HR: 17:30h
AN: H54A-05 [Abstracts]
TI: Surface Energy Balance Methods for Evapotranspiration - Some Enhancements and Applications
AU: * Gutschick, V P
EM: vince@nmsu.edu
AF: Dept. of Biology, New Mexico State Univ., MSC 3AF, Las Cruces, NM 88003, United States
AU: Wang, J
EM: jwang@nmsu.edu
AF: Dept. of Plant and Environmental Science, New Mexico State Univ., MSC 3Q, Las Cruces,
NM 88003, United States
AU: Sammis, T W
EM: tsammis@nmsu.edu
AF: Dept. of Plant and Environmental Science, New Mexico State Univ., MSC 3Q, Las Cruces,
NM 88003, United States
AB:
Satellite-received radiances and auxiliary ground-based information are routinely used to estimate the
evapotranspiration rate (ET, or LE as a latent heat energy flux density) on landscape elements. Many methods
compute LE as a residual, computing the terms Rn, G, and H in the full energy-balance equation, S = Rn - G
¬ H - LE, where S is surface (canopy) heat storage (often assumed near zero), Rn is net radiation, G is
heat flux into the (soil) surface, and H is the sensible heat flux. Computation of H is prone to errors in obtaining
accurate radiometric temperatures, TR, of the surface and in relating TR to the true kinetic temperature
of the surface heat source. The Surface Energy BAlance Land (SEBAL) method avoids the offset errors by
introducing an assumption of a linear relation of TR to the surface-to-air temperature difference. This
assumption, and several others, can introduce distinct errors and operational problems, which will be discussed,
along with several improvements under development. The latter include direct regression solutions for LE,
correcting for advection of energy and for the lapse rate of the surface (not air) temperature, and the use of
auxiliary radiance-based information on vegetation water stress. Also to be discussed are potential applications
of enhanced ET methods to estimate hydrologic redistributions (runon, runoff), the consequent spatial patterning
of vegetation, and the implications of both for ecological studies (equilibrium canopy development, long-term
acclimation of stomatal control) and ecosystem management (estimating forest water stress and its relations to
stand density, forest thinning exercises, and hazards of fire and insect outbreaks).
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0480 Remote sensing
DE: 1818 Evapotranspiration
DE: 1851 Plant ecology (0476)
DE: 1855 Remote sensing (1640)
SC: Hydrology [H]
MN: 2007 Joint Assembly