Some features of this site are not compatible with your browser. Install Opera Mini to better experience this site.

Earth Matters

It Was 20 Years Ago Today…

April 29th, 2019 by Mike Carlowicz

On April 29, 1999, NASA Earth Observatory (EO) started delivering science stories and imagery to the public through the Internet. So much has changed in those 20 years…

+ In 1999, about 3 to 5 percent of the world had Internet access. About 41 percent of American adults used the World Wide Web, most often to look at the weather. Today an estimated 56 percent of the world’s population (4.3 billion people) are active on the Internet. 

+ At the end of the 20th century, all EO readers came to us through a computer, mostly desktops. One third of them were connecting via dial-up modem. Today, about 40 percent of our audience arrives to the web site via mobile phones and tablets on public wifi and cellular networks. Yet even now, 65,000 of our most loyal followers subscribe to our newsletters. Many others subscribe to our RSS feeds.

The site has had five different designs over the decades.

+ In 1999, “social” media mostly consisted of chatrooms and newsgroups. Even by 2005, only 5 percent of Americans were using social media. Today about 69 percent of adults use social media, and people are just as likely to see Earth Observatory content on social platforms as on our web site. Ten million people follow EO and NASA Earth science on Facebook, with 1.3 million more on Twitter, and 500,000 on Instagram.

+ When EO launched, images from Earth science satellites were generally available about a month after acquisition. Public access to science data and imagery was extremely limited, highly filtered, and sometimes required a fee. Two decades later, many NASA Earth science observations are available freely on the web within hours of acquisition.

+ On our first day online, the site got 400 pageviews–most of them were likely colleagues and relatives. Today we get about 50,000 views per day.

Our baby portrait from 1999.

+ In our first year, we published 35 “Images of the Week” and 9 feature stories. By 2001, we started delivering an Image of the Day. Since launch, we have published more than 6,900 Images of the Day, 8,300 natural hazards images, and 450 features and videos. Yes, more than 15,000 image-driven stories, and all of them are still available in our archive.

+ In 1999, two members of our staff were in elementary school and three were in high school. The readers of EO Kids were not born yet.

The technology of science and the Internet has changed in a generation, and our site has evolved and grown with the changes. But our core values have not changed. You find us on more platforms and with some new approaches, but you can still count on us to deliver beautiful, newsworthy, interesting, and scientifically important images and stories. Our editorial team has more than 110 years of experience in science communication and data visualization, and we bring that depth of knowledge to every story, 365 days a year.

None of this would be possible without the many scientists, engineers, communicators, data hounds, patrons, and friends inside and outside of NASA who review our work, tip us off to stories and images, share their scientific insights, and inspire and challenge us. Thank you.

You can view a daily “greatest hit” from our archives at the On This Day page.

As we celebrate our 20th year, we are going to share some looks back and some looks ahead. In the next twelve months, look for…

  • EO on This Day – a chance to see some of the most memorable Images released on each day of the calendar year
  • New puzzlers, videos, and social media events
  • Stories of science evolving, as we revisit images, global maps, and science stories from the past 20 years and ask “what have we learned in two decades and where do we go next?”
  • Our first photo essay book, available in print, on the web, or downloadable to your tablet.

If you have been with us for many (or all) of our 20 years, thank you. We have some of the most engaged, challenging, and thoughtful readers on the planet, and we work hard to live up to your trust and interest. If you are new to the site, bring a friend. We have 15,000 stories about Earth to share, with more being added every day.

Related Links and References

Earth Observatory 10th Anniversary

Pew Research Center (2018)  World Wide Web Timeline

Internet World Stats (2019)  Internet Growth Statistics

Wikipedia (2019) Global Internet Usage

Earth Observation in the Palm of Your Hand

April 8th, 2019 by Russanne Low, IGES

Join a mosquito mapping blitz for Citizen Science Day through GLOBE Observer.

Earth observations take place on many spatial scales. Some observations originate from sensors in space; others can happen with a mobile phone in the palm of your hand. GLOBE Observer is a free mobile app that connects an international network of citizen scientists with the broader scientific community in an effort to document and analyze changes taking place in Earth’s air, land, water, and life. The app is the centerpiece of a citizen science blitz now underway.

Both globalization and a changing climate have caused countless living creatures to adjust their range and distribution. For human health, one of the most concerning impacts of a changing climate is the range expansion of mosquitoes. These flying vectors of disease are responsible for illness in millions of people; they also cause more than 700,000 deaths each year. 

Map of projected first appearance of mosquitoes, based on monthly minimum temperature data.  Map data from Anthony Arguez, lmke Durre, Scott Applequist, Mike Squires, Russell Vose, Xungang Yin, and Rocky Bilotta (2010). NOAA’s U.S. Climate Normals (1981-2010). NOAA National Centers for Environmental Information. Courtesy Andrew Clark, IGES.

The northern hemisphere is now greening up in response to changes in sunlight and temperatures, and mosquito season is either just beginning or underway in much of the contiguous United States. The map above indicates when the first appearance of mosquitoes can be expected based on past weather data. The actual time of first appearance in a region can vary by several weeks, depending on the weather and other variables. 

The GLOBE Observer app has a new tool known as the Mosquito Habitat Mapper, which makes it possible for citizen scientists to observe, record, and share data about mosquito breeding sites using a mobile phone. The data are important to scientists trying to predict disease outbreaks and epidemics. Observations provided by citizen scientists, combined with satellite observations and models, can make it possible to track the range and spread of invasive mosquitoes.

With the Mosquito Habitat Mapper, citizen scientists can report active and potential breeding sites in their communities. And using a built-in taxonomic key, GLOBE Observers can help determine whether the mosquito larvae have the potential to transmit disease pathogens to humans. 

The GLOBE Observer app can help you identify the species of larvae.

GLOBE Observers also can have an immediate impact on health in their community. In the last step of Mosquito Habitat Mapper, users report whether they were able to remove a breeding site. This can be accomplished in most cases by simply tipping and tossing standing water that is found in containers, or by covering stored water with a net or a lid. For larger water bodies such as ponds, irrigation ditches, or swamps, the reports about breeding sites can be used by mosquito surveillance agencies. 

In this way, GLOBE Observers are not only engaged scientifically, they can become agents of change in their community. The World Health Organization (WHO) identifies source reduction–the elimination of mosquito breeding sites–as the most effective way to protect human populations and reduce the threat of mosquito vector-borne disease.

The GLOBE Observer Mosquito Blitz kicked off on April 7, 2019, and ends on Citizen Science Day (April 13). Join in this effort by downloading the app. Follow GLOBE Observer on social media during Mosquito Blitz week on Facebook or Twitter. Check out the Mosquito Blitz website and GLOBE Mission Mosquito for more mosquito resources.

On February 27, 2014, a Japanese rocket launched NASA’s latest satellite to advance how scientists study raindrops from space. The satellite, the Global Precipitation Measurement (GPM) Core Observatory, paints a picture of global precipitation every 30 minutes, with help from its other international satellite partners. It has provided innumerable insights into Earth’s precipitation patterns, severe storms, and into the rain and snow particles within clouds. It has also helped farmers trying to increase crop yields, and aided researchers predicting the spread of fires.

In honor of GPM’s fifth anniversary, we’re highlighting some of our favorite and most unique Earth Observatory stories, as made possible by measurements taken by GPM.

Credit: NASA

The Second Wettest October in Texas Ever

In Fall 2018, storm after storm rolled through and dumped record rainfall in parts of Texas. When Hurricane Willa hit Texas around October 24, the ground was already soaked. One particularly potent cold front in mid-October dropped more than a foot of rain in areas. By the end of the month, October 2018 was the second wettest month in Texas on record.

Read the full story, “Rainy October Soaks Texas

GPM measured the total amount of rainfall over the region from October 1 to October 31, 2018. The brightest areas reflect the highest rainfall amounts, with many places receiving 25 to 45 centimeters (10 to 17 inches) or more during this period. The satellite imagery can also be seen from natural-color satellite imagery.

Observing Rivers in the Air

With the GPM mission’s global vantage point, we can more clearly see how weather systems form and connect with one another. In this visualization from October 11-22, 2017, note the long, narrow bands of moisture in the air, known as “atmospheric rivers.” These streams are fairly common in the Pacific Northwest and frequently bring much of the region’s heavy rains and snow in the fall and winter. But this atmospheric river was unusual for its length—extending roughly 8,000 kilometers (5,000 miles) from Japan to Washington. That’s about two to three times the typical length of an atmospheric river.

Read the full story, “A River of Rain Connecting Asia and North America

Since atmospheric rivers often bring strong winds, they can force moisture up and over mountain ranges and drop a lot of precipitation in the process. In this case, more than four inches of rain fell on the western slopes of the Olympic Mountains and the Cascade Range, while areas to the east of the mountains (in the rain shadow) generally saw less than one inch.

Increasing Crop Yield for Farmers in Pakistan

Knowing how much precipitation is falling or has fallen is useful for people around the world. Farmers, in particular, are interested in knowing precipitation amounts so they can prevent overwatering or underwatering their crops.

The Sustainability, Satellites, Water, and Environment (SASWE) research group at the University of Washington has been working with the Pakistan Council of Research in Water Resources (PCRWR) to bring this kind of valuable information directly to the cell phones of farmers. A survey by the PCRWR found that farmers who used the text message alerts reported a 40 percent savings in water. Anecdotally, many farmers say their income has doubled because they got more crops by applying the correct amount of water.

Read the full story, “Smart Phones Bring Smart Irrigation

The map above shows the forecast for evapotranspiration for October 16-22, 2018. Evapotranspiration is an indication of the amount of water vapor being removed by sunlight and wind from the soil and from plant leaves. It is calculated from data on temperature, humidity, wind speed, and solar radiation, as well as a global numerical weather model that assimilates NASA satellite data. The team also looks at maps of precipitation, temperature and wind speed to help determine crop conditions. Precipitation data comes from GPM that is combined with ground-based measurements from the Pakistan Meteorological Department.

Forecasting Fire

Precipitation can drastically affect the spread of a fire. For instance, if a region has not received normal precipitation for weeks or months, the vegetation might be drier and more prone to catching fire. 

NASA researchers recently created a model that analyzes various weather factors that lead to the formation and spread of fires. The Global Fire Weather Database (GFWED) accounts for local winds, temperatures, and humidity, while also being the first fire prediction model to include satellite–based precipitation measurements.

Read the full story, “Forecasting Fire

The animation above shows GFWED’s calculated fire danger around the world from 2015 to 2017. The model compiles and analyzes various data sets and produces a rating that indicates how likely and intense fire might become in a particular area. It is the same type of rating that many firefighting agencies use in their day–to–day operations. Historical data are available to understand the weather conditions under which fires have occurred in the past, and near–real–time data are available to gauge current fire danger.

Automatically Detecting Landslides

In this mountainous country of Nepal, 60 to 80 percent of the annual precipitation falls during the monsoon (roughly June to August). That’s also when roughly 90 percent of Nepal’s landslide fatalities occur. NASA researchers have designed an automated system to identify potential landslides that might otherwise go undetected and unreported. This information could significantly improve landslide inventories, leading to better risk management.

The computer program works by scanning satellite imagery for signs that a landslide may have occurred recently, looking at topographical features such as hill slopes.

Read the full story, “Automating the Detection of Landslides

The left and middle images above were acquired by the Landsat 8 satellite on September 15, 2013, and September 18, 2014—before and after the Jure landslide in Nepal on August 2, 2014. The image on the right shows that 2014 Landsat image processed with computer program. The red areas show most of the traits of a landslide, while yellow areas exhibit a few of the proxy traits.

The program also uses data from GPM to help pin when each landslide occurred. The GPM core satellite measures rain and snow several times daily, allowing researchers to create maps of rain accumulation over 24-, 48-, and 72-hour periods for given areas of interest—a product they call Detecting Real-time Increased Precipitation, or DRIP. When a certain amount of rain has fallen in a region, an email can be sent to emergency responders and other interested parties.


The GPM Core Observatory is a joint satellite project by NASA and the Japan Aerospace Exploration Agency. The satellite is part of the larger GPM mission, which consists of about a dozen international satellite partners to provide global observations of rain and snow.

To learn more about GPM’s accomplishments over the past five years, visit: https://pmm.nasa.gov/resources/featured-articles-archive

To learn more about the GPM mission, visit: https://www.nasa.gov/mission_pages/GPM/main/index.html

Highlights from The Earth Observer

November 7th, 2018 by Adam Voiland

A new edition of The Earth Observer, a bi-monthly publication that covers the nuts-and-bolts of NASA’s Earth Observing System, is out. Here are a few excerpts, along with some musical headlines that may get you humming as you read. You can download the full issue here. Back issues here.

ICE ICE BABY
The Advanced Topographic Laser Altimeter System (ATLAS), the lone instrument on ICESat-2, successfully fired its laser on September 30 after the mission operations team completed testing of the spacecraft and opened the door protecting the optics. The primary science mission for ICESat-2 is to gather enough observations to estimate the annual height change of the Greenland and Antarctic ice sheets to within four millimeters. Hundreds of billions of tons of land ice melt into the ocean annually, raising sea levels worldwide. In recent years, meltwater from Greenland and Antarctica alone has raised global sea level by more than a millimeter a year, and the rate is increasing.

THIS LANDSAT IS YOUR LANDSAT
In January 2008, the U.S. Geological Survey and NASA decided to open the full Landsat image archive for public access on a non discriminatory, no-cost basis. This change in Landsat’s data policy ushered in a new era of Landsat data uses and applications while also revolutionizing the way Landsat has been woven into scientific discovery, economic prosperity, and public policy for management of land and water resources across a range of scales.

DEVELOPING SATELLITE SKILLS FOR 525,600 MINUTES (TIMES TWENTY)
From 1998 to the current 2018 fall term, the NASA DEVELOP National Program has engaged 4,671 participants who have conducted 931 projects. The program bridges the gap between science and society by demonstrating how NASA Earth Science data can be applied to environmental decision making. These projects have demonstrated the applications of NASA Earth observations to a wide variety of sectors, addressing topics such as drought monitoring, vector-borne disease risk, water-quality assessments, pre- and post-wildfire mapping, agriculture monitoring, and critical habitat identification.

I CAN SEE CLEARLY NOW

The first Earth Science Decadal Survey identified CLARREO as a Tier-1 (i.e., highest) priority mission for development. The CLARREO Pre-Formulation Mission, referred to herein as the “Full” CLARREO mission, was recommended to better understand climate change. The foundation of CLARREO is the ability to produce highly accurate climate records to test climate projections in order to improve models and enable sound policy decisions.

If there was ever a satellite that deserves an award for longevity, it’s Terra. Designed for a mission of 6 years (or 30,000 orbits), the bus-sized spacecraft continues to cruise 705 kilometers (438 miles) above Earth’s surface nearly 19 years after launch. The spacecraft officially surpassed 100,000 orbits on October 6, 2018. To celebrate, here are ten things to know about the intrepid Earth-observing satellite. Click on each image to find out more.

1. Terra had to be designed from scratch. Unlike many of the smaller satellites that preceded it, engineers couldn’t riff off of an existing design.

 


2. The bus-sized spacecraft carries five scientific sensors — MODIS, MOPITT, MISR, ASTER, and CERES. All of them continue to send back useful data.

 

3. The MODIS sensor captures stunning images of hurricanes, wildfires, volcanoes, dust storms, oil spills, and other hazards.

 

4. Using MOPITT, atmospheric scientists have tracked global trends in carbon monoxide for nearly two decades. The good news: concentrations of the toxic air pollutant are declining.

 

5. Likewise, they have used the CERES sensor to measure whether Earth’s reflectivity—or albedo—has changed. Despite some fluctuations, there does not appear to be a trend.

 


6. The MISR sensor can detect the height of volcanic plumes, smoke plumes, dust plumes, and other aerosols. This is key to understanding where plumes will go and whether they will pose a threat to people on the ground.

 


7. Terra orbits 705 kilometers (438 miles) above the surface, about the distance between Boston, MA, and Washington, D.C.

 


8. A widely used global digital elevation map is based on data collected by ASTER.

 


9. Experts use Terra MODIS observations of NDVI — a measure of the greenness of plants — to help anticipate food shortages.

 

10. While in space, Terra has traveled the equivalent of 2.5 billion miles — nearly the distance to Neptune.

NASA has funded five new projects to develop tools and technology to make the agency’s massive Earth science datasets more accessible and user-friendly.

Wake up. Turn on laptop. Start processing airborne data of the Adirondack forests in New York. Make Coffee. Eat Breakfast. Fasten the open laptop’s seatbelt in the passenger seat as it continues to crunch numbers. Drive to work.

NASA Earth science datasets provide different perspectives and information on our planet, as seen here in this data visualization of observations of Hurricane Matthew in October 2016. Credits: NASA’s Scientific Visualization Studio

That used to be Sara Lubkin’s morning routine as an early career scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Once at work, she would use her desktop computer, while her laptop diligently spent the next 12 hours processing airborne instrument data for the relevant information she needed to study invasive pests of hemlock trees.

“I’m not a computer scientist, I’m an Earth scientist,” said Lubkin, who now works as a program officer for NASA Earth Science Data Systems’ Advancing Collaborative Connections for Earth Systems Science, or ACCESS program. But her experience as a researcher is not unique.

Spending large chunks of time simply getting Earth science data into a usable form for analysis is a common situation for researchers working with the big datasets that come from NASA field, airborne and satellite missions. Downloading huge files, converting data formats, locating the same study areas in multiple datasets, writing code to distinguish different land types in a satellite image – these types of tasks eat into time scientists would rather be using to analyze the actual information in the data.

That’s where the ACCESS program comes in. Part of the Earth Science Data Systems division since 2005, ACCESS finds innovative ways to streamline that cumbersome processing time. The program funds two-year research projects to improve behind-the-scenes data management and provide ready-to-use datasets and services to scientists, Lubkin said.

Sara Lubkin worked with NASA’s big data sets studying invasive pests in Adirondack hemlock trees as part of NASA’s Applied Sciences DEVELOP program, which addresses environmental and public policy issues through interdisciplinary research projects that apply the lens of NASA Earth observations to community concerns around the globe. Credit: Sara Lubkin

In June, NASA selected five teams of NASA, university and commercial computer science researchers from the 2017 round of submissions in a range of projects that will use machine learning, cloud computing and advanced search capabilities to develop tools to improve the behind-the-scenes management for selected NASA datasets.

“We continually invest in development and evaluation of the newest technologies to improve science data systems,” said Kevin Murphy, program executive for NASA’s Earth Science Data Systems at NASA Headquarters in Washington. But more than that, they want to make sure that the tools and technology help real scientists address real problems.

Each ACCESS project has Earth scientists and computer scientists involved from beginning to end, Murphy said. “With the ACCESS program, we’re really trying to understand, for example, how ocean currents work, but we’re trying to do that now with data that’s so large that we need a team of experts who can work together to solve the big science and big data questions.”

The projects will complement data management, distribution and other services provided by the Earth Observing System Data and Information System (EOSDIS), which manages and stores NASA data collected from Earth-observing satellites, aircraft and field campaigns. EOSDIS has 12 interconnected data and archive centers located across the United States, which are organized by discipline. Currently, these centers host 26 petabytes of Earth datasets – that’s 26 million gigabytes, or enough data to need 52,000 computers each with 500 gigabytes of storage space. That number is expected to grow to 150 petabytes within five years with the launch of new satellites.

“Satellite data is big data,” said Jeff Walter, one of the ACCESS 2017 principal investigators and lead engineer for Science Data Services at the Atmospheric Science Data Center at NASA’s Langley Research Center in Hampton, Virginia. “It’s very complex and sometimes difficult to use, even for expert users. In addition to the volume, which makes it difficult for users to acquire, store and manage, there’s also the complexity of both the format and content. Users often have to spend a lot of time understanding how the data is organized and what the various parameters represent.”

Walter’s project is one of three that will use cloud computing to alleviate download and storage issues for users. Starting with two atmospheric datasets, his team will also be developing a way to convert satellite data formats into those that can be read by commercial geospatial information system (GIS) software.

“Our project aims to lower the barrier to entry for a potential new user community who might find novel ways to use this data, and who are more familiar with GIS types of tools,” Walter said.

The two other cloud computing projects will be developing open source processing and analysis tools, including one designed for ocean datasets. A fourth project will use machine learning to detect changes over time in land observations, starting with the detection of landslides, floods and uplift caused by volcanic activity. The fifth project will develop an automated method for lining up datasets that observe the same location so researchers can combine more than one type of information about a place.

NASA has 26 Earth-observing satellites monitoring the vital signs of our home planet. Along with airborne and ground Earth science missions, their data is stored and managed by the Earth Observing System Data and Information System. Credit: NASA

Upon completion, the ACCESS researchers will work closely with EOSDIS teams to incorporate their advancements into the data centers’ day-to-day operations. Once those new tools are in place, that’s when the real power of open and freely available Earth science datasets can flourish, according to Murphy. Easy-to-use data means it gets into the hands of decision-makers, non-governmental organizations, scientists studying related applications and researchers in different fields that may have new uses for it.

“When you make these products open and accessible, you have a lot of unintended, good scientific consequences,” Murphy said, citing examples that include detecting groundwater movement from space, rapid wildfire detection and using night lights to study human energy use. “NASA has a lot of very valuable information, and the ACCESS program really tries to help scientists to not only address primary science questions but also help us understand our environment and plan for our future.”

To learn more about ACCESS, visit https://earthdata.nasa.gov/community/community-data-system-programs/access-projects

To learn more about NASA’s Earth Science Data Systems, visit https://earthdata.nasa.gov/

The Sounds of Satellites

June 28th, 2018 by Adam Voiland

Orbit Pavilion. Image courtesy of NASA/Jet Propulsion Laboratory-Caltech/The Studio/Dan Goods

Sure, space may be silent, or at least absent the sound waves that human ears can hear. But put that aside for a moment, and try to imagine the sound of a satellite orbiting hundreds of miles above Earth’s surface.

Now imagine 19 sounds for 19 Earth-observing satellites — the murmur of ocean waves for a spacecraft that studies the oceans, or the howl of winds for one that studies hurricanes. Then swirl all of those sounds into a shell-shaped silver sculpture that looks like something from a sci-fi film.

Put the shell at the Huntington Library in southern California, walk inside, and you have Orbit Pavilion — an immersive piece of art and science communication designed to envelop people in sounds that represents the orbital movements of NASA’s fleet of Earth-observing satellites.

Dan Goods and David Delgado, artists working at The Studio at NASA Jet Propulsion Laboratory, initially developed the sound concept. They commissioned sound artist Shane Myrbeck to compose the soundscape, and Jason Klimoski and Lesley Chang of StudioKCA to envision and design a form.

Myrbeck describes the pavilion’s soundscape this way:

“The piece is in two parts, each with one sound following the path of a satellite. One section demonstrates the movement of the satellites by compressing a day’s worth of trajectory data into one minute, so listeners are enveloped by a symphony of 19 sounds swirling around them. The other section represents the real-time position of the spacecraft: each satellite currently in our hemisphere will “speak” in sequence, and when a sound is playing, if a listener points to the direction of the sound, they are pointing to the satellite orbiting hundreds of miles above us….These satellites are all part of Earth science missions, studying our atmosphere, oceans, and geology — they are helping us better understand how our planet is changing, and potentially how we can be better stewards of it. In that way I see them as kind of sentinels or protectors.”

The result, as Myrebeck had hoped, is both enveloping and comforting.

Information about the orbits of 17 satellites and two sensors on the International Space Station feed into the Orbit Pavilion. Image Credit: StudioKCA

The current fleet of Earth-observing satellites. Image Credit: NASA/EOSPSO

For a deeper dive into the diversity of the data these satellites collect, try searching a satellite’s name on Visible Earth. Or browse NASA Earth Observatory’s global maps sections and Image of the Day archive.

For instance, the map below helped me understand our planet a little bit better. It depicts more than a decade of cloudiness data as observed by the MODIS sensor. Blue shows areas where clouds were infrequent; white indicates areas where they were common.

Image Credit: NASA Earth Observatory, based on data from MODIS.

Making a Map of Water and Ice

May 23rd, 2018 by NASA Earth Science News Team

This is a cross-post of a story by Ellen Gray. It provides deeper insight into our May 23 Image of the Day.

Ominous beginning: Garbage data from a new satellite

Six months after GRACE launched in March 2002, we got our first look at the data fields. They had these big vertical, pole-to-pole stripes that obscured everything. We’re like, holy cow this is garbage. All this work and it’s going to be useless.

But it didn’t take the science team long to realize that they could use some pretty common data filters to remove the noise, and after that they were able to clean up the fields and we could see quite a bit more of the signal. We definitely breathed a sigh of relief. Steadily over the course of the mission, the science team became better and better at processing the data, removing errors, and some of the features came into focus. Then it became clear that we could do useful things with it.

And then trends emerged

It only took a couple of years. By 2004, 2005, the science team working on mass changes in the Arctic and Antarctic could see the ice sheet depletion of Greenland and Antarctica. We’d never been able before to get the total mass change of ice being lost. It was always the elevation changes – there’s this much ice, we guess – but this was like wow, this is the real number.

Not long after that we started to see, maybe, that there were some trends on the land, although it’s a little harder on the land because with terrestrial water storage — the groundwater, soil moisture, snow, and everything. There’s inter-annual variability, so if you go from a drought one year to wet a couple years later, it will look like you’re gaining all this water, but really, it’s just natural variability.

By around 2006, there was a pretty clear trend over Northern India. At the GRACE science team meeting, it turned out another group had noticed that as well. We were friendly with them, so we decided to work on it separately. Our research ended up being published in 2009, a couple years after the trends had started to become apparent. By the time we looked at India, we knew that there were other trends around the world. Slowly not just our team but all sorts of teams, all different scientists around the world, were looking at different apparent trends and diagnosing them and trying to decide if they were real and what was causing them.

A world of big blobs of red and blue

I think the map, the global trends map, is the key. By 2010 we were getting the broad-brush outline, and I wanted to tell a story about what is happening in that map. For me the easiest way was to just look at the data around the continents and talk about the major blobs of red or blue that you see and explain each one of them and not worry about what country it’s in or placing it in a climate region or whatever. We can just draw an outline around these big blobs. Water is being gained or lost. The possible explanations are not that difficult to understand. It’s just trying to figure out which one is right.

Not everywhere you see as red or blue on the map is a real trend. It could be natural variability in part of the cycle where freshwater is increasing or decreasing. But some of the blobs were real trends. If it’s lined up in a place where we know that there’s a lot of agriculture, that they’re using a lot of water for irrigation, there’s a good chance it’s a decreasing trend that’s caused by human-induced groundwater depletion.

And then, there’s the question: are any of the changes related to climate change? There have been predictions of precipitation changes, that they’re going to get more precipitation in the high latitudes and more precipitation as rain as opposed to snow. Sometimes people say that the wet get wetter and the dry get dryer. That’s not always the case, but we’ve been looking for that sort of thing. These are large-scale features that are observed by a relatively new satellite system and we’re lucky enough to be some of the first to try and explain them.

What kept me up at night

The past couple years when I’d been working the most intensely on the map, the best parts of my time in the office were when I was working on it. Because I’m a lab chief, I spend about half my time on managerial and administrative things. But I love being able to do the science, and in particular this, looking at the GRACE data, trying to diagnose what’s happening, has been very enjoyable and fulfilling. We’ve been scrutinizing this map going on eight, nine years now, and I really do have a strong connection to it.

What kept me up at night was finding the right explanations and the evidence to support our hypotheses – or evidence to say that this hypothesis is wrong and we need to consider something else. In some cases, you have a strong feeling you know what’s happening but there’s no published paper or data that supports it. Or maybe there is anecdotal evidence or a map that corroborates what you think but is not enough to quantify it. So being able to come up with defendable explanations is what kept me up at night. I knew the reviewers, rightly, couldn’t let us just go and be completely speculative. We have to back up everything we say.

A tangled mix of answers

The world is a complicated place. I think it helped, in the end, that we categorized these changes as natural variability or as a direct human impact or a climate change related impact. But then there can be a mix of those – any of those three can be combined, and when they’re combined, that’s when it’s more difficult to disentangle them and say this one is dominant or whatever. It’s often not obvious. Because these are moving parts and particularly with the natural variability, you know it’s going to take another 15 years, probably the length of the GRACE Follow-On mission, before we become completely confident about some of these. So it’ll be interesting to return to this in 15 years and see which ones we got right and which ones we got wrong.

You can read about Matt’s research here: https://go.nasa.gov/2L7LXoP.

Explore Earth Your Way

April 19th, 2018 by Jennifer Brennan

Today’s blog is re-posted from NASA.gov in recognition of the agency’s Earth Day activities.

NASA’s Worldview app lets you explore Earth as it looks right now or as it looked almost 20 years ago. See a view you like? Take a snapshot and share your map with a friend or colleague. Want to track the spread of a wildfire? You can even create an animated GIF to see change over time.

Through an easy-to-use map interface, you can watch tropical storms developing over the Pacific Ocean; track the movement of icebergs after they calve from glaciers and ice shelves; and see wildfires spread and grow as they burn vegetation in their path. Pan and zoom to your region of the world to see not only what it looks like today, but to investigate changes over time. Worldview’s nighttime lights layers provide a truly unique perspective of our planet.

What else can you do with Worldview? Add imagery by discipline, natural hazard, or key word to learn more about what’s happening on this dynamic planet. View Earth’s frozen regions with the Arctic and Antarctic views. Take a look at current natural events like tropical storms, volcanic eruptions, wildfires, and icebergs at the touch of a button using the “events” tab.

https://worldview.earthdata.nasa.gov

Worldview is an open-source project at NASA. All data, software, and services are freely available to anyone for any purpose.  You can participate in the software development by visiting:

https://github.com/nasa-gibs/worldview.

In Case You Missed It – Dance of a Melting Snowflake

April 13th, 2018 by Mike Carlowicz

Today’s post is a reprint of recent story by Carol Rasmussen of NASA’s Earth Science News Team.

NASA has produced the first three-dimensional numerical model of melting snowflakes in the atmosphere. Developed by scientist Jussi Leinonen of NASA’s Jet Propulsion Laboratory, the model provides a better understanding of how snow melts. This can help scientists recognize the signature (in radar signals) of heavier, wetter snow the kind that snaps power lines and tree limbs and could be a step toward improving predictions of this hazard.

Leinonen’s model reproduces key features of melting snowflakes that have been observed in nature. First, meltwater gathers in any concave regions of the snowflake’s surface. These liquid-water regions then merge to form a shell of liquid around an ice core, and finally develop into a water drop. The modeled snowflake shown in the video is less than half an inch (one centimeter) long and composed of many individual ice crystals whose arms became entangled when they collided in midair.

Leinonen said he got interested in modeling melting snow because of the way it affects observations with remote sensing instruments. A radar “profile” of the atmosphere from top to bottom shows a very bright, prominent layer at the altitude where falling snow and hail melt much brighter than atmospheric layers above and below it. “The reasons for this layer are still not particularly clear, and there has been a bit of debate in the community,” Leinonen said. Simpler models can reproduce the bright melt layer, but a more detailed model like this one can help scientists to understand it better, particularly how the layer is related to both the type of melting snow and the radar wavelengths used to observe it.

A paper on the numerical model, titled “Snowflake melting simulation using smoothed particle hydrodynamics,” recently appeared in the Journal of Geophysical Research – Atmospheres.