NASA’s ‘SMAP’ satellite may help farmers prepare for drought


California has been enduring its worst drought in over a century. During the final week in August, the U.S. Drought Monitor released a graphic with much of the state blocked out in two shades of red: one indicating “extreme,” the other “exceptional,” both of which are the most severe conditions on the scale. Agricultural production is stalling, and many growers are drawing from well water to keep thirsty crops alive.


PHOTO: U.S. Drought Monitor


Forget the gold rush — the most precious commodity in California right now is water.


It’s timely, then, for NASA’s Jet Propulsion Laboratory to schedule the launch of its Soil Moisture Active Passive (SMAP) satellite in late 2014. Using a microwave radiometer and radar, SMAP will measure surface soil moisture and freeze-thaw levels across the entire globe every two to three days, providing what NASA calls the “most detailed maps yet made” of these conditions worldwide. By collecting data over a three-year period, the mission could make the forecasting and management of region-specific drought and flood more complete in the future.


“SMAP can assist in predicting how dramatic drought will be, and then its data can help farmers plan their recovery from drought,” said Narendra Das, a water and carbon cycle scientist from NASA’s Jet Propulsion Laboratory.


Agricultural drought happens when a crop’s need for water exceeds that available from precipitation, fresh surface water (lakes, streams, ponds, etc.), and groundwater reserves. Forrest Melton, a research scientist in the Ecological Forecasting Lab at NASA Ames Research Center, explained that with the snowpack and precipitation data from the beginning of this past spring, scientists could already tell how dire the California drought would be this summer. Unfortunately, it’s a lot more difficult to make such estimates in arid regions that mostly rely on stored groundwater sources, like the Middle East.

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But even with rainfall data applied, there still isn’t a way to fully keep track of soil moisture levels on a local basis. Ground sensors can only supply spot measurements, and that technology is rarely used in areas like Africa, South America, and Asia. On the other end of the spectrum, a satellite launched in 2009 by the European Space Agency is successful at broad-scope measurements, but skips over critical variations that occur on a smaller scale.


NASA expects SMAP to fill in some of the gaps left over by other moisture-measuring systems by monitoring the top two inches of soil with a resolution of approximately six miles. This means that while it won’t measure minute differences within a field, it will give a more defined reading of moisture trends within any given local region. Farmers could use the data to strategize how and when they plant, irrigate, and harvest their land, especially in drier zones.


“Scientists see tremendous potential in SMAP,” Melton said. “It is not going to provide field-level information, but it will give very useful new regional observations of soil moisture conditions, which will be important for drought monitoring and a wide range of applications related to agriculture. Having the ability provided by SMAP to continuously map soil moisture conditions over large areas will be a major advance.”


Data will be made publicly available through a NASA-designated data center in the months following SMAP’s early-November launch.



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