6533b82dfe1ef96bd1291634
RESEARCH PRODUCT
On the Use of the Eddy Covariance Latent Heat Flux and Sap Flow Transpiration for the Validation of a Surface Energy Balance Model
Antonino MalteseGiuseppe CiraoloGiovanni RalloHassan AwadaFulvio CapodiciGoffredo La Loggiasubject
CanopyAcquisition time; Flux tower; Heat dissipation technique; Spatial resolution; Time lag; Earth and Planetary Sciences (all)010504 meteorology & atmospheric sciencesScienceAcquisition time; Flux tower; Heat dissipation technique; Spatial resolution; Time lag; Earth and Planetary Sciences0208 environmental biotechnologyEnergy balanceEddy covariance02 engineering and technologyAtmospheric sciences01 natural sciencestime lagFlux (metallurgy)Latent heatEvapotranspirationSettore AGR/08 - Idraulica Agraria E Sistemazioni Idraulico-Forestaliflux tower; heat dissipation technique; time lag; spatial resolution; acquisition timeacquisition timeImage resolutionspatial resolution0105 earth and related environmental sciencesTranspirationSettore ICAR/02 - Costruzioni Idrauliche E Marittime E IdrologiaQ020801 environmental engineeringEarth and Planetary Sciencesheat dissipation techniqueGeneral Earth and Planetary SciencesEnvironmental scienceEarth and Planetary Sciences (all)Settore ICAR/06 - Topografia E Cartografiaflux towerdescription
Actual evapotranspiration is assessed via surface energy balance at an hourly rate. However, a robust estimation of daily evapotranspiration from hourly values is required. Outcomes of surface energy balance are frequently determined via measures of eddy covariance latent heat flux. Surface energy balance can be applied on images acquired at different times and spatial resolutions. In addition, hourly actual evapotranspiration needs to be integrated at a daily rate for operational uses. Questions arise whether the validation of surface energy balance models can benefit from complementary in situ measures of latent heat flux and sap flow transpiration. Here, validation was driven by image acquisition time, spatial resolution, and temporal integration. Thermal and optical images were collected with a proximity-sensing platform on an olive orchard at different acquisition times. Actual latent heat fluxes from canopy and sap flux at tree trunks were measured with a flux tower and heat dissipation probes. The latent heat fluxes were then further analyzed. A surface energy balance was applied over proximity sensing images re-sampled at different spatial resolutions with resulting latent heat fluxes compared to in situ ones. A time lag was observed and quantified between actual latent heat fluxes from canopy and sap flux at the tree trunk. Results also indicate that a pixel resolution comparable to the average canopy size was suitable for estimating the actual evapotranspiration via a single source surface energy balance model. Images should not be acquired at the beginning or the end of the diurnal period. Findings imply that sap flow transpiration can be used to measure surface energy balance at a daily rate or when images are found at an hourly rate near noon, and the existing time lag between the latent heat flux at the canopy and the sap flow at the trunk does not need to be taken into account.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2018-01-29 | Remote Sensing |