Directional radiance and emissivity measurement models for remote sensing of the surface energy balance

Interactions between remotely sensed data and radiation components of Soil Vegetation Atmosphere Transport (SVAT) models have included inputs in the form of parameters such as albedo and Leaf Area Index as well as validation of outputs such as actual Evapotranspiration (ET) and net radiation. Visible, near infrared and thermal region data can be effectively combined and used in these ways. However, the radiative transfer models involved in the production of these inputs from remotely sensed data or the derivation of outputs are often at least as complex as the SVAT. In many cases, the parameters input to the SVAT represent only a fraction of the information content of the remotely sensed data which has been established through understandings of the effects of landcover and structure on the observed radiance. in attempts to bring these systems together, a number of people are studying how remotely sensed data and SVAT models can be integrated directly to provide calibration of the models and validation of their performance or made consistent through use of the semi-empirical models used in remote sensing. The validation this provides is to the level of information the remote sensing can provide which in the case of regional fluxes may be all that can be provided. The key to this development is having a remote sensing “measurement model” that is consistent with the level of aggregation and scale of the SVAT. This paper describes the directional radiance and emissivity effects which need to be modelled to interpret regional remotely sensed data and the affect they have on the derivation of consistent information from SVATs.