Dec 14 2015
From The Space Library
Release 15-233 New NASA Satellite Maps Show Human Fingerprint on Global Air Quality
Using new, high-resolution global satellite maps of air quality indicators, NASA scientists tracked air pollution trends over the last decade in various regions and 195 cities around the globe. The findings were presented Monday at the American Geophysical Union meeting in San Francisco and published in the Journal of Geophysical Research.
"These changes in air quality patterns aren't random," said Bryan Duncan, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, who led the research. "When governments step in and say we're going to build something here or we're going to regulate this pollutant, you see the impact in the data."
Duncan and his team examined observations made from 2005 to 2014 by the Dutch-Finnish Ozone Monitoring Instrument aboard NASA's Aura satellite. One of the atmospheric gases the instrument detects is nitrogen dioxide, a yellow-brown gas that is a common emission from cars, power plants and industrial activity. Nitrogen dioxide can quickly transform into ground-level ozone, a major respiratory pollutant in urban smog. Nitrogen dioxide hotspots, used as an indicator of general air quality, occur over most major cities in developed and developing nations.
The science team analyzed year-to-year trends in nitrogen dioxide levels around the world. To look for possible explanations for the trends, the researchers compared the satellite record to information about emission controls regulations, national gross domestic product and urban growth.
"With the new high-resolution data, we are now able to zoom down to study pollution changes within cities, including from some individual sources, like large power plants," said Duncan.
Previous work using satellites at lower resolution missed variations over short distances. This new space-based view offers consistent information on pollution for cities or countries that may have limited ground-based air monitoring stations. The resulting trend maps tell a unique story for each region.
The United States and Europe are among the largest emitters of nitrogen dioxide. Both regions also showed the most dramatic reductions between 2005 and 2014. Nitrogen dioxide has decreased from 20 to 50 percent in the United States, and by as much as 50 percent in Western Europe. Researchers concluded that the reductions are largely due to the effects of environmental regulations that require technological improvements to reduce pollution emissions from cars and power plants.
China, the world's growing manufacturing hub, saw an increase of 20 to 50 percent in nitrogen dioxide, much of it occurring over the North China Plain. Three major Chinese metropolitan areas -- Beijing, Shanghai, and the Pearl River Delta -- saw nitrogen dioxide reductions of as much as 40 percent.
The South African region encompassing Johannesburg and Pretoria has the highest nitrogen dioxide levels in the Southern Hemisphere, but the high-resolution trend map shows a complex situation playing out between the two cities and neighboring power plants and industrial areas.
"We had seen seemingly contradictory trends over this area of industrial South Africa in previous studies," said Anne Thompson, co-author and chief scientist for atmospheric chemistry at Goddard. "Until we had this new space view, it was a mystery."
The Johannesburg-Pretoria metro area saw decreases after new cars were required in 2008 to have better emissions controls. The heavily industrialized area just east of the cities, however, shows both decreases and increases. The decreases may be associated with fewer emissions from eight large power plants east of the cities since the decrease occurs over their locations. However, emissions increases occur from various other mining and industrial activities to the south and further east.
In the Middle East, increased nitrogen dioxide levels since 2005 in Iraq, Kuwait and Iran likely correspond to economic growth in those countries. However, in Syria, nitrogen dioxide levels decreased since 2011, most likely because of the civil war, which has interrupted economic activity and displaced millions of people.
Release 15-220 NASA Studies High Clouds, Saharan Dust from EPIC View
From a dusty atmosphere stretching across the Atlantic Ocean to daily views of clouds at sunrise, a new NASA camera keeping a steady eye on the sunlit side of Earth is yielding new insights about our changing planet.
With NASA’s Earth Polychromatic Imaging Camera (EPIC), affixed to NOAA’s Deep Space Climate Observatory (DSCOVR) about one million miles from Earth, scientists are getting a new view of our planet’s clouds, land surfaces, aerosols and more. Science results from the first EPIC images were discussed Monday at a media briefing at the American Geophysical Union meeting in San Francisco.
EPIC captures a color image of the sunlit side of Earth at least once every two hours, allowing researchers to track features as the planet rotates in the instrument’s field of view.
“With EPIC, you see cloud structure from sunrise on the left to sunset on the right,” said Jay Herman, EPIC instrument lead investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland, Baltimore County. “It’s the only view we have like this where everything is at the exact same instant in time, even though the local times are different.”
EPIC takes measurements in visible, ultraviolet and near-infrared wavelengths. With the ultraviolet channels, Herman can watch as dust from the Sahara travels westward across the Atlantic. While other low-Earth orbit satellite instruments can pick this up as they orbit at a fixed local time, EPIC provides a day-long view of the process.
“We can see the progression in real time, as it flows across the Atlantic,” Herman said.
Researchers also can determine the height and location of daytime clouds by comparing EPIC images at two different wavelengths. This measurement is important in calculating Earth’s energy balance for climate studies, as well as for tracking weather. For example, hurricanes show up as a high spiral of clouds surrounding a clearly visible eye.
“Because of the unique location and field of view, every day brings something new and unexpected,” said Alexander Marshak, DSCOVR deputy project scientist at Goddard.
One example Marshak points out is that, even a million miles away, EPIC can see the tracks of ships crossing the ocean. Some of the first images from EPIC show the clouds that result from the ships’ smoke plumes.
Researchers also are analyzing EPIC data to better understand vegetation, aerosols, ozone and other features of Earth and its atmosphere.
DSCOVR was launched on Feb. 11 and, after a four-month journey, reached its orbit around the first Lagrange point, where the matching pull of gravity from the sun and Earth allows the satellite to stay relatively stable between the two bodies. The satellite, a joint mission between NOAA, NASA and the U.S. Air Force, also carries instruments facing the sun that will the study solar wind and its magnetic field.
A second NASA Earth-facing instrument on DSCOVR, the National Institute of Standards and Technology Advanced Radiometer (NISTAR), measures the total amount of solar energy that reflects off Earth, as well as the heat emitted from our planet, according to Steven Lorentz, NISTAR instrument lead investigator and president of L-1 Standards and Technology, Inc. Because of this, the instrument fills in a missing piece of energy information not observed by other satellites.
Even with less than a year’s worth of data, the energy reflected off Earth is showing patterns, he said. The instrument picks up fluctuations, with more light reflected from continents and clouds than from oceans.
“Whenever Africa is in view, we get the highest photoreflectance,” Lorentz said. “And, even though it’s the same planet spinning, the amount of cloudiness varies planet-wide every day.”
Earth’s reflectiveness varies throughout the year, as well. As Antarctica tilts towards the sun in November, NISTAR’s signal edges up as the massive ice sheet changes the planet’s energy budget. It’s a measurement that, over time, could help scientists studying how the reflectance of the sun’s energy back into space can impact Earth’s changing climate.
Release 15-033 (Goddard) Plunging into the Ionosphere: Satellite’s Last Days Improve Orbital Decay Predictions
Scientists are learning more about how the upper atmosphere and ionosphere affect space satellites as well as communications and navigation here on Earth, thanks to new data from a U.S. Air Force satellite that recently completed a more than seven-year mission.
The Communication/Navigation Outage Forecasting System (C/NOFS) satellite burned up in Earth’s atmosphere during a planned reentry on Nov. 28, leaving behind a treasure trove of data about a part of the space environment that’s difficult to study. The unique set of sustained observations from C/NOFS will greatly improve models currently used to predict satellite trajectories, orbital drag and uncontrolled re-entry.
Scientists from the U.S. Air Force, NASA, and the University of Texas (UT) at Dallas are presenting the results at the American Geophysical Union Fall Meeting in San Francisco.
Launched on April 16, 2008, C/NOFS studied a region high above in our atmosphere called the ionosphere, a layer of electrically charged particles created by ultra-violet radiation from the sun. This layer lies some 40 to 600 miles above the Earth’s surface, where it interacts and co-mingles with the neutral particles of the tenuous upper atmosphere. The upper atmosphere and ionosphere change constantly in response to forces from above and below, including explosions on the sun, intense upper atmosphere winds, and dynamic electric field changes. In addition to interfering with satellite orbits, such changes can produce turbulence in the ionosphere that cause what's known as scintillations, which interfere with radio wave navigation and communication systems, especially at low latitudes near the equator.
During most of its lifetime, C/NOFS never came closer than about 250 miles above the ground. However, as solar activity increased, C/NOFS began to orbit at lower and lower altitudes—ultimately descending to less than 160 miles above Earth.
During its last 13 months of operations, as its orbit decayed and it spiraled into lower altitudes and eventual re-entry into Earth’s atmosphere, C/NOFS satellite captured a unique set of comprehensive observations as it traveled through the very space environment that can directly cause premature orbital decay. Such regions have rarely been studied directly for extended periods of time, because orbits in this denser region of the atmosphere are not sustainable long-term without on board propulsion.
"One thing we learned clearly from C/NOFS is just how hard it is to predict the precise time and location of re-entry," said Cassandra Fesen, principal investigator for C/NOFS at the Air Force Research Laboratory at the Kirtland Air Force Base in Albuquerque, New Mexico.
The C/NOFS data at these lower altitudes show that the upper atmosphere and ionosphere react strongly to even small changes in near-Earth space, said Rod Heelis, principal investigator at the UT-Dallas for NASA's Coupled Ion-Neutral Dynamics Investigation (CINDI) instrument suite on board the satellite.
"The neutral atmosphere responds very dramatically to quite small energy inputs," said Heelis. "Even though the energy is put in at high latitudes – closer to the poles – the reaction at lower latitudes, near the equator, is significant."
Heelis also described research on a previously-hard-to-view sweet spot in the atmosphere, where the charged particles of the ionosphere and the neutral particles of the atmosphere directly affect each other. The CINDI observations show that the neutral wind creates piles of neutral gas pushed up against ionospheric density variations – similar to how blowing snow piles up in drifts against a building wall. This results in density striations in the atmosphere that were never previously observed. Such density variations are necessary data to include when modeling interference with radio waves or excess drag on a travelling spacecraft.
Rob Pfaff, project scientist for CINDI at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and principal investigator for another C/NOFS instrument, the Vector Electric Field Investigation, is studying observations that speak to one of the original goals of the C/NOFS program: Why does the low latitude ionosphere at night become so turbulent that it can wreak havoc on communications and navigation radio signals?
Developing the capability to predict such space weather disturbances has been a long-standing goal of the Air Force Research Laboratory. The C/NOFS low altitude observations were critical to form a complete picture of these disturbances, as the satellite ventured to the possible root of the largest ionospheric upheavals -- those that emanate from the bottom ledge of the ionosphere at night. The observations revealed the presence of strong shears in the horizontal ionosphere motions at the base of the ionosphere, places where charged particles flow by each other in opposite directions. C/NOFS observed shears and undulations along this boundary. Such shears and undulations -- spotted throughout the nighttime, equatorial ionosphere -- are believed to be the source of large-scale instabilities that ultimately drive the detrimental scintillations.
