REPROCESSING of SEA LEVEL L2P products for 28 years of altimetry missions

Marine Lievin (cls, France)

CoAuthors

Cecile Kocha (cls/celad, FRA); Bastien Courcol (cls/alten, FRA); Sabine Philipps (cls, FRA); Isabelino Denis (cnes, FRA); Thierry Guinle (cnes, FRA); Carolina Nogueira Loddo (eumetsat, Germany); Gerald Dibarboure (cnes, FRA); Nicolas Picot (cnes, FRA); Francois Bignalet-Cazalet (cnes, FRA)

Event: 2020 Ocean Surface Topography Science Team Meeting (virtual)

Session: Regional and Global CAL/VAL for Assembling a Climate Data Record

Presentation type: Type Forum

Since the launch of TOPEX/Poseidon and ERS-1 in the early 90’s more than 10 other Altimetry missions were launched and operated by different agencies. The level 2 data (destinated to expert users) are distributed using different file formats (binary, netcdf) and contain different geophysical standards used to compute the sea level anomaly. Some dataset evolve rapidly and are regularly reprocessed, whereas other datasets, especially from finished missions are seldom reprocessed or not at all (and therefore do not profit from new standards).
In the frame of the SALP (Service d’Altimétrie et de Localisation Précise) project supported by CNES (Centre National d’Etudes Spatiales) and of the Sentinel-3 Marine Altimetry L2P-L3 Service (operated under an EUMETSAT contract in the frame of the Copernicus Programme funded by the European Union) level 2P data are available to users for all the altimeter missions (TOPEX/Poseidon, Jason-1/2/3, ERS-1/2, Envisat, Saral/AltiKa, Sentinel-3A/B, GFO, Cryosat-2, HY-2A) in delayed time on AVISO+ ( https://www.aviso.altimetry.fr/en/data/products/sea-surface-height-products/global/along-track-sea-level-anomalies-l2p.html ).
L2P products are easy to use (netcdf format) homogenous along-track mono-mission products, providing as much as possible the same updated corrections and models for the altimeter missions, in order to facilitate inter-mission comparisons. The products contain the sea level anomaly as well as all the corrections used to compute it. The sea level anomaly is provided with a validity flag, enabling users to discard data with spurious measurements. Furthermore, an inter-mission bias is applied in order to have consistent time series since TOPEX/Poseidon.
The sea level anomaly level 2P products are, among other uses, the input data for level 3 products (Taburet et al. 2019, DUACS DT-2018: 25 years of reprocessed sea level altimeter products).
Considering recommendation of new standards from the OSTST and assessing thoroughly all the corrections used for the sea level anomaly, the best standards were chosen for the next L2P release. The whole altimetry L2P time-series was reprocessed during 2020. If available, the reprocessed L2P products were also based on recently reprocessed L2 data (Sentinel-3 SRAL data Baseline Collection 004, Cryosat Ocean Baseline C,…). The reprocessed L2P data set will be presented and assessed.
 
Marine Lievin
cls
France
ckocha@groupcls.com