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

摘要

In this study we evaluate a methodology for disaggregating land surfaceenergy fluxes estimated with the Two-Source Energy Balance (TSEB)-basedDual-Temperature Difference (DTD) model which uses day and night polarorbiting satellite observations of land surface temperature (LST) as aremotely sensed input. The DTD model is run with MODIS input data ata spatial resolution of around 1 km while the disaggregation uses Landsatobservations to produce fluxes at a nominal spatial resolution of 30 m. Thehigher-resolution modelled fluxes can be directly compared against eddycovariance (EC)-based flux tower measurements to ensure more accurate modelvalidation and also provide a better visualization of the fluxes' spatialpatterns in heterogeneous areas allowing for development of, for example,more efficient irrigation practices. The disaggregation technique isevaluated in an area covered by the Danish Hydrological Observatory (HOBE),in the west of the Jutland peninsula, and the modelled fluxes are comparedagainst measurements from two flux towers: the first one in a heterogeneousagricultural landscape and the second one in a homogeneous coniferplantation. The results indicate that the coarse-resolution DTD fluxesdisaggregated at Landsat scale have greatly improved accuracy as compared tohigh-resolution fluxes derived directly with Landsat data without thedisaggregation. At the agricultural site the disaggregated fluxes displaysmall bias and very high correlation (r ≈ 0.95) with EC-basedmeasurements, while at the plantation site the results are encouraging butstill with significant errors. In addition, we introduce a~modification tothe DTD model by replacing the "parallel" configuration of the resistancesto sensible heat exchange by the "series" configuration. The latter takesinto account the in-canopy air temperature and substantially improves theaccuracy of the DTD model.