Archive for the ‘Uncategorized’ Category

A View Inside Super Typhoon Usagi

September 23rd, 2013 by Adam Voiland

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As category 4 Super Typhoon Usagi churned toward Taiwan on September 19, 2013, a satellite orbiting hundreds of miles above used a radar instrument to map the storm’s inner structure. The instrument on the Tropical Rainfall Measuring Mission (TRMM) observed two tall complexes of rain clouds called hot towers in the inner eyewall, a sign that Usagi was a well-organized storm and strengthening.

Tropical cyclone “heat engines” extract heat from the ocean’s surface through evaporation and convert a portion of that energy into destructive winds that circle under the eyewall of the storm. All tropical cyclones have heat engines, but several features detected by TRMM suggested that Usagi’s was running particularly efficiently. Radars almost always see eyewalls in strong tropical cyclones, for instance, but they are rarely as symmetrical as Usagi’s is in the visualization shown above. NASA Goddard Space Flight Center researcher Owen Kelley produced the visualization based on TRMM data from the Precipitation Measurement Missions science team at NASA and from the Japan Aerospace Exploration Agency (JAXA).

In the 3D portion of the image, heavy precipitation is shown in dark red. Light precipitation is gray, green, yellow or light red, with the color reflecting how high the storm has lofted the rain production (higher than 8.5 kilometers is green; above 11.5 kilometers is yellow; and higher than 14 kilometers is red). Note that the underlying image, which shows the temperature of cloud tops, uses a different color scale.  In it, cool cloud tops are pink and white, medium temperature cloud tops are gray and blue, and warm cloud tops are dark gray and black.

Even the heavy precipitation at the base of the eyewall is fairly symmetric, which is somewhat unusual according to Kelley. Tropical cyclone eyewalls that are this symmetric are called “annular,” and they have a tendency to maintain their intensity for longer periods than tropical cyclones with more lopsided eyewalls. At two locations in the inner eyewall, updrafts were strong enough to produce hot towersfeatures that are associated with strengthening cyclones.  A few hours after TRMM collected the data visualized here, Usagi intensified briefly into a category 5 storm, the highest category on the scale. 

Read this Earth Observatory feature and blog post to learn more about how the late Joanne Simpson pioneered the study of hot towers. The video below, produced by NASA Goddard’s Scientific Visualization Studio, offers another view of how hot towers work.

Ocean Revealed or Hidden?

August 9th, 2013 by Holli Riebeek

Yesterday’s Image of the Day – Ocean Revealed – elicited an interesting response from Norman Kuring, a NASA oceanographer who frequently contributes to the Earth Observatory. He notes:

“There have indeed been a number of studies that exploit sunglint for ocean research since Paul Scully-Power made his statement. However, I disagree with the follow-on sentence that, “his observation holds true for satellite observations today.” While sunglint does reveal some information about the ocean beneath, for visible radiometry sensors it usually obscures more than it reveals.”

“We in the ocean-color community often bemoan the fact that the MODIS instruments and VIIRS do not tilt to avoid the worst of the glint field. SeaWiFS, which was primarily an ocean mission, tilted, and the upcoming ocean radiometer on PACE is also planned to be tiltable to avoid the worst of the glint.”

Good point, Norman. Sunglint hides the telltale shades of blue and green that point to phytoplankton growth in the ocean’s surface waters. Here’s a good example, originally published on the Earth Observatory in 2007.

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Notice how the bright sunglint obscures the color on the top and right side of the image. (NASA’s Ocean Color web site provides another good example with a more detailed description.) It’s no wonder that oceanographers like Norman cringe at the thought of sunglint in ocean images.

Blazing Hangout

August 7th, 2013 by Mike Carlowicz

Wildfires follow a simple but dangerous equation: Hotter, dryer conditions + more people in the world = a greater likelihood of ferocious wildfires threatening lives and property.

Fires in the western United States are burning earlier, longer and with more intensity, as shown by a decades-long record from ground surveys and NASA satellites. How much of this is due to climate change? And how do scientists see this trend developing in the coming decades, as temperatures rise, seasons shift, and precipitation patterns change?

Join researchers online at 1 p.m. EDT (10 a.m. PDT) on Friday, Aug. 9, for a NASA Google+ Hangout that will explore these questions. The Hangout will feature:

  • Doug Morton, research scientist at NASA’s Goddard Space Flight Center
  • Bill Patzert, research scientist at NASA’s Jet Propulsion Laboratory
  • Elizabeth Reinhardt, national program leader for fire research, research and development, Office of the Climate Change Advisor, U.S. Forest Service

The panelists will take questions from the press and the public during the Hangout. Submit questions on Google+, YouTube, Twitter, Facebook or other social media channels in advance and during the event using the hashtag #NASAFire. The URL for the hangout is https://plus.google.com/events/c6qkg3u1bbgvc81smsrqb84okcc

You can also find some background and imagery on wildfires here on the Earth Observatory.

+ Natural Hazards: Fires

+ Natural Disasters and NASA

+ World of Change: Burn Recovery in Yellowstone

+ Aerosols: Tiny Particles, Big Impact

+ Finding a Fire Cloud from Space

 

 

 

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NASA astronaut Karen Nyberg took this photograph of moonrise and sunrise over Earth’s limb on August 4, 2013. In a tweet, Nyberg noted that she also saw Jupiter and Mercury as she looked out from the International Space Station, but the glare of the Sun’s light hid them in her photo.

When astronomer and Slate blogger Phil Plait fired up the image processing software on his computer down on Earth, he enhanced the brightness on Nyberg’s photo so that Jupiter and Mercury show up quite nicely. (See the enhanced image below.) Read more about the remarkable photograph on the Bad Astronomy blog.

Follow Nyberg’s Twitter and Pinterst feeds at:

https://twitter.com/AstroKarenN
http://pinterest.com/knyberg/pins/

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Reader Question: Wild June Weather

July 31st, 2013 by Mike Carlowicz

Periodically, Earth Observatory answers reader questions on this blog. Here’s a recent note from Manny J of New York City:

“I recall that starting on May 15, 2013, the cold did not leave [New York]. In fact, it still felt like winter because it refused to warm up. Then came June 2013, with the sky overcast each and every day, with the humidity very high, hardly any sun except for an occasional peeping through. In fact as of June 30, 2013, there was no summer as summer used to be. The weather pattern was such that I had never seen anything like it. Do you know why?”

We asked Gavin Schmidt, deputy chief of NASA’s Goddard Institute for Space Studies (GISS) and a NYC resident, what he thought:

“The seasonal weather pattern in any particular location is very sensitive to the chaotic dynamics in the atmosphere. Our ability to attribute those changes to either ocean temperature patterns or external drivers is quite limited, and so we can’t provide an answer that can satisfactorily address this question. Things that we can say are caused (statistically) are generally on larger spatial scales and longer time scales.”

In recent years, many readers have asked Earth Observatory if a particular spell of crazy weather is a result of global warming. As Gavin pointed out and many others have explained, weather events and climate are different things. Climate is what you expect to happen, and weather is what actually happens on a  day-to-day, week-to-week time scale. There is inherent chaos and unpredictable variability in weather. Climate, on the other hand, is a matter of trends and long views. What might the season or year look like when compared to the averages of many years?  Is it getting warmer or cooler, wetter or drier? Can that be explained by some physical process?

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Above: temperature anomalies for June 2013, as calculated by NASA GISS

 

There were heat waves, cool spells, and weird weather long before anyone spoke of global warming. And global warming and climate change are not linear, everywhere-the-same patterns. But there is growing evidence that weather extremes are becoming more extreme, the unusual is becoming more usual — and global climate change is a key reason. The Intergovernmental Panel on Climate Change recently published a report on climate extremes, which is also summarized well by Climate Central.

As we explained in a feature story earlier this spring, the behavior of storms is growing more erratic. Other research has shown that heat waves have become more frequent and more likely to break records. This video below shows how the number of deviations from normal — the number of extreme heating or cooling events — has shifted toward more extreme highs and fewer lows.

 

While Manny and other New Yorkers had an unorthodox June, much of the rest of the United States and the world baked. According the NOAA National Climatic Data Center and meteorologist-blogger Jeff Masters of  Weather Underground, June 2013 was the fifth warmest June on record. July 2013 also was shaping up to be quite hot just about everywhere.

 

 

On June 19, 2013, the U.S. Geological Survey officially decommissioned Landsat 5 after an astonishing 29 years of operation. The satellite’s longevity was recognized by the Guinness Book of World Records, which dubbed Landsat 5 as the longest-operating Earth observation satellite.

I recently listened to Dr. Steve Covington — the flight systems manager for Landsat 5 since 2001 — recount some of the lucky circumstances and creative engineering that kept the satellite operating for nearly three decades. (The talk will be posted on the Library of Congress web site in the near future.)  Here are some of the highlights.

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Lucky circumstance 1: Landsat 5 had a twin, Landsat 4, which showed problems with its power system once it was in orbit. Those problems let engineers adjust Landsat 5 before it launched on March 1, 1984.

Lucky circumstance 2: Landsat 5 was equipped with a large auxiliary fuel tank designed to let the satellite fly down from its orbit to a lower orbit where astronauts could retrieve and repair it. The polar-orbiting space shuttle program that would enable these on-orbit repairs never got off the ground, and this left Landsat 5 with a whole lot of extra fuel. Mission operators used the fuel to extend the mission across decades.

Creative Engineering 1: In January 2005, Landsat 5′s primary solar array drive failed, and months later, in November, the backup drive failed. This key component turned the solar array to face the Sun straight on whenever the satellite was on the sunlit side of the Earth. Without the drive, the solar array was stuck in a single position, limiting the amount of energy it generated to power the instruments and spacecraft.

The failure of the drives looked to be a mission-ending event, since the Landsat 5′s batteries couldn’t be recharged sufficiently to continue science operations. But mission operation engineers came up with a novel solution: If the solar array couldn’t move, they would move the entire spacecraft. Before the satellite came across Earth’s shadow into the sunlight, they pitched the satellite to face the Sun. The satellite faced down again to acquire data, and then, approaching the shadow again, pitched out to face the Sun. This dance gave the satellite just enough extra Sun exposure to keep the batteries charged and execute its imaging duties.

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Creative Engineering 2: Landsat 5 had four pathways for sending data to the ground: two communication links with relay satellites, and two direct downlinks to ground stations. The last of these failed in 2012, preventing the satellite from sending data from its primary instrument (the Thematic Mapper) to the ground. The secondary instrument, the Multispectral Scanner (MSS) had been turned off in 1995. Mission operations engineers realized that the communication links used by MSS were still good, and the mission could continue if the MSS still worked. Seventeen years after turning the instrument off, engineers powered it back on, and amazingly, it worked. This allowed Landsat 5 to acquire one more year of data until Landsat 8 was ready to take its place in early 2013.

Do Not Adjust the Vertical…

June 12th, 2013 by Jesse Allen

One of the wonderful things about working for the Earth Observatory is that we often get first crack at examining imagery from satellites new and old. It’s been especially exciting to look at data from Landsat 8, a joint U.S. Geological Survey and NASA mission launched in February 2013.

But with new things comes new challenges. We’ve had some odd problems with the very intense memory demands of Landsat 8 imagery, for example. And when I saw the image below, I thought for sure I had stumbled on a processing error.

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This is a natural-color, pan-sharpened image of the Elbe River near Wittenberg, Germany, obtained by Landsat 8 on May 6, 2013. I had obtained this to compare to a new acquisition from June 7, 2013, which showed major flooding in the Elbe.

Oh dear. Look at that ripple pattern along the river banks. Superficially, it looks a lot like a software processing error. New code I wrote: my error, right?  In fact, at first glance, it looked a lot like Landsat data of a decade or so ago when the source files were being distributed with nearest-neighbor resampling–a technique used in remapping and resizing data which limits interactions between adjacent measures, something often useful in science measurements, but which causes jagged-looking edges.  Since this was not the first time my code had done something unexpected, it was the obvious first place to look for the cause.  The software failed me!  Again!

However, a quick glance through the data files showed that, whatever was going on, it was coming from the source data: the same rippling showed up in all the bands. Ha!  Someone else’s software had failed!

Because Landsat 8 is so new, it is easy to assume maybe I was not the only one having occasional processing problems with old software on new data. There was one more check I should have done before contacting customer service at USGS, but…

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…I didn’t think of it. If you see something odd in imagery, it is always good to check reality. In this case, a quick zoomed-in view in Google Earth (as shown here) would have informed me that the jagged edges along the banks of the river in the imagery are real jagged edges along the banks of the river.

In hindsight, there were other clues. Notice that the jagged features are present in some places and not others.  And notice that the rippled pattern along the banks bends and curves with the flow of the river. A processing artifact might only show up on very strongly contrasting features (the boundary between land and water here, for example), but would most likely be aligned consistently through the image.  It wouldn’t appear and disappear like it does here, and it would probably be more regular.  It would probably distort in the same direction every time it happened.

In the end, it turns out that all the new systems were working just fine and there really is a very oddly shaped series of features along the banks of the Elbe River near Wittenberg, presumably to stablize the banks of the river and control sediment flow.

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But there’s not much they can do in the face of severe flooding.

You’ve Come a Long Way, Landsat

June 10th, 2013 by Mike Carlowicz

Today’s guest post is from Kate Ramsayer of the NASA Earth Science News Team. Kate wrote the caption for today’s Image of the Day about El Paso and the mountains of data collected by Landsat over four decades.

When the first Landsat satellite — originally called the Earth Resources Technology Satellite (ERTS) — launched in 1972, it was no small feat to visualize the data it sent back and to conduct research with it.

“When ERTS was first launched, there was one cathode ray tube in the country that could take in the digital data and display an image,” said Jeff Masek, Landsat project scientist at NASA Goddard.

In the early years, satellite observations of the light reflected off of Earth were transmitted to receiving stations and mailed to processing centers. Computers translated the image data into photographic prints or transparencies that could be placed on light tables for interpretation. Alternatively, computers translated the numbers in each pixel into alpha-numeric symbols that were printed on large reams of paper. Analysts, often graduate students, could then color-in the symbols with crayon or magic markers. Standing on ladders over the colored-in data, they’d try to visualize the landscape represented by the maps.

“Things were pretty primitive in those days,” Masek said. “People say, ‘Why didn’t they produce a global land cover map in those first few years?’ They were lucky to be able to look at one image for a Ph.D. dissertation.”

Read more about the history of Landsat in “Landsat Looks and Sees.”

Here is the first published image from ERTS…nee, Landsat 1.

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The Tornado Chase

June 5th, 2013 by Erin Jones

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The following is a guest post from Erin Jones (pictured above), the scientific outreach lead for the Global Modeling and Assimilation Office at Goddard Space Flight Center. As a graduate student at Purdue University, she used to chase tornadoes. 

June 2, 2013, started as most Sundays do. My alarm went off; I got out of bed; I came downstairs, and I turned on my computer. I logged on to facebook. A quick look at my news feed told me that this Sunday would not be the same as most Sundays:

 Getting lots of rumors that veteran chasers were killed by the El Reno tornado. I really hope this is not real.

…  just received the news of the possible passing of Tim, Carl and Paul. We are in total shock… God rest their souls if this is true.

Hopes that messages about Tim Samaras are not true… Bad news if this is true…

I put my hand to my chest.

“No.”

The rumors were true. Tim Samaras, his son Paul, and his chase partner Carl Young were gone. They had been killed while chasing a storm on May 31 near El Reno, Oklahoma, when a large tornado hit their car and reduced it to scrap metal.

I was in shock.

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The storm that produced the El Reno tornado, as seen from the vantage point of mobile Doppler radar DOW8, near Mustang, OK. Photo courtesy of Paul Robinson.

The sad truth of the matter is that many in the community have thought for years that it was only a matter of time before a storm chaser was killed. Since the practice of storm chasing began over 50 years ago, not a single chaser had died in pursuit of a storm. Over the past several years, however, increased media coverage and TV shows like Storm Chasers have glamorized chasing and spurred the growth of an entire industry built around following storms.

The number of chasers has exploded, and it has made chasing for science more difficult and dangerous. I’ve seen it. I’ve felt what it’s like to be on a storm, just hoping that the circulation getting ready to pass over your head stays aloft because you’re stuck in chaser-induced gridlock and there’s no way you’d be able to escape if a tornado forms. I’ve known that fear. It’s like we have been on borrowed time.

As much as I dreaded the day when I would hear that a tornado had killed a storm chaser, I thought I was prepared for it. But nothing could have prepared me for what I heard on Sunday morning. Tim Samarasa pillar of the chase communitywas dead. He was a well-respected, veteran chaser. He wasn’t out for the thrill, and he wasn’t out to get the best picture or to take some extreme video. He was a serious scientist. And he was gone.

Why? How?

These questions have been at the forefront of the minds of many of my friends and colleagues over the past few days. As people begin to piece together accounts of what happened…as they process and analyze the data that were collected during the storm, a clearer picture is beginning to emerge. The tornado that hit near El Reno was more than 2.5 miles wide, making it the widest tornado ever recorded. It had a multiple vortex structure with wind speeds of up to 296 miles per hour. Toward the end of its life, it became occluded and turned northeast, deviating from its forecast path.

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Tim Samaras and Carl Young. Photo courtesy of Ryan McGinnis.

Tim Samaras and his crew had always chased safely. They knew what they were doing but it didn’t matter. Had they been caught off guard? Had they ended up stuck in traffic? Were they driving on unpaved roads that were difficult to navigate in storm conditions? Was the tornadic circulation so large that it was impossible for them to get to safety? We still don’t know.

Many of my friends were out there that day. By chance or circumstance, they all stationed themselves out of harm’s way. Three of them–Paul Robinson, Eddie Smith, and Jon Lutz–were several kilometers away from the tornado, collecting mobile Doppler radar data on the storm when it hit Tim Samaras. I asked them if they had any thoughts or stories they’d like to share about what happened.

“I’m not sure what to contribute,” Eddie said. “At the same time Paul, Jon, and I were high-fiving each other over our great positioning and the phenomenal data set we were recording, we were watching, in real-time, this thing kill our friends. How do you reconcile that?”

Jon reflected that “that thing could have killed any of us, depending on which way it turned.”

And Paul told me how he was struck by a sense of eerie irony when they ended up in Moore, Oklahoma, after fleeing the storm, where they then witnessed an EF-0 tornado disturb the same landscape that an EF-5 tornado had devastated just two weeks before.

We still don’t have a great understanding of how tornadoes form, and we still don’t know much about what the wind fields are like near the ground. Tim Samaras spent his career trying to answer these questions so that the losses due to tornadic storms might be minimized. When Tim left this world, his work was not done. It would be a disgrace to his memory if we were to stop trying to collect scientific data on severe storms and to retard the progress on tornado research that he so diligently strove for.

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During a chase on May 19, 2010, Jones’ team had to abort operations because heavy traffic made their attempts to collect data unsafe. Credit: Erin Jones.

Mammatus Clouds over Oklahoma

May 24th, 2013 by Adam Voiland

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Earth Observatory reader Warren Bonesteel sent us this shot of mammatus clouds over Duncan, Oklahoma, on May 20, 2013.  They were taken at about 7:00 p.m. CST, a few minutes after a large supercell storm passed. The same storm system spawned a violent tornado that devastated the nearby city of Moore. While most clouds form in rising air and have flat bottoms, mammatus clouds have pouch-like protrusions caused by sinking air that hang on their undersides.

Mammatus clouds can only form if the sinking air is cooler than the air around it. The sinking air must also have high water or ice content.  Though they are often associated with thunderstorms, the clouds are harmless and usually form in pockets of turbulent air after the worst of a storm has passed. They are not an indicator that a tornado is about to hit. You can learn more about mammatus clouds from  Astronomy Picture of the Day, Earth Science Picture of the Day, AccuWeather, CBC News, EarthSky, and UCAR.

Did you have other dramatic shots of this storm system that you would like to share? Please send them to adam.p.voiland@nasa.gov. I’ll add the best of what we receive to this post.

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Updates:

The photo below was taken on Sunday May 19, 2013, by Darren Purcell.  It was taken in advance of the storm that hit Norman, Oklahoma.

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