Initial validation of SMOS vegetation optical thickness in Iowa

The European Space Agency´s Soil Moisture and Ocean Salinity (SMOS) satellite mission provides microwave L-band measurements of vegetation optical thickness over the Earth. The optical thickness is related to water held in vegetation. The water content of crops varies over the growing season from a minimum at planting to a maximum during reproduction and back to a minimum during senescence. We found that in Iowa in 2010 the change in SMOS optical thickness over the growing season can be related to crop yields. However, there are inconsistencies in the optical thickness data, particularly high-frequency variation and unexpected changes during the non-growing season. We hypothesize that the unexpected changes during the dormant season are due to changes in soil surface roughness due to land management activities and show a relationship between changes in roughness and changes in optical thickness which may be confusing the SMOS retrieval algorithm.