search

NOAA-EMC / global-workflow

Global Superstructure/Workflow supporting the Global Forecast System (GFS)
https://global-workflow.readthedocs.io/en/latest
GNU Lesser General Public License v3.0
75 stars 168 forks source link

Enable tapering of atm ensemble spread at the model top #3096

Open CatherineThomas-NOAA opened 17 hours ago

CatherineThomas-NOAA commented 17 hours ago

What new functionality do you need?

The GSI EnKF was previously updated to allow for the tapering of the ensemble spread towards the model top. The needed update would turn on that feature by default for GFSv17.

What are the requirements for the new functionality?

When GFS experiments are run with the global workflow, the atmospheric ensemble perturbations should be reduced towards the model top automatically using the taperanalperts namelist variable in the EnKF.

Acceptance Criteria

taperanalperts=.true. in the GSI EnKF namelist and runs without failure

Suggest a solution (optional)

A PR will be opened to include the new variable in the config.eupd file as well as the update needed for the ex script to read and pass on the new variable.

CatherineThomas-NOAA commented 17 hours ago

Evaluation of the impact of the tapering can be found here. Two rounds of evaluation were performed, both before and after the GWD changes were included for HR4.