Category: Earth Observation

NASA scientists took infrared (IR) digital images of Mount Saint Helens’ last week. The images revealed signs of heat below the surface one day before the volcano erupted last Friday in southern Washington. The images may provide valuable clues as to how the volcano erupted.

Scientists flew an IR imaging system aboard a small Cessna Caravan aircraft over the mountain to acquire the data. “Based on the IR signal, the team predicted an imminent eruption,” said Steve Hipskind, acting chief of the Earth Science Division at NASA’s Ames Research Center (ARC), Moffett Field, Calif.

“We were seeing some thermal artifacts in the floor of the Mount Saint Helens’ crater in southern Washington,” said Bruce Coffland, a member of the Airborne Sensor Facility at ARC. ” We flew Thursday and used the 50-channel MODIS/ASTER Airborne Simulator (MASTER) digital imaging system. We are working to create images from the IR data that depict the thermal signatures on the dome,” Coffland added.

MASTER is an airborne simulator instrument similar to the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) high-resolution infrared imager carried on NASA’s Terra Earth observation satellite. Scientists plan to fly the MASTER instrument again over the volcano early this week.

The ARC airborne sensor team was in the area taking data for a United States Geological Survey (USGS) study examining some of the effects of the 1980 Mount Saint Helens’ eruption. “This had been planned for some time, and we were there totally by coincidence,” Coffland said. The science objectives for the USGS study were to outline the boundaries of the lava flows associated with Mt. St. Helens’ previous eruptions in 1980.

“We flew four flight lines over the mountain,” Coffland said. “It’s a continuous scan image, eight miles long (13 kilometers) and about 2.3 miles (3.7 kilometers) wide.” There were four adjoining flight lines flown for Joel Robinson, an investigator at USGS, Menlo Park, Calif.

After the plane landed, technicians downloaded data from a computer hard drive, and began to process the data to produce an image format for use by scientists. NASA will post the pre and post eruption infrared images on the Web.

Sky Research, based in Ashland, Ore. provided the Cessna Caravan, a propeller driven, single-engine airplane that carried the IR imager.

To access images on the Internet as they become available, visit:

Mt. St. Helens and http://masterweb.jpl.nasa.gov/

Original Source: NASA News Release

Since 2002, when the Larsen B ice shelf broke away from the coast of the Antarctic Peninsula, scientists have witnessed profound increases in the flow of nearby glaciers into the Weddell Sea. These observations were made possible through NASA, Canadian and European satellite data.

Two NASA-funded reports, appearing in the Geophysical Research Letters journal, used different techniques to arrive at similar results. Researchers from NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif., NASA’s Goddard Space Flight Center (GSFC), Greenbelt, Md., and the National Snow and Ice Data Center (NSIDC), Boulder, Colo., said the findings prove ice shelves act as “brakes” on the glaciers that flow into them. The results also suggest climate warming can rapidly lead to rises in sea level.

Large ice shelves in the Antarctic Peninsula disintegrated in 1995 and 2002, as a result of climate warming. Almost immediately after the 2002 Larsen B ice shelf collapse, researchers observed nearby glaciers flowing up to eight times faster than prior to the breakup. The speed-up also caused glacier elevations to drop, lowering them by as much as 38 meters (124 feet) in six months.

“Glaciers in the Antarctic Peninsula accelerated in response to the removal of the Larsen B ice shelf,” said Eric Rignot, a JPL researcher and lead author of one of the studies. “These two papers clearly illustrate, for the first time, the relationship between ice shelf collapses caused by climate warming, and accelerated glacier flow,” Rignot added.

Rignot’s study used data from European Space Agency Remote Sensing Satellites (ERS) and Canadian Space Agency RADARSAT satellite. The United States and Canada share a joint agreement on RADARSAT, which NASA launched.

Scambos and colleagues used five Landsat 7 images of the Antarctic Peninsula from before and after the Larsen B breakup. The images revealed crevasses on the surfaces of glaciers. By tracking the movement of crevasses in sequence from one image to the next, the researchers were able to calculate velocities of the glaciers.

The surfaces of glaciers dropped rapidly as the flow sped up, according to ICESat measurements. “The thinning of these glaciers was so dramatic that it was easily detected with ICESat, which can measure elevation changes to within an inch or two,” said Christopher Shuman, a GSFC researcher and a co-author on the Scambos paper.

The Scambos study examined the period right after the Larsen B ice shelf collapse to try to isolate the immediate effects of ice shelf loss on the glaciers. Rignot’s study used RADARSAT to take monthly measurements that are continuing. Clouds do not limit RADARSAT measurements, so it can provide continuous, broad velocity information.

According to Rignot’s study, the Hektoria, Green and Evans glaciers flowed eight times faster in 2003 than in 2000. They slowed moderately in late 2003. The Jorum and Crane glaciers accelerated two-fold in early 2003 and three-fold by the end of 2003. Adjacent glaciers, where the shelves remained intact, showed no significant changes according to both studies. The studies provide clear evidence ice shelves restrain glaciers, and indicate present climate is more closely linked to sea level rise than once thought, Scambos added.

Original Source: NASA News Release

Seen through the eyes of the Multi-angle Imaging SpectroRadiometer aboard NASA’s Terra satellite, the menacing clouds of Hurricanes Frances and Ivan provide a wealth of information that can help improve hurricane forecasts.

The ability of forecasters to predict the intensity and amount of rainfall associated with hurricanes still requires improvement, particularly on the 24- to 48-hour timescales vital for disaster planning. Scientists need to better understand the complex interactions that lead to hurricane intensification and dissipation, and the various physical processes that affect hurricane intensity and rainfall distributions. Because uncertainties in representing hurricane cloud processes still exist, it is vital that model findings be evaluated against actual hurricane observations whenever possible. Two-dimensional maps of cloud heights such as those provided by the Multi-angle Imaging SpectroRadiometer offer an unprecedented opportunity for comparing simulated cloud fields against actual hurricane observations.

The newly released images of Hurricanes Frances and Ivan were acquired Sept. 4 and Sept. 5, 2004, respectively, when Frances’ eye sat just off the coast of eastern Florida and Ivan was heading toward the central and western Caribbean. They are available at: http://photojournal.jpl.nasa.gov/catalog/PIA04367.

The left-hand panel in each image pair is a natural-color view from the instrument’s nadir camera. The right-hand panels are computer-generated cloud-top height retrievals produced by comparing the features of images acquired at different view angles. When these images were acquired, clouds within Frances and Ivan had attained altitudes of 15 and 16 kilometers (9.3 and 9.9 miles) above sea level, respectively.

The instrument is one of several Earth-observing experiments aboard Terra, launched in December 1999. The instrument acquires images of Earth at nine angles simultaneously, using nine separate cameras pointed forward, downward and backward along its flight path. It observes the daylit Earth continuously and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. It was built and is managed by NASA’s Jet Propulsion Laboratory, Pasadena, Calif. JPL is a division of the California Institute of Technology in Pasadena.

More information about the Multi-angle Imaging SpectroRadiometer is available at: http://www-misr.jpl.nasa.gov/.

Original Source: NASA/JPL News Release

Managers and meteorologists at NASA’s Kennedy Space Center (KSC) are closely monitoring Hurricane Ivan as it approaches the United States through the Caribbean Sea.

The latest computer models have the powerful storm moving west and farther away from KSC’s location on Florida’s east central coast (visit the National Hurricane Center for the latest forecasts and tracks).

With forecasters expecting KSC to receive maximum winds around 40 knots and four to six inches of rain from Ivan on Tuesday, NASA managers are planning to reopen KSC to its 14,000 employees Monday, as originally scheduled. With that model in mind, the KSC director will make a final decision about reopening on Sunday.

About 1,500 damage assessment and support personnel have spent the past week working to get KSC operational after last weekend’s hit from Hurricane Frances. Workers are continuing to prepare KSC this weekend for reopening and for Hurricane Ivan.

When KSC opens, about 700 employees will report to alternative worksites, because their buildings were damaged by Frances and require extensive repairs. All KSC employees will have facilities with power, air conditioning, voice and data communications.

NASA will provide updates about the Kennedy Space Center and Hurricane Ivan as new information becomes available. When information for KSC employees is available, it will be posted at http://www.nasa.gov/kennedy.

Original Source: NASA Update

For the first time, scientists have demonstrated that precise measurements of Earth’s changing gravity field can effectively monitor changes in the planet’s climate and weather.

This finding comes from more than a year’s worth of data from the Gravity Recovery and Climate Experiment, or Grace. Grace is a two-spacecraft, joint partnership of NASA and the German Aerospace Center.

Results published in the journal Science show that monthly changes in the distribution of water and ice masses could be estimated by measuring changes in Earth’s gravity field. The Grace data measured the weight of up to 10 centimeters (four inches) of groundwater accumulations from heavy tropical rains, particularly in the Amazon basin and Southeast Asia. Smaller signals caused by changes in ocean circulation were also visible.

Launched in March 2002, Grace tracks changes in Earth’s gravity field. Grace senses minute variations in gravitational pull from local changes in Earth’s mass. To do this, Grace measures, to one-hundredth the width of a human hair, changes in the separation of two identical spacecraft in the same orbit approximately 220 kilometers (137 miles) apart.

Grace maps these variations from month to month, following changes imposed by the seasons, weather patterns and short-term climate change. Understanding how Earth’s mass varies over time is an important component necessary to study changes in global sea level, polar ice mass, deep ocean currents, and depletion and recharge of continental aquifers.

Grace monthly maps are up to 100 times more accurate than existing ones, substantially improving the accuracy of many techniques used by oceanographers, hydrologists, glaciologists, geologists and other scientists to study phenomena that influence climate.

“Measurements of surface water in large, inaccessible river basins have been difficult to acquire, while underground aquifers and deep ocean currents have been nearly impossible to measure,” said Dr. Byron Tapley, Grace principal investigator at the University of Texas Center for Space Research in Austin, Texas. “Grace gives us a powerful new tool to track how water moves from one place to another, influencing climate and weather. These initial results give us great confidence Grace will make critical contributions to climate research in the coming years,” he added.

“The unparalleled accuracy of the Grace measurements opens a number of new scientific perspectives,” said Dr. Christoph Reigber of GeoForschungsZentrum Potsdam in Germany. “Observations of mass variations over the oceans will assist in interpreting annual signals in long-term sea-level change that have become an important climate change indicator,” Reigber said.

Dr. Michael Watkins, Grace project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., said the results mark the birth of a new field of remote sensing. “Over the past 20 years, we’ve made primitive measurements of changes in Earth’s gravity field over scales of thousands of kilometers, but this is the first time we’ve been able to demonstrate gravity measurements can be truly useful for climate monitoring,” he said.

“The Grace gravity measurements will be combined with water models to sketch an exceptionally accurate picture of water distribution around the globe. Together with other NASA spacecraft, Grace will help scientists better understand the global water cycle and its changes,” Watkins added.

The University of Texas Center for Space Research has overall mission responsibility. German mission elements are the responsibility of GeoForschungsZentrum Potsdam. Science data processing, distribution, archiving and product verification are managed under a cooperative arrangement between JPL, the University of Texas and GeoForschungsZentrum Potsdam.

For more information about Grace on the Internet, visit http://www.csr.utexas.edu/grace or http://www.gfz-potsdam.de/grace. For information about NASA programs on the Internet, visit http://www.nasa.gov.

Original Source: NASA/JPL News Release

Hurricanes are one of those forces of nature that can only fully be captured by satellite imagery. For Hurricane Frances, currently thundering towards the United States coast, ESA’s Envisat is going one better, peering through the hurricane from top to bottom, even helping to ‘see’ under the waves to map hidden forces powering the storm.

As its 235-km-per-hour winds passed the Bahamas, Frances was heading for landfall on the Florida coast some time on Saturday, and three quarters of a million Americans are in the process of evacuating their homes. To wait and watch for Frances might be suicidal for human beings, but space-based observers such as Envisat observe its passage without danger.

“Because of Envisat’s multi-sensor capability, we can slice right through the hurricane with just a single satellite,” explained Jos? Achache, ESA Director of Earth Observation Programmes.

“Effectively Frances is taken apart for meteorologists to study. The data returned by Envisat includes cloud structure and height at the top of the hurricane, wind and wave fields at the bottom, sea surface temperature and even sea height anomalies indicative of upper ocean thermal conditions that influence its intensity.”

Important processes occur at a range of altitudes and locations throughout a hurricane – basically a large powerful storm centred around a zone of extreme low pressure.

Strong low-level surface winds and bands of intense precipitation combine with strong updrafts and outflows of moist air at higher altitudes, with energy released as rainy thunderstorms. Until now, the only reliable source of such high-resolution measurements at different altitudes was from aircraft flown directly through the hurricane.

Envisat carries both optical and radar instruments, enabling researchers to observe high-atmosphere cloud structure and pressure in the visible and infrared spectrum, while at around the same time using radar backscatter to measure roughness of the sea surface and so derive the wind fields just over it.

Those winds converging on the low-pressure eye of the storm are what ultimately determine the spiralling cloud patterns that are characteristic of a hurricane.

Florida-based scientists have begun to take advantage of this unique single-spacecraft combination of instruments ? the Medium Resolution Imaging Spectrometer (MERIS) and Advanced Synthetic Aperture Radar (ASAR) ? as hurricane season gets into full swing.

The University of Miami’s Centre for Southeastern Tropical Advanced Remote Sensing (CSTARS) ground station has an agreement to acquire ASAR and MERIS data direct from Envisat, with ERS-2 wind scatterometer data set to follow in the near future. Their access to Envisat data has come just as the second hurricane in less than a month is heading towards the Florida coast.

“With MERIS and ASAR, Envisat can image both the ocean and atmosphere pretty much simultaneously, which is a very useful capability during hurricane season,” said Hans Graber, Professor of Applied Marine Physics at the University of Miami and Co-Director of CSTARS.

While MERIS returns detail on the swirling clouds at the top of the hurricane, ASAR pierces right through the clouds to show the wind-wracked face of the sea beneath the storm.

“Specifically in terms of Frances, the eye of the hurricane seems to be rolling a lot right now from the top of the clouds, looking quite unstable, the information from an ASAR image should help localise its size and position on the ocean,” Graber said. “And wind fields around the eye wall can be derived from ASAR data ? right now all we have to go on are measurements from the hurricane hunter planes that fly right through the storm.”

Simultaneous MERIS and ASAR acquisitions are planned for Friday by CSTARS, even as the storm comes closer to predicted landfall the following morning.

“Our current activity is along the lines of a shakedown ? we’re investigating how this can be used,” added Graber. “Our final goal is to get this working on an operational basis during hurricane season. We have a deal to use radar data from the Canadian Space Agency, and also have access to other satellite resources for high temporal coverage of the affected region.

“The potential is there to extract a large amount of useful information which can help the US National Hurricane Center increase the accuracy of their hurricane predictions and reduce danger to the public.”

Another instrument aboard Envisat is being used to take the temperature of Frances, both down at the surface of the ocean and at the heights of its towering clouds.

Water temperatures are the main underlying energy reservoir powering Frances; together with the correct atmospheric conditions, they need to exceed 26?C in order to form and maintain a tropical cyclone. Envisat’s Advanced Along Track Scanning Radiometer (AATSR) works like a space-based thermometer, acquiring the temperature of the sea surface down to a fraction of a degree.

Meanwhile AATSR also returns useful atmospheric data, measuring the temperature of the top of hurricane clouds ? the higher into the atmosphere they extend, the colder they are – and also deriving their ice content.

“We produced a combined AATSR sea surface temperature and cloud top temperature image, which shows the sea surface temperature to be as high as 29?C in the area,” remarked Carsten Brockmann of Brockmann Consult, a German company processing both MERIS and AATSR hurricane imagery. “This two-sensor combination gives meteorologists a lot of information to help them understand the dynamics of the hurricane and better predict its development.”

AATSR information can be correlated with MERIS data cloud height and development to gain a good estimate of the hurricane’s precipitation potential, and improve understanding of how this relates to its overall intensity. Condensation of water vapour releases latent heat, which warms the vicinity of the hurricane eye. This in turn evaporates more surface water and feeds the heat engine powering the hurricane.

Studying hidden depths that fuel the storm
The thermal energy of warm water, which partly powers a hurricane, is known as tropical cyclone heat potential (TCHP).

Oceanic features, such as warm core rings, eddies, and the Gulf Stream, represent a source of enhanced heat fluxes to the atmosphere that may cause the strengthening of tropical cyclones, such as hurricanes.

Warm waters may extend to at least 100 meters beneath the surface in many of these oceanic features, representing waters of very high heat content. Several hurricanes have intensified when their tracks pass over eddies or other masses of warm water with high TCHP values.

For example, in 1995 Hurricane Opal suddenly intensified in the Gulf of Mexico after passing over a warm ring with TCHP values of up to six times the threshold to sustain a tropical cyclone.

Previously, researchers used sea surface temperature alone to estimate the role of the upper ocean thermal conditions on hurricane intensification. The problem with this is that the sea surface temperature measured by AATSR or comparable satellite instruments may not by themselves show these warm upper ocean features, particularly during summer months in tropical regions.

In the past these upper ocean features have gone unseen by satellite-based temperature sensors because they are effectively camouflaged beneath a very shallow and stable layer of warmer water.

Tropical cyclone wind forces easily erode this thin upper layer by mixing the upper waters to depths that may go down to 100 meters, giving the tropical cyclones the potential to absorb ocean thermal energy, if conditions are appropriate. Now, estimates of TCHP based on satellite observations of sea surface temperature and sea surface height can detect these features.

Researcher Gustavo Goni, Joaquin Trinanes and Peter Black of the US National Oceanic and Atmospheric Administration’s Atlantic Oceanographic and Meteorological Laboratory (NOAA/AOML) are working on this original methodology to detect these warm water masses and to compute their tropical cyclone heat potential values using several satellite sensors including one on Envisat.

“These water features are critical for identifying regions of high TCHP values that may potentially contribute to the intensification of a hurricane?, Goni explained. “These regions of high TCHP values provide the hurricanes with the opportunity to absorb much more thermal energy if overall conditions are right. My research is taking advantage of the fact that these warm water masses cause an upward elevation in ocean height of up to 30 cm. Such sea height anomalies can then be mapped with space-based radar altimeter data.”

Radar altimeters, such as the Radar Altimeter-2 instrument on Envisat, fire hundreds of radar pulses down to Earth every second, and by timing their return down the nanosecond can measure sea height to a maximum accuracy of two centimetres from hundreds of kilometres above the Earth.

The US Naval Research Laboratory (NRL) combines Envisat RA-2 data with data from similar radar altimeters aboard the Jason-1 and GFO satellites to enhance overall accuracy and spatial and temporal coverage, forming the source for altimetry products which, in turn, form the basis for NOAA/AOML-produced maps of tropical cyclone heat potential depicting the upper ocean thermal conditions, shown here overlaid against Hurricane Frances’ track so far.

“At this time I use this product only for research purposes, providing an enhanced understanding of the life of a hurricane. However, analogous products are being produced and used operationally for forecasting by the National Hurricane Center”, Goni concluded.

Altimetry-based wind speed and wave height products are also distributed by the French firm Collecte Localisation Satellites (CLS), and can reveal sea surface features related to the presence of hurricanes.

Envisat results to be revealed
Launched in March 2002, ESA’s Envisat satellite is an extremely powerful means of monitoring the state of our world and the impact of human activities upon it. Envisat carries ten sophisticated instruments to observe and monitor the Earth’s atmosphere, land, oceans and ice caps, maintaining continuity with the Agency’s ERS missions started in 1991.

After two and a half years in orbit, more than 700 scientists from 50 countries are about to meet at a special symposium in Salzburg in Austria to review and discuss early results from the satellites, and present their own research activities based on Envisat data.

Starting on Monday, the Envisat Symposium will address almost all fields of Earth science, including atmospheric chemistry, coastal studies, radar and interferometry, winds and waves, vegetation and agriculture, landslides, natural risks, air pollution, ocean colour, oil spills and ice.

There are over 650 papers being presented at the Symposium, selected by peer review. Presentations will include results on the Prestige oil spill, last year’s forest fires in Portugal, the Elbe flooding in 2002, the evolution of the Antarctic ozone hole, the Bam earthquake and pollution in Europe.

Numerous demonstrations are planned during the week in the ESA Exhibit area. An industrial consortium exhibit on the joint ESA-European Commission Global Monitoring for Environment and Security (GMES) initiative is also planned.

Original Source: ESA News Release

NASA is keeping a close watch over Hurricane Frances as it churns toward the United States. International Space Station cameras are capturing spectacular images of the storm from above. On the Florida coast, NASA’s Kennedy Space Center (KSC) is making preparations to protect the Space Shuttle fleet, spacecraft hardware, and facilities against damage.

Video of Hurricane Frances taken by external television cameras aboard the Space Station at about 7:30 a.m. EDT today vividly depicts a classically shaped storm in the Atlantic Ocean. The video, along with additional views captured during the weekend, is airing on the NASA TV Video File throughout the day. NASA will release new footage of Frances as it becomes available.

NASA also has still images of the storm, taken by Astronaut Mike Fincke aboard the International Space Station, as well as NASA’s Terra satellite. They’re available at:

http://www.nasa.gov/vision/earth/lookingatearth/frances.html

At KSC, workers are powering down the Space Shuttle orbiters, closing their payload bay doors and stowing their landing gear. They are also taking precautions against flooding by moving spacecraft hardware off the ground and sandbagging facilities. NASA plans to release video of these activities beginning tomorrow.

NASA TV is available on the Web and via satellite, in the continental U.S. on AMC-6, Transponder 9C, C-Band, located at 72 degrees west longitude. The frequency is 3880.0 MHz. Polarization is vertical, and audio is monaural at 6.80 MHz. In Alaska and Hawaii, NASA TV is available on AMC-7, Transponder 18C, C-Band, located at 137 degrees west longitude. Frequency is 4060.0 MHz. Polarization is vertical, and audio is monaural at 6.80 MHz.

Original Source: NASA News Release

For the first time, scientists may now detect a phytoplankton bloom in its early stages by looking at its red “glow” under sunlight, due to the unique data from two NASA satellites. According to a study conducted in the Gulf of Mexico, this phenomenon can forewarn fishermen and swimmers about developing cases of red tides that occur within plumes of dark-colored runoff from river and wetlands, sometimes causing “black water” events.

Dark-colored river runoff includes nitrogen and phosphorus, which are used as fertilizers in agriculture. These nutrients cause blooms of marine algae called phytoplankton. During extremely large phytoplankton blooms where the algae is so concentrated the water may appear black, some phytoplankton die, sink to the ocean bottom and are eaten by bacteria. The bacteria consume the algae and deplete oxygen from the water that leads to fish kills.

Chuanmin Hu and Frank Muller-Karger, oceanographers at the College of Marine Science of University of South Florida, St. Petersburg, Fla., used fluorescence data from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard both NASA’s Terra and Aqua satellites. MODIS detects the glow or phytoplankton fluorescence, from the plant’s chlorophyll. The human eye cannot detect the red fluorescence.

The ability to detect glowing areas of water helps researchers identify whether phytoplankton are present in large dark water patches that form off the coast of Florida. Without these data, it is impossible to differentiate phytoplankton blooms from plumes of dark river runoff that contain few individual phytoplankton cells.

Because colored dissolved organic matter that originates in rivers can absorb similar amounts of blue and green color signals as plants do, traditional satellites that simply measure ocean color cannot distinguish phytoplankton blooms within such patches.

Although satellites cannot directly measure nutrients in lakes, rivers, wetlands and oceans, remote sensing technology measure the quantities of plankton. Scientists can then calculate how much nutrient might be needed to grow those amounts of plankton.

Hu and others used this technique to study the nature and origin of a dark plume event in the fall of 2003 near Charlotte Harbor, off the south Florida coast. Moderate concentrations of one of Florida’s red tide species, were found from water samples.

“Our study traces the black water patches near the Florida Keys to some 200 kilometers (124 miles) away upstream,” said Hu. “These results suggest that the delicate Florida Keys ecosystem is connected to what happens on land and in two remote rivers, the Peace and Caloosahatchee, as they drain into the ocean. Extreme climate conditions, such as abnormally high rainfall in spring and summer 2003, may accelerate such connections,” he added.

These findings are based on scientific analyses of several things. Data used include satellite ocean color from MODIS and Sea-viewing Wide Field-of-view Sensor (SeaWiFS), and wind data from NASA’s QuikSCAT satellite. U.S. Geological Survey, National Oceanic and Atmospheric Administration (NOAA), Florida?s Fish and Wildlife Research Institute, and other organizations provided rain, river discharge, and field survey information.

By knowing which way the winds blow and the currents flow, Hu and colleagues can predict where black water may move.

Red tides occur every year off Florida and are known to cause fish kills, coral stress and mortality, and skin and respiratory problems in humans. Previous studies show that prolonged “black water” patches cause water quality degradation and may cause coral death. The use of remote sensing satellites provides effective means for monitoring and predicting such events.

The link between coastal runoff and black water events is an example of how land and ocean ecosystems are linked together. “Coastal and land managers over large areas need to work together, to alleviate more black water events from taking place in the future,” said Muller-Karger.

This study appeared in a recent issue of the American Geophysical Union’s Geophysical Research Letters. Coauthors of the article include Gabriel Vargo and Merrie Beth Neely from University of South Florida and Elizabeth Johns from NOAA’s Atlantic Oceanographic and Meteorological Laboratory.

NASA’s Science Directorate works to improve the lives of all humans through the exploration and study of Earth’s system, the solar system and the Universe.

Original Source: NASA News Release

A few NASA satellites designed to study heights of Earth’s ocean surfaces are now also coming in handy for tracking water levels of inland lakes and reservoirs.

When analysts at the United States Department of Agriculture (USDA) Foreign Agriculture Service (FAS) learned that NASA satellites could be used for measuring lake water heights, they saw a chance to get vital information for managing irrigation and forecasting crop production in out-of-the way places.

Since early this year, NASA has supplied the USDA with near-real time data on lake and reservoir heights from around the world. The USDA has posted this information on a web site that allows users with a computer and Internet to access it for their varied uses. Analysts who forecast crop production, scientists, in-country water and irrigation managers, those involved in fishing industries, and the general public have all been making use of the site.

NASA and the French space agency Le Centre National d?Etudes Spatiales (CNES) teamed up to design, build and launch the TOPEX/Poseidon and the Jason-1 satellites. These satellites were designed to study many aspects of the ocean. The TOPEX/Poseidon satellite, for example, orbits at a height of 1336 kilometers (830 miles) above Earth, and can measure the height of the ocean surface directly underneath the satellite with an accuracy of 4-5 centimeters (better than 2 inches). Jason-1 and TOPEX/Poseidon cover the global oceans every 10 days. With these capabilities, this technology is surprisingly valuable for looking at larger areas of inland water.

“The satellites were designed with oceanographic objectives in mind, so the fact that they can be used for lakes and rivers are an added bonus,” said Charon Birkett, a University of Maryland researcher based at NASA’s Goddard Space Flight Center in Greenbelt, Md. It was Birkett’s work with satellites and inland water sources that caught the USDA’s interest.

Water level data for many lakes can be hard to get. Lakes may be located within inhospitable regions. Terrain may make it hard to install water level gauges, or some countries may not have the money for proper equipment. Even if there is equipment, someone must be available to regularly record the measurements. For an international agency like the USDA FAS, information on water levels in remote lakes in Africa or Asia, for example, may only be possible if a researcher happens to be passing by the area.

“Now we have this dataset which gives you a global picture of irrigation capabilities,” said Brad Doorn, Remote Sensing Technical Coordinator for the FAS. “It’s very much a night and day perspective as it relates to global irrigation potential.”

NASA/CNES satellites fly over 350 of the world’s largest lakes. The USDA decided to focus on about 150 of those that are important for agriculture. Of those, about 70 are currently online, with more being regularly added as Birkett and co-worker, Brian Beckley, from Raytheon’s Information Technology and Scientific Services (ITSS) team learn to extract information on the smaller lakes. Fifteen of the lakes that are currently online are in Africa.

The records begin with archived data from TOPEX/Poseidon, launched in 1992. They continued with data from the Jason-1 satellite, launched in December 2001. The two stayed in the same orbit for about 7 months, before the TOPEX/Poseidon satellite’s orbit was changed. These months of cross-over data were crucial for validating each of the satellites and for making sure the data records from Jason-1 were compatible with the TOPEX/Poseidon archive.

The information provided by the satellites, and made public through the web site, is a blessing to those who manage water for irrigation. Irrigated areas generally have less rainfall, and therefore crops in these drier regions are dependent on stores of water, like lakes, reservoirs and rivers.

The FAS analyzes crop production around the world. They regularly use computer models that simulate agricultural production based on inputs that include weather information. In this way they can examine global crop conditions and production. But in irrigated areas that are not rain fed, these methods are limited. For irrigated areas, you have to be able to determine how much water is actually stored, after seasonal precipitation passes.

“Satellite records of lake and reservoir water levels give you a good indication of whether there is going to be a systematic or major problem in water supply,” said Doorn. “If water is low, there may be problems for agricultural production.” This type of information is especially important for food aid partners, who must budget ahead for how much and where food aid is distributed.

Lake Tharthar in Central Iraq provides irrigation water to areas downstream. It is also linked to the Tigris and Euphrates Rivers. A drought that carried over many years severely cut grain output between 1999 and 2001. But since then, rainfall has increased, allowing grain production to recover and even surpass pre-drought levels. Knowledge of water levels in a region like this is crucial for the people who divvy out water for irrigation, and for those who plan aid.

The satellites have noticed some striking changes in lake levels around the world. In Iran, Lake Urmia has steadily decreased over the last 5 years. Also, between 1999 and 2001, Lake Hamoun in Iran near the Afghanistan border all but dried up and disappeared. By May 2003, water had returned to the lake. In that same time period, Lake Michigan levels have also declined.

On the other hand, when there is plenty of water, irrigation managers and farmers can assess the potential for more agriculture. When Caspian Sea levels rose in 1994, spill-over created a reservoir where little water existed before. As a result, the Kara Bogaz reservoir that borders the Caspian Sea was once largely desert and is now a large inland water body. Lake Nasser in Egypt also exists in a desert area where water supplies have increased.

As can be seen, the new technology allows researchers to get water level records regularly, globally, and in places where it is very hard to maintain or even acquire measurements. At the same time, there are also some limitations to the technology. For example, lake elevations can only be obtained during the lifetime of the satellite mission. Also, a satellite must pass directly over a lake for the radar to record water heights. But since the primary mission of these satellites is for studying the oceans, the fixed satellite orbit is determined by the community of oceanographers. That means people studying inland water have less input into the lakes that are monitored. In addition, some water bodies are simply too small for the instruments to pick up. These factors limit the number of observable lakes. “Sometimes, the lake that you want information about is the one you can’t get,” said Doorn.

Despite the current limitations, users like the FAS are thrilled to have access to the technology. Their web site provides new measurements to the public about a week to ten days after the satellite passes over.

“When USDA approached us, we told them the satellite record is not as accurate as a gauge sitting in a lake, but we can get good information within one to two weeks for many lakes in data-poor regions such as Africa and Asia,” said Birkett.

“It’s been a great USDA and NASA cooperative effort,” said Doorn. “It’s exactly what we needed and the type of cooperation provided has made it a real win-win situation.”

The project has been a collaborative effort between the NASA GSFC, USDA FAS, the University of Maryland, and Raytheon ITSS. The project was funded by the USDA/FAS.

Original Source: NASA News Release

ESA?s quartet of space-weather watchers, Cluster, has discovered vortices of ejected solar material high above the Earth. The superheated gases trapped in these structures are probably tunnelling their way into the Earth?s magnetic ?bubble?, the magnetosphere. This discovery possibly solves a 17-year-mystery of how the magnetosphere is constantly topped up with electrified gases when it should be acting as a barrier.

The Earth?s magnetic field is our planet?s first line of defence against the bombardment of the solar wind. The solar wind itself is launched from the Sun and carries the Sun?s magnetic field throughout the Solar System. Sometimes this magnetic field is aligned with Earth?s and sometimes it points in the opposite direction.

When the two fields point in opposite directions, scientists understand how ?doors? in Earth?s field can open. This phenomenon, called ?magnetic reconnection?, allows the solar wind to flow in and collect in the reservoir known as the boundary layer. On the contrary, when the fields are aligned they should present an impenetrable barrier to the flow. However, spacecraft measurements of the boundary layer, dating back to 1987, present a puzzle because they clearly show that the boundary layer is fuller when the fields are aligned than when they are not. So how is the solar wind getting in?

Thanks to the data from the four formation-flying spacecraft of ESA?s Cluster mission, scientists have made a breakthrough. On 20 November 2001, the Cluster flotilla was heading around from behind Earth and had just arrived at the dusk side of the planet, where the solar wind slides past Earth?s magnetosphere. There it began to encounter gigantic vortices of gas at the magnetopause, the outer ?edge? of the magnetosphere.

?These vortices were really huge structures, about six Earth radii across,? says Hiroshi Hasegawa, Dartmouth College, New Hampshire who has been analysing the data with help from an international team of colleagues. Their results place the size of the vortices at almost 40 000 kilometres each, and this is the first time such structures have been detected.

These vortices are known as products of Kelvin-Helmholtz instabilities (KHI). They can occur when two adjacent flows are travelling with different speeds, so one is slipping past the other. Good examples of such instabilities are the waves whipped up by the wind slipping across the surface of the ocean. Although KHI-waves had been observed before, this is the first time that vortices are actually detected.

When a KHI-wave rolls up into a vortex, it becomes known as a ?Kelvin Cat?s eye?. The data collected by Cluster have shown density variations of the electrified gas, right at the magnetopause, precisely like those expected when travelling through a ?Kelvin Cat?s eye?.

Scientists had postulated that, if these structures were to form at the magnetopause, they might be able to pull large quantities of the solar wind inside the boundary layer as they collapse. Once the solar wind particles are carried into the inner part of the magnetosphere, they can be excited strongly, allowing them to smash into Earth?s atmosphere and give rise to the aurorae.

Cluster?s discovery strengthens this scenario but does not show the precise mechanism by which the gas is transported into Earth?s magnetic bubble. Thus, scientists still do not know whether this is the only process to fill up the boundary layer when the magnetic fields are aligned. For those measurements, Hasegawa says, scientists will have to wait for a future generation of magnetospheric satellites.

Original Source: ESA News Release