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Satellites Unraveling Soil Moisture and Weather Patterns


As floodwaters drowned crops and submerged towns across Texas and Oklahoma last summer, media cameras captured hundreds of images of the damage.

But 426 miles above the earth, a much more sophisticated eye was taking it all in.

NASA launched its Soil Moisture Active Passive (SMAP) satellite in January 2015. The satellite was designed to use a unique combination of microwave sensors and radar to collect global soil moisture and freeze-thaw data from the top 2 inches of soil every two to three days.

For a year and a half, the satellite has been circling the globe, and the data it sends down to Earth is already being used by a multitude of parties, from the National Agricultural Statistics Service and the National Drought Mitigation Center to the U.S. military.

SMAP researchers are using weather stations and instruments across the world to validate the satellite’s readings and fine tune the algorithms that retrieve its data. Yet already, scientists are culling data to improve flood models, monitor drought, improve weather forecasting, predict dust storms and vastly improve soil moisture and crop monitoring.

But the satellite’s orbit has not been all smooth soaring. A technological glitch has greatly reduced the resolution of its data, and — like every brand new space mission — the length of its eventual mission life is uncertain.

A blurrier view than expected

By April 2015, the SMAP satellite was working perfectly — sending down streams of soil moisture data with an unprecedented resolution of 9 km, roughly 5.6 miles.

Through its data, scientists watched the fields and waterways of Oklahoma and Texas swell with water and slowly dry down — a valuable lesson on how the land responded to a record-breaking flood event after an historic drought, said Tom Jackson, a USDA-ARS hydrologist working to validate the satellite’s data.

Then, in early July 2015, the radar on the satellite abruptly died. For now, only the passive microwave sensor on the satellite is transmitting data. The long wavelengths this sensor detects give scientists a reliable and highly accurate view of soil moisture, but at a much coarser resolution of 40 km (about 25 miles), Jackson said.

This was a blow to early adopters of the program, conceded Susan Moran, a USDA-ARS research hydrologist based in Arizona. In particular, the U.S. military had hoped to rely on the high resolution data for detailed information on how well trucks and troops could move in parts of the world where they have no information on local weather conditions.

Nonetheless, the data still gives us an unprecedented view of global soil moisture, Jackson said. “It’s still the best instrument of its kind we’ve ever put up there,” he said.

NASA is now considering various ways to improve SMAP’s resolution. The options include altering SMAP’s orbit path to merge with the European Space Agency’s radar-driven Sentinel 1 satellite or using creative mathematical techniques to sharpen the data’s resolution.

A better picture of ag

Despite the lower resolution, a variety of organizations are already snagging the satellite’s data and using it to improve their vision of agriculture.

NASS relies heavily on 4,000 farmer and rancher “enumerators” around the country to produce its assessments of crop conditions and soil moisture. SMAP data is a gold mine of objective, reliable and accurate moisture data for the agency. It promises to sharpen NASS’s reporting and possibly replace part of that enumerator network, which would be a huge cost-savings to the agency, according to Rick Mueller, head of spatial analysis research at NASS.

The agency has also launched a website called VegScape, which will use SMAP’s soil moisture data to draw a detailed picture of crop and vegetation conditions across the country at any given moment. See the map here.

NASS is also preparing to use SMAP data to improve its state-by-state assessments of soil moisture released in USDA’s weekly crop progress reports, said Moran.

USDA’s Foreign Ag Service (FAS) has also seized upon the data, said Bob Tetrault, the agency’s deputy director. The agency monitors crop production around the world, a task made easier by reliable soil moisture data. In the past, FAS has been plagued by the lack of precipitation and moisture data in third-world regions such as Africa and countries that do not readily share data such as China and Russia, Jackson noted.

The lack of weather stations in these regions makes it hard to validate SMAP’s readings, but the data is still giving analysts a brand new view of these areas’ moisture situations, he said.

Moisture information, such as knowing the water-holding capacity of a crop at flowering, will greatly help FAS’s ability to predict global yields, Tetrault told DTN.

The data is also helping scientists unravel the relationship between soil moisture and weather patterns, with the aim of improving drought predictions, said Wade Crow, a USDA-ARS research hydrologist. “Soil moisture has a strong impact on where the sunlight’s energy and heat goes,” he explained. “That in turn has an impact on air temperature and the development of precipitation. If you know what soil moisture is, that can help you to better forecast how the land surface and atmosphere are going to interact two weeks from now, and that in turn will help you predict weather.”

The ultimate goal, which remains years away still, would be predicting droughts and famines months in advance, Crow said.

For now, the National Drought Mitigation Center is exploring the possibility of using SMAP data to improve its U.S. Drought Monitor’s weekly evaluations of soil moisture across the country, Moran said.

The future of SMAP

SMAP is funded for three years in orbit, but the satellite has a physical lifespan closer to 20 years, Jackson noted. At the end of its initial mission, SMAP will come up for review by NASA to determine its future. The goal is to become an “operational” satellite, which is permanently maintained, Jackson said.

Until that happens, the satellite’s uncertain future has made it a little difficult for organizations such as NASS, FAS, and the National Drought Mitigation Center to completely incorporate its data into their models, Moran said.

But the satellite’s budding value for important sectors like agriculture and national security is likely to boost its lifespan, Moran added. Plus, organizations like the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Geological Survey (USGS) have been known to pitch in when valuable missions come up for funding.

“There are many, many ways this mission could become operational, or at least extended,” she said. “Certainly when you get users as interested as ours, there is great potential for that.”

For more information on the SMAP satellite, see NASA’s detailed website.

Source: Emily Unglesbee, AgFax

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