Present status and future directions of GNSS assimilation at NRL
Presenter:
Benjamin Ruston
Naval Research Laboratory
1Naval Research Laboratory, 2UCAR
Talk
The use of Global Navigation Satellite System data for the Navy Global Environmental Model (NAVGEM) and its associated data assimilation system Naval Research Laboratory Atmospheric Variational Data Assimilation System-Accelerated Representer (NAVDAS-AR) is currently restricted to one-dimensional representation of GNSS radio occultation (GNSS-RO) with the assimilated parameter bending angle as a function of impact parameter. There has been aggressive use of new platforms recently, including AOPOD from KOMPSAT5 and the latest GRAS from MetOp-C which are both operational. Also capability and evaluations of ROHPP from PAZ are being completed so this can be readily incorporated. Further, commercial vendors such as SPIRE and GeoOptics are providing data for evaluation. For the short term gains in the current framework an improvement in the observation error modeling is expected to provide the greatest benefits. Further a 2D (ray tracing) treatment of the profile is expected to be implemented; however, the benefits may not be immediately realized until other improvements in the overall data assimilation strategy are developed. The GNSS-RO observations, along with many of the conventional in-situ observations are being used in a new effort to address NWP model driven “bias drift” in the satellite radiance bias correction coefficients. This has shown great promise to address some concerns in the analysis where persistent biases have been observed. Lastly, the GNSS-Reflectometry (GNSS-R) for use in winds and soil moisture will continue to be an active area of research. We expect a new wealth of information from this technology as it matures and continue to participate and be active in exploring use of GNSS-R.
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