Soil Moisture Active Passive (SMAP): From a Roadside View to a Global ViewJanuary 30th, 2015 by Kate Ramsayer
California road trips cry out for a game I like to call “Guess What’s Growing by the Side of the Road.” The rules are simple – glance at the green leaves sprouting from the ground and guess whether they’re carrots or kale – and you can discover fascinating facts (artichokes are thistles!). This week, I’ve introduced a colleague to the game as we drove back and forth between our hotel and Vandenberg Air Force Base in California, past vineyards and rows of green plants in dark soil.
We’re here for the launch of the Soil Moisture Active Passive satellite, NASA’s latest mission to look back at our home planet. SMAP is designed to measure water content with unprecedented accuracy – and after talking with scientists and listening to briefings all week, I can’t think about the mystery roadside crops without wondering about water.
Soil’s water content is a key element in Earth’s ecosystem, scientists involved with the mission said this week. While agricultural fields now produce substantially more crops per acre than they did 50 years ago, agriculture is still very vulnerable to ’shocks’ like droughts, said Wade Crow, a research physical scientist with the USDA and SMAP science team member. An agricultural drought was one of the triggers for the 2008 food crisis when global food prices shot up, causing humanitarian crises, he said.
And measurements of soil moisture – the kind of information SMAP will gather – are the most direct and earliest indicator of agricultural drought.
“If you detect that directly, you are in a position to mitigate the effects. With better monitoring you can better respond so you can have less humanitarian and economic impact,” Crow said.
Soil moisture measurements will also be plugged into the weather models that help meteorologists forecast the rain that falls on those crops and other surfaces. Soil has an ’inherent memory’ when it comes to moisture, said Randy Koster, SMAP science team member and hydrologist at NASA’s Goddard Space Flight Center.
If it’s rainy in mid-June and the soil is wetter than usual, for example, it will probably also be wetter than usual in July, he said. That could impact how much water evaporates into the atmosphere to fall back as rainfall, as well as air temperature. Rainfall on wet soil is also more likely to run off, compared to rainfall that’s soaked up by parched soil, leading to better stream flow predictions.
“SMAP’s going to be providing unprecedented amounts of data on soil moisture, and utilized in these kinds of ways, we have the potential for better forecasts,” Koster said.