Jp. Lhomme et al., DETERMINATION OF SENSIBLE HEAT-FLUX OVER SAHELIAN FALLOW SAVANNA USING INFRARED THERMOMETRY, Agricultural and forest meteorology, 68(1-2), 1994, pp. 93-105
The estimation of the partitioning of available energy from remote sen
sing techniques is addressed for a Sahelian fallow savannah. It is a c
omposite vegetation consisting of shrubs of Guiera senegalensis scatte
red above a stand of sparse grass. A two-layer model is employed to es
timate sensible heat flux (H) from radiometric surface temperature, wi
th data collected during the HAPEX-Sahel international experiment, car
ried out in Niger in 1992. The model, based upon the assumption that t
he radiometric surface temperature (T(r)) might be represented by the
composite surface temperature (area-weighted mean of shrub and grass t
emperatures), leads to a simple formulation of H as a function of the
temperature difference between the surface and the air (T(r) - T(a)) a
nd the temperature difference between the grass and the shrubs deltaT.
The estimates of the model compare fairly accurately with measurement
s obtained by the Bowen ratio-energy balance method, the root mean squ
are error being about 52 W m-2. Because deltaT is not easily measured
from remote sensing systems, it has been shown that for the fallow sav
annah this temperature difference is linearly correlated to (T(r) - T(
a)) with r2 = 0.94. Therefore, it is possible to estimate sensible hea
t flux from (T(r) - T(a)) without additional component temperature mea
surements.