Table 1: RMS of the differences for the zonal component U, the meridional component V, the current modulus and the direction of the current, of the independent drifting buoy velocities and the altimeter geostrophic velocities obtained using MDT solutions CNES-CLS22, CNES-CLS18 and the CNES-CLS22 first guess. The last two lines show the reduction/increase in RMS of the differences between two solutions: CNES-CLS22 versus CNES-CLS18 and CNES-CLS22 versus CNES-CLS22 first guess, in percent (a negative percentage is a decrease in the RMS of the differences). These statistics were generated using all available drifters up to 70°N.
Given the small number of independent drifters in Arctic, this area is treated separately. Table 2 summarizes the RMS of the differences between the geostrophic currents derived from drifters (degraded treatment) and the geostrophic currents derived from ADTs calculated with the CNES-CLS22, CNES-CLS18 and background CNES-CLS22 solutions. The last two lines show in percent the reduction in RMS of the differences between CNES-CLS22 and CNES-CLS18 MDT and its first guess. In the zonal and meridional components of the current, the new solution reduces the RMS of the differences compared with the drifters by 19% and 12% respectively. This improvement translates into a clear improvement in direction of 9%, which reduces the RMS of the differences from around 56° to 50°; but the RMS of the differences in current amplitude remains very slightly better for CNEs-CLS18. Note that, as the coverage is not quite identical, there are more points taken into account for CNES-CLS22 than for CNES-CLS18.