On surface-atmosphere interactions in the thermal infrared which impact satellite-derived land surface temperatures

Angular measurements of surface-emitted infrared radiation made using a scanning radiometer positioned 5 m above the ground at a semi-arid site near Alice Springs have been analysed together with coincident dual-angle thermal infrared data from the ATSR2 satellite sensor. The multiangular data set has been utilized to investigate how localized radiative signatures translate to the scale of the field of view of the satellite sensor. The scanning radiometer continuously acquires directional brightness temperature measurements which reveal the cyclical nature of the small scale radiative temperature distribution, both diurnally and seasonally. At night, angular variation in the directional brightness temperature is seen in the data and can be related to the angular variation of the surface emissivity. The combination of surface effects, such as these, with atmospheric processes such as absorption, added to the existence of variability in land surface temperature (LST) retrieval due solely to viewing geometry, make remote sensing of LST a complex problem. Results from both the in situ and satellite investigations are briefly discussed in relation to the surface-atmosphere interactions which impact upon remote sensing of LST.