Dara Entekhabi leads the international science team behind a NASA investigation that literally spans the entire planet and could have a similarly outsized effect on everything from our understanding of the conditions for life on Earth to agriculture in Africa. Key to the work? The first-ever global high-resolution observations of soil moisture from space.
“Soil moisture is the variable that links the water, energy, and carbon cycles, or the three cycles that make life possible on Earth. So my ultimate science goal is to use our data to globally understand how these three cycles should be coupled, like gears in a clock,” says Entekhabi, the Bacardi and Stockholm Water Foundations Professor. Such an understanding will allow more robust predictions of global change.
And that’s not all. “One of my other dreams is to bring applications like flood forecasting and drought monitoring into the 21st century,” says Entekhabi.
The Soil Moisture Active Passive (SMAP) mission is a NASA satellite launched in January 2015. Every two to three days, it creates a global map of the moisture in the top two inches of Earth’s soil. Before now, soil moisture was estimated based on the history of precipitation and other indirect indicators.
Key to the work are two complementary sensors aboard the satellite. One captures the low-frequency microwaves naturally emitted at the surface of the planet. The other actively beams low-frequency microwaves to the surface and captures what is reflected back. Soil minerals and water molecules have extremely different microwave emission and reflection properties, so the two sensors together allow the detection of the moisture content.
Entekhabi notes that in a first for NASA, routine data from the mission will be available almost immediately to a group of some 40 early adopters, agencies, and organizations from around the world with near-term applications. These include the US Department of Agriculture’s Foreign Agricultural Service, which will use the data to monitor global crop production, and the Masdar Institute of Science and Technology in the United Arab Emirates, which will map the extent of the Saharan dust emissions that can be hazardous to human health.
Over the last few years Entekhabi and colleagues have been working closely with these groups, providing them with simulated data similar to what they can expect from SMAP. The idea “was to let them get used to the data, and incorporate it into their decision support systems, so that when the data faucet is turned on [with SMAP’s commissioning] they’re ready to use it,” says Entekhabi, who has joint appointments in the Department of Civil and Environmental Engineering and the Department of Earth, Atmospheric and Planetary Sciences. “We’re going to see every granule of data used very quickly in very different domains.”
About one third of the early adopters have applications related to food, says Entekhabi. That’s because a knowledge of soil moisture can help monitor crop productivity. It can also be used to predict monsoon rainfall, data that will be especially important for places like West Africa. “Even an indication of above- or below-average forthcoming conditions is extremely important to these farmers, who rely on rainfall rather than irrigation for crops,” says Entekhabi. “At the beginning of the season they must decide whether to plant crops that have high caloric content but are very fragile with respect to drought, or hardier crops that have lower caloric content but are more resistant to drought.”
Entekhabi notes that of the 15 members of the SMAP science team, almost half have advanced degrees from MIT in a variety of disciplines. “That shows the footprint of MIT in advancing our capability to sense our environment from vantage points that are new and much more comprehensive than what we can have on the ground,” he says.
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