Abstract's details

Performances and benefits of a 1D-variational approach to retrieve the wet tropospheric correction: recent achievements for Sentinel-6 and Sentinel-3A and -3B topography missions

Ralf Bennartz (Univ. Vanderbilt, Nashville, TN, USA, United States)


Bruno Picard (Fluctus, France); Frank Fell (Informus, Deutschland); Estelle Olibis (EUMETSAT, Deutschland); Remko Scharroo (Eumetsat, Deutschland); Bruno Lucas (Eumetsat, Deutschland); Boyan Bojkov (Eumetsat, Deutschland)

Event: 2023 Ocean Surface Topography Science Team Meeting

Session: Instrument Processing: Propagation, Wind Speed and Sea State Bias

Presentation type: Type Oral

Contribution: PDF file


Statistical methods are usually used to provide estimates of total column water vapour (TCWV) and wet tropospheric correction (WTC), required to correct altimetry measurements for atmospheric path delays, using brightness temperatures (TB) measured at two or three low frequencies from a passive microwave radiometer (MWR) operated concomitantly with the altimeter. Despite their overall accuracy over oceanic surfaces, uncertainties remain in specific regions of complex atmospheric stratification. Thus, there is a need to further improve the currently used retrieval methods.

Within this context, a one-dimensional variational (1D-Var) method has been developed, assimilating the relevant passive microwave observations to retrieve the WTC and the TCWV over the ice-free global ocean. This physical approach has been applied to the whole Sentinel-3A and Sentinel-3B periods and validated over open ocean against an extensive set of references: the operational product, ERA-5 reanalysis, sample products of the latest AIRWAVE TCWV retrieval derived from SLSTR observations, as well as GPS-based high-quality TCWV retrievals from the year 2020.

This validation has allowed to qualify the 1D-var approach as a mature algorithm, capable of retrieving TCWV and WTC at a global performance level comparable to that of the operational product. Moreover, each value of the TCWV and WTC retrieved with the 1D-var method benefits from an associated uncertainty and a self-consistent quality flag greatly facilitating the assessment of the product.

A further step has been taken by applying the same approach to Sentinel-6 mission, based the 3-TB measurements provided by the on-board MWR AMR-C developed by the JPL. We will present the first results of the assessment of the WTC retrieval, illustrating the benefit of the 18.7 GHz channel and comparing the performance of the 1D-var against the operational products.

Oral presentation show times:

Room Start Date End Date
Grande Beach Room (#208) Wed, Nov 08 2023,15:00 Wed, Nov 08 2023,15:15
Ralf Bennartz
Univ. Vanderbilt, Nashville, TN, USA
United States