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NOAA-EMC / HDASApp

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Interpolating the GDAS ensemble onto the HAFS grid #3

Open XuLu-NOAA opened 4 months ago

XuLu-NOAA commented 4 months ago

Description

Ensemble covariance is needed for EnVar DA. Since we cannot currently afford an HAFS ensemble, using the GDAS ensemble is a substitute option. However, JEDI requires the ensemble to be on the model grid during DA. Therefore, we need to develop an efficient method to interpolate the GDAS ensemble onto the HAFS grid for DA.

Proposed solution

It is better if we can do it using existing JEDI functions.

ShunLiu-NOAA commented 4 months ago

@XuLu-NOAA As we discussed, chgres can be used to generate cold start IC for HAFS domain. If you have to use restart file, you can start an one-timestep forecast to get restart file. The method used in RRFS-EnKF initialization.

XuLu-NOAA commented 4 months ago

@XuLu-NOAA As we discussed, chgres can be used to generate cold start IC for HAFS domain. If you have to use restart file, you can start an one-timestep forecast to get restart file. The method used in RRFS-EnKF initialization.

Thanks, in that case, one-time step GDAS-interpolated HAFS ensemble can be generated using existing functions in HAFS workflow with some modifications.