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OpenET Moisture Measurement Tool is Proving Highly Accurate


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OpenET Moisture Measurement Tool is Proving Highly Accurate

This satellite image centers the meandering Sacramento river surrounded by rice fields. The fields are broken into primarily square and rectangular areas with the fields nearest the river being full of green and brown vegetation, and farther from the river they are flooded and appear dark blue.
This is a false-color image, acquired December 26, 2018, with the OLI (Operational Land Imager) on Landsat 8, and shows flooded rice fields along the Sacramento and Feather Rivers. Inundated fields appear dark blue; vegetation is bright green.  
NASA Earth Observatory / Lauren Dauphin

As the world looks for sustainable solutions, a system tapping into NASA satellite data for water management has passed a critical test.

Called OpenET, the system uses an ensemble of six satellite-driven models that harness publicly available data from the Landsat program to calculate evapotranspiration (ET)—the movement of water vapor from soil and plant leaves into the atmosphere. OpenET does this on a field-level scale that is greatly improving the way farmers, ranchers, and water resource managers steward one of Earth’s most precious resources.

Researchers have now conducted a large-scale analysis of how well OpenET is tracking evapotranspiration over crops and natural landscapes. The team compared OpenET data with measurements from 152 sites with ground-based instruments across the United States. In agricultural areas, OpenET calculated evapotranspiration with high accuracy, especially for annual crops such as wheat, corn, soy, and rice. The researchers reported their findings on January 15 in Nature Water.

“I was pleasantly surprised by the results,” said John Volk, lead author of the study and assistant research scientist and software engineer at Desert Research Institute in Reno, Nev. “The accuracy in croplands was quite strong, particularly in western arid regions, which are important areas for agriculture and have water sustainability challenges.”

That’s welcome news for regions where OpenET data is already being put to work. In Northern California’s Sacramento-San Joaquin Delta, water resource managers are using OpenET to help farmers comply with state rules requiring them to report aspects of their water use. The new study “gives us more confidence that these numbers are accurate, and that OpenET is continually improving over time,” said Lindsay Kammeier, a senior engineer with the California State Water Board in Sacramento, who was not involved in the new research.

“ET is notoriously difficult to calculate,” she added. “Having a really accurate number helps us to make decisions to manage the environment, manage for agricultural uses, and manage for urban uses better and from a common understanding.”

Tracking the Invisible Movement of Water

While many people are familiar with what one inch of rainfall means, few stop to think about one inch of evapotranspiration returning to the atmosphere, said Forrest Melton, the OpenET project scientist at NASA’s Ames Research Center in California’s Silicon Valley. “OpenET is working to make the unseen process of evapotranspiration as easy to track as checking the amount of rainfall in the daily weather forecast.”

Evapotranspiration is the natural process in which water moves to the atmosphere from the surface. The term combines evaporation—water changing from liquid to gas (vapor) and rising from soil, lakes, and oceans—and transpiration, the “exhaling” by plants as they release moisture back into the air. After precipitation, evapotranspiration is one of the most important factors for estimating how much water is available for crops or other plants.

This map shows evapotranspiration levels across Central California including the Bay Area. Darker blue can be seen in the Central Valley.
In California, state officials and farmers are using satellite data through OpenET to track evapotranspiration to better manage water resources. The process is a window into the water consumed by plants and crops, such as those grown in the Central Valley.
NASA Earth Observatory using openetdata.org

For farmers and water managers, accurate data provides a measure of the amount of water required through irrigation to replace the water that has been consumed by evapotranspiration. Knowing precisely how much water is available helps people give plants the moisture they need to flourish, without needing to apply too much. And that, in turn, can help save money for water and for the electricity used to pump water for irrigation.

But all that rising water vapor is invisible, making it difficult and expensive to track on the ground.

Farmers, scientists, and others previously relied on estimates of “potential evaporation” based on temperature, humidity, and other weather data. Or they turned to ground-based stations such as flux towers, equipped with sensors that monitor carbon dioxide, water vapor, and the exchange of heat between Earth’s surface and the atmosphere—a process crucial to calculating evapotranspiration.

But while they tend to be highly accurate, flux towers are expensive to set up and maintain, so there are a limited number, and their data is local and cannot represent wider regions. That’s where calculating evapotranspiration from space comes in. Satellites pass over the same areas regularly, offering consistent monitoring.

OpenET’s primary observations come from the Landsat 8 and 9 satellites, a partnership between NASA and the U.S. Geological Survey. The satellites combine data on land surface temperatures and the greenness of plants, among other things. Cooler land surface temperatures over areas with healthier, denser vegetation, for example, usually indicate higher levels of transpiration. 

That data is then fed into models to calculate evapotranspiration at high resolution—about a quarter of an acre for each image pixel.

The new results show that for agricultural lands, OpenET data for monthly, growing season, and annual timescales had an average error rate of about 10-20%.

The OpenET consortium includes NASA, USGS, and the U.S. Department of Agriculture working with Desert Research Institute and nearly a dozen other universities, Environmental Defense Fund, and Google Earth Engine.

For more information, go to: https://openetdata.org/

By: Emily DeMarco, NASA Earth Science Division

About the Author

Emily DeMarco



Last Updated
Feb 01, 2024
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      The future passive microwave radiometer constellation looks robust, with multiple sensors to be launched in the next decade. Small/CubeSat constellations are becoming a reality, and a plan to incorporate them quickly into the overall precipitation constellation is needed. A point of emphasis was that a sensor in an inclined orbit is a necessity when it comes to providing a reference measurement to support this effort – see Figure 3.
      Figure 3. Evaluation of passive microwave (PMW) frequencies and coverage to assess data gaps and needs for the future of precipitation constellation.Figure credit: Rachael Kroodsma/GSFC JAXA Precipitation Measuring Mission (JAXA PMM) Radar
      Plans call for JAXA’s next generation of precipitation radar to be deployed as part of the agency’s future Precipitating Measuring Mission (PMM – yes, the same acronym as the Precipitation Measurement Mission). Objectives for this next-generation precipitation radar include Doppler observations, higher sensitivity measurements, and scanning capability. JAXA has collaborated with a Japanese science team and user community to explore the feasibility of a next-generation, dual-frequency precipitation radar. The discussion focused on the importance of measuring convection through Doppler velocities from spaceborne radar. The EarthCARE mission will feature the first Cloud Profiling Radar (CPR) with Doppler capability in space. JAXA has participated in NASA’s AOS Pre-Phase A activities. The synergy between the GPM DPR and PMM/KuDPR is expected to contribute to the construction of a longer-term precipitation dataset by providing overlapping observations.
      Update on Cloud Services at NASA GES DISC
      NASA’s Goddard Earth Sciences Data and Information Services Center (GES DISC), one of two data archive centers for GPM, is moving its data archive to the cloud – with all GES DISC data and services remaining free to all users. This will offer quick access to and subsetting capability for a large volume of data through multiple data access methods (e.g., Amazon Simple Storage Service) and cloud services. Multidisciplinary NASA data will be in one place – the Earthdata Cloud – and available for online analysis and in the cloud environment. Expanded services (e.g., access to the Common Metadata Repository–SpatioTemporal Asset Catalog (CMR-STAC), Harmony – a collective Earth Observing System Data and Information System (EOSDIS) effort to make data access more consistent and easier across all DAACs and Zarr – a data format designed to store compressed multidimensional arrays and thus well suited to cloud computing) are expected to be implemented in the near future. With the migration of GES DISC data to the cloud, some services may look different with details on the exact changes to services coming soon.
      GPM Core Observatory Boost
      As George Huffman discussed in his presentation, based on forecasted solar activity, the GPM Core Observatory could run out of fuel as early as October 2025 if the current orbit altitude is maintained. To prolong its operations, NASA and JAXA have decided to boost the GPM Core Observatory orbit by ~35 km (~22 mi), which places GPM at an altitude of ~435 km (~270 mi)) – placing it above the International Space Station orbital altitude. The post-boost operations of the satellite are expected to continue through the early 2030s. The boost is expected to last only 2–4 days and occur in the time window between November 2023 and March 2024 (likely November 7–9, 2023, as stated above), the boost will permanently change the sensors’ Field of Views (FOVs) and likely cause a gap of several months in DPR product delivery.
      Precipitation in 2040
      Sarah Ringerud [GSFC] and George Huffman led this plenary discussion that explored two questions: What comes next? and What does the cutting edge of precipitation science look like 20 years from now? CubeSats, reduced volume of low-frequency-channel observations, shorter sensor lifetimes, increased sampling, and calibration challenges are recognized as inevitable. Exciting new developments are seen in the opportunity for data fusion and interdisciplinary work. Interagency and private sector collaborations are foreseen as critical points for maintaining optimal monitoring of Earth precipitation.
      The 2023 PMM STM brought together scientists from around the world to engage on a range of topics that advance the understanding of precipitation science, algorithms, and contributions to applications. The STM highlighted updates and activities enabled by the PMM scientific community. The closing session provided an opportunity for quick updates from precipitation working group members, who held splinter sessions. These updates were followed by an open discussion and review of PMM action items led by George Huffman. He reminded PMM STM participants of several important and noteworthy items, including updates on the orbit boost and subsequent algorithm adjustments, which will be available on the GPM website and be at the forefront for the project for the next six months; V08 of GPM data products are anticipated by early 2026; the budget reduction for the project – but not for current ROSES projects – will impact activities, including next year’s PMM STM; and the next NASA ROSES call might have a different package of opportunities, not strictly focused on PMM/GPM. He concluded by encouraging the PMM ST to share highlights and publications with the GPM Science Program Management Team as well as to continue to initiate collaborations with other colleagues to keep pushing the boundaries of science and outreach.
      The next PMM STM will likely be held in September 2024. Details will be posted on the GPM website once they become available.
      Acknowledgements The author would like to recognize the following individuals, all of whom made contributions to this article: Ali Behrangi [University of Arizona], Anthony Didlake [Penn State University], Gerry Heymsfield [GSFC], George Huffman [GSFC], Matthew Igel [University of California Davis], Toshio Iguchi [Osaka University], Dorian Janney [GSFC/ADNET Systems], Chuntao Liu [Texas A&M Corpus Christi], Veljko Petkovic [UMD], Courtney Schumacher [Texas A&M Corpus Christi], and Joe Turk [NASA/Jet Propulsion Laboratory].
      View the full article
    • By NASA
      4 min read
      What Are Hubble and Webb Observing Right Now? NASA Tool Has the Answer
      It’s not hard to find out what NASA’s Hubble and James Webb space telescopes have observed in the past. Barely a week goes by without news of a cosmic discovery made possible using images, spectra, and other data captured by NASA’s prolific astronomical observatories. 
      But what are Hubble and Webb looking at right this minute? A shadowy pillar harboring nascent stars? A pair of colliding galaxies? The atmosphere of a distant planet? Galactic light, stretched and distorted on a 13-billion-year journey across space?
      NASA’s Space Telescope Live, a web application originally developed in 2016 to deliver real-time updates on Hubble targets, now affords easy access to up-to-date information on current, past, and upcoming observations from both Hubble and Webb. 
      Designed and developed for NASA by the Space Telescope Science Institute in Baltimore, this exploratory tool offers the public a straightforward and engaging way to learn more about how astronomical investigations are carried out.
      With its redesigned user interface and expanded functionality, users can find out not only what planet, star, nebula, galaxy, or region of deep space each telescope is observing at the moment, but also where exactly these targets are in the sky; what scientific instruments are being used to capture the images, spectra, and other data; precisely when and how long the observations are scheduled to occur; the status of the observation; who is leading the research; and most importantly, what the scientists are trying to find out. 
      Information for observations from approved science programs is available via the Mikulski Archive for Space Telescopes. NASA’s Space Telescope Live offers easy access to this information – not only the current day’s targets, but the entire catalog of past observations as well – with Webb records dating back to its first commissioning targets in January 2022, and Hubble records all the way back to the beginning of its operations in May 1990. 
      The zoomable sky map centered on the target’s location was developed using the Aladin Sky Atlas, with imagery from ground-based telescopes to provide context for the observation. (Because the Hubble and Webb data must go through preliminary processing, and in many cases preliminary analysis, before being released to the public and astronomy community, real-time imagery is not available in this tool for either telescope.)
      Details such as target name and coordinates, scheduled start and end times, and the research topic, are pulled directly from the observation scheduling and proposal planning databases. Links within the tool direct users to the original research proposal, which serves as a gateway to more technical information. 
      While this latest version of NASA’s Space Telescope Live constitutes a significant transformation from the previous release, the team is already gathering feedback from users and planning additional enhancements to provide opportunities for deeper exploration and understanding.  
      NASA’s Space Telescope Live is designed to work on desktop and mobile devices, and is accessible via NASA’s official Hubble and Webb websites. Additional details about the content, including public-friendly explanations of the information displayed in the tool, can be found in the User Guide.
      The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.
      The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. Goddard also conducts mission operations with Lockheed Martin Space in Denver, Colorado. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble and Webb science operations for NASA.
      Learn More:

      Selecting What Webb Observes Next

      Media Contacts:
      Claire Andreoli – claire.andreoli@nasa.gov
      Laura Betz – laura.e.betz@nasa.gov
      NASA’s Goddard Space Flight Center, Greenbelt, MD
      Margaret W. Carruthers, Christine Pulliam
      Space Telescope Science Institute, Baltimore, MD

      Last Updated Mar 06, 2024 Editor Andrea Gianopoulos Location Goddard Space Flight Center Related Terms
      Astrophysics Astrophysics Division Goddard Space Flight Center Hubble Space Telescope James Webb Space Telescope (JWST) Missions Keep Exploring Discover More Topics From NASA
      Hubble Space Telescope

      Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.

      James Webb Space Telescope

      Webb is the premier observatory of the next decade, serving thousands of astronomers worldwide. It studies every phase in the…

      International Observe the Moon Night

      2024 Total Eclipse

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    • By NASA
      An extra-tropical cyclone seen in the Pacific Ocean off the coast of Japan on March 10, 2014, by NASA’s GPM Microwave Imager.Credit: NASA NASA’s Global Precipitation Measurement Mission: 10 years, 10 stories
      From peering into hurricanes to tracking El Niño-related floods and droughts to aiding in disaster responses, the Global Precipitation Measurement (GPM) mission has had a busy decade in orbit. As the GPM mission team at NASA and the Japan Aerospace Exploration Agency (JAXA) commemorates its Feb. 27, 2014 launch, here are 10 highlights from the one of the world’s most advanced precipitation satellites.

      First Images Available from NASA-JAXA Global Rain and Snowfall Satellite
      Less than a month after launch, NASA and JAXA released the first images captured by the GPM Core Observatory. It measured precipitation falling inside a March 10, 2014, cyclone over the northwest Pacific Ocean, approximately 1,000 miles east of Japan.
      Read the Full Article NASA Releases First Global Rainfall and Snowfall Map from New Mission
      Combining data from a constellation of satellites that together observe every part of the world roughly every three hours, the GPM team mapped how rain and snow storms move around the planet. As scientists have worked to understand all the elements of Earth’s climate and weather systems – and how they could change in the future – GPM has provided comprehensive and consistent measurements of precipitation.
      Read the Full Article GPM Satellite Sees First Atlantic Hurricane
      The GPM Core Observatory flew over Hurricane Arthur five times between July 1 to 5, 2014 – the first time a precipitation-measuring satellite was able to follow a hurricane through its full life cycle with high-resolution measurements. In the July 3 image, Arthur was just off the coast of South Carolina. GPM data showed that the hurricane was asymmetrical, with spiral arms (rain bands) on the eastern side of the storm but not on the western side.
      Read the Full Article NASA Working with Partners to Provide Response to Harvey
      In 2017, NASA used assets and expertise from across the agency to help respond to Hurricane Harvey in southern Texas. The agency’s GPM mission team produced rainfall accumulation graphics and unique views of the structure of Harvey during various phases of development and landfall.
      Read the Full Article Predicting Floods 
      Predicting floods is notoriously tricky, as the events depend on a complex mixture of rainfall, soil moisture, the recent history of precipitation, and much more. Snowmelt and storm surges can also contribute to unexpected flooding. With funding from NASA, researchers developed a tool that maps flood conditions across the globe.
      Read the Full Article NASA, Pacific Disaster Center Increase Landslide Hazard Awareness
      A NASA-based team built a new tool to examine the risk of landslides. They developed a machine learning model that combines data on ground slope, soil moisture, snow, geological conditions, distance to faults, and the latest near real-time precipitation data from NASA’s IMERG product (part of the GPM mission). The model has been trained on a database of historical landslides and the conditions surrounding them, allowing it to recognize patterns that indicate a landslide is likely.
      Read the Full Article NASA Measures Raindrop Sizes From Space to Understand Storms
      For the first time, scientists collected three-dimensional snapshots from space of raindrops and snowflakes around the world. With this detailed global dataset, scientists started to improve rainfall estimates from satellite data and in numerical weather forecast models. This is particularly helpful for understanding and preparing for extreme weather events.
      This is a conceptual image showing how the size and distribution of raindrops varies within a storm. Blues and greens represent small raindrops that are 0.5-3mm in size. Yellows, oranges, and reds represent larger raindrops that are 4-6mm in size. A storm with a higher ratio of yellows, oranges, and reds will contain more water than a storm with a higher ratio of blues and greens.Credit: NASA Goddard Read the Full Article NASA Maps El Niño’s Shift on U.S. Precipitation
      The GPM team amassed and analyzed data to show the various changes in precipitation across the United States due to the natural weather phenomenon known as El Niño.
      Read the Full Article Using Satellites to Predict Malaria Outbreaks
      University researchers turned to data from NASA’s fleet of Earth-observing satellites to track environmental events that typically precede a malaria outbreak. With NASA funding and a partnership with the Peruvian government, they worked to develop a system to help forecast potential malaria outbreaks down to the neighborhood level and months in advance. This gave authorities a tool to help prevent outbreaks from happening.
      Read the Full Article Two Decades of Rain, Snowfall from NASA’s Precipitation Missions
      NASA’s Precipitation Measurement Missions (PMM) – including GPM and the Tropical Rainfall Measurement Mission ­– have together collected rain and snowfall from space for more than 20 years. Since 2019, scientists have been able to access PMM’s multi-satellite record as one dataset.
      Read the Full Article View the full article
    • By NASA
      The New Shepard crew capsule descends under parachutes during its launch Tuesday, Dec. 19, 2023.Photo Credit: Blue Origin Researchers are studying data from a recent suborbital flight test to better understand lunar regolith, or Moon dust, and its potentially damaging effects as NASA prepares to send astronauts back to the lunar surface under the Artemis campaign. The experiment, developed jointly by NASA and the University of Central Florida, sheds light on how these abrasive dust grains interact with astronauts, their spacesuits, and other equipment on the Moon. 
      The Electrostatic Regolith Interaction Experiment (ERIE) was one of 14 NASA-supported payloads launched on Dec. 19 aboard Blue Origin’s New Shepard uncrewed rocket from Launch Site One in West Texas. During the flight test, ERIE collected data to help researchers at the agency’s Kennedy Space Center in Florida study tribocharging, or friction-induced charges, in microgravity.  
      The Moon is highly charged by phenomena such as solar wind and ultraviolet light from the Sun. Under those conditions, regolith grains are attracted to lunar explorers and their equipment – think of it as similar to the static created by rubbing a balloon on a person’s head. Enough regolith can cause instruments to overheat or not function as intended.  
      “For example, if you get dust on an astronaut suit and bring it back into the habitat, that dust could unstick and fly around the cabin,” said Krystal Acosta, a researcher for NASA’s triboelectric sensor board component inside the ERIE payload. “One of the major problems is that there’s no way to electrically ground anything on the Moon. So even a lander, rover, or really any object on the Moon will have polarity to it. There’s no good solution to the dust charging problem right now.” 
      A Kennedy team designed and built the triboelectric sensor board inside the ERIE payload, which reached an altitude of 351,248 feet aboard New Shepard. In the microgravity phase of this flight, dust grains simulating regolith particles brushed up against eight insulators within ERIE, creating a tribocharge. The electrometer measured the negative and positive charge of the simulated regolith as it traveled through an electric field applied during microgravity. 
      “We want to know what causes the dust to charge, how it moves around, and where it ultimately settles. The dust has rough edges that can scratch surfaces and block thermal radiators,” said Jay Phillips, lead of Electrostatics Environments and Spacecraft Charging at NASA Kennedy. 
      University of Central Florida (UCF) and NASA physicists who worked on the ERIE payload pose with Blue Origin booster after launch Tuesday, Dec. 19, 2023. From left to right, Addie Dove, UCF PI for ERIE, Krystal Acosta, NASA researcher, and Jay Phillips, NASA researcher. The ERIE payload spent approximately three minutes in microgravity during the New Shepard capsule’s suborbital flight, which lasted about 10 minutes before landing safely back on Earth in the Texas desert. A camera recorded the interactions, and Philips and his team are reviewing the data.  
      The results will inform applications for future missions destined for the lunar surface. For example, by using triboelectric sensors on a rover’s wheels, astronauts can measure the positive and negative charges between the vehicle and regolith on the lunar surface. The end goal is to develop technologies that will help keep it from sticking to and damaging astronaut suits and electronics during missions. 
      The flight was supported by the Flight Opportunities program, part of NASA’s Space Technology Mission Directorate, which rapidly demonstrates space technologies with industry flight providers. 
      View the full article
    • By NASA
      1 min read
      Preparations for Next Moonwalk Simulations Underway (and Underwater)
      David Scarborough
      Auburn University
      Professor Scarborough will develop and implement tools to extract critical data from experimental measurements of plume surface interaction (PSI) to identify and classify dominant regimes, develop physics-based, semi-empirical models to predict the PSI phenomena, and quantify the uncertainties. The team will adapt and apply state-of-the-art image processing techniques such as edge detection, 3D-stereo reconstruction to extract the cratering dynamics, and particle tracking velocimetry to extract ejecta dynamics and use supervised Machine Learning algorithms to identify patterns. The models developed will establish a relationship between crater geometry and ejecta dynamics, including quantified uncertainties.
      Back to ESI 2023
      Keep Exploring Discover More Topics From STRG
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