of X-rays and gamma rays.

The authors "combined observations of lightning-produced X-rays and gamma rays with computer models of the movement of high-energy particles to estimate the amount of radiation that could be produced within, or very near, thunderclouds during lightning storms," said Hamid Rassoul, a co-author and senior researcher from Florida Tech.

The observations included those made from orbiting satellites of "terrestrial gamma-ray flashes," or TGFs, mysterious phenomena that appear to originate within thunderstorms at the same altitudes used by jet airliners. They also included measurements of X-rays and gamma rays from natural lightning on the ground, as well as artificial lightning triggered with wire-trailing rockets fired into storm clouds. Researchers believe the phenomena are linked, because both produce high levels of gamma rays and X-rays and occur along with the actual lightning flash.

The scientists concluded the radiation in a football field-sized space around these lightning events could reach "biologically significant levels," up to 10 rem, according to their paper.

"If an aircraft happened to be in or near the high-field region when either a lightning discharge or a TGF event is occurring, then the radiation dose received by passengers and crew members inside the aircraft could potentially approach 10 rem in less than one millisecond," the paper says.

Ten rem is considered the maximum safe radiation exposure over a person's lifetime. It is equal to 400 chest X-rays, three CAT scans or 7,500 hours of flight time in normal conditions. All airplane passengers are exposed to slightly elevated radiation levels due to cosmic rays.

While the research raises obvious concerns, the scientists stressed that they don't know how often the high-radiation events occur — or how often planes are nearby enough to expose passengers and flight crews to potential danger.

David Smith, an associate professor of physics at UC-Santa Cruz, said recent airborne research suggests the incidents are rare. Flying aboard a National Science Foundation/National Center for Atmospheric Research aircraft this past summer in Florida, Smith and several of the other researchers used a highly sophisticated instrument to measure gamma ray flashes from thunderstorms. Over the course of several flights, they were only able to detect one such flash, at a safe distance from the plane.

"These observations show that although thunderstorms do occasionally create intense gamma-ray flashes, the chance of accidently being directly hit by one is small," Smith said.

Martin Uman, another author and a distinguished professor of electrical and computer engineering at UF, noted that airline pilots typically seek to avoid flying through storms.

However, he said, the fact that commercial planes are struck once or twice a year suggests more inquiry is needed. He said he would recommend to the Federal Aviation Administration that it place detectors aboard planes capable of measuring the storm-related, brief and intense radiation bursts to determine how often they occur. He also said more research on the phenomena that generates the bursts is clearly needed.

"What we need to do is supply the right kind of detectors to a lot of planes, and see if this ever happens," he said. "We also need to spend more time looking at gamma and x-ray radiation from lightning and thunderstorms and trying to understand how it works."

The paper drew on data from numerous observations and experiments, including experiments involving artificial "triggered" lightning at UF/Florida Tech International Center for Lightning Research and Testing at the Camp Blanding Army National Guard Base near Starke, Florida. UF and Florida Tech researchers at the center were the first to identify X-ray emissions from triggered lightning. >>

Las Olas Beach in Maldonado, Uruguay

> They are most common when an advancing storm front causes moist air to rise, then cool to the point where it becomes a cloud known as the dew point. When this happens along a front, a roll cloud can form, often with air actually circulating along the horizontal axis of the cloud.

Although it looks like a sideways tornado, these clouds cannot become one.