LENGTH SCALES OF REMOTELY SENSED VEGETATION, SURFACE RADIOMETRIC TEMPERATURE, AND DERIVED SURFACE ENERGY FLUXES

摘要

The airborne data are dominated by the presence of a 800 m length scale in both the fractional vegetation and the radiometric temperature fields. The temperature data also exhibit a length scale on the order of 24 m. The cospectra between these data and the derived energy fluxes show small scale behavior on the order of 24 m. This indicates that the fluxes are responding primarily to small scale differences in temperature (due to the fact that no peak is observed at 24 m in the Fr data), rather than changes in the fractional vegetation. In the case of the AVHRR, the large scale variability dominates. The cospectra between Fr and temperature exhibits a small scale (2000 m) peak not observed in either spectra individually. This small scale activity is observed in the evaporation Fr cospectra. This is due to the radiative balance of the surface. With the AVHRR data, the initial pixel size is too coarse to observe local (field to field) variability in Fr that dominated over the temperature variability in the high resolution airborne data. At coarser pixel resolution (2000 m), the Fr spatial variability dominates over the importance in the temperature data, resulting in the peak in the evaporation at 2000 m. However, at even larger scales, neither Fr nor temperature dominates and the resultant fluxes have large contributions from both fields.