Location: Hydrology and Remote Sensing LaboratoryTitle: A review of satellite-based methods of estimating live fuel moisture content for fire danger assessment: moving towards operational products Author
|Hunt, Earle - Ray|
Submitted to: Remote Sensing of Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2013
Publication Date: 6/22/2013
Publication URL: http://handle.nal.usda.gov/10113/59826
Citation: Yebra, M., Chuvieco, E., Jurdao, S., Danson, M., Dennison, P., Hunt, E.R., Qi, Y., Riano, D., Zylstra, P. 2013. A review of satellite-based methods of estimating live fuel moisture content for fire danger assessment: Moving towards operational products. Remote Sensing of Environment. 136:455-468. Interpretive Summary: Fire danger ratings for forests, shrublands and grasslands are based on the dryness of living vegetation, expressed as fuel moisture content (FMC). Currently, FMC is measured for a few scattered individual plants, which is assumed to be representative of the vegetation in the area. Satellite remote sensing may provide timely estimates of FMC over the entire landscape, and thus provide important information for wildfire management. Water in live foliage may be estimated by measuring reflectances at different wavelengths of solar radiation. However, it is very difficult to determine FMC knowing only the amount of water in foliage. We review the recent peer-reviewed literature and discuss promising methods of determining FMC from remote sensing measurements. The most promising methods will not be feasible for wildfire management because current satellite sensors will not measure reflected solar radiation at the necessary wavelengths. A future satellite from NASA called the Hyperspectral InfraRed Imager (HyspIRI) will measure the correct wavelengths, but will not make the measurements frequently enough for monitoring FMC. With current sensors such as NASA's MODerate resolution Imaging Spectroradiometer (MODIS) and NOAA's Visible Infrared Imaging Radiometer Suite (VIIRS), it is possible to use site-specific empirical relationships that have a scientifically-based method for calibration.
Technical Abstract: One of the primary variables affecting ignition and spread of wildfire is fuel moisture content (FMC), which is the ratio of water mass to dry mass in living and dead plant material. Because dead FMC may be estimated from available weather data, remote sensing is needed to monitor the spatial distribution of live FMC. Water strongly absorbs different wavelengths in the near- and shortwave-infrared spectral regions, which provides a physical basis for estimating live FMC. However, there are fundamental problems that must be answered before remote sensing may be used for operational programs. Coarse spatial and spectral resolution sensors such as MODIS and VIIRS provide various spectral indices frequently, but need empirical relationships to estimate FMC. Radiative transfer model inversions do not work well because the spectral absorption coefficients for dry matter are usually less than those for water and there is more water mass than dry matter in a canopy, so water masks out the signals from dry matter. Absorption at wavelengths of 1722 or 2305 nm may be used to create spectral indices related to canopy dry matter, but it will be years before narrow-band hyperspectral sensors could be used for monitoring. While empirical relationships will always be site specific, current results show that physically-based algorithms may be used for calibration of pixel-specific relationships. With the current progress, remote sensing scientists now must work the global fire-science community to incorporate remotely sensed live FMC into wildfire behavior models.