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Title:   Author  item
                                            Jackson, Thomasitem
                                            CHEN, D - UNIV. OF MANCHESTERitem
                                            Cosh, Michaelitem
                                            Li, Fuqinitem
                                            ANDERSON, M. - UNIV. OF WIitem
                                            Walthall, Charlesitem
                                            Doraiswamy, Paulitem
                                            Hunt Jr, Earle
  Submitted to: Remote Sensing of Environment
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 3/1/2004
                                    Publication  Date: 9/1/2004
                                    Citation: Jackson, T., Chen, D., Cosh, M., Li, F., Anderson, M., Walthall, C., Doraiswamy, P., Hunt, E.R. 2004. Vegetation water content mapping using Landsat data normalized difference water index (NDWI) for corn and soybean. Remote Sensing of Environment. 92(4):475-482.Interpretive Summary: As part of a large-scale field campaign called the Soil Moisture Experiments 2002 (SMEX02) we explored the potential of using remote sensing to map and monitor vegetation water content (VWC) for corn and soybean canopies.  Landsat Thematic Mapper and Enhanced Thematic Mapper Plus data and ground based VWC measurements were used to establish relationships based on remotely sensed indices.  The two indices studied were the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Water Index (NDWI).  The NDVI saturated during the study period while the NDWI continued to reflect changes in VWC. NDWI was found to be superior based upon a quantitative analysis of bias and standard error. The method developed was used to map daily VWC for the watershed for the one-month experiment period. It was also extended to a larger regional domain.  VWC is an important parameter in agricultural and forestry applications.  The VWC could possibly provide information for agriculture that can be used to infer water stress for irrigation decisions, aid in yield estimation, assessment of drought conditions, fire susceptibility, and in microwave based soil moisture mapping.
                                Technical Abstract: Information about vegetation water content (VWC) has widespread utility in agriculture, forestry, and hydrology. It is also useful in retrieving soil moisture from microwave remote sensing observations.  Providing a VWC estimate allows us to control a degree of freedom in the soil moisture retrieval process. However, these must be available in a timely fashion in order to be of value to routine applications, especially soil moisture retrieval. As part of the Soil Moisture Experiments 2002 (SMEX02) the potential of using satellite spectral reflectance measurements to map and monitor VWC for corn and soybean canopies was evaluated. Landsat Thematic Mapper and Enhanced Thematic Mapper Plus data and ground based VWC measurements were used to establish relationships based on remotely sensed indices.  The two indices studied were the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Water Index (NDWI).  The NDVI saturated during the study period while the NDWI continued to reflect changes in VWC. NDWI was found to be superior based upon a quantitative analysis of bias and standard error. The method developed was used to map daily VWC for the watershed for the one-month experiment period. It was also extended to a larger regional domain.  In order to develop more robust and operational methods we need to look at how we can utilize the MODIS instruments on the Terra and Aqua platforms, which can provide daily temporal coverage.


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