Remote Sensing of Soil Moisture
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EASTING (m)
BRIGHTNESS
TEMPERATURE (I<)
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381
Figure 14.9: Brightness temperature maps obtained using the PBMR (Push Broom Microwave
Radiometer) at L-band (H pol.) for five days of July 1990 (before and after a rainfall) (after
Jackson et ai., 1994).
From these measurements, worked out by means of ground based and airborne sensors, it is
confirmed that microwave emission from soil is very well correlated to its moisture content and
that, at frequencies around 1.5 GHz or lower, the sensitivity to SMC of the first 5 cm layer is
fairly high even for vegetated fields and ranges between ~ 3.5 KIO.01 g cm- 3 for smooth bare
surfaces to R; 1KIO.01 g cm- 3 due to the effect of surface roughness and presence of vegetation.
A good correlation was also found with SMC of layers down to 20 cm; however, due a to fairly