Assimilation of Radial Velocity and Satellite Data in the HRRR and Rap Models

This presentation will provide a summary of ongoing research for adding new observation data sets to the HRRR and RAP assimilation for the next operational upgrade (RAPv4 / HRRRv3 planned for late 2017 or early 2018).  Key among these research tasks is assimilation of radial velocity data in the HRRR and addition of direct readout ATMS and CrIS polar orbiter satellite radiance data in the RAP.  Other planned additions include Goes-based cloud-top cooling rate data and potentially expanded lightning data assimilation.

The NCEP operational RAP/HRRR upgrade scheduled for August 2016 includes assimilation of WSR-88D radar radial velocity observations for the 13-km RAP model with a slight forecast improvement from these data.  Testing and development is ongoing to add radial velocity assimilation for the 3-km HRRR for the next operational implementation.  Current work is focusing on a two-pass application of the gridpoint statistical interpolation (GSI) analysis to assimilate the radial velocity data with shorter length scales following the assimilation of other observations.  Preliminary test results indicate that this approach yields the small-scale detail desired for initializing storm-scale wind features in the 3-km HRRR.  Work is continuing to optimize the length scale specification and assess the impact of the 2^nd GSI pass on the balance from the combined assimilation in the first pass.  Other storm-scale work is focused on assimilation of GOES-based cloud-top cooling rate data via a latent heating approach.  The goal of this cloud-top cooling rate assimilation is to reduce the time-lag in capturing initial storm development in the HRRR assimilation system.

Description of the HRRR 3-km radial velocity assimilation results will be complemented by presentation of the direct readout ATMS and CrIS polar orbiter satellite assimilation results.  Key aspects for the assimilation of these data are optimizing the bias correction and the channel selection.  The talk will conclude with an assessment of the combined effects on the RAP and HRRR of the addition of all these new data sets.