Category: Earth Observation

Image credit: NASA

NASA scientists have discovered that a “hot tower” of cloud rising above the eye of a hurricane can increase its intensity. The scientists used data gathered by the TRMM satellite; a joint project by NASA and the Japanese Aerospace Exploration Agency. After compiling statistics from several storms, they found that when a hot tower forms up to 15 kilometres above the eye, the hurricane will become much more intense within six hours. This research could help improve forecasts of which hurricanes have the potential to cause the most damage.

They are called hurricanes in the Atlantic, typhoons in the West Pacific, and tropical cyclones worldwide; but wherever these storms roam, the forces that determine their severity now are a little less mysterious. NASA scientists, using data from the Tropical Rainfall Measuring Mission (TRMM) satellite, have found “hot tower” clouds are associated with tropical cyclone intensification.

Owen Kelley and John Stout of NASA’s Goddard Space Flight Center, Greenbelt, Md., and George Mason University will present their findings at the American Meteorological Society annual meeting in Seattle on Monday, January 12.

Kelley and Stout define a “hot tower” as a rain cloud that reaches at least to the top of the troposphere, the lowest layer of the atmosphere. It extends approximately nine miles (14.5 km) high in the tropics. These towers are called “hot” because they rise to such altitude due to the large amount of latent heat. Water vapor releases this latent heat as it condenses into liquid.

A particularly tall hot tower rose above Hurricane Bonnie in August 1998, as the storm intensified a few days before striking North Carolina. Bonnie caused more than $1 billion damage and three deaths, according to the National Oceanic and Atmospheric Administration National Hurricane Center.

Kelley said, “The motivation for this new research is that it is not enough to predict the birth of a tropical cyclone. We also want to improve our ability to predict the intensity of the storm and the damage it would cause if it struck the coast.” The pioneering work of Joanne Simpson, Jeffrey Halverson and others has already shown hot towers increase the chance a new tropical cyclone will form. Future work may use this association to improve forecasts of a cyclone’s destructive potential.

To achieve their goal, Kelley and Stout needed to compile a special kind of global statistics on the occurrence of hot towers inside tropical cyclones. The only possible data source was TRMM satellite, a joint effort of NASA and the Japan Aerospace Exploration Agency. “Many satellites can see the top of a hot tower, but what’s special about this satellite’s Precipitation Radar is that it gives you ‘X-ray vision’ so you can see inside a hot tower,” Kelley said. To compile global statistics, the radar needs to be orbiting the Earth.

After compiling the statistics, Kelley and Stout found a tropical cyclone with a hot tower in its eyewall was twice as likely to intensify within the next six hours than a cyclone that lacked a tower. The “eyewall” is the ring of clouds around a cyclone’s central eye. Kelley and Stout considered many alternative definitions for hot towers before concluding the nine-mile height threshold was statistically significant.

Funding for the research was provided by NASA’s Earth Science Enterprise. The Enterprise strives to advance Earth System Science and to improve the prediction of climate, weather and natural hazards from the unique vantage point of space.

Original Source: NASA News Release

Image credit: NASA

Geologists at the University of Berkeley believe that radioactive potassium might be a substantial source of heat in the Earth’s core. The problem has been that scientists haven’t found as much potassium in the Earth’s crust as they would have expected from the Earth’s early bombardment period by asteroids. However, the geologists discovered that potassium can form a heavy alloy with iron under high temperatures and pressures, so it might have just sunk to the middle of the Earth, and could form a minute component of the core – but a fifth of its heat.

Radioactive potassium, common enough on Earth to make potassium-rich bananas one of the “hottest” foods around, appears also to be a substantial source of heat in the core of Earth, according to recent experiments by University of California, Berkeley, geophysicists.

Radioactive potassium, uranium and thorium are thought to be the three main sources of heat in the Earth’s interior, aside from that generated by the formation of the planet. Together, the heat keeps the mantle actively churning and the core generating a protective magnetic field.

But geophysicists have found much less potassium in the Earth’s crust and mantle than would be expected based on the composition of rocky meteors that supposedly formed the Earth. If, as some have proposed, the missing potassium resides in the Earth’s iron core, how did an element as light as potassium get there, especially since iron and potassium don’t mix?

Kanani Lee, who recently earned her Ph.D. from UC Berkeley, and UC Berkeley professor of earth and planetary science Raymond Jeanloz have discovered a possible answer. They’ve shown that at the high pressures and temperatures in the Earth’s interior, potassium can form an alloy with iron never before observed. During the planet’s formation, this potassium-iron alloy could have sunk to the core, depleting potassium in the overlying mantle and crust and providing a radioactive potassium heat source in addition to that supplied by uranium and thorium in the core.

Lee created the new alloy by squeezing iron and potassium between the tips of two diamonds to temperatures and pressures characteristic of 600-700 kilometers below the surface – 2,500 degrees Celsius and nearly 4 million pounds per square inch, or a quarter of a million times atmospheric pressure.

“Our new findings indicate that the core may contain as much as 1,200 parts per million potassium -just over one tenth of one percent,” Lee said. “This amount may seem small, and is comparable to the concentration of radioactive potassium naturally present in bananas. Combined over the entire mass of the Earth’s core, however, it can be enough to provide one-fifth of the heat given off by the Earth.”

Lee and Jeanloz will report their findings on Dec. 10, at the American Geophysical Union meeting in San Francisco, and in an article accepted for publication in Geophysical Research Letters.

“With one experiment, Lee and Jeanloz demonstrated that potassium may be an important heat source for the geodynamo, provided a way out of some troublesome aspects of the core’s thermal evolution, and further demonstrated that modern computational mineral physics not only complements experimental work, but that it can provide guidance to fruitful experimental explorations,” said Mark Bukowinski, professor of earth and planetary science at UC Berkeley, who predicted the unusual alloy in the mid-1970s.

Geophysicist Bruce Buffett of the University of Chicago cautions that more experiments need to be done to show that iron can actually pull potassium away from the silicate rocks that dominate in the Earth’s mantle.

“They proved it would be possible to dissolve potassium into liquid iron,” Buffet said. “Modelers need heat, so this is one source, because the radiogenic isotope of potassium can produce heat and that can help power convection in the core and drive the magnetic field. They proved it could go in. What’s important is how much is pulled out of the silicate. There’s still work to be done ”

If a significant amount of potassium does reside in the Earth’s core, this would clear up a lingering question – why the ratio of potassium to uranium in stony meteorites (chondrites), which presumably coalesced to form the Earth, is eight times greater than the observed ratio in the Earth’s crust. Though some geologists have asserted that the missing potassium resides in the core, there was no mechanism by which it could have reached the core. Other elements like oxygen and carbon form compounds or alloys with iron and presumably were dragged down by iron as it sank to the core. But at normal temperature and pressure, potassium does not associate with iron.

Others have argued that the missing potassium boiled away during the early, molten stage of Earth’s evolution.

The demonstration by Lee and Jeanloz that potassium can dissolve in iron to form an alloy provides an explanation for the missing potassium.

“Early in Earth’s history, the interior temperature and pressure would not have been high enough to make this alloy,” Lee said. “But as more and more meteorites piled on, the pressure and temperature would have increased to the point where this alloy could form.”

The existence of this high-pressure alloy was predicted by Bukowinski in the mid-1970s. Using quantum mechanical arguments, he suggested that high pressure would squeeze potassium’s lone outer electron into a lower shell, making the atom resemble iron and thus more likely to alloy with iron.

More recent quantum mechanical calculations using improved techniques, conducted with Gerd Steinle-Neumann at the Universit?t Bayreuth’s Bayerisches Geoinstit?t, confirmed the new experimental measurements.

“This really replicates and verifies the earlier calculations 26 years ago and provides a physical explanation for our experimental results,” Jeanloz said.

The Earth is thought to have formed from the collision of many rocky asteroids, perhaps hundreds of kilometers in diameter, in the early solar system. As the proto-Earth gradually bulked up, continuing asteroid collisions and gravitational collapse kept the planet molten. Heavier elements ? in particular iron – would have sunk to the core in 10 to 100 million years’ time, carrying with it other elements that bind to iron.

Gradually, however, the Earth would have cooled off and become a dead rocky globe with a cold iron ball at the core if not for the continued release of heat by the decay of radioactive elements like potassium-40, uranium-238 and thorium-232, which have half-lives of 1.25 billion, 4 billion and 14 billion years, respectively. About one in every thousand potassium atoms is radioactive.

The heat generated in the core turns the iron into a convecting dynamo that maintains a magnetic field strong enough to shield the planet from the solar wind. This heat leaks out into the mantle, causing convection in the rock that moves crustal plates and fuels volcanoes.

Balancing the heat generated in the core with the known concentrations of radiogenic isotopes has been difficult, however, and the missing potassium has been a big part of the problem. One researcher proposed earlier this year that sulfur could help potassium associate with iron and provide a means by which potassium could reach the core.

The experiment by Lee and Jeanloz shows that sulfur is not necessary. Lee combined pure iron and pure potassium in a diamond anvil cell and squeezed the small sample to 26 gigapascals of pressure while heating the sample with a laser above 2,500 Kelvin (4,000 degrees Fahrenheit), which is above the melting points of both potassium and iron. She conducted this experiment six times in the high-intensity X-ray beams of two different accelerators – Lawrence Berkeley National Laboratory’s Advanced Light Source and the Stanford Synchrotron Radiation Laboratory – to obtain X-ray diffraction images of the samples’ internal structure. The images confirmed that potassium and iron had mixed evenly to form an alloy, much as iron and carbon mix to form steel alloy.

In the theoretical magma ocean of a proto-Earth, the pressure at a depth of 400-1,000 kilometers (270-670 miles) would be between 15 and 35 gigapascals and the temperature would be 2,200-3,000 Kelvin, Jeanloz said.

“At these temperatures and pressures, the underlying physics changes and the electron density shifts, making potassium look more like iron,” Jeanloz said. “At high pressure, the periodic table looks totally different.”

“The work by Lee and Jeanloz provides the first proof that potassium is indeed miscible in iron at high pressures and, perhaps as significantly, it further vindicates the computational physics that underlies the original prediction,” Bukowinski said. “If it can be further demonstrated that potassium would enter iron in significant amounts in the presence of silicate minerals, conditions representative of likely core formation processes, then potassium could provide the extra heat needed to explain why the Earth’s inner core hasn’t frozen to as large a size as the thermal history of the core suggests it should.”

Jeanloz is excited by the fact that theoretical calculations are now not only explaining experimental findings at high pressure, but also predicting structures.

“We need theorists to identify interesting problems, not only check our results after the experiment,” he said. “That’s happening now. In the past half a dozen years, theorists have been making predictions that experimentalists are willing to spend a few years to demonstrate.”

The work was funded by the National Science Foundation and the Department of Energy.

Original Source: University of Berkeley News Release

Image credit: NASA

Using data from several NASA satellites, scientists believe that the Spring thaws in the Northern latitudes are arriving earlier and earlier each year. The change is so dramatic, that the thawing has come on average one day earlier each year since 1988. The shorter Winter warms up areas that were previously permafrost (permanently frozen), and this releases additional carbon dioxide into the atmosphere. Scientists are just starting to understand what role the polar areas have in the regulation of the Earth’s climate.

Using a suite of microwave remote sensing instruments aboard satellites, scientists at NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif., and the University of Montana, Missoula, have observed a recent trend of earlier thawing across the northern high latitudes.

This regional thawing trend, advancing almost one day a year since 1988, has the potential to alter the cycle of atmospheric carbon dioxide intake and release by vegetation and soils across the region, potentially resulting in changes in Earth’s climate. The lengthening growing season appears to be promoting more carbon uptake by the vegetation than is being released into the atmosphere for the region. How long this trend will occur depends on whether soils continue to remain cold and wet.

Research scientists have been studying freeze/thaw dynamics in North America and Eurasia’s boreal forests and tundra to decipher effects on the timing and length of the growing season. These regions encompass almost 30 percent of global land area. They store a major portion of Earth’s carbon in vegetation, in seasonally frozen and permafrost soils. Large expanses of boreal forest and tundra are underlain by permafrost, a layer of permanently frozen soil found underneath the active, seasonally thawed soil.

“Frozen soil can store carbon for hundreds to thousands of years,” said lead author Dr. Kyle McDonald of JPL, “but when the permafrost thaws and begins to dry out, it releases the carbon back into the atmosphere.” The concern is that eventually carbon released from the soil will prevail over the amount being taken in by growing plants. Carbon dioxide levels in the atmosphere would increase at an accelerated rate, fostering even greater warming of the region and affecting global climate.

With help from NASA radars and other orbiting satellite microwave remote sensing instruments, including the National Oceanic and Atmospheric Administration’s Special Scanning Microwave/Imager, scientists can monitor growing season dynamics of the global boreal forest and tundra daily. These instruments sense the electrical properties of water in the landscape, allowing scientists to determine exactly when and where the springtime thaw occurs.

Because of the large extent and location of boreal forest and tundra, and the global reservoir of carbon stored in their vegetation and soils, this region is extremely sensitive to environmental change. It has the capacity to dramatically impact Earth’s climate.

“If global climate change is happening, here’s where you would expect to see it first,” McDonald said.

As the research team observed, the earlier the spring thaw occurs, the longer the growing season. These changes appear to be promoting plant growth for the region. The longer growing season allows plants to remove more carbon dioxide from the atmosphere over a longer period of time.

Carbon dioxide is an important greenhouse gas that, if left in the atmosphere, would promote additional warming. The plants release oxygen and store the carbon as biomass that eventually decomposes and transfers the carbon into the soil. Soil microbes decompose dead plant material, returning a portion of the soil carbon back into the atmosphere. The rate which soil microbes decompose plant material and release carbon to the atmosphere is also very sensitive to temperature. It could potentially increase with warming temperatures and longer growing seasons.

>From this general study, McDonald, Dr. John Kimball of the University of Montana, and JPL’s Erika Podest have lead three different investigations, each focusing on different noticeable changes in the boreal region. Results of three related papers on this research will be presented to the American Geophysical Union’s Fall Meeting this week in San Francisco.

The research is funded by NASA’s Earth Science Enterprise. The Enterprise is dedicated to understanding the Earth as an integrated system and applying Earth System Science to improve prediction of climate, weather, and natural hazards using the unique vantage point of space. The California Institute of Technology, Pasadena, manages JPL for NASA.

Original Source: NASA News Release

Image credit: NASA

NASA’s Ice, Cloud and land Elevation Satellite (ICESat) has been churning out spectacular 3-D images of the Earth’s icecaps, clouds, mountains and forests as part of its mission to help understand how our planet is affected by climate change. ICESat’s principal mission is to measure the surface elevations of large ice sheets to determine how much they’re changing. The spacecraft’s images of Antarctica revealed details of ice streams along several glaciers, and megadunes in the continent’s interior.

NASA’s Ice, Cloud and land Elevation Satellite (ICESat) is sending home important scientific data and spectacular 3-D views of Earth’s polar ice sheets, clouds, mountains, and forestlands. The data are helping scientists understand how life on Earth is affected by changing climate.

The principal objective of the ICESat mission, and its Geoscience Laser Altimeter System (GLAS) instrument, is to measure the surface elevations of the large ice sheets covering Antarctica and Greenland and determine how they are changing. Much of an ice sheet’s behavior and response to changes in climate are apparent in their shape and how that shape changes with time. The laser sends short pulses of green and infrared light to Earth 40 times a second and collects the reflected laser light with a one-meter telescope.

The measurements have provided revolutionary accuracy and detail about the elevation of ice sheets and the elevation structure of land surfaces. ICESat is providing scientists with the most accurate measurements to date of the heights of clouds. It is also providing critical observations of atmospheric particles, called aerosols, over the ice sheets and the rest of the world. These help climate modelers, who reconstruct the past and project future climate.

“NASA has developed tremendous capabilities over the last several decades for observing our Earth in two dimensions. With ICESat, we can see the critical third-dimension, that is, the vertical dimension of land, water, and the atmosphere, in new and innovative ways,” said Waleed Abdalati, ICESat Program Scientist, NASA Headquarters, Washington. “The first few months of ICESat data have really been phenomenal. We can see detail in ice and land features that were never visible before from space.”

Scientists are using ICESat data to develop what are called “Digital Elevation Models,” 3-D high-resolution images of ice sheets in Greenland and Antarctica. Gathering these data from space will allow scientists, to obtain an unprecedented view of how and where ice sheets are growing and shrinking. This information is critical to understanding how the Earth’s changing ice cover affects sea level.

Earlier this year, ICESat’s first topographic profiles across Antarctica revealed details never before seen of features such as the ice streams of the Siple Coast, the Amery Ice Shelf, and megadunes in the Antarctic interior.

“The amount and coverage of heavy dust and pollution loading in many regions of the Earth that we are seeing in the initial ICESat data are unexpected,” said James Spinhirne, principal atmospheric scientist for ICESat at NASA’s Goddard Space Flight Center, Greenbelt, Md. These include the rivers of dust from the Sahara desert, massive dust storms, and large-scale smoke from burning vegetation. The observations tie smoke, dust and clouds directly to winds and global transport.

ICESat was launched January 12, 2003. It is the latest in a series of NASA Earth observation spacecraft designed to study the environment of our home planet and how it may be changing. NASA’s Earth Science Enterprise is dedicated to understanding the Earth as an integrated system and applying Earth System Science to improve prediction of climate, weather and natural hazards using the unique vantage point of space.

ICESat scientists will present the latest results from ICESat during a press conference on December 9 at 3:00 pm PT in Room 2012 Moscone West, at the 2003 Fall Meeting of the American Geophysical Union in San Francisco. They will also convene special sessions C31A and C31D detailing these results on December 10, beginning at 10:20am PT in the Moscone Center, Room MCC 3010.

Original Source: NASA News Release

Image credit: NASA/JPL

One aspect of the Earth’s climate, the distribution of water vapour, might have significant implications for climate change and ozone depletion. To understand its significance, NASA scientists are using special aircraft to build a detailed map of how water vapour moves around in the atmosphere, from the surface of the Earth up to an altitude of 40 km, where the air completely dries out. They were able to tell which vapour was created at high altitudes and which was moved up by air currents.

NASA scientists have opened a new window for understanding atmospheric water vapor, its implications for climate change, and ozone depletion.

The scientists have created the first detailed map of water containing heavy hydrogen and heavy oxygen atoms in and out of clouds, from the surface of Earth to some 25 miles upward, to better understand the dynamics of how water gets into the stratosphere.

Only small amounts of water reach the arid stratosphere, 10 to 50 kilometers (6 to 25 miles) above Earth, so any increase in the water content could potentially lead to destruction of some ozone-shielding capability in this part of the atmosphere. This could produce larger ozone depletions over the North and South Poles as well as at mid-latitudes.

Water shapes Earth’s climate. The large amount of it in the lower atmosphere, the troposphere, controls how much sunlight gets through to the planet, how much is trapped in our skies, and how much goes back out to space. Higher in the stratosphere, where most of the Earth’s ozone shield protects the surface from harmful ultraviolet rays, there is very little water (less than .001 of the surface concentration). Scientists don’t fully understand how air is dried before it gets to this region.

In the troposphere, water exists as vapor in air, as liquid droplets in clouds, and as frozen ice particles in high altitude cirrus clouds. Since there is so much water closer to Earth and so few miles above, it is important to understand how water enters and leaves the stratosphere. The “isotopic content,” the natural fingerprint left by the heavy forms of water, is key to understanding the process. An isotope is any of two or more forms of an element having the same or very closely related chemical properties and the same atomic number, but different atomic weights. An example is oxygen 16 versus oxygen 18– both are oxygen, but one is heavier than the other.

Heavy water is more readily condensed or frozen out from its vapor, causing the nature of its distribution to differ somewhat from the usual isotopic form of water. A measurement of the isotopic make-up of water vapor enables scientists to determine how water gets into the stratosphere.

“For the first time, we have water isotope content mapped in incredible detail,” said Dr. Christopher R. Webster, a senior research scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. Webster is principal author of a scientific paper announcing the new findings in the journal Science. Dr. Andrew J. Heymsfield, of the National Center for Atmospheric Research, Boulder, Colo., is co-author.

Measuring water isotopes is extremely challenging, because they represent only a small fraction, less than one percent, of the total water in the atmosphere. Detailed measurements were made using an Aircraft laser infrared absorption spectrometer (Alias) flying aboard NASA’s WB-57F high- altitude jet aircraft in July 2002. This new laser technique enables mapping of water isotopes with sufficient resolution to help researchers understand both water transport and the detailed microphysics of clouds, key parameters for understanding atmospheric composition, storm development and weather prediction.

“The laser technique gives us the ability to measure the different types of isotopes found in all water,” said Webster. “With the isotopic fingerprint, we discovered the ice particles found under the stratosphere were lofted from below, and some were grown there in place.”

The data help explain how the water content of air entering the stratosphere is reduced, and show that gradual ascent and rapid upward motion associated with tall cloud systems (convective lofting) both play roles in establishing the dryness of the stratosphere.

The purpose of the aircraft mission was to understand the formation, extent and processes associated with cirrus clouds. The mission used six aircraft from NASA and other federal agencies to make observations above, in and below the clouds. By combining aircraft data with ground-based data and satellites, scientists have a better picture of the relationship between clouds, water vapor and atmospheric dynamics than previously. They also can better interpret satellite measurements routinely made by NASA.

The mission was funded by NASA’s Earth Science Enterprise. The Enterprise is dedicated to understanding the Earth as an integrated system and applying Earth System Science to improve prediction of climate, weather and natural hazards using the unique vantage point of space. For more information about Alias, visit: http://laserweb.jpl.nasa.gov.

For information about NASA, visit: http://www.nasa.gov.

JPL is managed for NASA by the California Institute of Technology in Pasadena

Original Source: NASA/JPL News Release

Image credit: NASA

Researchers have discovered that temporary cracks can form in the Earth’s magnetic field that can permit some of the solar wind’s energy to slip through and disrupt electronics and communications. These observations were made using NASA’s Imager for Magnetopause to Aurora Global Exploration (IMAGE) satellite, which tracked a large aurora for several hours. The ESA’s Cluster satellites flew over the same location and spotted a stream of ions slipping through a crack which normally should have been deflected by the Earth’s magnetosphere.

Immense cracks in the Earth’s magnetic field remain open for hours, allowing the solar wind to gush through and power stormy space weather, according to new observations from the IMAGE and Cluster satellites.

The cracks were detected before but researchers now know they can remain open for long periods, rather than opening and closing for just very brief intervals. This new discovery about how the Earth’s magnetic shield is breached is expected to help space physicists give better estimates of the effects of severe space weather.

“We discovered that our magnetic shield is drafty, like a house with a window stuck open during a storm,” said Dr. Harald Frey of the University of California, Berkeley, lead author of a paper on this research published Dec. 4 in Nature. “The house deflects most of the storm, but the couch is ruined. Similarly, our magnetic shield takes the brunt of space storms, but some energy continually slips through its cracks, sometimes enough to cause problems with satellites, radio communication, and power systems.”

“The new knowledge that the cracks are open for long periods, instead of opening and closing sporadically, can be incorporated into our space weather forecasting computer models to more accurately predict how our space weather is influenced by violent events on the Sun,” said Dr. Tai Phan, also of UC Berkeley, co-author of the Nature paper.

The solar wind is a stream of electrically charged particles (electrons and ions) blown constantly from the Sun (Image 1). The solar wind transfers energy from the Sun to the Earth through the magnetic fields it carries and its high speed (hundreds of miles/kilometers per second). It can get gusty during violent solar events, like Coronal Mass Ejections (CMEs), which can shoot a billion tons of electrified gas into space at millions of miles per hour.

Earth has a magnetic field that extends into space for tens of thousands of miles, surrounding the planet and forming a protective barrier to the particles and snarled magnetic fields the Sun blasts toward it during CMEs. However, space storms, which can dump 1,000 billion watts — more than America’s total electric generating capacity — into the Earth’s magnetic field, indicated that the shield was not impenetrable.

In 1961, Dr. Jim Dungey of the Imperial College, United Kingdom, predicted that cracks might form in the magnetic shield when the solar wind contained a magnetic field that was oriented in the opposite direction to a portion of the Earth’s field. In these regions, the two magnetic fields would interconnect through a process known as “magnetic reconnection,” forming a crack in the shield through which the electrically charged particles of the solar wind could flow. (Image 2 illustrates the crack formation, and Animation 1 shows how solar wind particles flow through the crack by following invisible magnetic field lines.) In 1979, Dr. Goetz Paschmann, of the Max Planck Institute for Extraterrestrial Physics, Germany, detected the cracks using the International Sun Earth Explorer (ISEE) spacecraft. However, since this spacecraft only briefly passed through the cracks during its orbit, it was unknown if the cracks were temporary features or if they were stable for long periods.

In the new observations, the Imager for Magnetopause to Aurora Global Exploration (IMAGE) satellite revealed an area almost the size of California in the arctic upper atmosphere (ionosphere) where a 75-megawatt “proton” aurora flared for hours (Image 4). This aurora, energetic enough to power 75,000 homes, was different from the visible aurora known as the Northern and Southern lights. It was generated by heavy particles (ions) hitting the upper atmosphere and causing it to emit ultraviolet light, which is invisible to the human eye but detectable by the Far Ultraviolet Imager on IMAGE. (Image 6 and Animation 4 show IMAGE’s observations of the proton aurora).

While the aurora was being recorded by IMAGE, the 4-satellite Cluster constellation flew far above IMAGE, directly through the crack, and detected solar wind ions streaming through (Image 5). Normally, these solar wind ions would be deflected by Earth’s shield (Image 3), so Cluster’s observation showed a crack was present. This stream of solar wind ions bombarded our atmosphere in precisely the same region where IMAGE saw the proton aurora. The fact that IMAGE was able to view the proton aurora for more than 9 hours, until IMAGE progressed in its orbit to where it could not observe the aurora, implies that the crack remained continuously open. (Animation 2 shows how the spacecraft worked together to reveal the crack.) Estimating from the IMAGE and Cluster data, the crack was twice the size of the Earth at the boundary of our magnetic shield, about 38,000 miles (60,000 km) above the planet’s surface. Since the magnetic field converges as it enters the Earth in the polar regions, the crack narrowed to about the size of California down near the upper atmosphere.

IMAGE is a NASA satellite launched March 25, 2000 to provide a global view of the space around Earth influenced by the Earth’s magnetic field. The Cluster satellites, built by the European Space Agency and launched July 16, 2000, are making a three-dimensional map of the Earth’s magnetic field.

Original Source: NASA News Release

Image credit: ESA

The Earth’s wetlands are home to some of the most fragile and diverse ecosystems on the planet, and they’re under constant threat from human agriculture, pollution, and settlement. This month the European Space Agency began a program to map 50 wetland areas around the Earth from space to help keep track of their health. ESA’s Envisat is able to tell the difference between dry and waterlogged areas, and will be able to provide annual data about how various wetlands change throughout the seasons.

Dotted across varied regions of our planet are the waterlogged landscapes known as wetlands. Often inaccessible, these muddy areas are actually treasure houses of ecological diversity ? their overall value measured in trillions of Euros.

For much of the last century wetlands have been drained or otherwise degraded, but scientific understanding of their important roles in terms of biology and the water cycle has grown, spurring international efforts to preserve them. On 20 November ESA formally began a project to map wetlands from space, providing data on around 50 sites in 21 countries worldwide.

In 1971 an inter-governmental treaty established the Ramsar Convention on Wetlands, establishing a framework for the stewardship and preservation of wetlands. Today more than 1310 wetlands have been designated as Wetlands of International Importance, a total area of 111 million hectares. The Convention’s 138 national signatories are obliged to report on the state of listed wetlands they are responsible for.

ESA’s new ?1 million Globwetland project is producing satellite-derived and geo-referenced products including inventory maps and digital elevation models of wetlands and the surrounding catchment areas. These products will aid local and national authorities in fulfilling their Ramsar obligations, and should also function as a helpful tool for wetland managers and scientific researchers.

“The Ramsar Convention on Wetlands stresses that targeted assessment and monitoring information is vital for ensuring effective management planning for wetlands, their hydrology and their catchments,” explained Nick Davidson, Ramsar’s Deputy Secretary General. “Yet for wetland managers and decision-makers in many countries access to sound information about wetlands and how they are changing is often a critical gap.

“By working with users at site and catchment scales the Globwetland project should contribute significantly to helping achieve effective management of these critical important ecosystems for biodiversity and human well-being.”

With wetlands often made up of difficult and inaccessible terrain, satellites can help provide information on local topography, the types of wetland vegetation, land cover and use and the dynamics of the local water cycle. In particular radar imagery of the type provided by ESA’s Envisat is able to differentiate between dry and waterlogged surfaces, and so can provide multitemporal data on how given wetlands change seasonally.

Data gathered over four continents
Globwetland products are being provided for a wide range of terrain types to users across four continents: North and South America, Africa, Asia and Europe, including European Russia. In Spain the Globwetland end-user is the government’s Ministry of the Environment.

“We have previously used aerial photography to prepare wetland maps, but this is the first time we will use Earth Observation data,” said Jos? Ram?n Picatoste Ruggeroni, Director General of Nature Conservation and Subdirector General of Biodiversity Conservation. “The areas we are most interested in are land cover and land cover analysis, topography dynamics and subsidence layers, water cycle and quality maps.

“In co-operation with the Spanish regional authorities involved in nature conservation and local wetland managers, we hope to investigate the possibility of achieving a common standard of regularly updated geoinformation to monitor ecological changes in the Spanish Ramsar sites.”

At the other side of the continent, wetlands comprise a third of the territory of the Russian Federation, the majority of it in the form of peatlands. Through much of the 20th century these areas were regarded as wasteland and drained for peat extraction – ending up as unproductive lands that do not contribute either economically or in terms of biodiversity, and also cause ecological problems such as dust storms and uncontrolled carbon dioxide emissions from smouldering peat fires.

In Russia the Globwetland partner is the Ministry of Ecology and Land Use of Moscow region, and has a particular interest in using periodic satellite data to monitor peat fires and estimate how effective a new rewetting project is in preventing further outbreaks.

While in South Africa, Globwetland partner the Department of Environmental Affairs and Tourism (DEAT) seeks to use satellite data to help fulfil its Ramsar obligations for its existing three-site wetlands inventory. The Department also plans to map a separate site, the Prince Edward Islands Special Nature Reserve, for the first time.

South Africa hopes to propose the offshore Reserve for designation as a new Ramsar Wetland of International Importance, but its uncharted nature is currently an obstacle to achieving this. This Southern Ocean site is also being nominated next year as a UNESCO World Heritage Site.

Why are wetlands so valuable?
Studies of wetlands show they store and purify water for domestic use, recharge natural aquifers as they run low, retain nutrients in floodplains, help control flooding and shore erosion and regulate local climate.

Most of all, wetlands support life in spectacular variety and numbers: freshwater wetlands alone are home to four in ten of all the world’s species, and one in eight of global animal species.

An assessment of the monetary value of natural ecosystems published in Nature in 1997 arrived at a figure of 27.7 trillion Euros (33 trillion dollars), with wetland ecosystems making up ?12.5 trillion ($14.9 trillion) ? or 45% – of this total.

Much of human civilisation has been based around river valleys and floodplains. However, global freshwater consumption rose sixfold during the 20th century, a rate more than double that of population growth. And world population is set to rise by 70 million people a year for the next two decades.

Couple that trend with the threat of accelerating climate change, and biologically-productive and hydrologically-stabilising wetlands look like necessities we can ill do without.

Original Source: ESA News Release

Image credit: ESA

The European Space Agency’s Envisat Earth observation satellite captured images of a gigantic iceberg as it broke up during an Antarctic storm. The iceberg, called B-15A, was created in March 2000 when a Jamaican-sized chunk of ice broke away from the Ross Ice Shelf. It broke into smaller pieces shortly after that, but the largest chunk, B-15A grounded itself off the coast and stuck around for a few years. Finally in October, 2003, a giant storm helped split the iceberg up.

ESA’s Envisat satellite was witness to the dramatic last days of what was once the world’s largest iceberg, as a violent Antarctic storm cracked a 160-km-long floe in two.

A series of Envisat Advanced Synthetic Aperture Radar (ASAR) instrument images acquired between mid-September and October record how the bottle-shaped iceberg B-15A was split by the onslaught of powerful storms, waves and ocean currents as its own weight kept it fixed on the floor of Antarctica’s Ross Sea.

ASAR is especially useful for polar operations because its radar signal can pierce thick clouds and works through both day and night. Radar imagery charts surface roughness, so can easily differentiate between different ice types. Old ice ? as on the surface of B-15A ? is rougher than newly formed ice.

B-15A began its existence as B-15 in March 2000 – with an area of 11,655 sq km it was the world’s largest known iceberg. This Jamaica-sized floe was created when it broke away from the Ross Ice Shelf. The initial monster berg split into numerous pieces shortly afterwards, with the largest piece designated B-15A.

Like a wall of ice, B-15A remained a stubborn presence for the next two and a half years, diverting ocean currents. This caused increased ice around Ross Island that disrupted breeding patterns for the local penguin colony and required extra icebreaker activity to maintain shipping access to the US base at McMurdo Sound.

B-15A’s end came in sight on 7 October this year, as 120 kph winds buffeted the grounded iceberg during a storm. Two cracks ran into the heart of the iceberg from opposite ends until finally the entire berg gave way.

The larger of the two new pieces has inherited the name B-15A, and the smaller berg named B-15J. They remain largely locked in place, some 3,800 kilometres south of New Zealand. The bergs could persist there for many years ? a GPS station has been placed on the 3,496 sq km B-15A to enable study of its future progress.

Despite events such as these there is so far no conclusive evidence as to whether polar ice is actually thinning. Next year will see the launch of ESA?s CryoSat mission, a dedicated ice-watching satellite designed to map precise changes in the thickness of polar ice-sheets and floating sea-ice.

CryoSat will be the first satellite to be launched as part of the Agency?s Living Planet Programme. This small research mission will carry a radar altimeter that is based on a heritage from existing instruments, but with several major enhancements to improve the measurement of icy surfaces.

By determining rates of ice-thickness change CryoSat will contribute to our understanding of the relationship between the Earth?s ice cover and global climate.

Original Source: ESA News Release

Image credit: ESA

When a powerful earthquake shook the ground in Alaska a year ago, it also set the Earth’s atmosphere shaking. A team of European scientists used the Global Positioning System to map disturbances in the Earth’s ionosphere after a 7.9 magnitude earthquake struck Denali, Alaska. The ionosphere starts at 75 km and goes up to 1,000 km altitude, and it amplifies any disturbance that happens on the ground beneath it – one millimeter disturbance on the ground could become a 100 metre oscillation at 75 km altitude. This gives scientists a new tool to track earthquakes around the world.

A violent earthquake that cracked highways in Alaska set the sky shaking as well as the land, an ESA-backed study has confirmed.

This fact could help improve earthquake detection techniques in areas lacking seismic networks, including the ocean floor.

A team from the Institut de Physique du Globe de Paris and the California Institute of Technology has successfully used the Global Positioning System (GPS) satellite constellation to map disturbances in the ionosphere following last November?s magnitude 7.9 earthquake in Denali, Alaska.

Their paper has been published in the scientific journal Geophysical Research Letters. The research itself was carried out in support of ESA?s Space Weather Applications Pilot Project, aimed at developing operational monitoring systems for space conditions that can influence life here on Earth.

The ionosphere is an atmospheric region filled with charged particles that blankets the Earth between altitudes of about 75 to 1000 km. It has a notable ability to interfere with radio waves propagating through it.

In the particular case of GPS navigational signals, received on Earth from orbiting satellites, fluctuations in the ionosphere ? known as ‘ionospheric scintillations’ – have the potential to cause signal delays, navigation errors or in extreme cases several hours of service lockouts at particular locations.

But while such interference can be an inconvenience for ordinary GPS users, it represents a boon for scientists. By measuring even much smaller-scale shifts in GPS signal propagation time – caused by variations in local electron density as the signal passes through the ionosphere – researchers have at their fingertips a means of mapping ionospheric fluctuations in near real time.

The French and US team made use of dense networks of hundreds of fixed GPS receivers in place across California. These networks were originally established to measure small ground movements due to geological activity, but they can also be utilised to plot the ionosphere structure across three dimensions and in fine detail.

Then when the Denali earthquake occurred on 3 November 2002, the team had a chance to use this technique to investigate another distinctive property of the ionosphere, its ability to work like a natural amplifier of seismic waves moving across the Earth?s surface.

There are several different types of seismic waves moving the ground during an earthquake, the largest scale and the one that does most of the movement is known as a Rayleigh Wave. This type of wave rolls along the ground up and down and side-to-side, in the same way as a wave rolls along the ocean.

Previous research has established that shock waves from Rayleigh Waves in turn set up large-scale disturbances in the ionosphere. A one millimetre peak-to-peak displacement at ground level can set up oscillations larger than 100 metres at an altitude of 150 km.

What the team were able to do following the Denali quake was detect a distinctive wavefront moving through the ionosphere. “Using the network allowed us to observe the propagation of the waves,” explained co-author Vesna Ducic. “We could also separate the small total electron content signal from the very large total electron content variations related to the daily variation of the ionosphere.”

The team observed a signal two to three times larger than the noise level, arriving about 660 to 670 seconds after the arrival of Rayleigh Waves on the ground. And because around six GPS satellites are visible to every ground receiver they were able to calculate the altitude of maximum perturbation ? around 290 to 300 km up.

The signals were weak and only sampled every 30 seconds, with a maximum resolution of 50 km and the overall noise rate high. But the ionospheric signal observed had a clear pattern consistent with models of seismic behaviour. The hope is that the technique can be improved in future, and used to detect earthquakes in areas without seismic detectors, such as the deep ocean or near islands.

“In the framework of Galileo we plan to develop this research,? said Ducic. “Galileo will double the number of satellites and therefore will allow much more precise maps of the ionosphere. We can also foresee that Europe will develop a dense network of Galileo/GPS stations that will take part in the monitoring of these phenomena.

“ESA, together with the French Ministry of Research and CNES have already decided to fund a pre-operational project called SPECTRE – Service and Products for Ionosphere Electronic Content and Tropospheric Refractive index over Europe from GPS – devoted to the high-resolution mapping of the ionosphere. We will be carrying out mapping above Europe as well as California.

“These investigations will support the French space agency CNES?s DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) microsatellite, to be launched in 2004 and devoted to the detection in the ionosphere of seismic, volcanic and man-made signals. These ESA activities will be performed in the framework of the Space Weather Applications Pilot Project.”

The Space Weather Applications Pilot Project is an ESA initiative which has already begun to develop a wide range of application-oriented services based around space weather monitoring.

The co-funded services under development – of which this project is one – also include forecasting disruption to power and communication systems, and the provision of early warning to spacecraft operators of the hazards presented by increased solar and space weather activities. The hope is that an a seismic detection service based on ionospheric measurements may in future supplement existing resources in Europe and elsewhere.

Original Source: ESA News Release

Image credit: ESA

The European Space Agency’s Cluster spacecraft were perfectly positioned to watch the effect of the recent solar storms on the Earth’s magnetosphere. Normally the magnetosphere bubbles out in front of the Earth by about 64,000 km, but during the storm it was down to only 43,000 km. The speed at which the magnetosphere compressed will help scientists calculate the power of the storm, and make more accurate predictions for what will happen in future storms.

On the 24th of October 2003, the SOHO spacecraft registered a huge Coronal Mass Ejection (CME), emitted by the Sun. Several hours later this eruption reached the Earth and was detected by a number of spacecraft including Cluster.

The ACE spacecraft, situated along the Sun/Earth direction, was situated about 1 500 000 km upstream from the Earth, monitoring the solar wind. At about 14:49 UT, ACE recorded a sharp increase on the proton velocity, which jumped from about 450 kms-1 to more than 600 km-1 . The proton density, which was about 3 to 4 particles cm-3 , increased to more than 20. The proton temperature in the solar wind at this instant was also multiplied by a factor of 8.

The four Cluster spacecraft were in the southern magnetospheric lobe, inbound towards their perigee. Note that the Sun, ACE, Cluster and the Earth were almost aligned when the CME was ejected from the Sun. Cluster was situated close to the inner magnetosphere (near to the ring current region) when it detected the effects of the solar wind pressure on the magnetosphere: The sudden increase of the solar wind pressure registered by ACE arrived at the Earth?s magnetosphere about 40 minutes later. It provoked a huge compression of the dayside magnetosphere. The Cluster spacecraft detected this compression by getting suddenly out of the southern magnetospheric lobe into the Magnetosheath. They thus detected the Magnetopause, moving earthward, at about 15:25 UT. They remained into the Magnetosheath until about 17:00 UT, when they were only at a 6.8 RE (Earth radii) distance from the Earth. The transition between the lobes and the Magnetosheath was characterised by an important ion density increase (from close to 0 in the lobe to more than 160 particles cm-3 in the Magnetosheath) as well as a very clear signature in the velocity components, as measured by the CIS experiment onboard Cluster (P.I: Henri R?me).

This is a very unusual position for the Magnetopause, which on the average is standing ahead of the Earth at about 10 to 11 RE. Such compressions can have dramatic space weather effects, particularly to geostationnary satellites which are orbiting the Earth at a distance of about 6.6 RE. Further analysis of the four spacecraft data will tell us at what speed the magnetopause moved which will give information on the strength of the CME.

Original Source: ESA News Release