The SIR-C/X-SAR experiment on Montespertoli: sensitivity to hydrological parameters

Multi-frequency and multi-temporal polarimetric SAR measurements, carried o ut during SIR-C/X-SAR missions over the Montespertoli area have been analys ed and compared with data collected at the same frequency and polarization, but at different dates, with the NASA/JPL AIRSAR. This paper presents an a nalysis of the achieved results aiming at evaluating the contribution of SA R data for estimating some geophysical parameters which play a significant role in hydrological processes and in particular soil moisture and roughnes s. The study has pointed out that in the scale of surface roughness typical of agricultural areas, a co-polar L-band sensor gives the highest information content for estimating soil moisture and surface roughness. The sensitivit y to soil moisture and surface roughness for individual fields is rather lo w since both parameters affect the radar signal. However, considering data collected at different dates and averaged over a relatively wide area that includes several fields, the correlation to soil moisture is significant, s ince the effects of spatial roughness variations are smoothed. On the other hand the sensitivity to surface roughness is better manifested at a spatia l scale, integrating on time to reduce the effects of moisture variation. T he retrieval of both soil moisture and surface roughness has been performed with good results by means of a semi-empirical model.