Using SMOS L-band Optical Depth to Monitor Productivity in Agricultural Ecosystems.

Brian Hornbuckle, Iowa State University, bkh@iastate.edu (Presenter)
Jason Patton, Iowa State University, jpatton@iastate.edu

NASA's SMAP mission will measure L-band terrestrial brightness temperature in order to estimate soil moisture. Besides soil moisture, the L-band brightness temperature is also sensitive to water in vegetation. Soil moisture retrieval algorithms account for this effect by taking into account the L-band optical depth of the vegetation. The European Space Agency's SMOS (Soil Moisture and Ocean Salinity) mission is already in space and has been making measurements of terrestrial L-band brightness temperature since late 2009. SMOS natively derives vegetation optical depth by measuring the change in brightness temperature across multiple incidence angles. SMAP, in contrast, will measure the L-band brightness temperature at only a single incidence angle and hence will have to use ancillary data to determine the optical depth. Our long-term goals are: to use SMOS optical depth data to monitor the productivity of agricultural ecosystems in the US Midwest; and to assist the SMAP mission in producing estimates of vegetation optical depth so that it can meet its mission requirements. As a first step in assessing SMOS optical depth data, we will test the following hypotheses. (1) The timing of minimum and maximum vegetation biomass in US Midwest row crops correlates with the timing of minimum and maximum optical depth. (2) The change in optical depth over the growing season can be related to crop yield. These hypotheses require that we assume that vegetation water content is strongly correlated with total crop biomass, and that crop yield mainly depends on the total biomass of the crop (i.e. the harvest index does not vary widely among a single crop type). Our presentation at the workshop will examine 2010 SMOS optical depth and county-level USDA yield data over counties in Iowa that do not have a large urban land use component.

Presentation Type:  Poster

Session:  Science in Support of Decision Making   (Wed 10:00 AM)

Associated Project(s): 

• Hornbuckle, Brian: Comparing Different Sources of Vegetation Water Content Data for Use in SMAP Soil Moisture Retrieval ...details

Poster Location ID: 167