Sea ice and its snow coverage has important effects on the global climate.

Sea ice thickness (SIT) measurement relies on the “Freeboard” method. It consists in calculating the height difference between the floes (range above the ice) and the leads (range above the water in ice fractures).

Alti Snow Depth (SD) : The difference of the scattering properties of the AltiKa Ka-band (on Saral/AltiKa) and the Siral Ku-band (on Cryosat-2) altimeters provides a good proxy of the snow depth using an adapted processing chain. According to the selected product, the Snow Depth could have 3 origins:

- Modified Warren99 climatology (in Arctic only)

- AMSR (for now in Antarctic only)

- Altimetry Snow Depth (ASD ou KaKu) for both hemisphere but only for 2013-2019 as it uses Saral Ka altimeter.

For each data, an estimation of uncertainties is also provided. More detail on computation will be described soon in an handbook.

All months are concatened in one netcdf file.

File names are built as follow: SIT_{HEMISPHERE}_{start_year}_{end_year}_{SATELLITE}_Snow{snow_origin}.ease2_{pixel_size}_smth{filtering_radius}.nc

with:

- {HEMISPHERE} in [NH, SH]

- {SATELLITE} in [ENV, CS2] for Envisat or CryoSat-2

- {snow_orgin} in [W99m, AMSR, KaKu]

This Snow Depth is the one used to compute the Sea Ice Thickness

- {filtering_radius} in [25000, 50000] which are the radius in meters

References:

- For Envisat and CryoSat-2 FB and SIT :

Guerreiro, K., Fleury, S., Zakharova, E., Kouraev, A., Rémy, F., Maisongrande, P., 2017. Comparison of CryoSat-2 and ENVISAT radar freeboard over Arctic sea ice: toward an improved Envisat freeboard retrieval. The Cryosphere 11, 2059–2073. https://doi.org/10.5194/tc-11-2059-2017

- For the Snow Depth :

- Garnier, F., Fleury, S., Garric, G., Bouffard, J., Tsamados, M., Laforge, A., Bocquet, M., Fredensborg Hansen, R. M., and Rémy, F.: Advances in altimetric snow depth estimates using bi-frequency SARAL/CryoSat-2 Ka/Ku measurements, The Cryosphere Discuss. [preprint], https://doi.org/10.5194/tc-2021-79 , in review, 2021.

- Guerreiro, K., Fleury, S., Zakharova, E., Rémy, F., Kouraev, A., 2016. Potential for estimation of snow depth on Arctic sea ice from CryoSat-2 and SARAL/AltiKa missions. Remote Sensing of Environment 186, 339–349. https://doi.org/10.1016/j.rse.2016.07.013