Location: Hydrology and Remote Sensing LaboratoryTitle: Quantitative assessment of satellite L-band vegetation optical depth in the U.S. corn belt
|TOGLIATTI, K. - Iowa State University|
|LEWIS-BECK, C. - Iowa State University|
|WALKER, V. - University Of Montana|
|HARTMAN, T. - Iowa State University|
|VAN LOOCKE, A. - Iowa State University|
|HORNBUCKLE, B. - Iowa State University|
Submitted to: Geoscience and Remote Sensing Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2020
Publication Date: 11/6/2020
Citation: Togliatti, K., Lewis-Beck, C., Walker, V.A., Hartman, T., Van Loocke, A., Cosh, M.H., Hornbuckle, B. 2020. Quantitative assessment of satellite L-band vegetation optical depth in the U.S. corn belt. Geoscience and Remote Sensing Letters. 1-5. https://doi.org/10.1109/LGRS.2020.3034174.
Interpretive Summary: Vegetation Optical Depth as a satellite measurement is primarily a measurement of the vegetation water content. For a field experiment conducted in South Fork, Iowa, it was demonstrated that the satellite product from the Soil Moisture Active Passive (SMAP) mission is biased low as compared to three other products derived from in situ measurements and models. We theorize that other land surface parameters are also present in the satellite product and these should be incorporated in future algorithm development. This work is of value to remote sensors and agriculturalists who are interested in vegetation parameterization.
Technical Abstract: Satellite L-band vegetation optical depth (L-VOD) contains new information about terrestrial ecosystems. However, it has not been evaluated against the geophysical variable that it represents, plant water, the mass of liquid water contained within vegetation tissue per ground area. We quantitatively assess the seasonal variation of three L-VOD products at the South Fork Core Validation Site in the Corn Belt state of Iowa where LVOD is directly proportional to crop plant water. We use three satellite-scale crop plant water estimates: in situ measurements; a normalized difference water index (NDWI) calibrated with in situ measurements; and a crop model. We find that overall the LVOD satellite products are 0.02 to 0.09 Np (0.4 to 1.7 kg/m/m) lower than the three estimates. We show that overestimation of L-VOD can be attributed to dynamic soil surface roughness, and hypothesize that crop plant water observations will require the incorporation of this effect into retrieval algorithms