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Images remotely sensed aboard aircraft during FIFE, namely, PBMR (microwave) soil nwisture and NS001 thermal infrared surface temperature, were mapped on the same coordinate system covering the 20 km×20 km experimental site. For both kinds of image data, the. frequency distributions were close to symmetric, and the area averages compared reasonably well with the ground based measurements. For any image on any given day, the correlation between the remotely sensed values and collocated ground based measurements over the area was usually high in the case of NS001 surface temperature but low in the case of PBMR soil moisture. On the other hand, at any given flux station the correlation between the PBMR and gravimetrie soil moisture over all available days was usually high. The correlation pixel by pixel between images of PBMR on different days was generally high. The preservation of the spatial patterns of soil moisture was also evaluated by considering the correlation. station b y station between ground-based soil moisture measurements on different days; no persistence of spatial pattern. was apparent during wet periods, but a definite pattern gradually established itself toward the end of each drying episode. The spatial patterns of surface: temperature revealed by NS001 were not preserved even within a single day. The cross-correlations among the two kinds of images and the vegetation index NDVI were normally poor. This suggests that different time scales were involved in the different processes of vegetation growth, and of the near-surface soil water and energy budgets. |
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