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Sea State Bias Research at UNH

Global ocean models for ocean surface gravity waves are combined with satellite radar altimeter measurements to obtain small cm-level corrections to the sea level measurements routinely produced by ocean altimeters.

UNH Project PI: D. Vandemark NASA Grant: NNX13AE17G


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Results: Improvement (cm2) in sea level noise characteristics after application of new 3D SSB models as demonstrated zonally. Biggest improvements are seen at highest latitudes. Better results for Jason altimeters than for Topex.

Satellite Altimeter Sea State Bias Corrections


One key geophysical correction that must be applied to satellite ocean altimeter data is known as the sea state bias. This cm-level range adjustment is needed to correct for the fact that radar reflection intensity from the ocean is skewed, with less signal coming from wave crests than the smoother wave troughs. The methods to determine this bias have been refined over many years of work with the NASA/CNES Ocean Surface Topography Science team and involve a correction that depends on wind and wave data that change along the altimeter ground track, most often provided by the altimeter itself. Our work builds on this to add additional wavefield data derived from ocean wave models with improved results. This page holds links to correction look up tables and/or data related to sea state bias corrections for numerous satellite altimeters that have been developed at UNH by OPAL PIs Feng and Vandemark with ongoing collaboration with Dr. Ngan Tran at CLS and wave model support from Fabrice Ardhuin at IFREMER and Lotfi Aouf at Meteo-France.

SSB Model Data Access


The links below provide access to recent (2015-version) satellite altimeter sea state bias (SSB) correction models and data for NASA/CNES TOPEX, Jason-1, Jason-2, and AltiKa sensors. The models were developed at UNH and differ from the SSB correction models provided in the respective mission GDR datasets. The 3D SSB models require additional ocean wave model data to derive along-track corrections. Users can access these data and our SSB corrections in ancillary "correction file" netCDF datafiles via the THREDDS links below. These files are are named and formatted for direct one-to-one use with GDR products. If you encounter any trouble, please send an email to doug.vandemark@unh.edu .


References

Vandemark, D, H.Feng, N. Tran, B. Beckley, and B. Chapron, 2014. Multi-mission sea state bias modeling: development and assessment, OSTST meeting, Lake Constance, Germany. http://meetings.aviso.altimetry.fr/fileadmin/user_upload/tx_ausyclsseminar/ files/28Ball1400-6_vandemark_SSB_ostst_2014.pdf

Feng, H., D. Vandemark and P. Callahan, 2015. Revised sea state bias models for retracked TOPEX altimeter data, 2015 OSTST meeting, Reston, VA. http://meetings.aviso.altimetry.fr/fileadmin/user_upload/tx_ausyclsseminar/files/feng_etal_TxRGDR-poster_ostst2015.pdf

Feng, H., D. Vandemark, N. Tran, B. Beckley, and B. Chapron, 2014. Multi-mission sea state bias modeling: development and assessment, 2014 OSTST meeting, Lake Constance, Germany. http://meetings.aviso.altimetry.fr/fileadmin/user_upload/tx_ausyclsseminar/files/28Ball1400-6_vandemark_SSB_ostst_2014.pdf

Feng, H., S. Yao, L. Li, N. Tran, D. Vandemark, and S. Labroue. 2010. Spline-based nonparametric estimation of the altimeter sea state bias correction, IEEE Geoscience and Remote Sensing Letters, vol. 7, issue 3, pp. 577-581.

Rascle, N. and F. Ardhuin. 2013. A global wave parameter database for geophysical applications. Part 2: Model validation with improved source term parameterization. Ocean Modelling, (70) , 174– 188. http://dx.doi.org/10.1016/j.ocemod.2012.12.001

Feng, H., D. Vandemark, Y. Quilfen, B. Chapron, and B. Beckley, 2006. Assessment of wind forcing impact on a global wind-wave model using the TOPEX altimeter, Ocean Eng., 33, 1431 – 1461, doi:10.1016/j.oceaneng.2005.10.015.

Tran, N., D. Vandemark, B. Chapron, S. Labroue, H. Feng, B. Beckley, and P. Vincent. 2006. New models for satellite altimeter sea state bias correction developed using global wave model data. J. Geophys. Res. 111:C09009, doi: 10.1029/2005JC003406.

Tran,N., S. Labroue , S. Philipps , E. Bronner and N. Picot. 2010a. Overview and Update of the Sea State Bias Corrections for the Jason-2, Jason-1 and TOPEX Missions, Marine Geodesy, 33:S1, 348-362, doi:10.1080/01490419.2010.487788

Tran, N., D. Vandemark, S. Labroue, H. Feng, B. Chapron, J. Lambin, N. Picot, and H. L. Tolman. 2010b. The sea state bias in altimeter sea level estimates determined by combining wave model and satellite data. J. Geophys. Res., doi:10.1029/2009JC005534.