Case 2: Single observation test with NAM BE

Case 2: Single observation test with NAM BE cindyhg Mon, 07/15/2019 - 14:42

ARW SINGLE OBSERVATION TEST W/ NAM BE

Introduction

This exercise consists of running the GSI analysis with a single pseudo observation at a specified location, to illustrate how that observation influences the analysis.

Further information on setting up a single observation test is available in section 4.2 of the GSI User's Guide.

The ARW background field is provided in netcdf format, and the NAM (North American Mesoscale Model) BE is employed as the background error covariance.

Setting up the Run Script

Setting up the Run Script cindyhg Mon, 07/15/2019 - 14:43

ARW SINGLE OBSERVATION TEST W/ NAM BE

Setting up the Run Script

For this exercise, make a copy of the prepared basic run script:
cp run_gsi_regional.ksh_basic run_gsi_regional.ksh_psot.

Make the following additional modifications to the script run_gsi_regional.ksh_psot:

Set the name/path for the analysis run directory

Set up the one observation test option to true

if_oneob=Yes

Select the background field format

bk_core=ARW

Select the NAM background error covariance

bkcv_option=NAM

An example of this run script is available from the link run_gsi_regional.ksh

Check the GSI namelist

Users can check the namelist to see how to set up a single observation test. The related namelist options include :

oneobtest=.true.

Set the location of the pseudo observation: &SINGLEOB_TEST
maginnov=1.0,magoberr=0.8,oneob_type='t',
oblat=38.,oblon=279.,obpres=500.,obdattim=${ANAL_TIME},
obhourset=0.,
/

An example namelist is available here.

Running the Script

Running the Script cindyhg Mon, 07/15/2019 - 14:44

ARW SINGLE OBSERVATION TEST W/ NAM BE

Running the Script

In this example, GSI is run as a 4-core MPI job. If you named your run script run_gsi_regional.ksh and 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 Mon, 07/15/2019 - 14:45

ARW SINGLE OBSERVATION TEST W/ NAM BE

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 statistics are available from the fit files (namedfort.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).

Visualizing the Analysis

The model analysis may be visualized through use of the ncl script GSI_singleobs_arw.ncl provided with the community GSI under ./util/Analysis_Utilities/plots_ncl. It plots the XY (left column) and XZ (right column) cross sections of the analysis increment fields through the grid point that has the maximum temperature increment.

To visualize your output, copy the ncl script to run directory and change lines:

change cdf_analysis = addfile("wrf_inout.cdf","r") to point to analysis results.

change cdf_bk = addfile("${DATA_ROOT}/wrfout_d01_2018-08-12_12:00:00.cdf","r") to point to background.

A sample script can be found at GSI_singleobs_arw.ncl

Once you have customized the script, run the script with the command:
ncl GSI_singleobs_arw.ncl

The script will generate a file: GSI_singleObse_T_arw.pdf. Use display GSI_singleObse_T_arw.pdf to show the image. Compare this image with the reference solution [PDF] for this configuration.