Case 5: 3D Hybrid EnVar

Case 5: 3D Hybrid EnVar cindyhg Tue, 07/16/2019 - 10:53

GSI 3D HYBRID FOR ARW USING GLOBAL ENSEMBLE FORECAST

Introduction

This exercise runs the GSI 3 Dimensional Ensemble-Variational (EnVar) hybrid analysis with the ARW background, conventional data at 12z August 12, 2018. 

Please note the ARW background field is provided in netcdf format, and the NAM BE is employed as the background error covariance in this experiment. The global ensemble forecasts are linked to run this GSI hybrid test.

Setting up the Run Script for GSI hybrid analysis

Setting up the Run Script for GSI hybrid analysis cindyhg Tue, 07/16/2019 - 10:53

GSI 3D HYBRID FOR ARW USING GLOBAL ENSEMBLE FORECAST

Setting up the Run Script for GSI hybrid analysis

Copy the sample run script run_gsi_regional.ksh from the practical case 3 (ARW 3DVAR with PrepBUFR) to a working directory and make the following modifications to run GSI hybrid analysis:

  • Set the name/path for the analysis run directory to
  • WORK_ROOT=${run directory}
  • Set the location of the ensemble files in the variable ENS_ROOT=...
  • Set to run GSI hybrid analysis: if_hybrid=Yes
  • Set not to run GSI 4D hybrid analysis: if_4DEnVar=No

Please note that the sample script provides links to the GFS ensemble data for this tutorial case only. If you are running your own GSI hybrid case with a different date, please make any necessary modifications to specify the variable ENS_ROOT and ENSEMBLE_FILE_mem in the run script.

Running the Script

Running the Script cindyhg Tue, 07/16/2019 - 10:54

SETUP GSI 3D HYBRID FOR ARW USING GLOBAL ENSEMBLE FORECAST

Running the Script

If you run on PBS system (Cheyenne), type: 

qsub run_gsi_regional.ksh 

to launch the job. 

The progress of the job can be monitored by examining the tail of the standard out file in the run directory as specified in the variable WORK_ROOT: 

tail stdout

When completed, the contents of this run directory are provided in the following list .

Results

Results cindyhg Tue, 07/16/2019 - 10:55

SETUP GSI 3D HYBRID FOR ARW USING GLOBAL ENSEMBLE FORECAST

Results

The standard output file stdout contains the run diagnostics, such as convergence information, and observation distribution from the GSI run. Details of the standard output file are available in section 4.1 of the GSI User's Guide.

Information about the use of observations by the analysis, and the corresponding innovations are available from the fit files (named fort.2*). The fit files located in the run directory should agree with the following fit files for temperature (fit_t1); wind(fit_w1); moisture (fit_q1); surface pressure (fit_p1); and radiance (fit_rad1); and GPS (fort.212); and radar radial velocity(fort.209).

Convergence information is available in the file: fort.220

Visualizing the Analysis

Use the same method as the practical case 3 (ARW 3DVAR) to make plots of the analysis increments. This time, plots will be made for the 2nd level (kmax=1) and level 21 (kmax=20). Once done pdf files GSI_Analysis_increment_1.pdf and GSI_Analysis_increment_20.pdf will be generated in the run directory. Compare these images with the reference solution [level 2 ] and [level 21].