Spatial and temporal resolution of the L4 gridded products

The DUACS gridded products are delivered with a 1/4°x1/4° (global products) or 1/8°x1/8° (regional products) spatial sampling and 1-day temporal sampling. Note however that the spatial and temporal scales of the variability that is resolved in the DUACS merged products are imposed by the altimeter constellation sampling capabilities and the spatial and temporal correlation function used in the mapping procedure, as described in Pujol et al (2016).

Optimal Interpolation (see DUACS processing) used in DUACS processing does not allow the restitution of the full dynamical spectrum limiting the capability of retrieving small mesoscale in L4 products. The resulting mean spatial resolution of the DUACS DT2014 (ref produit) global gridded SLA slightly less than 200 km at mid-latitudes (Chelton et al., 2011, 2014). The comparison with the spectral content computed from full-resolution Saral/AltiKa 1 Hz along-track measurements shows that nearly 60% of the energy observed in along-track measurements at wavelengths ranging from 200 to 65 km is missing in the SLA gridded products.