Crop analysts must estimate root-zone soil moisture, the amount of water beneath the surface available for plants to absorb. But estimating the amount of water in soil has posed challenges. Ground-level sensors for rainfall and temperature -- the two key elements for estimating soil moisture are often sparsely located in the developing nations that need them the most. Hard-to-reach terrain like mountains or desert, lack of local cooperation as well as high maintenance costs, can lead to sensors more than 500 miles apart.
Under a new NASA-USDA collaboration known as the Global Agriculture Monitoring Project, Bolten and colleagues from the USDA's Agricultural Research Service are using AMSR-E to fill the data gaps with daily soil moisture "snapshots." Since its launch in 2002, the instrument has "seen" through clouds, and light vegetation like crops and grasses to detect the amount of soil moisture beneath Earth's surface.
AMSR-E uses varying frequencies to detect the amount of emitted electromagnetic radiation from the Earth's surface. Within the microwave spectrum, this radiation is closely related to the amount of water that is in the soil, allowing researchers to remotely sense the amount of water in the soil across any geographic landscape.
Following a test of their system over the United States, Bolten's team tracked West African rainfall, temperature, and model assessments of soil moisture with and without the AMSR-E satellite sensor observations. They used West Africa as a model because the landscape provides varying cover, from desert and semi-arid landscape in the north to grasslands, lush forests, and crop land to the south. Rainfall in the region is highly variable yet sparsely monitored by ground-based sensors. They also targeted West Africa to demonstrate the possibility for improving the assessment of drought-caused food shortages on the region's dense population.
"Many developing countries a
|Contact: Sarah DeWitt|
NASA/Goddard Space Flight Center