How eddy covariance LE data can be used to precisely estimate ET over a fetch region? Can remote sensing ET estimate be better if we use LE instead of H in calculation?
Dear Sumanta,
According to the manual of Metric (Allen et al. 2012) the following are the definition of Latent heat flux LE.
The ET flux is calculated for each pixel of the image as a “residual”
of the surface energy budget equation and is expressed as the energy consumed by the
evaporation process:
LE = Rn – G – H
LE is the latent heat flux (W/m2), Rn is the net radiation flux at the surface (W/m2),
G is the soil heat flux (W/m2), and H is the sensible heat flux to the air (W/m2). LE is
converted into ET, expressed as a depth of water per time, by dividing by the latent heat of
vaporization.
the soil heat flux (G) and sensible heat flux (H) are subtracted from the net radiation flux at the surface (Rn) to compute the “residual” energy available for evapotranspiration (LE). Soil heat flux is empirically calculated using vegetation indices, surface temperature, and surface albedo. Sensible heat flux is computed using wind speed observations, estimated surface roughness, and near surface air temperature differences.
So according to the above equation H is different from LE and to calculate LE Sensible Heat flux, Soil Heat Flux and net radiation should be calculated first for every pixel in a satellite image.
Best regards
For some inspiration, here is the story of METRIC.
https://earthobservatory.nasa.gov/Features/WaterWatchers/page1.php
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