The two-source energy balance (TSEB) model uses remotely sensed maps of land–surface temperature (LST)along with local air temperature estimates at a nominal blending height to model heat and water fluxesacross a landscape, partitioned between dual sources of canopy and soil. For operational implementation ofTSEB, however, it is often difficult to obtain representative air temperature data that are compatible withthe LST retrievals, which may themselves have residual errors due to atmospheric and emissivity corrections. Toaddress this issue, two different strategies in applying the TSEB model without requiring local air temperaturedata were tested over a typical Mediterranean agricultural area using a set of high-resolution multispectral airborneremote sensing images. Alleviating the need for accurate local air temperature data as input, these two approachesestimate the surface-to-air temperature gradient that drives the sensible heat flux by directly exploiting the informationavailable in the image. The two approaches include: 1) a scene-based internal calibration (TSEB-IC) procedurethat estimates air temperature over a well-watered and fully vegetated pixel in the LST image, and 2) adisaggregation scheme (DisALEXI) that uses air temperature estimates from a time-differential coupled TSEBatmosphericboundary layer model of atmosphere–land exchange (ALEXI). A comparison of the air temperaturesmodeled by TSEB-IC and DisALEXI with in situ weather station observations shows good agreement, with averagedifferences on the order of 1 K, comparable with the uncertainties in the remotely sensed surface temperaturemaps. Surface fluxes estimated by each method agree well with micro-meteorological measurements acquiredover an olive orchard within the aircraft imaging domain. In comparison with fluxes generated with TSEB usinglocal measurements of air temperature, instantaneous fluxes from these alternative methods show good spatialagreement, with differences of less than 10 W/m^2 across the domain. Finally, a sensitivity analysis of the threemodels, performed by introducing artificial errors into the model inputs, demonstrates that the DisALEXI andTSEB-IC approaches are relatively insensitive to errors in absolute surface temperature calibration, while turbulentfluxes from TSEB applications using local air temperature measurements show sensitivity of approximately30 W/m^2 per degree temperature perturbation. This highlights the value of both internal calibration and timedifferentialestimation of the surface-to-air temperature gradient within a surface energy balance framework.
|Numero di pagine||14|
|Rivista||Remote Sensing of Environment|
|Stato di pubblicazione||Published - 2012|
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