7th Workshop on Forest Fire Management - EARSeL, European ...

Remote sensing of fuel moisture content: advances in measurement and modelling 17
3 - Use of radiative transfer models
Canopy reflectance models use radiative transfer theory to describe the
interaction of radiation with plant canopies and include variables like leaf
chlorophyll, leaf water content, and canopy leaf area index. Since these
variables may be correlated in ‘real’ canopies, radiative transfer models
allow sensitivity analyses to be performed, in which variables may be coupled
or decoupled, in order to better understand the relationships between
leaf water content and spectral reflectance. This approach also allows definition
of the conditions under which FMC may be reliably estimated from
remotely sensed data. Sensitivity analyses have demonstrated the importance
of interactions between EWT, DM, LAI and FMC at leaf and canopy
level (Ceccato et al., 2002, Bowyer & Danson, 2004). A few subsequent
papers have used radiative transfer models to estimate FMC in laboratory
and field experiments and it is clear from this work that, when the models
can be constrained using measured ranges of the relevant variables at a
given site, the estimation of FMC is more accurate. This work is at an early
stage and further work combining field measurements and modelling is still
required.
4 - Research priorities
A survey of published journal papers from 2002 onwards, and focused on
the estimation of FMC from remotely sensed data, was conducted for the
purposes of this review. A total of 21 papers were identified and classified
according to the ecosystem within which the work took place and the main
sensor used. In addition, the papers were classified according to the
methodology adopted; papers using bivariate or multivariate correlation
and regression analyses and the application of vegetation indices formed
one group; papers that primarily used radiative transfer models formed a
second group.
Target ecosystem
Sensor Mediterranean Savanna Other
Modis 6 (1) (2)
SPOT VGT 2 1
AVHRR 3
Landsat TM 2
Hyperspectral 3 (1)
Table 1 - Survey of 21 papers on remote sensing of FMC published between 2002 and 2009.
Figures indicate number of empirical studies and in brackets model based studies.