Data Assimilation Development for the 2019 Operational FV3-GFS

As part of the Next Generation Global Prediction System (NGGPS), NCEP is replacing the spectral dynamical core of the Global Forecast System (GFS) with the Finite-Volume Cubed-Sphere Dynamical Core (FV3). The initial beta version of the FV3-GFS is planned to go into operations on July 1, 2018, where it will run in parallel with the current operational GFS. The beta implementation was targeted to contain similar components and run at a comparable resolution to operations with the following 2019 implementation replacing current operations and including new features.

This presentation will explore the planned 2019 FV3-GFS implementation and the accompanying modifications to the Global Data Assimilation System (GDAS). One of the biggest challenges for the FY19 implementation concerns an increase in the resolution, both horizontal and vertical, and a raising of the model top to approximately 80 km. New parameters need to be derived for the static background error, ensemble covariance localization scales, and hybrid covariance weights. The impact of the change in the model top also needs to be evaluated for several existing components, such as the normal mode constraint, stochastic physics, and channel selection for satellite radiances. Other new features under consideration for the implementation are the 4DIAU, changing the EnKF solver to the LETKF, moving the EnKF update to the early cycle, and correlated observation errors. Details of the various components and preliminary results from a low resolution framework will be presented.