Table 4: Correlations between PALS horizontal polarization brightness temperatures and soil moisture in the 0-1 cm and 0–6 cm layers. Correlations generally reduce with increasing vegetation water content. The 2.5 kg/m2 < VWC < 3.5 kg/m2 and 1.0 kg/m2 < VWC < 2.5 kg/m2 classes consist mostly of measurements made in the corn fields for the dry days of June 25th and 26th when the contribution of radiation from soil is masked out by the overlying vegetation and the coefficient of correlation is seen to be positive [41].

VWC (kg/m2)No. of pointsGSM (0-1 cm)GSM (0–6 cm)
(LH) (SH) (LH) (SH)

VWC < 1.052−0.881−0.885−0.808−0.846
1.0 < VWC < 2.560.1420.2780.4200.562
2.5 < VWC < 3.521−0.094−0.1970.2580.161
3.5 < VWC < 4.513−0.950−0.863−0.847−0.833
VWC > 4.548−0.690−0.641−0.676−0.626