Archive for the ‘Uncategorized’ Category

A New Perspective on Precipitation

January 23rd, 2013 by Michon Scott

In late 2012, floods swamped the United Kingdom and news reports said tens of thousands of residents had been affected. It was the kind of natural hazard the Earth Observatory tries to cover, but floods can be hard to see. When heavy rains are in progress, storm clouds typically hide the flooding from satellite sensors. Even if flooding lingers after the clouds clear away, certain types of land cover (such as dense forests) can make floods notoriously difficult to spot.

Another way of seeing floods caused by rainfall is to look at the rainfall itself. The Earth Observatory sometimes publishes imagery from the Multisatellite Precipitation Analysis (MPA). MPA estimates rainfall by combining measurements from multiple satellites and calibrating them using rainfall measurements from the Tropical Rainfall Measuring Mission (TRMM) satellite.

But as its name implies, TRMM focuses on the tropics. More specifically, TRMM specializes in picturing moderate to heavy rainfall over the tropical and subtropical regions. So we can visualize rainfall at relatively low latitudes, but places like the United Kingdom are too far north for this approach to work well.

GPM satellite constellation. Courtesy NASA Precipitation Measurement Missions.

Fortunately a solution is on the horizon—or more accurately, set to launch next year. The Global Precipitation Measurement (GPM) mission is an international collaboration spearheaded by NASA and the Japan Aerospace Exploration Agency (JAXA). Scheduled to launch in June 2014, the GPM Core Observatory will improve upon TRMM by extending observations to higher latitudes. And GPM won’t just focus on heavy rain; it will also observe light rain and snow, which comprise a significant portion of the precipitation at higher latitudes.

The NASA overview of GPM explains:

GPM will provide global precipitation measurements with improved accuracy, coverage, and dynamic range for studying precipitation characteristics. GPM is also expected to improve weather and precipitation forecasts through assimilation of instantaneous precipitation information.

So although the EO can’t visualize heavy rains in places like the UK now, that situation should change after the launch of GPM.

Wild Weather off Alaska

January 18th, 2013 by Mike Carlowicz

The weather seems to be getting weirder by the month. Perhaps we are more attuned to it now, in our hyper-connected, 24-hour-news-cycle world where the news from faraway places is almost as accessible as the news form our hometown. But the research and the models say that weather extremes should grow more extreme, and the observations seem to be living up to the predictions.

The latest case in point comes from the North Pacific and Alaska. This week, a huge storm system with hurricane-force winds lashed the Aleutian Islands in an unusual winter storm. See the video of the cyclone coming over the horizon, as viewed by a GOES satellite.

According to the Alaska Dispatch, winds at Shemya (site of a former U.S. Air Force base) reached 70 miles per hour and the U.S. Coast Guard was mobilizing to “safeguard the crab fleet and other fishing vessels in the area.” According to Climate Central, the storm generated open ocean waves approaching 62 feet and “had an air pressure reading of about 932 mb, roughly equivalent to a Category 4 hurricane, and more intense than Hurricane Sandy as that storm moved toward the New Jersey coastline in October.”

The storm was weakening as it moved northeast and was not expected to have a serious impact on the mainland of Alaska.

A Big Thank You To Our 100,000 Facebook Fans

January 12th, 2013 by Adam Voiland

On March 11, 2009, we posted our first image on Facebook, a spectacular view of ash billowing from Mount Etna (below). At the time, we had just a handful of friends on Facebook, and just a few of them shared it with theirs.

Fast forward three years…and tens of thousands of you have joined our Facebook community. We routinely receive dozens of comments and hundreds of you share nearly every image we post. On January 12, 2013, thanks to all of you, we hit a milestone we’ve been eying for months: 100,000 fans. The friends of these 100,000 fans, Facebook tells us, number over 34 million.

That’s an extraordinary number, but what’s even more notable is how much we’ve learned from all of you since that first post. You’ve told us what you like, what you don’t, and why. You’ve given us countless story ideas, and you have pushed us to keep digging and learning about images long after we hit the publish button. You’ve taught us—and each other—more than we could have imagined when we posted that first image.

So from all of us at the Earth Observatory, THANK YOU! To mark the occasion, we’ve pulled together (above) a few of our favorite craters, plus an atoll in French Polynesia that’s conveniently shaped like a 1. The craters include Pingualuit and Manicouagan in Canada, Lonar in India, Tenoumer in Mauritania, and Crater Lake in the United States. We’ll leave it to you to figure out which is which.

In the meantime, please keep your feedback coming. We love hearing from you, and it helps make our site better. And one last plea: please share this post with your friends, tell them to join our Facebook page, and let them know that we’d love to hear from them as well.

Arctic Report Card

December 10th, 2012 by Michon Scott

On December 5, 2012, the National Oceanic and Atmospheric Administration (NOAA) released its annual Arctic Report Card, covering late 2011 through late 2012. The report listed a number of significant events in a record-breaking and sometimes sobering year.

Photo courtesy NOAA ClimateWatch Magazine.

One of the biggest stories was the record-low sea ice extent in the Arctic Ocean. Arctic sea ice shrinks and grows every year, typically reaching its minimum in September. The last decade, however, has seen a series of below-normal extents, with new records set in 2002, 2005, 2007, and 2012. By mid-September 2012, Arctic sea ice had dropped to 3.41 million square kilometers (1.32 million square miles), which was significantly below the 2007 record of 4.17 million square kilometers (1.61 million square miles). (See Visualizing the 2012 Sea Ice Minimum for prior Earth Observatory coverage of this event.)

NOAA data for high latitudes during June indicated that snow cover extent has declined by 17.6 percent per decade—an even faster rate of decline than the sea ice extent. From June 2008 to June 2012, North America experienced three record-low snow cover extents, and Eurasia experienced five straight record lows.

The summer of 2012 also brought widespread melting on the Greenland Ice Sheet. An estimated 97 percent of the ice surface was melting at some point on July 11–12. July 2012 also brought an unusually high melt index—calculated by multiplying the number of days when melt occurred by the area that melted. Compared to the 1979–2012 average, the 2012 melt index was +2.4, nearly twice the previous melt index record set in 2010. (See Satellites Observe Widespread Melting Event on Greenland for prior Earth Observatory coverage of this event.)

The Greenland melting was linked to a drop in albedo—the amount of sunlight reflected back into space—on the ice sheet in 2012. A drop in albedo can set up a feedback loop; as the ice surface melts, it grows darker, absorbing more sunlight and melting more ice.

Other highlights of the 2012 Arctic Report Card include an increase in the length of the high-latitude growing season, record-high permafrost temperatures, a giant phytoplankton bloom under the ice in the Chukchi Sea, the threat of extinction to the Arctic fox, and severe weather events. (including a strong storm off Alaska and a strong summer storm over the Arctic.)

Reflecting on the year’s events, Mark Serreze, director of the National Snow and Ice Data Center, remarked: “The year 2012 was nature’s kick in the pants. Arctic sea ice and snow cover were at record lows and nearly the entire Greenland ice sheet saw surface melt. Climate change is here and Mother Nature is giving us a stern warning of bigger changes to come.”

For more information, see NOAA ClimateWatch Magazine, which offers report card highlights.

Dune Gallery

November 2nd, 2012 by Michon Scott

The November 2012 issue of National Geographic features an article, “Sailing the Dunes,” about aerial trips over sandy deserts. The author, George Steinmetz, has flown in light aircraft in high winds—a dangerous combination. Yet the same winds that make the flying so dangerous also sculpt some of the world’s most beautiful landscapes. Several of the places mentioned in the article have also been covered by the Earth Observatory. Here is a sampling of some of those places, plus some additional dune-rich landscapes.

The Sahara Desert spans northern Africa, covering about 9.4 million square kilometers (3.6 million square miles). Within the Sahara are multiple sand seas, or ergs — big, windswept landscapes of shifting sands. The ergs can be as photogenic as they are forbidding.

Issaouane Erg in Algeria holds multiple crescent-shaped (barchan) dunes and star dunes. Winds blowing mostly from one direction create barchan dunes while variable winds create star dunes. Low-angled sunlight highlights the varied dune shapes in this region. Story: Issaouane Erg, Algeria

Besides barchan dunes and star dunes, Issaouane Erg is also home to mega-dunes. Mega-dunes likely take hundreds of thousands of years to form, and may have started their formation when the Sahara—once a more hospitable place—began to dry. In between the big dunes, winds have swept sand away from the desert surface altogether, revealing gray-beige mud and salts. Story: Dune Types in the Issaouane Erg, Eastern Algeria

The flat areas between dunes are known as dune streets, and they are unmistakable in Algeria’s Erg Oriental. In between the streets, star dunes sit atop linear dunes. Story: Erg Oriental, Algeria

Nearly sand-free basins also separate complex dunes in the Marzuq Sand Sea of southwestern Libya. The big sand masses are known as “draa” dunes, Arabic for “arm.” Extending from some of the draa dunes are snakelike linear dunes. Story: Sand Dunes, Marzuq Sand Sea, Southwest Libya

Dunes form in arid conditions, but conditions can change. The manmade Toshka Lakes of Egypt flooded old dune landscapes. Depending on lake levels and the underlying topography, some dunes are completely flooded while the crests of others poke above the water surface. Story: Toshka Lakes, Egypt

Although it covers an area much smaller than the Sahara Desert, the Arabian Peninsula’s Empty Quarter, also known as Rub’ al Khali, holds half as much sand as the entire Sahara. Salt flats—sebkhas or sabkhas—separate the towering dunes. Story: Empty Quarter

Though it lacks the massive sand seas of the Sahara and the Arabian Peninsula, the United States sports some impressive dune fields of its own. White Sands National Monument holds gleaming white sands formed from gypsum. These brilliant white dunes occur at the northern edge of the Chihuahuan Desert, which extends across the U.S.-Mexico border. Story: White Sands National Monument

The Algodones Dunes of southeastern California lack the snowy look of White Sands, but make up for it by hosting a complex assortment of dune formations. Smaller dunes sit on top of giant crescent-shaped dunes. Wind does not act alone in shaping this landscape; water flows off the Cargo Muchacho Mountains to the east, making its way into the dune field and sustaining some plant life. Story: The Algodones Dunes

Some of the world’s most complex dune formations occur in the Badain Jaran Desert of Inner Mongolia. Small lakes dot flat areas in between dunes, which have been characterized as “complex reversing mega-dunes developed from compound barchanoid mega-dunes.” Story: Elevation Map of the Badain Jaran Desert

And sometimes a single desert can host completely different landscapes. Identified by satellite data as the hottest place on Earth, Iran’s Lut Desert contains two completely different landscapes. The central portion is home to wind-sculpted linear ridges known as yardangs. The southeastern part of the desert hosts dunes that soar to 300 meters (1,000 feet) alternating with salt pans. Story: Diverse Terrain of Iran’s Dasht-e Lut

Note that due to the angle of sunlight, some of these images produce an optical illusion known as relief inversion.

Crane Glacier Terminus Retreat

November 2nd, 2012 by Adam Voiland

On October 25, 2012, we published a set of images that shows how the Hektoria and Green glaciers on the Antarctic Peninsula have continued thinning since the Larsen-B ice shelf’s collapse in 2002.  Though those two glaciers have been some of the fastest changing in recent years, they aren’t the only Larsen-B tributary glaciers that have lost ice over the last decade.

In all, the 15 glaciers that flow into the ice shelf have lost more than 10 gigatons (one gigaton equals one billion tons) of mass per year, according to research published in the Journal of Glaciology. Some of the most dramatic changes have occurred at Crane, the longest of the Larsen B tributary glaciers. Since the collapse of the ice shelf, Crane Glacier has retreated by more than 12 kilometers (7 miles).

This visualization, based on an image captured by the Advanced Land Imager (ALI) instrument on the Earth Observing-1 (EO-1) satellite, shows the location of the terminus in April 2002, February 2003, and February 2006. Since 2006, the terminus has stayed in the same general position. The image was acquired on February 24, 2012.  For another view of Crane glacier’s retreating terminus, please see this image.

NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team.

A view of Sandy from the TRMM satellite

October 29th, 2012 by Adam Voiland

 Check our Hurricane Sandy event page, our YouTube page, and NASA’s Hurricane Resource page for the latest storm images from NASA.

NASA hurricane researcher Owen Kelley prepared this image and caption.

The day before Hurricane Sandy’s center was forecast to make landfall in New Jersey, the radar on the Tropical Rainfall Measuring Mission (TRMM) satellite observed the hurricane’s center.

At 2:20 EDT on Sunday October 28, Hurricane Sandy was a marginal category 1 hurricane and its eyewall was modest, as TRMM reveals, which gives us hints about its possible future strength.

The eyewall was somewhat compact with its 40 km diameter; the eyewall contained only relatively light precipitation; and none of Sandy’s eyewall storm cells managed to burst through, or even reach, the tropopause, which has about a 10 km height at mid-latitudes. Evidence of the weak updrafts in the eyewall comes from the fact that the TRMM radar’s reflectivity stayed under 40 dBZ, a commonly cited signal strength at which updrafts can be vigorous enough to form hail and to lift smaller ice particles up through the tropopause and into the stratosphere.

But placed in context, the TRMM-observed properties of Hurricane Sandy’s eyewall are evidence of remarkable vigor. Most hurricanes
only have well-formed and compact eyewalls at category 3 strength or higher.  Sandy was not only barely a category 1 hurricane, but
Sandy was also experiencing strong wind shear, Sandy was going over ocean typically too cold to form hurricanes, and Sandy had been limping along as a marginal hurricane for several days.

With infrared satellite observations (as in the background of the images show), one can speculate about what the sort of convective storms are developing under the hurricane’s cloud tops, but Sandy was sneaking up the East Coast too far out at sea for land-based radars to provide definitive observations of the rain regions inside of the hurricane’s clouds. The radar on the TRMM satellite provided this missing information during this overflight of Hurricane Sandy.

The TRMM satellite also showed that the super-sized rainband that extended to the west and north of the center did contain vigorous
storm cells, as indicated by the red regions of radar reflectivity in excess of 40 dBZ. This rainband is expected to lash the coast well before the hurricane’s center make landfall.  Even further west, at the upper left corner of the image, one can see two small storm cells.  These storm cells are the southern-most tip of the independent weather system that is coming across the United States and that is expected to merge and possibly reinvigorate the remnants of Hurricane Sandy after Sandy makes landfall.

TRMM is a joint mission between NASA and JAXA, the Japan Space Exploration Agency.  Some of the questions about hurricanes left unanswered by the TRMM satellite will be explored by the Global Precipitation Measuring (GPM) satellite scheduled for launch in 2014.  For more information, visit

Keeping track of changing landscapes

October 23rd, 2012 by Mike Carlowicz

When you look at a parcel of Earth’s surface at a moment in time, it can be hard to grasp the story behind the image. It’s a snapshot, a fleeting glimpse. Does it always look like that?  Am I seeing this place on a normal day, an abnormal day, an everyday? Where’s the motion, the action, the dynamics?

For instance, take a look at this collection of lakes amidst the barren, salt-crusted landscape of central Asia.

The size of these freshwater lakes is compelling…tens to hundreds of kilometers long…oases of green and blue amidst the tans of the desert. These “inland seas” are impressive. That is, until you look at that same region a decade earlier (below)…or forty years earlier.

Through the lens of time, the planet comes to life. The color of the landscape changes, waters rise and fall, ice advances and retreats. The planet has vital signs. Earth Observatory’s World of Change series offers some visual vital signs for 23 different landscapes and locales on Earth, with images updated across seasons to decades, depending on the length of the satellite record.

Our newest updates include 2012 images for the Aral Sea (sampled above) and for the Hobet Mine, a mountaintop coal-mining operation in West Virginia.

What do you think we should show in future installments of World of Change?  (Keep in mind that it has to be something we can see or measure via satellite.)

Which do you prefer: active fires or burn scars?

October 22nd, 2012 by Adam Voiland

The Pole Creek fire is hardly breaking news. As of October 20, 2012, authorities announced that the blaze was 100 percent contained. In early October, when we first published this image that the Terra satellite acquired in September, the fire was still burning wildly and sending up smoke plumes that shrouded the Three Sisters and the surrounding communities in a heavy layer of smoke.

A few weeks later, on October 5, a different instrument on a different satellite—the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 satellite—acquired a false-color view of the fire (below). Rather than smoke billowing from an actively burning fire, the image features the burn scar left behind.

In ideal circumstances, we publish images of a fire while it is actively burning and also after the fact. But, in some cases, either because the satellites don’t acquire usable images or because we simply don’t have time to post them, we end up showing one view or the other.

There’s no shortage of fires we could show. (To get a sense of this, take a look at this map of global fire activity to see the constant presence of wildfires on our planet.) If we wanted, we could show only active fires with smoke, only burn scars, or any combination of the two and still have far more images than we could possibly post.

But which view do you prefer?  And how late is too late? If a fire has been under control for day or weeks are you still interested in seeing the event or the scars that it left behind?

And what about other types of natural disasters like storms or volcanic eruptions?  If a storm has already broken up, if a volcanic ash plume has dissipated, if a hurricane has no chance of making landfall…are you still interested in seeing it, or does it just feel like old news?

Well…how did I get here?

October 16th, 2012 by Mike Carlowicz

As part of Earth Science Week, various NASA scientists and staff have been writing and talking about what it is like to work in science. One of those staff members is our colleague, Jefferson Beck, a documentary producer turned NASA science communicator…

So I’m flying at 1,500 feet above a giant crack in the Pine Island Glacier. By “giant” I mean up to 800 feet across, deeper than the Statue of Liberty, and 18 miles long.  I’m in a NASA DC-8 aircraft with Operation IceBridge, the first airborne mission to take detailed measurements of such a massive calving event in progress.  If this chunk of the Antarctic ice shelf splits off and floats away as one big piece, it will be the size of New York City. 

As the video producer assigned to this mission, I’m trying to make the most out of the few moments where the scenery isn’t just impressive, but truly stunning.  My stomach is tight with excitement and worry that I’ll miss the best shots.  I have one camera set up recording a time-lapse out one window, and I’m holding another camera against another window. I’m bracing myself with a ratty piece of foam against the fuselage and trying to find a clear spot among the window’s many scratches as the plane bounces along.  The Crack looms large for a while, then quickly fades from sight and gets lost in the whiteness.

After we finish our flight lines, we bank out over the razor-sharp edge where the ancient Antarctic ice meets the dark water.  We start to gain altitude for the long flight back to Punta Arenas, Chile, a port city on the Strait of Magellan.  As we climb, I think about how few people have gotten to see the frozen continent from this perspective.  Then I look around at the amazingly talented group of people on board, and think: “how did I wind up here?”

You’d think that most people who work at NASA are numerical geniuses who spent their high school years building robots and answering math problems for fun.  And we do have people like that.  We also have people who could rebuild an engine when they were 14 and people who had their pilot’s license at 17.

But for me, high school was many things and the path was not always clear.  High school was cross country and track, the school newspaper, reading lots of science fiction, smudging my way through art classes, dropping an essay-writing class to have double-lunch with my girlfriend, struggling a bit with math, and really enjoying most of my science courses.

My continuing issues with math — and, as it turned out, chemistry — didn’t stop me from becoming a biology major in college. There I focused on ecology and natural history.  After that, my plan was to become a biologist, so for a while I ended up in Alaska standing in frozen streams and counting wild salmon.  I loved being in the field and I loved the natural world, but slowly the idea of being a research scientist began to fade.

Not knowing what to do next, I went back home to Ohio.  I couch-surfed for a while before landing a job as a reporter for a small-town newspaper.  Then I helped build a local bike trail, did some reporting for radio, and then got involved with non-profit community-building work.  For a while, I was a bouncer in a bar one night a week.  Finally, I landed in filmmaking.  I took some film classes, worked on a couple of indie features, and made some little films of my own.

It all kind of looks like a jumbled mess, doesn’t it?  It doesn’t make you think, “well, here’s a guy who is destined for NASA.”  It’s what career-minded people call “lateral moves,” jumping sideways from one career track to another without much advancement – the kinds of moves that make some parents scratch their heads and start to worry.

But all that experience led me to finally apply to a grad school program in science and nature filmmaking at Montana State University.  I got accepted, and later got my job at NASA, because I was able to tell a story – a true story – using the skills I had gained from all those lateral moves.  I could write, manage a project, understand scientists, recognize news, work in the field, dig deep and endure adversity [claiming this one from my 10 years running cross country and track], and make a video.

So my take home message is this:  If you’re one of those focused people who know exactly what they want to do and head straight for it, fantastic.  One day you’ll be flying the plane I’m riding in, designing one of our satellites, or sending us to Mars.  And I’ll be grateful for your skills.  But if your career path wanders, don’t worry.  If you keep learning as you go, one day it will make for a very interesting true story.

This month I’m heading back to Chile, and back to flying at 1,500 feet over the Antarctic ice, and maybe even back to the Pine Island Glacier, which finally seems ready to give up its New York City-sized chunk of ice.   Wherever we fly, it will be exciting.  And difficult, and beautiful, and scientifically valuable.  There will be a lot of true stories out there, and I’ll do my best to bring them home.

Watch Jefferson’s video: Flying through the Rift: An update on the crack in the Pine Island Glacier.

Learn more about other Earth Explorers like Jefferson on the NASA Earth Science Week website.