Are Single‐Source, Remote‐Sensing Surface‐Flux Models Too Simple?

Both one‐source and two‐source parameterizations of surface sensible heat flux exchange using radiometric surface temperature have been proposed. Although one‐source algorithms may provide reliable heat fluxes, they often require field calibration and hence are unable to accommodate the diverse range of surface conditions often encountered over a landscape. Two‐source models require fewer assumptions and no a priori calibration, and therefore have a wider range of applicability without requiring any additional input data. A one‐source scheme (SEBAL) that performs an “internal calibration” using hydrologic extremes (hot/dry and wet/cool pixels) encountered within a remote sensing scene has been proposed as a way to eliminate a priori calibration and the need for ancillary data. In this paper, some of the key assumptions in SEBAL are evaluated using a two‐source model, field data, and simulations from a complex soil‐vegetation‐atmosphere transfer (SVAT) model, Cupid.