SPATIAL-DISTRIBUTION AND PATTERN PERSISTENCE OF SURFACE SOIL-MOISTUREAND TEMPERATURE OVER PRAIRIE FROM REMOTE-SENSING

Images remotely sensed aboard aircraft during FIFE, namely, PBMR (micr owave) soil moisture and NS001 thermal infrared surface temperature, w ere mapped on the same coordinate system covering the 20 km x 20 km ex perimental site. For both kinds of image data, the frequency distribut ions were close to symmetric, and the area averages compared reasonabl y 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, fit ally given flux station the correlation betwe en the PBMR and gravimetric soil moisture over all available clays was usually high. The correlation pixel by pixel between images of PBMR o n different days was generally high. The preservation of the spatial p atterns of soil moisture was also evaluated by considering the correla tion station by station between ground-based soil moisture measurement s on different days; no persistence of spatial pattern was apparent cu ring 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 veg etation index NDVI were normally poor. This suggests that different ti me scales were involved in the different processes of vegetation growt h, and of the near-surface soil water and energy budgets. (C) Elsevier Science Inc., 1997.