(a) RMSE between the CRYSAT2-SMOS observations and INTAROS-ctrl, INTAROS-opt, TOPAZ4, and PIOMAS. The remaining panels show the mean SIT differences between CRYSAT2-SMOS merged data and (b) INTAROS-ctrl, (c) INTAROS-opt, (d) TOPAZ4, and (e) PIOMAS. The contour interval is 0.1 m.