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By NASA
4 min read
NASA Satellites Reveal Abrupt Drop in Global Freshwater Levels
Earth (ESD) Earth Home Explore Climate Change Science in Action Multimedia Data For Researchers GRACE satellites measure gravity as they orbit the planet to reveal shifting levels of water on the Earth (artist’s concept). NASA/JPL-Caltech An international team of scientists using observations from NASA-German satellites found evidence that Earth’s total amount of freshwater dropped abruptly starting in May 2014 and has remained low ever since. Reporting in Surveys in Geophysics, the researchers suggested the shift could indicate Earth’s continents have entered a persistently drier phase.
From 2015 through 2023, satellite measurements showed that the average amount of freshwater stored on land — that includes liquid surface water like lakes and rivers, plus water in aquifers underground — was 290 cubic miles (1,200 cubic km) lower than the average levels from 2002 through 2014, said Matthew Rodell, one of the study authors and a hydrologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “That’s two and a half times the volume of Lake Erie lost.”
During times of drought, along with the modern expansion of irrigated agriculture, farms and cities must rely more heavily on groundwater, which can lead to a cycle of declining underground water supplies: freshwater supplies become depleted, rain and snow fail to replenish them, and more groundwater is pumped. The reduction in available water puts a strain on farmers and communities, potentially leading to famine, conflicts, poverty, and an increased risk of disease when people turn to contaminated water sources, according to a UN report on water stress published in 2024.
The team of researchers identified this abrupt, global decrease in freshwater using observations from the Gravity Recovery and Climate Experiment (GRACE) satellites, operated by the German Aerospace Center, German Research Centre for Geosciences, and NASA. GRACE satellites measure fluctuations in Earth’s gravity on monthly scales that reveal changes in the mass of water on and under the ground. The original GRACE satellites flew from March 2002 to October 2017. The successor GRACE–Follow On (GRACE–FO) satellites launched in May 2018.
This map shows the years that terrestrial water storage hit a 22-year minimum (i.e., the land was driest) at each location, based on data from the GRACE and GRACE/FO satellites. A significantly large portion of the global land surface reached this minimum in the nine years since 2015, which happen to be the nine warmest years in the modern temperature record. Image by NASA Earth Observatory/Wanmei Liang with data courtesy of Mary Michael O’Neill The decline in global freshwater reported in the study began with a massive drought in northern and central Brazil, and was followed shortly by a series of major droughts in Australasia, South America, North America, Europe, and Africa. Warmer ocean temperatures in the tropical Pacific from late 2014 into 2016, culminating in one of the most significant El Niño events since 1950, led to shifts in atmospheric jet streams that altered weather and rainfall patterns around the world. However, even after El Niño subsided, global freshwater failed to rebound. In fact, Rodell and team report that 13 of the world’s 30 most intense droughts observed by GRACE occurred since January 2015. Rodell and colleagues suspect that global warming might be contributing to the enduring freshwater depletion.
Global warming leads the atmosphere to hold more water vapor, which results in more extreme precipitation, said NASA Goddard meteorologist Michael Bosilovich. While total annual rain and snowfall levels may not change dramatically, long periods between intense precipitation events allow the soil to dry and become more compact. That decreases the amount of water the ground can absorb when it does rain.
“The problem when you have extreme precipitation,” Bosilovich said, “is the water ends up running off,” instead of soaking in and replenishing groundwater stores. Globally, freshwater levels have stayed consistently low since the 2014-2016 El Niño, while more water remains trapped in the atmosphere as water vapor. “Warming temperatures increase both the evaporation of water from the surface to the atmosphere, and the water-holding capacity of the atmosphere, increasing the frequency and intensity of drought conditions,” he noted.
While there are reasons to suspect that the abrupt drop in freshwater is largely due to global warming, it can be difficult to definitively link the two, said Susanna Werth, a hydrologist and remote sensing scientist at Virginia Tech, who was not affiliated with the study. “There are uncertainties in climate predictions,” Werth said. “Measurements and models always come with errors.”
It remains to be seen whether global freshwater will rebound to pre-2015 values, hold steady, or resume its decline. Considering that the nine warmest years in the modern temperature record coincided with the abrupt freshwater decline, Rodell said, “We don’t think this is a coincidence, and it could be a harbinger of what’s to come.”
By James R. Riordon
NASA’s Earth Science News Team
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Last Updated Nov 15, 2024 Editor James Riordon Contact James Riordon james.r.riordon@nasa.gov Location NASA Goddard Space Flight Center Related Terms
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By NASA
2 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
About 20,000 guests visited NASA’s tent at the Miramar Air Show in San Diego, California, Sept. 27-29, 2024. NASA Lee esta historia en Español aquí.
In September, the three NASA centers in California came together to share aerospace innovations with thousands of guests at the Miramar Air Show in San Diego, California. Agency experts talked about the exciting work NASA does while exploring the secrets of the universe for the benefit of all.
Under a large tent near the airfield, guests perused exhibits from different centers and projects, like a model of the Innovator rover or the Alta-X drone, from Sept. 27 through 29. Agency employees from NASA’s Armstrong Flight Research Center in Edwards, California; Ames Research Center in Moffett Field, California; and Jet Propulsion Laboratory (JPL) in Southern California guided guests through tours and presentations and shared messages about NASA missions.
“The airshow is about the people just as much as it is about the aircraft and technology,” said Derek Abramson, chief engineer for the Subscale Flight Research Laboratory at NASA Armstrong. “I met many new people, worked with an amazing team, and developed a comradery with other NASA centers, talking about what we do here as a cohesive organization.”
Experts like flight controls engineer Felipe Valdez shared the NASA mission with air show guests, and explained the novelty of airborne instruments like the Alta-X drone at the Miramar Air Show in San Diego, California, Sept. 27-29, 2024.NASA On Sept. 29, pilots from Armstrong joined the event to take photos with guests and answer questions from curious or enthusiastic patrons. One air show guest had a special moment with NASA pilot Jim Less.
“One of my favorite moments was connecting with a young man in his late teens who stopped by the exhibit tent numerous times, all in hopes of being able to meet Jim Less, our X-59 pilot,” said Kevin Rohrer, chief of Communications at NASA Armstrong. “It culminated with a great conversation with the two and Jim [Less] autographing a model of the X-59 aircraft the young man had been carrying around.”
“I look forward to this tradition continuing, if not at this venue, at some other event in California,” Rohrer continued. “We have a lot of minds hungry and passionate to learn more about all of NASA missions.”
The Miramar Air Show is an annual event that happens at the Miramar Air Base in San Diego, California.
Professionals like Leticha Hawkinson, center right, and Haig Arakelian, center left, shared learning and career opportunities for NASA enthusiasts visiting the Miramar Air Show in San Diego, California, Sept. 27-29, 2024.NASA Share
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Last Updated Oct 30, 2024 EditorDede DiniusContactErica HeimLocationArmstrong Flight Research Center Related Terms
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By NASA
A mentor of research scientist Meloë Kacenelenbogen once shared a sentiment from French author André Gide: “You cannot discover new oceans unless you have the courage to lose sight of the shore.” Kacenelenbogen pushes beyond her comfort zone to explore the unknown.
Name: Meloë S. Kacenelenbogen
Formal Job Classification: Research scientist
Organization: Climate and Radiation Laboratory, Science Directorate (Code 613)
Dr. Meloë S. Kacenelenbogen is a research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. She studies the impact of aerosols on air quality and the Earth’s climate.Photo courtesy of Meloë Kacenelenbogen What do you do and what is most interesting about your role here at Goddard?
I study the impact of aerosols — suspended particles from, for example, wildfire smoke, desert dust, urban pollution, and volcanic eruptions — on air quality and the Earth’s climate. I use space, air, and ground-based observations, as well as models.
Why did you become a scientist? What is your educational background?
I never made a deliberate choice to become a scientist. I started with very little confidence as a child and then built up my confidence by achieving things I thought I could not do. I chose the hardest fields to work on along the way. Science looked hard and so did fluid mechanics, remote sensing, and atmospheric physics. I have failed many times, but I always learn something and move on. I do get scared and maybe even paralyzed for a day or two, but I never let fear or failure immobilize me for long.
I was born in Maryland, but my family moved to France when I was young, so I am fluent in French. I have a bachelor’s and master’s degree in mechanical engineering, and physical methods in remote sensing from the Université Pierre et Marie Curie (Paris VI, Jussieu). In 2008, I got a Ph.D. in atmospheric physics for applying satellite remote sensing to air quality at the Université des Sciences et Technologies de Lille (USTL), France.
What are some of your career highlights?
After my Ph.D., I worked for the Atmospheric Lidar Group at the University of Maryland, Baltimore County (UMBC), on spaceborne and ground-based lidars. In 2009, I got a NASA Post-doctoral Program (NPP) fellowship at the agency’s Ames Research Center in California’s Silicon Valley, where I worked for 13 years on space-based, aircraft-based, and ground-based atmospheric aerosol vertical distribution and aerosol typing.
In 2022, I came to work at the Climate and Radiation Lab at Goddard.
What is most interesting about aerosols?
Aerosols are very topical because they have a huge impact on the air we breathe and our Earth’s climate. The smaller the aerosol, the deeper it can get into our lungs. Among other sources, aerosols can come from cars, factories, or wildfires. We all know that wildfires are becoming bigger and more frequent. They are expected to happen even more frequently in the future due to climate change. Both when I was living in California and here in Maryland, I have experienced first-hand choking from the wildfire smoke. I will always remember how apocalyptic it felt back in the summer of 2020 in California when wildfire smoke was paired with COVID confinement, and the sky turned Mars-like orange.
Please tell us about your involvement with the Atmosphere Observing System (AOS)?
I am incredibly lucky to be able to contribute to the next generation of NASA’s satellites. I am working on AOS, which will observe aerosols, clouds, convention, and precipitation in the Earth’s atmosphere. I am part of the team that is helping design several instruments and algorithms.
My role is to connect this spaceborne observing system to all our other space, ground, and air-based measurements at the time of launch. We are making a mesh of observations to address the science questions, run the algorithms, and validate the spaceborne measurements. I am constantly pushed to expand my horizon and my own knowledge.
Why do you enjoy always challenging yourself intellectually?
I started that way. I had no confidence, so I felt that the only way I could build my confidence was to try doing things that scared me. I may sometimes be a little scared, but I am never bored.
What did you learn from your mentors?
A few years ago, a mentor shared a quote from André Gide with me that encapsulates what we are talking about: “You cannot discover new oceans unless you have the courage to lose sight of the shore.” In other words, it is OK, maybe preferable, to be out of my comfort zone to explore the unknown as scary as it may be.
Along the way, it has been extremely important for me to deliberately choose mentors. To me, a good mentor has earned the respect of all who have worked with them, is uplifting, reassuring, and gives me the invaluable guidance and support that I need. I deliberately try to surround myself with the right people. I have been very, very fortunate to find incredible people to encourage me.
As a mentor, what do you advise?
I tell them to deliberately choose their mentors. I also tell them that it is OK to be uncomfortable. Being uncomfortable is the nature of our field. To do great things, we often need to be uncomfortable.
Why do you enjoy working on a team?
I love working on teams, I love to feed off the positive energy of a team whether I lead it or am part of it. In my field, teamwork with a positive energy is incredibly satisfying. Everybody feeds off everybody’s energy, we go further, are stronger, and achieve more. This may not happen often, but when it does it makes it all worth it.
What are the happiest moments in your career?
I am always happiest when the team publishes a paper and all our efforts, are encapsulated in that one well-wrapped and satisfying peer-reviewed paper that is then accessible to everyone online. Every paper we publish feels, to me, the same as a Ph.D. in terms of the work, pain, energy, and then, finally, satisfaction involved.
What do you hope to achieve in your career?
I want to have been a major contributor to the mission by the time the AOS satellites launch.
What do you do for fun?
I do mixed martial arts. I love the ocean, diving, and sailing. I also love going to art galleries, especially to see impressionist paintings to reconnect with my Parisian past.
Meloë Kacenelenbogen once shared a sentiment from French author André Gide: “You cannot discover new oceans unless you have the courage to lose sight of the shore.”Photo courtesy of Meloë Kacenelenbogen Who is your favorite author?
I love Zweig, Kafka, Dostoyevsky, Saint-Exupéry, and Kessel. The latter two wrote a lot about aviators in the early 1900s back in the days when it was new and very dangerous. Those pilots, like Mermoz, were my heroes growing up.
Who would you like to thank?
I would like to thank my family for being my rock.
What are your guiding principles?
To paraphrase Dostoevsky, everyone is responsible to all men for all men and for everything. I have a strong sense of purpose, pride, justice, and honor. This is how I try to live my life for better or for worse.
By Elizabeth M. Jarrell
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Conversations With Goddard is a collection of Q&A profiles highlighting the breadth and depth of NASA’s Goddard Space Flight Center’s talented and diverse workforce. The Conversations have been published twice a month on average since May 2011. Read past editions on Goddard’s “Our People” webpage.
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Last Updated Oct 22, 2024 EditorMadison OlsonContactRob Garnerrob.garner@nasa.govLocationGoddard Space Flight Center Related Terms
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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Clean air is essential for healthy living, but according to the World Health Organization (WHO), almost 99% of the global population breathes air exceeding their guideline limits of air pollution. “Air quality is a measure of how much stuff is in the air, which includes particulates and gaseous pollutants,” said Kristina Pistone, a research scientist at NASA Ames Research Center. Pistone’s research covers both atmospheric and climate areas, with a focus on the effect of atmospheric particles on climate and clouds. “It’s important to understand air quality because it affects your health and how well you can live your life and go about your day,” Pistone said. We sat down with Pistone to learn more about air quality and how it can have a noticeable impact on human health and the environment.
What makes up air quality?
There are six main air pollutants regulated by the Environmental Protection Agency (EPA) in the United States: particulate matter (PM), nitrogen oxides, ozone, sulfur oxides, carbon monoxide, and lead. These pollutants come from from natural sources, such as the particulate matter that rises into the atmosphere from fires and desert dust, or from human activity, such as the ozone generated from sunlight reacting to vehicle emissions.
Satellite image showing wildfire smoke drifting down from Canada into the American Midwest, captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on June 09, 2015. NASA/Jeff Schmaltz
What is the importance of air quality?
Air quality influences health and quality of life. “Just like we need to ingest water, we need to breathe air,” Pistone said. “We have come to expect clean water because we understand that we need it to live and be healthy, and we should expect the same from our air.”
Poor air quality has been tied to cardiovascular and respiratory effects in humans. Short-term exposure to nitrogen dioxide (NO2), for example, can cause respiratory symptoms like coughing and wheezing, and long-term exposure increases the risk of developing respiratory diseases such as asthma or respiratory infections. Exposure to ozone can aggravate the lungs and damage the airways. Exposure to PM2.5 (particulates 2.5 micrometers or smaller) causes lung irritation and has been linked to heart and lung diseases.
In addition to its impacts on human health, poor air quality can damage the environment, polluting bodies of water through acidification and eutrophication. These processes kill plants, deplete soil nutrients, and harm animals.
Measuring Air Quality: the Air Quality Index (AQI)
Air quality is similar to the weather; it can change quickly, even within a matter of hours. To measure and report on air quality, the EPA uses the United States Air Quality Index (AQI). The AQI is calculated by measuring each of the six primary air pollutants on a scale from “Good” to “Hazardous,” to produce a combined AQI numeric value 0-500.
“Usually when we’re talking about air quality, we’re saying that there are things in the atmosphere that we know are not good for humans to be breathing all the time,” Pistone said. “So to have good air quality, you need to be below a certain threshold of pollution.” Localities around the world use different thresholds for “good” air quality, which is often dependent on which pollutants their system measures. In the EPA’s system, an AQI value of 50 or lower is considered good, while 51-100 is considered moderate. An AQI value between 100 and 150 is considered unhealthy for sensitive groups, and higher values are unhealthy to everyone; a health alert is issued when the AQI reaches 200. Any value over 300 is considered hazardous, and is frequently associated with particulate pollution from wildfires.
NASA Air Quality Research and Data Products
Air quality sensors are a valuable resource for capturing air quality data on a local level.
In 2022, the Trace Gas GRoup (TGGR) at NASA Ames Research Center deployed Inexpensive Network Sensor Technology for Exploring Pollution, or INSTEP: a new network of low-cost air quality sensors that measures a variety of pollutants. These sensors are capturing air quality data in certain areas in California, Colorado, and Mongolia, and have proven advantageous for monitoring air quality during California’s fire season.
The 2024 Airborne and Satellite Investigation of Asian Air Quality (ASIA-AQ) mission integrated sensor data from aircraft, satellites, and ground-based platforms to evaluate air quality over several countries in Asia. The data captured from multiple instruments on these flights, such as the Meteorological Measurement System (MMS) from NASA Ames Atmospheric Science Branch, are used to refine air quality models to forecast and assess air quality conditions.
Agency-wide, NASA has a range of Earth-observing satellites and other technology to capture and report air quality data. In 2023, NASA launched the Tropospheric Emissions: Monitoring of Pollution (TEMPO) mission, which measures air quality and pollution over North America. NASA’s Land, Atmosphere Near real-time Capability for Earth Observations (LANCE) tool provides air quality forecasters with measurements compiled from a multitude of NASA instruments, within three hours of its observation.
Nitrogen dioxide levels over the D.C./Philadelphia/New York City region measured by TEMPO.NASA/Scientific Visualization Studio
Air Quality Resources to Learn More
In addition to the EPA’s website, which houses air-quality related sources, the EPA also has a platform called AirNow, which reports the local AQI across the United States and allows users to check air quality levels in their area. Pistone also recommends looking at Purple Air’s real-time map, which displays PM data taken from a crowd-sourced network of low-cost sensors and translates those measurements to estimate AQI. For those concerned about air quality, Pistone recommends checking out https://cleanaircrew.org/ for resources on indoor air quality, breathing safely with wildfire smoke, and even building your own box fan filter.
To learn more about air quality research applications, see NASA’s Applied Sciences Program’s Health & Air Quality program area, which details the use of Earth observations to assess and address air quality concerns at local, regional, and national levels. Additionally, the NASA Health and Air Quality Applied Sciences Team (HAQAST) helps connect NASA data and tools with stakeholders to better share and understand the effects of air quality on human health.
Written by Katera Lee, NASA Ames Research Center
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Last Updated Oct 18, 2024 Related Terms
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