Comparison of vegetation water contents derived from shortwave-infrared and passive-microwave sensors over central Iowa

Date

2011-09-15

Author

Hunt, E. Raymond
Li, Li
Yılmaz, Mustafa Tuğrul
Jackson, Thomas J.

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Retrieval of soil moisture content using the vertical and horizontal polarizations of multiple frequency bands on microwave sensors can provide an estimate of vegetation water content (VWC). Another approach is to use foliar-water indices based on the absorption at shortwave-infrared wavelengths by liquid water in the leaves to determine canopy water content, which is then related to VWC. An example of these indices is the normalized difference infrared index (NDII), which was found to be linearly related to canopy water content using various datasets, including data from the Soil Moisture Experiments 2002 and 2005 in central Iowa. Here we compared independent estimates of VWC from WindSat to Moderate resolution Imaging Spectroradiometer (MODIS) NDII over central Iowa from 2003 to 2005. Results showed that there was a linear relationship between the MODIS and WindSat estimates of VWC, although WindSat-retrieved VWC was greater than MODIS-retrieved VWC. WindSat and MODIS have different satellite overpass times and in most climates we expect VWC to vary over a day due to transpiration and plant water stress. However, a sensitivity analysis indicated that the diurnal variation of VWC should not have a significant effect on retrievals of VWC by either method. The results of this study indicated that soil moisture retrievals from microwave sensors may be improved using VWC from optical sensors determined by foliar-water indices and classifications of land cover type.

Subject Keywords

Canopy Water Content, Normalized Difference Infrared Index, MODIS, Windsat, Soil Moisture Experiment, SAIL Model, PROSPECT Model

URI

https://hdl.handle.net/11511/47779

Journal

Remote Sensing of Environment

DOI

https://doi.org/10.1016/j.rse.2011.04.037

Collections

Department of Civil Engineering, Article

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Remote sensing of canopy water content during SMEX'04 and SMEX'05 using shortwave-infrared reflectances Hunt Jr., E. Raymond; Yılmaz, Mustafa Tuğrul; Jackson, Thomas J. (2008-12-01) The Soil Moisture Experiments in 2004 and 2005 were conducted to validate algorithms for soil moisture retrievals. One of the key parameters for determination of soil moisture from microwave sensors is the vegetation water content of canopy and stems. We tested if canopy water content could be determined from reflectances in the shortwave-infrared and if the amount of canopy water content was related to the total vegetation water content by allometric equations. The normalized difference infrared index (NDI...
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Citation Formats

E. R. Hunt, L. Li, M. T. Yılmaz, and T. J. Jackson, “Comparison of vegetation water contents derived from shortwave-infrared and passive-microwave sensors over central Iowa,” Remote Sensing of Environment, pp. 2376–2383, 2011, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/47779.