Remotely sensed land-surface energy fluxes at sub-field scale in heterogeneous agricultural landscape and coniferous plantation.

In this study we evaluate a methodology for disaggregating land surface energy fluxes estimated with the Dual Time Difference (DTD) model which uses the day and night polar orbiting satellites observations of Land Surface Temperature (LST) as a remotely sensed input. The DTD model is run with MODIS input data at a spatial resolution of around 1 km while the disaggregation uses Landsat observations of LST to produce fluxes at a nominal spatial resolution of 30 m. The higher resolution modeled fluxes can be directly compared against eddy-covariance based flux tower measurements to ensure more accurate model validation and also provide a better visualization of fluxes' spatial patterns in heterogeneous areas allowing for development of, for example, more efficient irrigation practices. The disaggregation technique is evaluated in an area covered by the Danish Hydrological Observatory (HOBE), in the west of the Jutland peninsula, and the modeled fluxes are compared against measurements from two flux towers: first one in a heterogeneous agricultural landscape and second one in a homogeneous conifer plantation. The results indicate that the disaggregated fluxes have greatly improved accuracy as compared to high resolution fluxes derived directly with Landsat data without the disaggregation. At the agricultural site the disaggregated fluxes display negligible bias and almost perfect correlation (r > 0.90) with Eddy Covariance based measurements, while at the plantation site the results are encouraging but not ideal. In addition we introduce a modification to the DTD model by replacing the "parallel" configuration of the resistances to sensible heat exchange by the "series" configuration. The later takes into account the in-canopy air temperature and substantially improves the accuracy of the DTD model. [ABSTRACT FROM AUTHOR]