The main objective of the SWIM Level 2S (L2S) product is to provide along-track directional wave spectra measures, as well as the integrated parameters of the associated wave systems (wave length, significant wave height, direction), over the global ocean, as observed with SWIM instrument onboard CFOSAT. CFOSAT (Chinese French Ocean SATellite) is a french-chinese mission launched in 2018, whose aim is to provide wind (SCAT instrument) and wave (SWIM instrument) measurements over the sea surface.

The wave spectra and their associated partitions are provided independently for each SWIM incidence (from 2° to 10°), together with the sigma0 resampled at a 20m resolution. They are complemented with information from the nadir beam such as the sigma0, wind speed, significant wave height or rain flag.

The SWIM level 2S (L2S) product is generated in delayed mode, a few days after acquisition. It complements the Near-Real Time (NRT) L2 product delivered by the CWWIC center by providing an alternative and evolutive processing to test and implement quickly new algorithms for the wave inversion over the whole mission archive. These evolutions may take advantage of better ancillary data not available in NRT (ice mask product, best estimates of wind or wave model), of the combination with wind measurements from the onboard SCAT scatterometer. The product is also designed to handle complex situations such as coastal areas and heterogeneous seas. These complex situations are by nature of particular scientific interest (e.g. wind wave interactions, wave evolution in coastal region).

This version 2 improves the previous release in particular through a new empirical modulation transfer function (MTF) and better partitioning. The dataset is also lighter in size. It has been completely reprocessed from SWIM Level 1 archive. Note that the dataset is split on the access server in two different sub-versions (**2.0** for the L2S using Level 1 in OP06 version, **2.1** for the L2S using Level 1 in OP07 version). No major differences are expected.

The SWIM L2S product is generated and distributed by Ifremer / CERSAT in the frame of the Ifremer Wind and Wave Operation Center (IWWOC) co-funded by Ifremer and CNES and dedicated to the processing of the delayed mode data of CFOSAT mission.