Algorithms for extracting information from remote thermal-IR observations of the earth's surface

Thermal infrared remote sensing offers the possibility of monitoring the surface energy budget on regional and global scales. However, thermal observations have had limited utility because of difficulties associated with unknown surface emissivities, challenging atmospheric corrections, and the presence of numerous variables that affect the relationship between thermal radiance and the partitioning of energy fluxes at the surface. The importance of distinguishing between aerodynamic and radiative temperatures is discussed and definitions for each are proposed. Considerable progress is being made with atmospheric corrections and measurement of surface emissivity so that accuracies of 1° to 2°C in surface infrared temperature and 0.01 to 0.02 in surface emissivity may be within reach. Five methods are described for extracting information about the surface energy budget from a combination of satellite thermal observations and various amounts of ancillary data. Although no single method appears to work under all conditions, uncertainties in daily fluxes of surface sensible and latent heat appear to be 1 to 2 MJ m −2 based on past studies. Thermal infrared observations toill continue to play an essential role in partitioning available surface energy into sensible and latent heat components.