News•April 23, 2015

New NASA Satellite Gets the Dirt on Soil Moisture

Tracking soil moisture is a dirty job, but someone’s gotta do it.

Soil moisture is a critical indicator of drought. For decades, ground observations have done the heavy lifting but they’re few and far between. That’s why NASA spent $1 billion to launch a soil moisture monitoring satellite earlier this year. After months of calibration, the satellite dubbed the Soil Moisture Active Passive mission or SMAP (go ahead and try not to say “oh, SMAP” in your head), has sent back the first global view of soil moisture.

Click image to enlarge. Credit: NASA Jet Propulsion Laboratory-Caltech/GSFC

SMAP uses two instruments — a radar and radiometer — to measure soil moisture at a 5.6-mile resolution, all with the goal of providing a better view of how water moves across the planet, particularly on land (a helpful piece of knowledge for humans). The above map was created using the radar, which sends microwave pulses from the satellite down to the Earth’s surface 426 miles below, and then measures the backscatter that pops back up. For the map, good soil moisture in places such as the Amazon basin and forests of northern Canada is indicated in red. In comparison, drier spots from the Arctic tundra to the Sahara Desert are in blue.

The shifts in soil moisture from week-to-week or year-to-year is a key piece of information for people working in fields and forests. It provides a key measure of drought and an indicator for forecasting out river flows, reservoir levels, the severity of wildfire season and crop irrigation availability.

SMAP’s equipment also allow it to monitor whether soil is frozen, muddy or dried out. The frozen-or-not part could prove particularly insightful for Arctic permafrost, which stores large quantities of methane, a potent greenhouse gas. That permafrost is expected to thaw as the planet warms, but observation stations in the region are sparse and estimates of that thaw could get a boost with the new data.

More soil moisture data is also key for climate scientists looking to understand what areas are likely to get drier due to climate change. SMAP’s high-resolution data means they’ll be able to refine their models and help everyone from farmers to firefighters understand what the future could have in store.

In the near term, the data could improve drought outlooks and weather forecasts. But it’ll be another month until data becomes available on a regular basis, so you’ll just have to enjoy the sneak peek in the meantime.