As parts of Central America and the U.S. Southwest endure some of the worst droughts to hit those areas in decades, scientists have unearthed new evidence about ancient dry spells that suggest the future could bring even more serious water shortages. Three researchers speaking at the annual meeting of the American Geophysical Union in San Francisco on Dec. 5, 2011, presented new findings about the past and future of drought.

Pre-Columbian Collapse

Ben Cook, a climatologist affiliated with NASA’s Goddard Institute for Space Studies (GISS) and Columbia University’s Lamont-Doherty Earth Observatory in New York City, highlighted new research that indicates the ancient Meso-American civilizations of the Mayans and Aztecs likely amplified droughts in the Yucatán Peninsula and southern and central Mexico by clearing rainforests to make room for pastures and farmland.

Converting forest to farmland can increase the reflectivity, or albedo, of the land surface in ways that affect precipitation patterns. “Farmland and pastures absorb slightly less energy from the sun than the rainforest because their surfaces tend to be lighter and more reflective,” explained Cook. “This means that there’s less energy available for convection and precipitation.”

Cook and colleagues used a high-resolution climate model developed at GISS to run simulations that compared how patterns of vegetation cover during pre-Columbian (before 1492 C.E.) and post-Columbian periods affected precipitation and drought in Central America. The pre-Columbian era saw widespread deforestation on the Yucatán Peninsula and throughout southern and central Mexico. During the post-Columbian period, forests regenerated as native populations declined and farmlands and pastures were abandoned.

Cook’s simulations include input from a newly published land-cover reconstruction that is one of the most complete and accurate records of human vegetation changes available. The results are unmistakable: Precipitation levels declined by a considerable amount — generally 10 to 20 percent — when deforestation was widespread. Precipitation records from stalagmites, a type of cave formation affected by moisture levels that paleoclimatologists use to deduce past climate trends, in the Yucatán agree well with Cook’s model results.

The effect is most noticeable over the Yucatán Peninsula and southern Mexico, areas that overlapped with the centers of the Mayan and Aztec civilizations and had high levels of deforestation and the most densely concentrated populations. Rainfall levels declined, for example, by as much as 20 percent over parts of the Yucatán Peninsula between 800 C.E. and 950 C.E.

Cook’s study supports previous research that suggests drought, amplified by deforestation, was a key factor in the rapid collapse of the Mayan empire around 950 C.E. In 2010, Robert Oglesby, a climate modeler based at the University of Nebraska, published a study in the Journal of Geophysical Research that showed that deforestation likely contributed to the Mayan collapse. Though Oglesby and Cook’s modeling reached similar conclusions, Cook had access to a more accurate and reliable record of vegetation changes.

During the peak of Mayan civilization between 800 C.E. and 950 C.E., the land cover reconstruction Cook based his modeling on indicates that the Maya had left only a tiny percentage of the forests on the Yucatán Peninsula intact. By the period between 1500 C.E. and 1650 C.E., in contrast, after the arrival of Europeans had decimated native populations, natural vegetation covered nearly all of the Yucatán. In modern times, deforestation has altered some areas near the coast, but a large majority of the peninsula’s forests remain intact.

“I wouldn’t argue that deforestation causes drought or that it’s entirely responsible for the decline of the Maya, but our results do show that deforestation can bias the climate toward drought and that about half of the dryness in the pre-Colonial period was the result of deforestation,” Cook said.

Northeastern Megadroughts

The last major drought to affect the Northeast occurred in the 1960s, persisted for about three years and took a major toll on the region. Dorothy Peteet, a paleoclimatologist also affiliated with NASA GISS and Columbia University, has uncovered evidence that shows far more severe droughts have occurred in the Northeast.

By analyzing sediment cores collected from several tidal marshes in the Hudson River Valley, Peteet and her colleagues at Lamont-Doherty have found evidence that at least three major dry spells have occurred in the Northeast within the last 6,000 years. The longest, which corresponds with a span of time known as the Medieval Warm Period, lasted some 500 years and began around 850 C.E. The other two took place more than 5,000 years ago. They were shorter, only about 20 to 40 years, but likely more severe.

“People don’t generally think about the Northeast as an area that can experience drought, but there’s geologic evidence that shows major droughts can and do occur,” Peteet said. “It’s something scientists can’t ignore. What we’re finding in these sediment cores has big implications for the region.”

Peteet’s team detected all three droughts using a method called X-ray fluorescence spectroscopy. They used the technique on a core collected at Piermont Marsh in New York to search for characteristic elements — such as bromine and calcium — that are more likely to occur at the marsh during droughts.

Fresh water from the Hudson River and salty water from the Atlantic Ocean were both predominant in Piermont Marsh at different time periods, but saltwater moves upriver during dry periods as the amount of fresh water entering the marsh declines. Peteet’s team detected extremely high levels of both bromine and calcium, both of them indicators of the presence of saltwater and the existence of drought, in sections of the sediment cores corresponding to 5,745 and 5,480 years ago.

During the Medieval Warm Period, the researchers also found striking increases in the abundance of certain types of pollen species, especially pine and hickory, that indicate a dry climate. Before the Medieval Warm Period, in contrast, there were more oaks, which prefer wetter conditions. They also found a thick layer of charcoal demonstrating that wildfires, which are more frequent during droughts, were common during the Medieval Warm Period.

“We still need to do more research before we can say with confidence how widespread or frequent droughts in the Northeast have been,” Peteet said. There are certain gaps in the cores Peteet’s team studied, for example, that she plans to investigate in greater detail. She also expects to expand the scope of the project to other marshes and estuaries in the Northeast and to collaborate with climate modelers to begin teasing out the factors that cause droughts to occur in the region.

The Future of Food

Climate change, with its potential to redistribute water availability around the globe by increasing rainfall in some areas while worsening drought in others, might negatively impact crop yields in certain regions of the world.

New research conducted by Princeton University hydrologist Justin Sheffield shows that areas of the developing world that are drought-prone and have growing population and limited capabilities to store water, such as sub-Saharan Africa, will be the ones most at risk of seeing their crops decrease their yields in the future.

Sheffield and his team ran hydrological model simulations for the 20th and 21st centuries and looked at how drought might change in the future according to different climate change scenarios. They found that the total area affected by drought has not changed significantly over the past 50 years globally.

However, the model shows reductions in precipitation and increases in evaporative demand are projected to increase the frequency of short-term droughts. They also found that the area across sub-Saharan Africa experiencing drought will rise by as much as twofold by mid-21st century and threefold by the end of the century.

When the team analyzed what these changes would mean for future agricultural productivity around the globe, they found that the impact on sub-Saharan Africa would be especially strong.

Agricultural productivity depends on a number of factors beyond water availability including soil conditions, available technologies and crop varieties. For some regions of sub-Saharan Africa, the researchers found that agricultural productivity will likely decline by over 20 percent by mid-century due to drying and warming.

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The Visible Infrared Imager Radiometer Suite (VIIRS) onboard NASA’s newest Earth-observing satellite, NPP, acquired its first measurements on Nov. 21, 2011. This high-resolution image is of a broad swath of Eastern North America from Canada’s Hudson Bay past Florida to the northern coast of Venezuela. The VIIRS data were processed at the NOAA Satellite Operations Facility (NSOF) in Suitland, Md.

VIIRS is one of five instruments onboard the National Polar-orbiting Operational Environmental Satellite System Preparatory Project (NPP) satellite that launched from Vandenberg Air Force Base, Calif., on Oct. 28. Since then, NPP reached its final orbit at an altitude of 512 miles (824 kilometers), powered on all instruments and is traveling around the Earth at 16,640 miles an hour (eight kilometers per second).

“This image is a next step forward in the success of VIIRS and the NPP mission,” said James Gleason, NPP project scientist at NASA’s Goddard Space Flight Center, Greenbelt, Md.

VIIRS will collect radiometric imagery in visible and infrared wavelengths of the Earth’s land, atmosphere, and oceans. By far the largest instrument onboard NPP, VIIRS weighs about 556 pounds (252 kilograms). Its data, collected from 22 channels across the electromagnetic spectrum, will be used to observe the Earth’s surface including fires, ice, ocean color, vegetation, clouds, and land and sea surface temperatures.

“VIIRS heralds a brightening future for continuing these essential measurements of our environment and climate,” said Diane Wickland, NPP program scientist at NASA headquarters in Washington. She adds that all of NPP’s five instruments will be up and running by mid-December and NPP will begin 2012 by sending down complete data.

“NPP is right on track to ring in the New Year,” said Ken Schwer, NPP project manager at NASA Goddard. “Along with VIIRS, NPP carries four more instruments that monitor the environment on Earth and the planet’s climate, providing crucial information on long-term patterns to assess climate change and data used by meteorologists to improve short-term weather forecasting.”

NPP serves as a bridge mission from NASA’s Earth Observing System (EOS) of satellites to the next-generation Joint Polar Satellite System (JPSS), a National Oceanic and Atmospheric Administration (NOAA) program that will also collect weather and climate data. NASA Goddard manages the NPP mission for the Earth Science Division of the Science Mission Directorate at NASA Headquarters in Washington. The JPSS program provides the NPP ground system and NOAA provides operational support.

During NPP’s five-year life, the mission will extend more than 30 key long-term datasets that include measurements of the atmosphere, land and oceans. NASA has been tracking many of these properties for decades. NPP will continue measurements of land surface vegetation, sea surface temperature, and atmospheric ozone that began more than 25 years ago.

“The task now for the science community is to evaluate VIIRS performance and determine the accuracy of its data products,” said Chris Justice a professor of geography at the University of Maryland, College Park, who will be using VIIRS data in his research.

“These long-term data records are critical in monitoring how the Earth’s surface is changing – either from human activity or through climate change.”

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In between recess, geography class and eating the lunch their moms packed, NASA scientists have found the time to help validate Earth-observing satellites.

These scientists are the younger variety — students in NASA’s S’COOL project (Students’ Cloud Observations On-Line), a worldwide effort to collect cloud observations from the ground.

The students make observations like a NASA scientist and submit reports for their area to NASA. In return, the students receive a corresponding cloud observation from a NASA satellite to help them compare and learn.

This week, the S’COOL program received its 100,000th cloud observation, prompting a look into what NASA has been doing with all of these cloud observations.

“We often hear about how NASA satellite data helps students, but there are also quite a few things the students do for us,” says Lin Chambers, the lead for the S’COOL program, which is based out of NASA’s Langley Research Center in Hampton, Va.

According to Chambers, the most common way S’COOL ground observations help scientists is by confirming the presence of clouds in areas and under conditions that are challenging for satellite instruments.

For example, in a number of instances, students submitted cloud observations that reported a single layer of clouds in their area while the corresponding satellite was reporting a clear sky.

When the S’COOL team looked further into this discrepancy, they found that students were reporting small amounts of thin cirrus clouds, which are not detectable by the Clouds and Earth’s Radiant Energy System (CERES)/Imager algorithm for the Tropical Rainforest Measuring Mission (TRMM) spacecraft or the CERES/Imager algorithms for the Terra and Aqua satellites. With these student observations, scientists can now quantify how often satellites overlook cirrus clouds.

“The data are most useful to help confirm the cloud scenes that we know are difficult to detect with passive remote sensing,” says David Young, a NASA climate scientist who served as the first S’COOL science advisor. “You can’t see through layers, so you often miss low clouds that are under high clouds. It has been useful to get these data to see how often that occurs.”

Other tricky circumstances for satellites are observing clouds in areas with bright surfaces, such as snow, and complex surfaces, such as mountains.

Strong agreement between satellite data and student observations from snowy or icy areas helped NASA scientists confirm that the CERES instrument can in fact make cloud observations when surfaces are bright. To analyze satellite capabilities in areas with complex backgrounds, scientists looked instead toward student observations that reported clear skies.

“Seeing a completely clear sky from the satellite can be a challenge in certain circumstances, given the variable background of the Earth’s surface,” explained Chambers. “Once again, S’COOL observers helped scientists make sure that their satellites were making accurate observations.”

Student observations have also provided a more accurate approach for comparing cloud cover between the ground and the satellite. This improvement came as a result of another inconsistency found between satellite and S’COOL observations — students were reporting clear skies while satellites were reporting overcast skies.

“The S’COOL team found this difference often occurred when observers were located on the edge of a longitude and latitude line, and in many cases, student observations were being compared to satellite data that covered a different grid region than their actual location,” explains Chambers.

Additional studies are currently underway comparing S’COOL student reports to new data on cloud layers from the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) and CloudSat satellites in NASA’s A-Train satellite constellation. A fifth edition of CERES will also be launching October 2011 on the NPOESS Preparatory Project (NPP) satellite, providing another opportunity for S’COOL observers to coordinate cloud observations.

While science goals were never the primary goal of the S’COOL program, Young explains that he and other scientists are proud that these results have been published, especially since these science outcomes are not very common with student outreach projects.

“People often ask why we don’t just use the data from trained cloud observers at the weather stations and airports,” says Young. “The answer is that we do. However, the S’COOL measurements are valuable because they are timed to coincide with the CERES measurements, and they provide observations from a wide variety of locations all over the world.”

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Circling the Earth at a distance of only 240,000 miles, the moon has captivated humanity’s collective imagination since ancient times. Humans have studied the moon for hundreds of years — first with telescopes, then with robotic probes, even sending twelve American astronauts to the lunar surface. But many mysteries remain.

The Gravity Recovery and Interior Laboratory mission, or GRAIL, features twin spacecraft embarking on a challenging mission to map the moon’s gravity.

“Trying to understand how the moon formed, and how it evolved over its history, is one of the things we’re trying to address with the GRAIL mission,” says Maria Zuber, principal investigator for GRAIL from the Massachusetts Institute of Technology. “But also, (we’re) trying to understand how the moon is an example of how terrestrial planets in general have formed.”

“GRAIL is a mission that will study the inside of the moon from crust to core,” Zuber says.

The mission’s two spacecraft will fly in formation above the lunar surface to measure the variations in gravity. The mission seeks to reveal clues about our moon’s thermal history, and how the inner solar system’s rocky planets developed.

GRAIL is set to depart from Space Launch Complex 17B at Cape Canaveral Air Force Station in Florida on Sept. 8 at 8:37 a.m. Prelaunch processing — and the final countdown — are managed by NASA’s Launch Services Program (LSP) at nearby Kennedy Space Center.

“Our team, especially, gets excited whenever we leave Earth orbit, and going to the moon excites us and excites the public,” says LSP’s Tim Dunn, the NASA Launch Manager for GRAIL.

The two spacecraft — called GRAIL-A and GRAIL-B — are riding into space side-by-side aboard a powerful Delta II Heavy rocket built by United Launch Alliance. It’s a rocket with an impressive reliability record.

“NASA has a terrific history with the Delta family of rockets,” Dunn says. “If we just look at the Delta II rocket, which is the version of the vehicle that we fly today, NASA has a perfect launch record, 48 for 48.”

The payload for NASA’s most recent lunar mission, called LRO-LCROSS, weighed in at 6,600 pounds and was the size of a minivan. It launched in 2009 aboard a massive Atlas V rocket. Compare that to the GRAIL spacecraft, which together weigh only about 1,600 pounds. Each unit is about the size of a washing machine, designed to be compact and rugged.

“Whenever you have two spacecraft, it does increase the amount of work you have to do,” explains Bruce Reid, the GRAIL mission manager for LSP.

“Both spacecraft have to go through environmental testing. And then, for instance, on launch day, we have two dedicated teams — one to GRAIL-A and one to GRAIL-B. And they’ll have to individually power up each spacecraft, and go through their health checks, and put the spacecraft in the proper configuration for launch.”

After the climb to orbit, the GRAIL spacecraft will be released from the launch vehicle one at a time. Although most launches conclude with a single “spacecraft separation” — the moment when launch and mission personnel cheer a successful deployment — there will have to be two good separations for the GRAIL mission to begin.

“So we will definitely wait to celebrate until both spacecraft are safe and are on their translunar cruise to the moon,” Reid says.

GRAIL’s journey to the moon will take three-and-a-half months, a mission plan offering plenty of time for controllers to make sure the spacecraft are ready to get to work. The 42-day launch window opens Sept. 8, but the probes’ arrival at the moon will remain fixed, regardless of the liftoff date. GRAIL-A will reach the moon on New Year’s Eve of 2011; GRAIL-B will follow on New Year’s Day of 2012.

Each spacecraft will have to execute a 38-minute lunar orbit insertion burn — enough to slow the forward speed by 427 miles per hour. Once the spacecraft have slipped into lunar orbit, they’ll spend the next five weeks reducing their orbit period. Then, the twin orbiters will be maneuvered into formation, kicking off the mission’s three-month science phase.

During the next 82 days, the moon will rotate three times beneath the two GRAIL spacecraft as they calculate the gravity they encounter. Each 27-day rotation is called a “mapping cycle.”

“The lead spacecraft will accelerate, speed up, in response to a mass and cause the distance between the two to increase,” Zuber explains. “Then, as the second spacecraft comes over this greater mass, it will speed up and get closer to the first spacecraft. So we’re essentially taking the distance between two points, and watching how that distance changes.”

The GRAIL mission also marks the first time students have a dedicated camera on board a planetary spacecraft. The digital video imaging system, called MoonKAM, will offer middle-school students the chance to request photography of lunar targets for classroom study. The project is headed by Dr. Sally Ride, the first American woman to fly in space.

The path from the Earth to the moon has been well traveled in recent decades by pioneers like Surveyor, the Apollo astronauts, Clementine, Lunar Prospector and many more. Today, GRAIL is ready to take its place in this long line of lunar explorers.

“I’m going to be passing Complex 17 about 3:30 a.m. on my way to console,” Dunn says about launch day. “And that hour of the morning, looking off to the east, seeing the rocket bathed in spotlights… It’s an emotional time for all of us on the launch team.”

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Much of the United States sweated through an unusually humid heat wave during July, a month that brought record-breaking temperatures to many areas across the Great Plains. As temperatures soared, NASA satellites observed the unusual weather from above.

The Atmospheric Infrared Sounder (AIRS), an instrument launched on the Aqua satellite in 2002, is unique in its ability to yield highly accurate data about the troposphere, the lowest layer of the atmosphere and the part that most directly affects life on Earth.

Hot temperatures struck Texas and Oklahoma particularly hard, AIRS observed. Large swaths of both of these states persistently experienced highs above 100° F (311 K) during the day for the month of July. Nights offered only minimal relief with low temperatures averaging close to 90° F (305 K) for the month. That’s about 20° F warmer, both day and night, than the average July temperatures for the past eight years of AIRS observations.

AIRS also offered clues about what may have caused the persistent heat spell. Domes of high atmospheric surface pressure (corresponding to the red colors in the figure below) normally intensify in the summer over both the Atlantic and Pacific oceans. However, AIRS data shows they were abnormally strong in July.

Meanwhile, AIRS and modeled wind data from the Goddard Earth Observing System Model (GEOS-5) reveals a clockwise vortex of winds (shown with arrows below) driven by the high pressure in the North Atlantic. The vortex continuously pumped hot and humid air from the tropics through the heart of the Gulf of Mexico and into much of the continental United States throughout July.

The jet stream, which typically produces loops around low-pressure areas that break off and brings cooler air and precipitation, offered little relief. As seen below, the flow of the jet stream (approximated by green and yellow) instead consistently bulged over the high-pressure aloft over the United States (shown in red).

AIRS data are distributed by the Goddard Earth Sciences Data and Information Services Center at NASA Goddard Space Flight Center, Greenbelt, Md. AIRS is managed by NASA’s Jet Propulsion Laboratory, Pasadena, Calif., under contract to NASA. JPL is a division of the California Institute of Technology in Pasadena. GEOS-5 is a product of the Global Modeling and Assimilation Office at Goddard Space Flight Center.

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A NASA-led research team has confirmed what Walt Disney told us all along: Earth really is a small world, after all.

Since Charles Darwin’s time, scientists have speculated that the solid Earth might be expanding or contracting. That was the prevailing belief, until scientists developed the theory of plate tectonics, which explained the large-scale motions of Earth’s lithosphere, or outermost shell. Even with the acceptance of plate tectonics half a century ago, some Earth and space scientists have continued to speculate on Earth’s possible expansion or contraction on various scientific grounds.

Now a new NASA study, published recently in Geophysical Research Letters, has essentially laid those speculations to rest. Using a cadre of space measurement tools and a new data calculation technique, the team detected no statistically significant expansion of the solid Earth.

So why should we care if Mother Nature is growing? After all, Earth’s shape is constantly changing. Tectonic forces such as earthquakes and volcanoes push mountains higher, while erosion and landslides wear them down. In addition, large-scale climate events like El Nino and La Nina redistribute vast water masses among Earth’s ocean, atmosphere and land.

Scientists care because, to put movements of Earth’s crust into proper context, they need a frame of reference to evaluate them against. Any significant change in Earth’s radius will alter our understanding of our planet’s physical processes and is fundamental to the branch of science called geodesy, which seeks to measure Earth’s shape and gravity field, and how they change over time.

To make these measurements, the global science community established the International Terrestrial Reference Frame. This reference frame is used for ground navigation and for tracking spacecraft in Earth orbit. It is also used to monitor many aspects of global climate change, including sea level rise and its sources; imbalances in ice mass at Earth’s poles; and the continuing rebound of Earth’s surface following the retreat of the massive ice sheets that blanketed much of Earth during the last Ice Age.

But measuring changes in Earth’s size hasn’t exactly been easy for scientists to quite literally “get their arms around.” After all, they can’t just wrap a giant tape measure around Earth’s belly to get a definitive reading. Fortunately, the field of high-precision space geodesy gives scientists tools they can use to estimate changes in Earth’s radius. These include:

Satellite laser ranging — a global observation station network that measures, with millimeter-level precision, the time it takes for ultrashort pulses of light to travel from the ground stations to satellites specially equipped with retroreflectors and back again.
Very-long baseline interferometry — a radio astronomy technology that combines observations of an object made simultaneously by many telescopes to simulate a telescope as big as the maximum distance between the telescopes.
Global Positioning System — the U.S.-built space-based global navigation system that provides users around the world with precise location and time information.
Doppler Orbitography and Radiopositioning Integrated by Satellite — a French satellite system used to determine satellite orbits and positioning. Beacons on the ground emit radio signals that are received by satellites. The movement of the satellites causes a frequency shift of the signal that can be observed to determine ground positions and other information.

Scientists use all these techniques to calculate the International Terrestrial Reference Frame. Central to the reference frame is its point of origin: the precise location of the average center of mass of the total Earth system (the combination of the solid Earth and the fluid envelope of ocean, ice and atmosphere that surrounds it, around which all Earth satellites orbit). Scientists currently determine this origin point based on a quarter century of satellite laser ranging data, considered the most accurate space geodetic tool for this purpose.

But the accuracy of the satellite laser ranging data and all existing space geodesy technologies is contaminated, both by the effects of other major Earth processes, and limited ground measurement sites. Think of it this way: if all of Earth’s GPS stations were located in Norway, their data would indicate that Earth is growing, because high-latitude countries like Norway are still rising in elevation in response to the removal of the weight of Ice Age ice sheets. So how can scientists be sure the reference frame is accurate?

Enter an international group of scientists led by Xiaoping Wu of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and including participants from the Institut Geographique National, Champs-sur-Marne in France, and Delft University of Technology in The Netherlands. The team set out to independently evaluate the accuracy of the International Terrestrial Reference Frame and shed new light on the Earth expansion/contraction theory.

The team applied a new data calculation technique to estimate the rate of change in the solid Earth’s average radius over time, taking into account the effects of other geophysical processes. The previously discussed geodetic techniques (satellite laser ranging, very-long baseline interferometry and GPS) were used to obtain data on Earth surface movements from a global network of carefully selected sites. These data were then combined with measurements of Earth’s gravity from NASA’s Gravity Recovery and Climate Experiment (GRACE) spacecraft and models of ocean bottom pressure, which help scientists interpret gravity change data over the ocean.

The result? The scientists estimated the average change in Earth’s radius to be 0.004 inches (0.1 millimeters) per year, or about the thickness of a human hair, a rate considered statistically insignificant.

“Our study provides an independent confirmation that the solid Earth is not getting larger at present, within current measurement uncertainties,” said Wu.

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NASA Watches Birth of Another Tropical Storm from 4 Atlantic Lows: Gert

Tropical Storm Gert was born from one of four North Atlantic Ocean low pressure areas that NASA was watching last Friday. NASA’s Aqua satellite flew over Gert and noticed high, strong thunderstorms around her center of circulation. Meanwhile, two other areas of low pressure behind Gert have diminished in their chances of development.

During the early morning hours (EDT) on August 14, the low pressure area called System 94L strengthened into Tropical Depression 7 (TD7). Tropical Storm warnings were posted for Bermuda. At 10 a.m. EDT that morning, TD7 was near 28.2N 63.2W, just 300 miles (480 km) south-southeast of Bermuda. Maximum sustained winds were near 35 mph, and it was moving to the west-northwest near 7 mph. Pressure 1010 millibars.

Later in the day, at 17:40 UTC (1:40 p.m. EDT), TD7 strengthened into Tropical Storm Gert.

By Monday, August 15 at 11 a.m. EDT, Gert’s maximum sustained winds had reached up to 60 mph. The National Hurricane Center (NHC) reported that tropical-storm-force winds extend outward up to 70 miles (110 km) from the center and mainly to the north and east of the center.

Gert is moving toward the north near 12 mph (19 km/h) and is expected to turn toward the north-northeast then northeast while speeding up. The NHC said that “Gert is expected to pass well to the east of Bermuda later today.” At 11 a.m. EDT Gert’s center was about 95 miles (155 km) east-southeast of Bermuda near 32.0 North and 63.2 West. Because tropical storm-force winds only extend out to 70 miles from the center (and away from Bermuda), the island is not expected to feel winds of that strength as Gert passes by.

At 17:40 UTC on Sunday, August 14, The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA’s Aqua satellite captured a visible image of Tropical Storm Gert in the North Atlantic Ocean, south-southeast of Bermuda. The image revealed higher thunderstorms around the center of Gert’s circulation that were casting shadows on the lower, surrounding thunderstorms. That indicates strong convection and strength within the core of the storm’s heat engine. On August 15, satellite data revealed a tightening of circulation around the center, and what appeared to be “a small 6 to 8 nautical mile-wide (in diameter) eye-like feature,” according to NHC. The strong convection then weakened as dry air entered.

Because Gert is smaller than the average tropical cyclone (it’s less than 140 miles in diameter) it is more susceptible to being weakened by wind shear and dry air. In addition, by Wednesday morning, August 16, Gert will be moving over cooler waters which will help sap her strength.

Two other low pressure areas in the Atlantic are also being watched for possible development. One however, System 92L is too close to Tropical Storm Gert to develop on its own. The NHC gives it a “near zero percent” chance of development today.

System 93L, however, located about 325 miles east of the Lesser Antilles has a large amount of thunderstorms and clouds and has a 10 percent chance of organizing in the next two days. It continues to move westward between 15 and 20 mph and is expected to bring gusty winds and heavy rainfall over parts of the central and northern Lesser Antilles through Tuesday.

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Motorists in the Baltimore-Washington area have one less thing to keep an eye on as of July 30.

NASA’s field study to assess air quality over northeast Maryland has concluded. Over the last month, two research airplanes – one flying high and the other low – completed 14 flight days sampling in coordination with ground sites monitoring air quality. These flights were able to sample pollutants in the lower atmosphere over major interstates, densely populated areas, small towns, and the Chesapeake Bay.

“These flights have allowed us to gather an unprecedented dataset for evaluating the factors governing air quality over the Maryland-DC area,” said Jim Crawford, the mission’s principal investigator, who is based at NASA’s Langley Research Center in Hampton, Va. “We look forward to sharing the data and results over the coming months.”

One of the planes, a NASA P-3B, spiraled over six ground stations in Maryland, flying as low as 1,000 feet and gathering just over 250 soundings. The 117-foot aircraft gathered air-quality data for the mission called DISCOVER-AQ (Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality).

A second aircraft, a UC-12, used a lidar (laser) to observe “profiles” of particulate pollution in the atmosphere, while a second instrument took measurements of gaseous pollution beneath the aircraft flying at 26,000 feet.

The mission measured gaseous and particulate pollution over the populous region to better understand how satellites can be used to improve air-quality forecasts.

By analyzing data from instruments on both airplanes, scientists hope to get a clearer picture of how satellites in space might be used to provide a broader geographical view of air quality near the Earth’s surface beyond what can be provided by ground sites.

A challenge for satellites measuring air quality is to distinguish between pollution high in the atmosphere and that near the surface, where people live and breathe.

More DISCOVER-AQ deployments are planned in coming years with anticipated stops in Texas, California, and a yet to be determined location.

The mission is led by NASA’s Langley Research Center in Hampton, Va. Other NASA participants are Goddard Space Flight Center in Greenbelt, Md. and Wallops Flight Facility on Virginia’s Eastern Shore.

Major partners in the recent campaign include the Maryland Department of the Environment, National Center for Atmospheric Research, University of California-Berkeley, University of Innsbruck, University of Maryland-Baltimore County, Penn State, Millersville University, Howard University, and University of Maryland.

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NASA satellites beam data from space; now the Agency is beaming it straight to your iPad.

Software and media specialists at the NASA Goddard Space Flight Center in Greenbelt, Md., today released a new iPad app — the NASA Visualization Explorer — that allows users to easily interact with extraordinary images, video, and information about NASA’s latest Earth science research.

Cutting-edge visualization has long been a staple of NASA Earth science and in particular the Scientific Visualization Studio (SVS) at Goddard Space Flight Center. The iPad presented NASA a new and easily accessible way to put stunning and beautiful Earth science visualizations directly in people’s hands.

The app’s science features will include high-resolution movies and stills and short written stories to put all the pieces in context. Most of the movies are simply real satellite data, visualized. Other features will include interviews with scientists or imagery from supercomputer modeling efforts. The app includes social networking interfaces, including links to Facebook and Twitter, for easy sharing of stories.

The application is free to the public and available from the App Store via iTunes.

The app editorial team plans to develop two new science features per week. After publishing an initial batch of six features with the launch, new features will publish to the app on Tuesdays and Thursdays. In the future the app could include occasional stories about the Sun, the other planets in our Solar System, and exotic objects far out in the cosmos.

The Goddard team designed the application essentially as a mobile multimedia magazine. “Its one-of-a-kind content is geared to the general public, students, educators — “anyone interested in the natural world,” said Michael Starobin, a senior producer at Goddard Space Flight Center who spearheaded the app’s editorial direction. “The app will explore stories of climate change, Earth’s dynamic systems, plant life on land and in the oceans — all of the small and large stories captured in data by NASA satellites and then visualized.”

“Science should be accessible to everyone, and visualization reveals the meaning and value of the often intangible, but essential, data delivered by NASA’s research efforts,” Starobin said. “Data visualization makes information immediately visual and understandable when it otherwise might go unnoticed, and the app makes it easy to explore in an engaging, easy-to-consume, thoroughly modern style.”

“The NASA visualization app is the latest step in a rich tradition of content production and application development,” added Project Manager Helen-Nicole Kostis. “With its release, I’m inviting everyone on a journey of scientific knowledge and visual wonder.”

Work began on the NASA Visualization Explorer shortly after Apple released its electronic tablet in April 2010. “We just knew immediately that the iPad provided the perfect platform to showcase NASA science,” said Christopher Smith, the principal designer of the application’s user interface.

Administrators of Goddard’s Inclusive Innovation Program agreed. The pilot program, which Goddard management rolled out last year to support ideas that would advance non-science and non-engineering functions and services, awarded seed funding to the team to develop the concept. “Our evaluation process was rigorous,” said Goddard Chief Technologist Peter Hughes, who administered the program for the center. “This proposal stood out for its immediate utility and potential impact.”

With the one-year funding in hand, the three principal creators assembled a multidisciplinary team of experts from the center’s SVS, one of the nation’s premiere data visualization labs, and the center’s Television and Multimedia Department, which has earned a reputation as one of the federal government’s best media-production departments. “Through our team’s unique talents, I believe we’ve created an application that is worthy of the NASA badge,” Starobin said.

“The heart of NASA data visualization beats at SVS,” Kostis added. “This is where science, data, and storytelling come together.”

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A study published July 21 in Science and led by Susan Solomon, of the National Oceanographic and Atmospheric Administration (NOAA), presents new evidence that particles located in the upper layer of the atmosphere — also called the stratosphere — have played a significant role in cooling the climate in the past decade, despite being at persistently low levels.

According to the paper, “The Persistently Variable ‘Background’ Stratospheric Aerosol Layer and Global Climate Change,” stratospheric aerosols, which are small droplets consisting of sulfuric acid and water, have been reflecting some sunlight back into space, which would have otherwise warmed the Earth.

“Stratospheric aerosols are a small variable in the climate change equation,” said Larry Thomason, a scientist at NASA’s Langley Research Center in Hampton, Va and co-author on the paper. “But if you compare the climate system to a balanced scale, it doesn’t take much to tip that scale. Stratospheric aerosols have that potential.”

Thomason and Jean-Paul Vernier, a co-author on the paper and a NASA Post-Doctoral Fellow at Langley, have worked closely with colleagues to build a record of stratospheric aerosol observations with satellite instruments, which have observed the presence of sulfuric acid droplets in the stratosphere.

NASA’s Stratospheric Aerosol and Gas Experiment (SAGE II) monitored them from 1984 to 2005, and the joint NASA/CNES Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) has been able to estimate the amount of particles in the stratosphere since its launch in 2006. The NASA data was also combined with data from Global Ozone Monitoring by Occultation of Stars (GOMOS), a European Space Agency instrument. These results, which have been reported in the June 30, 2011 issue of Geophysical Research Letters, show that there has been a slow increase of the stratospheric aerosols during the past decade.

“None of the climate models, including those used by the IPCC [Intergovernmental Panel on Climate Change] incorporate this slow increase,” said Vernier. “If you do not include this effect, you are going to miss a significant cooling component during this decade.”

These stratospheric aerosols that need to be taken into account are heavily influenced by a natural source – volcanic eruptions.

When a volcanic plume reaches the stratosphere, it may inject sulfur dioxide. Within a month, the sulfur dioxide transforms into sulfuric acid droplets, which linger in the stratosphere and reflect sunlight. Human activities, such as burning wood and coal, can also increase the amount of sulfate aerosols in the stratosphere; however, human-caused effects are small compared to those of volcanoes.

“Even in times without major eruptions, the role of the stratosphere’s sulfuric aerosol in climate has remained significant. If they are neglected, it can result in overestimates of global warming in coming decades, particularly if these aerosols remain present at current values or increase,” said Thomason.

Vernier explains that the radiative effects of aerosols are noteworthy – about 1/3 that of carbon dioxide over the past decade. The average radiative forcing between 2000 and 2010 by stratospheric aerosols has cooled the Earth down at 0.1 watts per meter squared, while the amount of carbon dioxide emitted in the same decade has warmed the Earth at 0.3 watts per meter squared.

“Climate simulations should include the temporary cooling effect of stratospheric particles, said Vernier. “They have partially masked the warming from human derived greenhouse gases in the last decade.”

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