Chapter 6: WRF-VAR

Chapter 6: WRF Data Assimilation

Introduction
Installing WRFDA
Installing WRFNL and WRFPLUS
Running Observation Preprocessor (OBSPROC)
Running WRFDA
Radiance Data Assimilations in WRFDA
WRFDA Diagnostics
Updating WRF boundary conditions
Running gen_be
Additional WRFDA Exercises
Hybrid Data Assimilation
Description of Namelist Variables

Introduction

Data assimilation is the technique by which observations are combined with a NWP product (the first guess or background forecast) and their respective error statistics to provide an improved estimate (the analysis) of the atmospheric (or oceanic, Jovian, whatever) state. Variational (Var) data assimilation achieves this through the iterative minimization of a prescribed cost (or penalty) function. Differences between the analysis and observations/first guess are penalized (damped) according to their perceived error. The difference between three-dimensional (3D-Var) and four-dimensional (4D-Var) data assimilation is the use of a numerical forecast model in the latter.

The MMM Division of NCAR supports a unified (global/regional, multi-model, 3/4D-Var) model-space data assimilation system (WRFDA) for use by NCAR staff and collaborators, and is also freely available to the general community, together with further documentation, test results, plans etc., from the WRFDA web-page http://www.mmm.ucar.edu/wrf/users/wrfda/Docs/user_guide_V3.2/users_guide_chap6.htm.

Various components of the WRFDA system are shown in blue in the sketch below, together with their relationship with rest of the WRF system.

x^b: first guess either from previous WRF forecast or from WPS/REAL output.

x^lbc: lateral boundary from WPS/REAL output.

x^a: analysis from WRFDA data assimilation system.

x^f: WRF forecast output.

y^o: observations processed by OBSPROC. (note: PREPBUFR input, Radar and Radiance data don’t go through OBSPROC)

B₀: background error statistics from generic BE data (CV3) or gen_be.

R: observational and representative error statistics.

In this chapter, you will learn how to run the various components of WRFDA system. For the training purpose, you are supplied with a test case including the following input data: a) observation file (in the format prior to OBSPROC), b) WRF NetCDF background file (WPS/REAL output used as a first guess of the analysis), and c) Background error statistics (estimate of errors in the background file). You can download the test dataset from http://www.mmm.ucar.edu/wrf/users/wrfda/download/testdata.html. In your own work, you have to create all these input files yourselves. See the section Running Observation Preprocessor for creating your observation files. See section Running gen_be for generating your background error statistics file if you want to use cv_options=5.

Before using your own data, we suggest that you start by running through the WRFDA related programs at least once using the supplied test case. This serves two purposes: First, you can learn how to run the programs with data we have tested ourselves, and second you can test whether your computer is adequate to run the entire modeling system. After you have done the tutorial, you can try running other, more computationally intensive, case studies and experimenting with some of the many namelist variables.

WARNING: It is impossible to test every code upgrade with every permutation of computer, compiler, number of processors, case, namelist option, etc. The “namelist” options that are supported are indicated in the “WRFDA/var/README.namelist” and these are the default options.

Running with your own domain. Hopefully, our test cases will have prepared you for the variety of ways in which you may wish to run WRFDA. Please inform us about your experiences.

As a professional courtesy, we request that you include the following reference in any publications that makes use of any component of the community WRFDA system:

Barker, D.M., W. Huang, Y.R. Guo, and Q.N. Xiao., 2004: A Three-Dimensional (3DVAR) Data Assimilation System For Use With MM5: Implementation and Initial Results. Mon. Wea. Rev., 132, 897-914.

Huang, X.Y., Q. Xiao, D.M. Barker, X. Zhang, J. Michalakes, W. Huang, T. Henderson, J. Bray, Y. Chen, Z. Ma, J. Dudhia, Y. Guo, X. Zhang, D.J. Won, H.C. Lin, and Y.H. Kuo, 2009: Four-Dimensional Variational Data Assimilation for WRF: Formulation and Preliminary Results. Mon. Wea. Rev., 137, 299–314.

Running WRFDA requires a Fortran 90 compiler. We have currently tested the WRFDA on the following platforms: IBM (XLF), SGI Altix (INTEL), PC/Linux (PGI, INTEL, GFORTRAN), and Apple (G95/PGI). Please let us know if this does not meet your requirements, and we will attempt to add other machines to our list of supported architectures as resources allow. Although we are interested to hear of your experiences on modifying compile options, we do not yet recommend making changes to the configure file used to compile WRFDA.

Installing WRFDA

a. Obtaining WRFDA Source Code

Users can download the WRFDA source code from http://www.mmm.ucar.edu/wrf/users/wrfda/download/get_source.html.

After the tar file is unzipped (gunzip WRFDAV3.2.tar.gz) and untarred (untar WRFDAV3.2.tar), the directory WRFDA should be created; this directory contains the WRFDA source, external libraries, and fixed files. The following is a list of the system components and the content for each directory:

Directory Name	Content
var/da	WRFDA source code
var/run	Fixed input files required by WRFDA, such as background error covariances, and radiance related files CRTM coefficients, radiance_info and VARBC.in.
var/external	Library needed by WRFDA, include crtm, bufr, lapack, blas
var/obsproc	Obsproc source code , namelist, and observation error file.
var/gen_be	Source code of generate background error
var/build	Build all .exe files.

b. Compile WRFDA and Libraries

Start with V3.1.1, to compile the WRFDA code, it is necessary to have installed the NetCDF library. The NetCDF library is the only mandatory library to install WRFDA, if only conventional observational data from LITTLE_R format file is to be used.

Only if you intend to use observational data with PREPBUFR format, an environment variables is needed to be set like (using the C-shell),

> setenv BUFR 1

In addition to BUFR library, if you intend to assimilate satellite radiance data with CRTM (V2.0.2),

> setenv CRTM 1

The CRTM will be compiled with WRFDA together. You don’t need to install the CRTM separately any more since CRTM V2.0.2. However, if you intend to use RTTOV (8.7) to assimilate radiance data, which still have to be installed separately. RTTOV (8.7) can be downloaded from http://www.metoffice.gov.uk/science/creating/working_together/nwpsaf_public.html. The additional necessary environment variables needed are set (again using the C-shell), by commands looking something like

> setenv RTTOV /usr/local/rttov87

(Note: make a linkage of $RTTOV/librttov.a to $RTTOV/src/librttov8.7.a)

Note: Make sure the required libraries were all compiled using the same compiler that will be used to build WRFDA, since the libraries produced by one compiler may not be compatible with code compiled with another.

Assuming all required libraries are available and the WRFDA source code is ready, start to install the WRFDA as following step:

To configure WRFDA, enter the WRFDA directory and type

> ./configure wrfda

A list of configuration options for your computer should appear. Each option combines a compiler type and a parallelism option; since the configuration script doesn’t check which compilers are actually available, be sure to only select among the options for compilers that are available on your system. The parallelism option allows for a single-processor (serial) compilation, shared-memory parallel (smpar) compilation, distributed-memory parallel (dmpar) compilation and distributed-memory with shared-memory parallel (sm+dm) compilation. For example, on a Macintosh computer, the above steps look like:

> ./configure wrfda

checking for perl5... no

checking for perl... found /usr/bin/perl (perl)

Will use NETCDF in dir: /users/noname/work/external/g95/netcdf-3.6.1

PHDF5 not set in environment. Will configure WRF for use without.

$JASPERLIB or $JASPERINC not found in environment, configuring to build without grib2 I/O...

------------------------------------------------------------------------

Please select from among the following supported platforms.

1. Darwin (MACOS) PGI compiler with pgcc (serial)

2. Darwin (MACOS) PGI compiler with pgcc (smpar)

3. Darwin (MACOS) PGI compiler with pgcc (dmpar)

4. Darwin (MACOS) PGI compiler with pgcc (dm+sm)

5. Darwin (MACOS) intel compiler with icc (serial)

6. Darwin (MACOS) intel compiler with icc (smpar)

7. Darwin (MACOS) intel compiler with icc (dmpar)

8. Darwin (MACOS) intel compiler with icc (dm+sm)

9. Darwin (MACOS) intel compiler with cc (serial)

10. Darwin (MACOS) intel compiler with cc (smpar)

11. Darwin (MACOS) intel compiler with cc (dmpar)

12. Darwin (MACOS) intel compiler with cc (dm+sm)

13. Darwin (MACOS) g95 with gcc (serial)

14. Darwin (MACOS) g95 with gcc (dmpar)

15. Darwin (MACOS) xlf (serial)

16. Darwin (MACOS) xlf (dmpar)

Enter selection [1-10] : 13

------------------------------------------------------------------------

Compile for nesting? (0=no nesting, 1=basic, 2=preset moves, 3=vortex following) [default 0]:

Configuration successful. To build the model type compile .

……

After running the configuration script and choosing a compilation option, a configure.wrf file will be created. Because of the variety of ways that a computer can be configured, if the WRFDA build ultimately fails, there is a chance that minor modifications to the configure.wrf file may be needed.

Note: WRF compiles with –r4 option while WRFDA compiles with –r8. For this reason, WRF and WRFDA cannot reside and be compiled under the same directory.

Hint: It is helpful to start with something simple, such as the serial build. If it is successful, move on to build dmpar code. Remember to type ‘clean –a’ between each build.

To compile the code, type

> ./compile all_wrfvar >&! compile.out

Successful compilation of ‘all_wrfvar” will produce 32 executables in the var/build directory which are linked in var/da directory, as well as obsproc.exe in var/obsproc/src directory. You can list these executables by issuing the command (from WRFDA directory)

> ls -l var/build/*exe var/obsproc/src/obsproc.exe

-rwxr-xr-x 1 noname users 641048 Mar 23 09:28 var/build/da_advance_time.exe

-rwxr-xr-x 1 noname users 954016 Mar 23 09:29 var/build/da_bias_airmass.exe

-rwxr-xr-x 1 noname users 721140 Mar 23 09:29 var/build/da_bias_scan.exe

-rwxr-xr-x 1 noname users 686652 Mar 23 09:29 var/build/da_bias_sele.exe

-rwxr-xr-x 1 noname users 700772 Mar 23 09:29 var/build/da_bias_verif.exe

-rwxr-xr-x 1 noname users 895300 Mar 23 09:29 var/build/da_rad_diags.exe

-rwxr-xr-x 1 noname users 742660 Mar 23 09:29 var/build/da_tune_obs_desroziers.exe

-rwxr-xr-x 1 noname users 942948 Mar 23 09:29 var/build/da_tune_obs_hollingsworth1.exe

-rwxr-xr-x 1 noname users 913904 Mar 23 09:29 var/build/da_tune_obs_hollingsworth2.exe

-rwxr-xr-x 1 noname users 943000 Mar 23 09:28 var/build/da_update_bc.exe

-rwxr-xr-x 1 noname users 1125892 Mar 23 09:29 var/build/da_verif_anal.exe

-rwxr-xr-x 1 noname users 705200 Mar 23 09:29 var/build/da_verif_obs.exe

-rwxr-xr-x 1 noname users 46602708 Mar 23 09:28 var/build/da_wrfvar.exe

-rwxr-xr-x 1 noname users 1938628 Mar 23 09:29 var/build/gen_be_cov2d.exe

-rwxr-xr-x 1 noname users 1938628 Mar 23 09:29 var/build/gen_be_cov3d.exe

-rwxr-xr-x 1 noname users 1930436 Mar 23 09:29 var/build/gen_be_diags.exe

-rwxr-xr-x 1 noname users 1942724 Mar 23 09:29 var/build/gen_be_diags_read.exe

-rwxr-xr-x 1 noname users 1941268 Mar 23 09:29 var/build/gen_be_ensmean.exe

-rwxr-xr-x 1 noname users 1955192 Mar 23 09:29 var/build/gen_be_ensrf.exe

-rwxr-xr-x 1 noname users 1979588 Mar 23 09:28 var/build/gen_be_ep1.exe

-rwxr-xr-x 1 noname users 1961948 Mar 23 09:28 var/build/gen_be_ep2.exe

-rwxr-xr-x 1 noname users 1945360 Mar 23 09:29 var/build/gen_be_etkf.exe

-rwxr-xr-x 1 noname users 1990936 Mar 23 09:28 var/build/gen_be_stage0_wrf.exe

-rwxr-xr-x 1 noname users 1955012 Mar 23 09:28 var/build/gen_be_stage1.exe

-rwxr-xr-x 1 noname users 1967296 Mar 23 09:28 var/build/gen_be_stage1_1dvar.exe

-rwxr-xr-x 1 noname users 1950916 Mar 23 09:28 var/build/gen_be_stage2.exe

-rwxr-xr-x 1 noname users 2160796 Mar 23 09:29 var/build/gen_be_stage2_1dvar.exe

-rwxr-xr-x 1 noname users 1942724 Mar 23 09:29 var/build/gen_be_stage2a.exe

-rwxr-xr-x 1 noname users 1950916 Mar 23 09:29 var/build/gen_be_stage3.exe

-rwxr-xr-x 1 noname users 1938628 Mar 23 09:29 var/build/gen_be_stage4_global.exe

-rwxr-xr-x 1 noname users 1938732 Mar 23 09:29 var/build/gen_be_stage4_regional.exe

-rwxr-xr-x 1 noname users 1094740 Mar 23 09:29 var/build/gen_be_vertloc.exe

-rwxr-xr-x 1 noname users 1752352 Mar 23 09:29 var/obsproc/src/obsproc.exe

da_wrfvar.exe is the main executable for running WRFDA. Make sure it is created after the compilation. Sometimes (unfortunately) it is possible that other utilities get successfully compiled, while the main da_wrfvar.exe fails; please check the compilation log file carefully to figure out the problem.

The basic gen_be utility for regional model consists of gen_be_stage0_wrf.exe, gen_be_stage1.exe, gen_be_stage2.exe, gen_be_stage2a.exe, gen_be_stage3.exe, gen_be_stage4_regional.exe, and gen_be_diags.exe.

da_updated_bc.exe is used for updating WRF boundary condition after a new WRFDA analysis is generated.

da_advance_time.exe is a very handy and useful tool for date/time manipulation. Type “da_advance_time.exe” to see its usage instruction.

In addition to the executables for running WRFDA and gen_be, obsproc.exe (the executable for preparing conventional data for WRFDA) compilation is also included in “./compile all_wrfvar”.

Go to /external/bufr and /external/crtm to check if the libbufr.a and libcrtm.a were generated if you use BUFR and CRTM library.

c. Clean Compilation

To remove all object files and executables, type:

clean

To remove all build files, including configure.wrfda, type:

clean -a

The clean command is recommended if compilation fails or configuration file is changed.

Installing WRFNL and WRFPLUS (For 4D-Var only)

If you intend to run WRF 4D-Var, it is necessary to have installed the WRFNL (WRF nonlinear model) and WRFPLUS (WRF adjoint and tangent linear model). WRFNL is a modified version of WRF V3.2 and can only be used for 4D-Var purposes. WRFPLUS contains the adjoint and tangent linear models based on a simplified WRF model, which only includes some simple physical processes such as vertical diffusion and large-scale condensation.

To install WRFNL:

Get the WRF zipped tar file from:

http://www.mmm.ucar.edu/wrf/users/download/get_source.html

Unzip and untar the file, name the directory WRFNL

> cd WRFNL

> gzip -cd WRFV3.TAR.gz | tar -xf - ; mv WRFV3 WRFNL

Get the WRFNL patch zipped tar file from:

http://www.mmm.ucar.edu/wrf/users/wrfda/download/wrfnl.html

unzip and untar the WRFNL patch file

> gzip -cd WRFNL3.2_PATCH.tar.gz | tar -xf -

> ./configure

serial means single processor

dmpar means Distributed Memory Parallel (MPI)

smpar is not supported for 4D-Var

Please select 0 for the second option for no nesting

Compile the WRFNL

> ./compile em_real

> ls -ls main/*.exe

If you built the real-data case, you should see wrf.exe

To install WRFPLUS:

Get the WRFPLUS zipped tar file from:

http://www.mmm.ucar.edu/wrf/users/wrfda/download/wrfplus.html

Unzip and untar the file to WRFPLUS

> gzip -cd WRFPLUS3.2.tar.gz | tar -xf -

> cd WRFPLUS

> ./configure wrfplus

serial means single processor

dmpar means Distributed Memory Parallel (MPI)

Note: wrfplus was tested on following platforms:

IBM AIX: xlfrte 11.1.0.5

Linux : pgf90 6.2-5 64-bit target on x86-64 Linux (environmental variable PGHPF_ZMEM=yes is needed)

Mac OS (Intel) : g95 0.91!

Compile WRFPLUS

> ./compile wrf

> ls -ls main/*.exe

You should see wrfplus.exe

Running Observation Preprocessor (OBSPROC)

The OBSPROC program reads observations in LITTLE_R format (a legendary ASCII format, in use since MM5 era). Please refer to the documentation at http://www.mmm.ucar.edu/mm5/mm5v3/data/how_to_get_rawdata.html for LITTLE_R format description. For your applications, you will have to prepare your own observation files. Please see http://www.mmm.ucar.edu/mm5/mm5v3/data/free_data.html for the sources of some freely available observations and the program for converting the observations to LITTLE_R format. Because the raw observation data files could be in any of formats, such as ASCII, BUFR, PREPBUFR, MADIS, HDF, etc. Further more, for each of formats, there may be the different versions. To make WRFDA system as general as possible, the LITTLE_R format ASCII file was adopted as an intermediate observation data format for WRFDA system. Some extensions were made in the LITTLE_R format for WRFDA applications. More complete description of LITTLE_R format and conventional observation data sources for WRFDA could be found from the web page: 2010 Winter Tutorial by clicking “Observation Pre-processing”. The conversion of the user-specific-source data to the LITTLE_R format observation data file is the users’ task.

The purposes of OBSPROC are:

· Remove observations outside the time range and domain (horizontal and top).

· Re-order and merge duplicate (in time and location) data reports.

· Retrieve pressure or height based on observed information using the hydrostatic assumption.

· Check vertical consistency and super adiabatic for multi-level observations.

· Assign observational errors based on a pre-specified error file.

· Write out the observation file to be used by WRFDA in ASCII or BUFR format.

The OBSPROC program—obsproc.exe should be found under the directory WRFDA/var/obsproc/src if “compile all_wrfvar” was completed successfully.

a. Prepare observational data for 3D-Var

To prepare the observation file, for example, at the analysis time 0h for 3D-Var, all the observations between ±1h (or ±1.5h) will be processed, as illustrated in following figure, which means that the observations between 23h and 1h are treated as the observations at 0h.

Before running obsproc.exe, create the required namelist file namelist.obsproc (see WRFDA/var/obsproc/README.namelist, or the section Description of Namelist Variables for details).

For your reference, an example file named “namelist_obsproc.3dvar.wrfvar-tut” has already been created in the var/obsproc directory. Thus, proceed as follows.

> cp namelist.obsproc.3dvar.wrfvar-tut namelist.obsproc

Next, edit the namelist file namelist.obsproc by changing the following variables to accommodate your experiments.

&record1

obs_gts_filename='obs.2008020512'

&record2

time_window_min = '2008-02-05_11:00:00',: The earliest time edge as ccyy-mm-dd_hh:mn:ss

time_analysis = '2008-02-05_12:00:00', : The analysis time as ccyy-mm-dd_hh:mn:ss

time_window_max = '2008-02-05_13:00:00',: The latest time edge as ccyy-mm-dd_hh:mn:ss

&record6,7,8

Edit all the domain setting according with your own experiment. You may pay special attention on NESTIX and NESTJX, which is described in the section Description of Namelist Variables for details).

&record9

use_for = '3DVAR', ; used for 3D-Var, default

To run OBSPROC, type

> obsproc.exe >&! obsproc.out

Once obsproc.exe has completed successfully, you will see an observation data file, obs_gts_2008-02-05_12:00:00.3DVAR, in the obsproc directory. This is the input observation file to WRFDA.

obs_gts_2008-02-05_12:00:00.3DVAR is an ASCII file that contains a header section (listed below) followed by observations. The meanings and format of observations in the file are described in the last six lines of the header section.

TOTAL = 9066, MISS. =-888888.,

SYNOP = 757, METAR = 2416, SHIP = 145, BUOY = 250, BOGUS = 0, TEMP = 86,

AMDAR = 19, AIREP = 205, TAMDAR= 0, PILOT = 85, SATEM = 106, SATOB = 2556,

GPSPW = 187, GPSZD = 0, GPSRF = 3, GPSEP = 0, SSMT1 = 0, SSMT2 = 0,

TOVS = 0, QSCAT = 2190, PROFL = 61, AIRSR = 0, OTHER = 0,

PHIC = 40.00, XLONC = -95.00, TRUE1 = 30.00, TRUE2 = 60.00, XIM11 = 1.00, XJM11 = 1.00,

base_temp= 290.00, base_lapse= 50.00, PTOP = 1000., base_pres=100000., base_tropo_pres= 20000., base_strat_temp= 215.,

IXC = 60, JXC = 90, IPROJ = 1, IDD = 1, MAXNES= 1,

NESTIX= 60,

NESTJX= 90,

NUMC = 1,

DIS = 60.00,

NESTI = 1,

NESTJ = 1,

INFO = PLATFORM, DATE, NAME, LEVELS, LATITUDE, LONGITUDE, ELEVATION, ID.

SRFC = SLP, PW (DATA,QC,ERROR).

EACH = PRES, SPEED, DIR, HEIGHT, TEMP, DEW PT, HUMID (DATA,QC,ERROR)*LEVELS.

INFO_FMT = (A12,1X,A19,1X,A40,1X,I6,3(F12.3,11X),6X,A40)

SRFC_FMT = (F12.3,I4,F7.2,F12.3,I4,F7.3)

EACH_FMT = (3(F12.3,I4,F7.2),11X,3(F12.3,I4,F7.2),11X,3(F12.3,I4,F7.2))

#------------------------------------------------------------------------------#

…… observations ………

Before running WRFDA, you may like to learn more about various types of data that will be passed to WRFDA for this case, for example, their geographical distribution, etc. This file is in ASCII format and so you can easily view it. To have a graphical view about the content of this file, there is a “MAP_plot” utility to look at the data distribution for each type of observations. To use this utility, proceed as follows.

> cd MAP_plot

> make

We have prepared some configure.user.ibm/linux/mac/… files for some platforms, when “make” is typed, the Makefile will use one of them to determine the compiler and compiler option. Please modify the Makefile and configure.user.xxx to accommodate the complier on your platform. Successful compilation will produce Map.exe. Note: The successful compilation of Map.exe requires pre-installed NCARG Graphics libraries under $(NCARG_ROOT)/lib.

Modify the script Map.csh to set the time window and full path of input observation file (obs_gts_2008-02-05_12:00:00.3DVAR). You will need to set the following strings in this script as follows:

Map_plot = /users/noname/WRFDA/var/obsproc/MAP_plot

TIME_WINDOW_MIN = ‘2008020511’

TIME_ANALYSIS = ‘2008020512’

TIME_WINDOW_MAX = ‘2008020513’
OBSDATA = ../obs_gts_2008-02-05_12:00:00.3DVAR

Next, type

> Map.csh

When the job has completed, you will have a gmeta file gmeta.{analysis_time} corresponding to analysis_time=2008020512. This contains plots of data distribution for each type of observations contained in the OBS data file: obs_gts_2008-02-05_12:00:00.3DVAR. To view this, type

> idt gmeta.2008020512

It will display (panel by panel) geographical distribution of various types of data. Following is the geographic distribution of “sonde” observations for this case.

There is an alternative way to plot the observation by using ncl script: WRFDA/var/graphics/ncl/plot_ob_ascii_loc.ncl. However, with this way, you need to provide the first guess file to the ncl script, and have ncl installed in your system.

b. Prepare observational data for 4D-Var

To prepare the observation file, for example, at the analysis time 0h for 4D-Var, all observations from 0h to 6h will be processed and grouped in 7 sub-windows from slot1 to slot7, as illustrated in following figure. NOTE: The “Analysis time” in the figure below is not the actual analysis time (0h), it just indicates the time_analysis setting in the namelist file, and is set to three hours later than the actual analysis time. The actual analysis time is still 0h.

An example file named “namelist_obsproc.4dvar.wrfvar-tut” has already been created in the var/obsproc directory. Thus, proceed as follows:

> cp namelist.obsproc.4dvar.wrfvar-tut namelist.obsproc

In the namelist file, you need to change the following variables to accommodate your experiments. In this test case, the actual analysis time is 2008-02-05_12:00:00, but in namelist, the time_analysis should be set to 3 hours later. The different value of time_analysis will make the different number of time slots before and after time_analysis. For example, if you set time_analysis = 2008-02-05_16:00:00, and set the num_slots_past = 4 and time_slots_ahead=2. The final results will be same as before.

&record1

obs_gts_filename='obs.2008020512'

&record2

time_window_min = '2008-02-05_12:00:00',: The earliest time edge as ccyy-mm-dd_hh:mn:ss

time_analysis = '2008-02-05_15:00:00', : The analysis time as ccyy-mm-dd_hh:mn:ss

time_window_max = '2008-02-05_18:00:00',: The latest time edge as ccyy-mm-dd_hh:mn:ss

&record6,7,8

Edit all the domain setting according with your own experiment. You may pay special attention on NESTIX and NESTJX, which is described in the section Description of Namelist Variables for details).

&record9

use_for = '4DVAR', ; used for 3D-Var, default

; num_slots_past and num_slots_ahead are used ONLY for FGAT and 4DVAR:

num_slots_past = 3, ; the number of time slots before time_analysis

num_slots_ahead = 3, ; the number of time slots after time_analysis

To run OBSPROC, type

> obsproc.exe >&! obsproc.out

Once obsproc.exe has completed successfully, you will see 7 observation data files:

obs_gts_2008-02-05_12:00:00.4DVAR

obs_gts_2008-02-05_13:00:00.4DVAR

obs_gts_2008-02-05_14:00:00.4DVAR

obs_gts_2008-02-05_15:00:00.4DVAR

obs_gts_2008-02-05_16:00:00.4DVAR

obs_gts_2008-02-05_17:00:00.4DVAR

obs_gts_2008-02-05_18:00:00.4DVAR

They are the input observation files to WRF 4D-Var. You can also use “MAP_Plot” to view the geographic distribution of different observations at different time slots.

Running WRFDA

a. Download Test Data

The WRFDA system requires three input files to run:

a) A WRF first guess and boundary input files output from either WPS/real (cold-start)

or WRF forecast (warm-start)

b) Observations (in ASCII format, PREBUFR or BUFR for radiance)

c) A background error statistics file (containing background error covariance)

The following table summarizes the above info:

Input Data	Format	Created By
First Guess	NETCDF	WRF Preprocessing System (WPS) and real.exe or WRF
Observations	ASCII (PREPBUFR also possible)	Observation Preprocessor (OBSPROC)
Background Error Statistics	Binary	WRFDA gen_be utility /Default CV3

In the test case, you will store data in a directory defined by the environment variable $DAT_DIR. This directory can be at any location and it should have read access. Type

> setenv DAT_DIR your_choice_of_dat_dir

Here, "your_choice_of_dat_dir" is the directory where the WRFDA input data is stored. Create this directory if it does not exist, and type

> cd $DAT_DIR

Download the test data for a “Tutorial” case valid at 12 UTC 5^thFebruary 2008 from http://www.mmm.ucar.edu/wrf/users/wrfda/download/testdata.html

Once you have downloaded “WRFDAV3.2-testdata.tar.gz” file to $DAT_DIR, extract it by typing

> gunzip WRFDAV3.2-testdata.tar.gz
> tar -xvf WRFDAV3.2-testdata.tar

Now you should find the following three sub-directories/files under “$DAT_DIR”

ob/2008020512/ob.2008020512.gz # Observation data in “little_r” format
rc/2008020512/wrfinput_d01   # First guess file
rc/2008020512/wrfbdy_d01     # lateral boundary file
be/be.dat                    # Background error file

......

You should first go through the section “Running Observation Preprocessor (OBSPROC)” and have a WRF-3D-Var-ready observation file (obs_gts_2008-02-05_12:00:00.3DVAR) generated in your OBSPROC working directory. You could then copy or move obs_gts_2008-02-05_12:00:00.3DVAR to be in $DAT_DIR/ob/2008020512/ob.ascii.

If you want to try 4D-Var, please go through the section “Running Observation Preprocessor (OBSPROC)” and have the WRF-4D-Var-ready observation files (obs_gts_2008-02-05_12:00:00.4DVAR,……). You could copy or move the observation files to $DAT_DIR/ob using following commands:

> mv obs_gts_2008-02-05_12:00:00.4DVAR $DAT_DIR/ob/2008020512/ob.ascii+

> mv obs_gts_2008-02-05_13:00:00.4DVAR $DAT_DIR/ob/2008020513/ob.ascii

> mv obs_gts_2008-02-05_14:00:00.4DVAR $DAT_DIR/ob/2008020514/ob.ascii

> mv obs_gts_2008-02-05_15:00:00.4DVAR $DAT_DIR/ob/2008020515/ob.ascii

> mv obs_gts_2008-02-05_16:00:00.4DVAR $DAT_DIR/ob/2008020516/ob.ascii

> mv obs_gts_2008-02-05_17:00:00.4DVAR $DAT_DIR/ob/2008020517/ob.ascii

> mv obs_gts_2008-02-05_18:00:00.4DVAR $DAT_DIR/ob/2008020518/ob.ascii-

At this point you have three of the input files (first guess, observation and background error statistics files in directory $DAT_DIR) required to run WRFDA, and have successfully downloaded and compiled the WRFDA code. If this is correct, you are ready to learn how to run WRFDA.

b. Run the Case—3D-Var

The data for this case is valid at 12 UTC 5^th February 2008. The first guess comes from the NCEP FNL (Final) Operational Global Analysis data, passed through the WRF-WPS and real programs.

To run WRF 3D-Var, first create and cd to a working directory, for example, WRFDA/var/test/tutorial, and then follow the steps below:

> cd WRFDA/var/test/tutorial

> ln -sf WRFDA/run/LANDUSE.TBL ./LANDUSE.TBL

> ln -sf $DAT_DIR/rc/2008020512/wrfinput_d01 ./fg (link first guess file as fg)

> ln -sf WRFDA/var/obsproc/obs_gts_2008-02-05_12:00:00.3DVAR ./ob.ascii (link OBSPROC processed observation file as ob.ascii)

> ln -sf $DAT_DIR/be/be.dat ./be.dat (link background error statistics as be.dat)

> ln -sf WRFDA/var/da/da_wrfvar.exe ./da_wrfvar.exe (link executable)

We will begin by editing the file, namelist.input, which is a very basic namelist.input for running the tutorial test case is shown below and provided as WRFDA/var/test/tutorial/namelist.input. Only the time and domain settings need to be specified in this case, if we are using the default settings provided in WRFDA/Registry/Registry.wrfvar)

&wrfvar1

print_detail_grad=false,
/
&wrfvar2
/

&wrfvar3

&wrfvar4

&wrfvar5

&wrfvar6

&wrfvar7

&wrfvar8

&wrfvar9

&wrfvar10

&wrfvar11

&wrfvar12

&wrfvar13

&wrfvar14

&wrfvar15

&wrfvar16

&wrfvar17

&wrfvar18

analysis_date="2008-02-05_12:00:00.0000",

&wrfvar19

&wrfvar20

&wrfvar21

time_window_min="2008-02-05_11:00:00.0000",

&wrfvar22

time_window_max="2008-02-05_13:00:00.0000",

&wrfvar23

&time_control

start_year=2008,

start_month=02,

start_day=05,

start_hour=12,

end_year=2008,

end_month=02,

end_day=05,

end_hour=12,

&dfi_control

&domains

e_we=90,

e_sn=60,

e_vert=41,

dx=60000,

dy=60000,

&physics

mp_physics=3,

ra_lw_physics=1,

ra_sw_physics=1,

radt=60,

sf_sfclay_physics=1,

sf_surface_physics=1,

bl_pbl_physics=1,

cu_physics=1,

cudt=5,

num_soil_layers=5, (IMPORTANT: it’s essential to make sure the setting here is consistent with the number in your first guess file)

mp_zero_out=2,

co2tf=0,

&fdda

&dynamics

&bdy_control

&grib2

&namelist_quilt

> da_wrfvar.exe >&! wrfda.log

The file wrfda.log (or rsl.out.0000 if run in distributed-memory mode) contains important WRFDA runtime log information. Always check the log after a WRFDA run:

*** VARIATIONAL ANALYSIS ***

DYNAMICS OPTION: Eulerian Mass Coordinate

WRF NUMBER OF TILES = 1

Set up observations (ob)

Using ASCII format observation input

scan obs ascii

end scan obs ascii

Observation summary

ob time 1

sound 85 global, 85 local

synop 531 global, 525 local

pilot 84 global, 84 local

satem 78 global, 78 local

geoamv 736 global, 719 local

polaramv 0 global, 0 local

airep 132 global, 131 local

gpspw 183 global, 183 local

gpsrf 0 global, 0 local

metar 1043 global, 1037 local

ships 86 global, 82 local

ssmi_rv 0 global, 0 local

ssmi_tb 0 global, 0 local

ssmt1 0 global, 0 local

ssmt2 0 global, 0 local

qscat 0 global, 0 local

profiler 61 global, 61 local

buoy 216 global, 216 local

bogus 0 global, 0 local

pseudo 0 global, 0 local

radar 0 global, 0 local

radiance 0 global, 0 local

airs retrieval 0 global, 0 local

sonde_sfc 85 global, 85 local

mtgirs 0 global, 0 local

tamdar 0 global, 0 local

Set up background errors for regional application

WRF-Var dry control variables are:psi, chi_u, t_u and psfc

Humidity control variable is q/qsg

Using the averaged regression coefficients for unbalanced part

Vertical truncation for psi = 15( 99.00%)

Vertical truncation for chi_u = 20( 99.00%)

Vertical truncation for t_u = 29( 99.00%)

Vertical truncation for rh = 22( 99.00%)

Calculate innovation vector(iv)

Minimize cost function using CG method

For this run cost function diagnostics will not be written

Starting outer iteration : 1

Starting cost function: 2.28356084D+04, Gradient= 2.23656955D+02

For this outer iteration gradient target is: 2.23656955D+00

----------------------------------------------------------

Iter Gradient Step

1 1.82455068D+02 7.47025772D-02

2 1.64971618D+02 8.05531077D-02

3 1.13694365D+02 7.22382618D-02

4 7.87359568D+01 7.51905761D-02

5 5.71607218D+01 7.94572516D-02

6 4.18746777D+01 8.30731280D-02

7 2.95722963D+01 6.13223951D-02

8 2.34205172D+01 9.05920463D-02

9 1.63772518D+01 6.48090044D-02

10 1.09735524D+01 7.71148550D-02

11 8.22748934D+00 8.81041046D-02

12 5.65846963D+00 7.89528133D-02

13 4.15664769D+00 7.45589721D-02

14 3.16925808D+00 8.35300020D-02

----------------------------------------------------------

Inner iteration stopped after 15 iterations

Final: 15 iter, J= 1.76436785D+04, g= 2.06098421D+00

----------------------------------------------------------

Diagnostics

Final cost function J = 17643.68

Total number of obs. = 26726

Final value of J = 17643.67853

Final value of Jo = 15284.64894

Final value of Jb = 2359.02958

Final value of Jc = 0.00000

Final value of Je = 0.00000

Final value of Jp = 0.00000

Final J / total num_obs = 0.66017

Jb factor used(1) = 1.00000

Jb factor used(2) = 1.00000

Jb factor used(3) = 1.00000

Jb factor used(4) = 1.00000

Jb factor used(5) = 1.00000

Jb factor used = 1.00000

Je factor used = 1.00000

VarBC factor used = 1.00000

*** WRF-Var completed successfully ***

A file called namelist.output (which contains the complete namelist settings) will be generated after a successful da_wrfvar.exe run. The settings appearing in namelist.output, but not specified in your namelist.input, are the default values from WRFDA/Registry/Registry.wrfvar.

After successful completion of job, wrfvar_output (the WRFDA analysis file, i.e. the new initial condition for WRF) should appear in the working directory along with a number of diagnostic files. Various text diagnostics output files will be explained in the next section (WRFDA Diagnostics).

In order to understand the role of various important WRFDA options, try re-running WRFDA by changing different namelist options. Such as making WRFDA convergence criteria more stringent. This is achieved by reducing the value of the convergence criteria “EPS” to e.g. 0.0001 by adding "EPS=0.0001" in the namelist.input record &wrfvar6. See section (WRFDA additional exercises) for more namelist options

c. Run the Case—4D-Var

To run WRF 4D-Var, first create and cd to a working directory, for example, WRFDA/var/test/4dvar; next assuming that we are using the C-shell, set the working directories for the three WRF 4D-Var components WRFDA, WRFNL and WRFPLUS thusly

> setenv WRFDA_DIR /ptmp/$user/WRFDA

> setenv WRFNL_DIR /ptmp/$user/WRFNL

> setenv WRFPLUS_DIR /ptmp/$user/WRFPLUS

Assume the analysis date is 2008020512 and the test data directories are:

> setenv DATA_DIR /ptmp/$user/DATA

> ls –lr $DATA_DIR

ob/2008020512

ob/2008020513

ob/2008020514

ob/2008020515

ob/2008020516

ob/2008020517

ob/2008020518

rc/2008020512

Note: Currently, WRF 4D-Var can only run with the observation data processed by OBSPROC, and cannot work with PREPBUFR format data; Although WRF-4DVar is able to assimilate satellite radiance BUFR data, but this capability is still under testing.

Assume the working directory is:

> setenv WORK_DIR $WRFDA_DIR/var/test/4dvar

Then follow the steps below:

1) Link the executables.

> cd $WORK_DIR

> ln -fs $WRFDA_DIR/var/da/da_wrfvar.exe .

> cd $WORK_DIR/nl

> ln -fs $WRFNL_DIR/main/wrf.exe .

> cd $WORK_DIR/ad

> ln -fs $WRFPLUS_DIR/main/wrfplus.exe .

> cd $WORK_DIR/tl

> ln -fs $WRFPLUS_DIR/main/wrfplus.exe .

2) Link the observational data, first guess and BE. (Currently, only LITTLE_R formatted observational data is supported in 4D-Var, PREPBUFR observational data is not supported)

> cd $WORK_DIR

> ln -fs $DATA_DIR/ob/2008020512/ob.ascii+ ob01.ascii

> ln -fs $DATA_DIR/ob/2008020513/ob.ascii ob02.ascii

> ln -fs $DATA_DIR/ob/2008020514/ob.ascii ob03.ascii

> ln -fs $DATA_DIR/ob/2008020515/ob.ascii ob04.ascii

> ln -fs $DATA_DIR/ob/2008020516/ob.ascii ob05.ascii

> ln -fs $DATA_DIR/ob/2008020517/ob.ascii ob06.ascii

> ln -fs $DATA_DIR/ob/2008020518/ob.ascii- ob07.ascii

> ln -fs $DATA_DIR/rc/2008020512/wrfinput_d01 .

> ln -fs $DATA_DIR/rc/2008020512/wrfbdy_d01 .

> ln -fs wrfinput_d01 fg

> ln -fs wrfinput_d01 fg01

> ln -fs $DATA_DIR/be/be.dat .

3) Establish the miscellaneous links.

> cd $WORK_DIR

> ln -fs nl/nl_d01_2008-02-05_13:00:00 fg02

> ln -fs nl/nl_d01_2008-02-05_14:00:00 fg03

> ln -fs nl/nl_d01_2008-02-05_15:00:00 fg04

> ln -fs nl/nl_d01_2008-02-05_16:00:00 fg05

> ln -fs nl/nl_d01_2008-02-05_17:00:00 fg06

> ln -fs nl/nl_d01_2008-02-05_18:00:00 fg07

> ln -fs ad/ad_d01_2008-02-05_12:00:00 gr01

> ln -fs tl/tl_d01_2008-02-05_13:00:00 tl02

> ln -fs tl/tl_d01_2008-02-05_14:00:00 tl03

> ln -fs tl/tl_d01_2008-02-05_15:00:00 tl04

> ln -fs tl/tl_d01_2008-02-05_16:00:00 tl05

> ln -fs tl/tl_d01_2008-02-05_17:00:00 tl06

> ln -fs tl/tl_d01_2008-02-05_18:00:00 tl07

> cd $WORK_DIR/ad

> ln -fs ../af01 auxinput3_d01_2008-02-05_12:00:00

> ln -fs ../af02 auxinput3_d01_2008-02-05_13:00:00

> ln -fs ../af03 auxinput3_d01_2008-02-05_14:00:00

> ln -fs ../af04 auxinput3_d01_2008-02-05_15:00:00

> ln -fs ../af05 auxinput3_d01_2008-02-05_16:00:00

> ln -fs ../af06 auxinput3_d01_2008-02-05_17:00:00

> ln -fs ../af07 auxinput3_d01_2008-02-05_18:00:00

4) Run in single processor mode (serial compilation required for WRFDA, WRFNL and WRFPLUS)

Edit $WORK_DIR/namelist.input to match your experiment settings.

> cp $WORK_DIR/nl/namelist.input.serial $WORK_DIR/nl/namelist.input

Edit $WORK_DIR/nl/namelist.input to match your experiment settings.

> cp $WORK_DIR/ad/namelist.input.serial $WORK_DIR/ad/namelist.input

> cp $WORK_DIR/tl/namelist.input.serial $WORK_DIR/tl/namelist.input

Edit $WORK_DIR/ad/namelist.input and $WORK_DIR/tl/namelist.input to match your experiment settings, but only change following variables:

&time_control

run_hours=06,

start_year=2008,

start_month=02,

start_day=05,

start_hour=12,

end_year=2008,

end_month=02,

end_day=05,

end_hour=18,

......

&domains

time_step=360, # NOTE:MUST BE THE SAME WITH WHICH IN $WORK_DIR/nl/namelist.input

e_we=90,

e_sn=60,

e_vert=41,

dx=60000,

dy=60000,

......

> cd $WORK_DIR

> setenv NUM_PROCS 1

> ./da_wrfvar.exe >&! wrfda.log

5) Run with multiple processors with MPMD mode. (dmpar compilation required for WRFDA, WRFNL and WRFPLUS)

Edit $WORK_DIR/namelist.input to match your experiment settings.

> cp $WORK_DIR/nl/namelist.input.parallel $WORK_DIR/nl/namelist.input

Edit $WORK_DIR/nl/namelist.input to match your experiment settings.

> cp $WORK_DIR/ad/namelist.input.parallel $WORK_DIR/ad/namelist.input

> cp $WORK_DIR/tl/namelist.input.parallel $WORK_DIR/tl/namelist.input

Edit $WORK_DIR/ad/namelist.input and $WORK_DIR/tl/namelist.input to match your experiment settings.

Currently, parallel WRF 4D-Var is a MPMD (Multiple Program Multiple Data) application. Because there are so many parallel configurations across the platforms, it is very difficult to define a generic way to run the WRF 4D-Var parallel. As an example, to launch the three WRF 4D-Var executables as a concurrent parallel job on a 16 processor cluster, use:

> mpirun –np 4 da_wrfvar.exe: -np 8 ad/wrfplus.exe: -np 4 nl/wrf.exe

In the above example, 4 processors are assigned to run WRFDA, 4 processors are assigned to run WRFNL and 8 processors for WRFPLUS due to high computational cost in adjoint code.

The file wrfda.log (or rsl.out.0000 if running in parallel mode) contains important WRF-4DVar runtime log information. Always check the log after a WRF-4DVar run.

Radiance Data Assimilations in WRFDA

This section gives a brief description for various aspects related to radiance assimilation in WRFDA. Each aspect is described mainly from the viewpoint of usage rather than more technical and scientific details, which will appear in separated technical report and scientific paper. Namelist parameters controlling different aspects of radiance assimilation will be detailed in the following sections. It should be noted that this section does not cover general aspects of the WRFDA assimilation. These can be found in other sections of chapter 6 of this users guide or other WRFDA documentation.

a. Running WRFDA with radiances

In addition to the basic input files (LANDUSE.TBL, fg, ob.ascii, be.dat) mentioned in “Running WRFDA” section, the following extra files are required for radiances: radiance data in NCEP BUFR format, radiance_info files, VARBC.in, RTM (CRTM or RTTOV) coefficient files.

Edit namelist.input (Pay special attention to &wrfvar4, &wrfvar14, &wrfvar21, and &wrfvar22 for radiance-related options. A very basic namelist.input for running the radiance test case is provided as WRFDA/var/test/radiance/namelist.input)

> ln -sf ${DAT_DIR}/gdas1.t00z.1bamua.tm00.bufr_d ./amsua.bufr

> ln -sf ${DAT_DIR}/gdas1.t00z.1bamub.tm00.bufr_d ./amsub.bufr

> ln -sf WRFDA/var/run/radiance_info ./radiance_info # (radiance_info is a directory)

> ln -sf WRFDA/var/run/VARBC.in ./VARBC.in

(CRTM only) > ln -sf WRFDA/var/run/crtm_coeffs ./crtm_coeffs #(crtm_coeffs is a directory)

(RTTOV only) > ln -sf rttov87/rtcoef_rttov7/* . # (a list of rtcoef* files)

See the following sections for more details on each aspect.

b. Radiance Data Ingest

Currently, the ingest interface for NCEP BUFR radiance data is implemented in WRFDA. The radiance data are available through NCEP’s public ftp server ftp://ftp.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gdas.${yyyymmddhh} in near real-time (with 6-hour delay) and can meet requirements both for research purposes and some real-time applications.

So far, WRFDA can read data from the NOAA ATOVS instruments (HIRS, AMSU-A, AMSU-B and MHS), the EOS Aqua instruments (AIRS, AMSU-A) and DMSP instruments (SSMIS). Note that NCEP radiance BUFR files are separated by instrument names (i.e., each file for one type instrument) and each file contains global radiance (generally converted to brightness temperature) within 6-hour assimilation window from multi-platforms. For running WRFDA, users need to rename NCEP corresponding BUFR files (table 1) to hirs3.bufr (including HIRS data from NOAA-15/16/17), hirs4.bufr (including HIRS data from NOAA-18, METOP-2), amsua.bufr (including AMSU-A data from NOAA-15/16/18, METOP-2), amsub.bufr (including AMSU-B data from NOAA-15/16/17), mhs.bufr (including MHS data from NOAA-18 and METOP-2), airs.bufr (including AIRS and AMSU-A data from EOS-AQUA) and ssmis.bufr (SSMIS data from DMSP-16, AFWA provided) for WRFDA filename convention. Note that airs.bufr file contains not only AIRS data but also AMSU-A, which is collocated with AIRS pixels (1 AMSU-A pixels collocated with 9 AIRS pixels). Users must place these files in the working directory where WRFDA executable is located. It should also be mentioned that WRFDA reads these BUFR radiance files directly without use if any separate pre-processing program is used. All processing of radiance data, such as quality control, thinning and bias correction and so on, is carried out inside WRFDA. This is different from conventional observation assimilation, which requires a pre-processing package (OBSPROC) to generate WRFDA readable ASCII files. For reading the radiance BUFR files, WRFDA must be compiled with the NCEP BUFR library (see http://www.nco.ncep.noaa.gov/sib/decoders/BUFRLIB/).

Table 1: NCEP and WRFDA radiance BUFR file naming convention

NCEP BUFR file names	WRFDA naming convention
gdas1.t00z.1bamua.tm00.bufr_d	amsua.bufr
gdas1.t00z.1bamub.tm00.bufr_d	amsub.bufr
gdas1.t00z.1bhrs3.tm00.bufr_d	hirs3.bufr
gdas1.t00z.1bhrs4.tm00.bufr_d	hirs4.bufr
gdas1.t00z.1bmhs.tm00.bufr_d	mhs.bufr
gdas1.t00z.airsev.tm00.bufr_d	airs.bufr

Namelist parameters are used to control the reading of corresponding BUFR files into WRFDA. For instance, USE_AMSUAOBS, USE_AMSUBOBS, USE_HIRS3OBS, USE_HIRS4OBS, USE_MHSOBS, USE_AIRSOBS, USE_EOS_AMSUAOBS and USE_SSMISOBS control whether or not the respective file is read. These are logical parameters that are assigned to FALSE by default; therefore they must be set to true to read the respective observation file. Also note that these parameters only control whether the data is read, not whether the data included in the files is to be assimilated. This is controlled by other namelist parameters explained in the next section.

NCEP BUFR files downloaded from NCEP’s public ftp server ftp://ftp.ncep.noaa.gov/pub/data/nccf/com/gfs/prod/gdas.${yyyymmddhh} are Fortran-blocked on big-endian machine and can be directly used on big-endian machines (for example, IBM). For most Linux clusters with Intel platforms, users need to first unblock the BUFR files, and then reblock them. The utility for blocking/unblocking is available from http://www.nco.ncep.noaa.gov/sib/decoders/BUFRLIB/toc/cwordsh

c. Radiative Transfer Model

The core component for direct radiance assimilation is to incorporate a radiative transfer model (RTM, should be accurate enough yet fast) into the WRFDA system as one part of observation operators. Two widely used RTMs in NWP community, RTTOV8* (developed by EUMETSAT in Europe), and CRTM (developed by the Joint Center for Satellite Data Assimilation (JCSDA) in US), are already implemented in WRFDA system with a flexible and consistent user interface. Selecting which RTM to be used is controlled by a simple namelist parameter RTM_OPTION (1 for RTTOV, the default, and 2 for CRTM). WRFDA is designed to be able to compile with only one of two RTM libraries or without RTM libraries (for those not interested in radiance assimilation) by the definition of environment variables “CRTM” and “RTTOV” (see Installing WRFDA section).

Both RTMs can calculate radiances for almost all available instruments aboard various satellite platforms in orbit. An important feature of WRFDA design is that all data structures related to radiance assimilation are dynamically allocated during running time according to simple namelist setup. The instruments to be assimilated are controlled at run time by four integer namelist parameters: RTMINIT_NSENSOR (the total number of sensors to be assimilated), RTMINIT_PLATFORM (the platforms IDs array to be assimilated with dimension RTMINIT_NSENSOR, e.g., 1 for NOAA, 9 for EOS, 10 for METOP and 2 for DMSP), RTMINIT_SATID (satellite IDs array) and RTMINIT_SENSOR (sensor IDs array, e.g., 0 for HIRS, 3 for AMSU-A, 4 for AMSU-B, 15 for MHS, 10 for SSMIS, 11 for AIRS). For instance, the configuration for assimilating 12 sensors from 7 satellites (what WRFDA can assimilated currently) will be

RTMINIT_NSENSOR = 12 # 5 AMSUA; 3 AMSUB; 2 MHS; 1 AIRS; 1 SSMIS

RTMINIT_PLATFORM = 1,1,1,9,10, 1,1,1, 1,10, 9, 2

RTMINIT_SATID = 15,16,18,2,2, 15,16,17, 18,2, 2, 16

RTMINIT_SENSOR = 3,3,3,3,3, 4,4,4, 15,15, 11, 10

The instrument triplets (platform, satellite and sensor ID) in the namelist can be ranked in any order. More detail about the convention of instrument triplet can be found at the tables 2 and 3 in RTTOV8/9 Users Guide (http://www.metoffice.gov.uk/research/interproj/nwpsaf/rtm/rttov8_ug.pdf Or http://www.metoffice.gov.uk/research/interproj/nwpsaf/rtm/rttov9_files/users_guide_91_v1.6.pdf)

CRTM uses a different instrument naming method. A convert routine inside WRFDA is already created to make CRTM use the same instrument triplet as RTTOV such that the user interface remains the same for RTTOV and CRTM.

When running WRFDA with radiance assimilation switched on (RTTOV or CRTM), a set of RTM coefficient files need to be loaded. For RTTOV option, RTTOV coefficient files are to be directly copied or linked under the working directory; for CRTM option, CRTM coefficient files are to be copied or linked to a sub-directory “crtm_coeffs” under the working directory. Only coefficients listed in namelist are needed. Potentially WRFDA can assimilate all sensors as long as the corresponding coefficient files are provided with RTTOV and CRTM. In addition, necessary developments on corresponding data interface, quality control and bias correction are also important to make radiance data assimilated properly. However, a modular design of radiance relevant routines already facilitates much to add more instruments in WRFDA.

RTTOV packages are not distributed with WRFDA due to license and support issues. Users are encouraged to contact the corresponding team for obtaining RTMs. See following links for more information.

http://www.metoffice.gov.uk/research/interproj/nwpsaf/rtm/index.html .

CRTM pakages are now distributed with WRFDA, which locate in the WRFDA/var/external/crtm. Users can still find it on the following link:

ftp://ftp.emc.ncep.noaa.gov/jcsda/CRTM.

d. Channel Selection

Channel selection in WRFDA is controlled by radiance ‘info’ files located in the sub-directory ‘radiance_info’ under the working directory. These files are separated by satellites and sensors, e.g., noaa-15-amsua.info, noaa-16-amsub.info, dmsp-16-ssmis.info and so on. An example for 5 channels from noaa-15-amsub.info is shown below. The fourth column is used by WRFDA to control if assimilating corresponding channel. Channels with the value “-1” indicates that the channel is “not assimilated” (channels 1, 2 and 4 in this case), with the value “1” means “assimilated” (channels 3 and 5). The sixth column is used by WRFDA to set the observation error for each channel. Other columns are not used by WRFDA. It should be mentioned that these error values might not necessarily be optimal for your applications; It is user’s responsibility to obtain the optimal error statistics for your own applications.

sensor channel IR/MW use idum varch polarisation(0:vertical;1:horizontal)

415 1 1 -1 0 0.5500000000E+01 0.0000000000E+00

415 2 1 -1 0 0.3750000000E+01 0.0000000000E+00

415 3 1 1 0 0.3500000000E+01 0.0000000000E+00

415 4 1 -1 0 0.3200000000E+01 0.0000000000E+00

415 5 1 1 0 0.2500000000E+01 0.0000000000E+00

e. Bias Correction

Satellite radiance is generally considered biased with respect to a reference (e.g., background or analysis field in NWP assimilation) due to system error of observation itself, reference field and RTM. Bias correction is a necessary step prior to assimilating radiance data. In WRFDA, there are two ways of performing bias correction. One is based on Harris and Kelly (2001) method and is carried out using a set of coefficient files pre-calculated with an off-line statistics package, which will apply to a training dataset for a month-long period. The other is Variational Bias Correction (VarBC). Only VarBC is introduced here and recommended for users because of its relative simplicity in usage.

f. Variational Bias Correction

Getting started with VarBC

To use VarBC, set namelist option USE_VARBC to TRUE and have a VARBC.in file in the working directory. VARBC.in is a VarBC setup file in ASCII format. A template is provided with the WRFDA package (WRFDA/var/run/VARBC.in).

Input and Output files

All VarBC input is passed through one single ASCII file called VARBC.in file. Once WRFDA has run with the VarBC option switched on, it will produce a VARBC.out file which looks very much like the VARBC.in file you provided. This output file will then be used as input file for the next assimilation cycle.

Coldstart

Coldstarting means starting the VarBC from scratch i.e. when you do not know the values of the bias parameters.

The Coldstart is a routine in WRFDA. The bias predictor statistics (mean and standard deviation) are computed automatically and will be used to normalize the bias parameters. All coldstarted bias parameters are set to zero, except the first bias parameter (= simple offset), which is set to the mode (=peak) of the distribution of the (uncorrected) innovations for the given channel.

A threshold of number of observations can be set through a namelist option VARBC_NOBSMIN (default = 10), under which it is considered that not enough observations are present to keep the Coldstart values (i.e. bias predictor statistics and bias parameter values) for the next cycle. In this case, the next cycle will do another Coldstart.

Background Constraint for the bias parameters

The background constraint controls the inertia you want to impose on the predictors (i.e. the smoothing in the predictor time series). It corresponds to an extra term in the WRFDA cost function.

It is defined through an integer number in the VARBC.in file. This number is related to a number of observations: the bigger the number, the more inertia constraint. If these numbers are set to zero, the predictors can evolve without any constraint.

Scaling factor

The VarBC uses a specific preconditioning, which can be scaled through a namelist option VARBC_FACTOR (default = 1.0).

Offline bias correction

The analysis of the VarBC parameters can be performed "offline", i.e. independently from the main WRFDA analysis. No extra code is needed, just set the following MAX_VERT_VAR* namelist variables to be 0, which will disable the standard control variable and only keep the VarBC control variable.

MAX_VERT_VAR1=0.0

MAX_VERT_VAR2=0.0

MAX_VERT_VAR3=0.0

MAX_VERT_VAR4=0.0

MAX_VERT_VAR5=0.0

Freeze VarBC

In certain circumstances, you might want to keep the VarBC bias parameters constant in time (="frozen"). In this case, the bias correction is read and applied to the innovations, but it is not updated during the minimization. This can easily be achieved by setting the namelist options:

USE_VARBC=false

FREEZE_VARBC=true

Passive observations

Some observations are useful for preprocessing (e.g. Quality Control, Cloud detection) but you might not want to assimilate them. If you still need to estimate their bias correction, these observations need to go through the VarBC code in the minimization. For this purpose, the VarBC uses a separate threshold on the QC values, called "qc_varbc_bad". This threshold is currently set to the same value as "qc_bad", but can easily be changed to any ad hoc value.

g. Other namelist variables to control radiance assimilation

RAD_MONITORING (30)

Integer array of dimension RTMINIT_NSENSER, where 0 for assimilating mode, 1 for monitoring mode (only calculate innovation).

THINNING

Logical, TRUE will perform thinning on radiance data.

THINNING_MESH (30)

Real array with dimension RTMINIT_NSENSOR, values indicate thinning mesh (in KM) for different sensors.

QC_RAD

Logical, control if perform quality control, always set to TRUE.

WRITE_IV_RAD_ASCII

Logical, control if output Observation minus Background files which are in ASCII format and separated by sensors and processors.

WRITE_OA_RAD_ASCII

Logical, control if output Observation minus Analysis files (including also O minus B) which are ASCII format and separated by sensors and processors.

USE_ERROR_FACTOR_RAD

Logical, controls use of a radiance error tuning factor file “radiance_error.factor”, which is created with empirical values or generated using variational tunning method (Desroziers and Ivanov, 2001)

ONLY_SEA_RAD

Logical, controls whether only assimilating radiance over water.

TIME_WINDOW_MIN

String, e.g., "2007-08-15_03:00:00.0000", start time of assimilation time window

TIME_WINDOW_MAX

String, e.g., "2007-08-15_09:00:00.0000", end time of assimilation time window

CRTM_ATMOSPHERE

Integer, used by CRTM to choose climatology reference profile used above model top (up to 0.01hPa).

0: Invalid (default, use U.S. Standard Atmosphere)

1: Tropical

2: Midlatitude summer

3: Midlatitude winter

4: Subarctic summer

5: Subarctic winter

6: U.S. Standard Atmosphere

USE_ANTCORR (30)

Logical array with dimension RTMINIT_NSENSER, control if performing Antenna Correction in CRTM.

AIRS_WARMEST_FOV

Logical, controls whether using the observation brightness temperature for AIRS Window channel #914 as criterium for GSI thinning.

USE_CRTM_KMATRIX

Logical, controls whether using CRTM K matrix rather than calling CRTM TL and AD routines for gradient calculation.

h. Diagnostics and Monitoring

(1) Monitoring capability within WRFDA.

Run WRFDA with the rad_monitoring namelist parameter in record wrfvar14 in namelist.input.

0 means assimilating mode, innovations (O minus B) are calculated and data are used in minimization.

1 means monitoring mode: innovations are calculated for diagnostics and monitoring. Data are not used in minimization.

Number of rad_monitoring should correspond to number of rtminit_nsensor. If rad_monitoring is not set, then default value of 0 will be used for all sensors.

(2) Outputing radiance diagnostics from WRFDA

Run WRFDA with the following namelist variables in record wrfvar14 in namelist.input.

write_iv_rad_ascii=.true.

to write out (observation-background) and other diagnostics information in plain-text files with prefix inv followed by instrument name and processor id. For example, 01_inv_noaa-17-amsub.0000 (01 is outerloop index, 0000 is processor index)

write_oa_rad_ascii=.true.

to write out (observation-background), (observation-analysis) and other diagnostics information in plain-text files with prefix oma followed by instrument name and processor id. For example, 01_oma_noaa-18-mhs.0001

Each processor writes out information of one instrument in one file in the WRFDA working directory.

(3) Radiance diagnostics data processing

A Fortran90 program is used to collect the 01_inv* or 01_oma* files and write out in netCDF format (one instrument in one file with prefix diags followed by instrument name, analysis date, and suffix .nc)) for easier data viewing, handling and plotting with netCDF utilities and NCL scripts.

(4) Radiance diagnostics plotting

NCL scripts (WRFDA/var/graphics/ncl/plot_rad_diags.ncl and WRFDA/var/graphics/ncl/advance_cymdh.ncl) are used for plotting. The NCL script can be run from a shell script, or run stand-alone with interactive ncl command (need to edit the NCL script and set the plot options. Also the path of advance_cymdh.ncl, a date advancing script loaded in the main NCL plotting script, may need to be modified).

Step (3) and (4) can be done by running a single ksh script (WRFDA/var/scripts/da_rad_diags.ksh) with proper settings. In addition to the settings of directories and what instruments to plot, there are some useful plotting options, explained below.

export OUT_TYPE=ncgm	ncgm or pdf pdf will be much slower than ncgm and generate huge output if plots are not split. But pdf has higher resolution than ncgm.
export PLOT_STATS_ONLY=false	true or false true: only statistics of OMB/OMA vs channels and OMB/OMA vs dates will be plotted. false: data coverage, scatter plots (before and after bias correction), histograms (before and after bias correction), and statistics will be plotted.
export PLOT_OPT=sea_only	all, sea_only, land_only
export PLOT_QCED=false	true or false true: plot only quality-controlled data false: plot all data
export PLOT_HISTO=false	true or false: switch for histogram plots
export PLOT_SCATT=true	true or false: switch for scatter plots
export PLOT_EMISS=false	true or false: switch for emissivity plots
export PLOT_SPLIT=false	true or false true: one frame in each file false: all frames in one file
export PLOT_CLOUDY=false	true or false true: plot cloudy data. Cloudy data to be plotted are defined by PLOT_CLOUDY_OPT (si or clwp), CLWP_VALUE, SI_VALUE settings.
export PLOT_CLOUDY_OPT=si	si or clwp clwp: cloud liquid water path from model si: scatter index from obs, for amsua, amsub and mhs only
export CLWP_VALUE=0.2	only plot points with clwp >= clwp_value (when clwp_value > 0) clwp > clwp_value (when clwp_value = 0)
export SI_VALUE=3.0

(5) evolution of VarBC parameters

NCL scripts (WRFDA/var/graphics/ncl/plot_rad_varbc_param.ncl and WRFDA/var/graphics/ncl/advance_cymdh.ncl) are used for plotting evolutions of VarBC parameters.

WRFDA Diagnostics

WRFDA produces a number of diagnostic files that contain useful information on how the data assimilation has performed. This section will introduce you to some of these files, and what to look for.

Having run WRFDA, it is important to check a number of output files to see if the assimilation appears sensible. The WRFDA package, which includes lots of useful scripts may be downloaded from http://www.mmm.ucar.edu/wrf/users/wrfda/download/tools.html

The content of some useful diagnostic files are as follows:

cost_fn and grad_fn: These files hold (in ASCII format) WRFDA cost and gradient function values, respectively, for the first and last iterations. However, if you run with PRINT_DETAIL_GRAD=true, these values will be listed for each iteration; this can be helpful for visualization purposes. The NCL script WRFDA/var/graphcs/ncl/plot_cost_grad_fn.ncl may be used to plot the content of cost_fn and grad_fn, if these files are generated with PRINT_DETAIL_GRAD=true.

Additional WRFDA Exercises:

(a) Single Observation response in WRFDA:

With the single observation test, you may get the ideas of how the background and observation error statistics working in the model variable space. Single observation test is done in WRFDA by setting num_pseudo=1 along with other pre-specified values in record &wrfvar15 and &wrfvar19 of namelist.input,

With the settings shown below, WRFDA generates a single observation with pre-specified innovation (Observation – First Guess) value at desired location e.g. at (in terms of grid coordinate) 23x23, level 14 for “U” observation with error characteristics 1 m/s, innovation size = 1.0 m/s.

&wrfvar15

num_pseudo = 1,

pseudo_x = 23.0,

pseudo_y = 23.0,

pseudo_z = 14.0,

pseudo_err = 1.0,

pseudo_val = 1.0,

&wrfvar19

pseudo_var = “u”, (Note: pseudo_var can be u, v, t, p, q.
If pseudo_var is q, then the reasonable values of pseudo_err and pseudo_val are 0.001)

Note: You may like to repeat this exercise for other observations like temperature (“t”), pressure “p”, specific humidity “q” etc.

(b) Response of BE length scaling parameter:

Run single observation test with following additional parameters in record &wrfvar7 of namelist.input

&wrfvar7

len_scaling1 = 0.5, # reduce psi length scale by 50%

len_scaling2 = 0.5, # reduce chi_u length scale by 50%

len_scaling3 = 0.5, # reduce T length scale by 50%

len_scaling4 = 0.5, # reduce q length scale by 50%

len_scaling5 = 0.5, # reduce Ps length scale by 50%

Note: You may like to try the response of an individual variable by setting one parameter at one time. See the spread of analysis increment.

(c) Response of changing BE variance:

Run single observation test with following additional parameters in record &wrfvar7 of namelist.input

&wrfvar7

var_scaling1 = 0.25, # reduce psi variance by 75%

var_scaling2 = 0.25, # reduce chi_u variance by 75%

var_scaling3 = 0.25, # reduce T variance by 75%

var_scaling4 = 0.25, # reduce q variance by 75%

var_scaling5 = 0.25, # reduce Ps variance by 75%

Note: You may like to try the response of individual variable by setting one parameter at one time. See the magnitude of analysis increments.

(d) Response of convergence criteria:

Run tutorial case with

&wrfvar6

eps = 0.0001,

You may like to compare various diagnostics with earlier run.

(e) Response of outer loop on minimization:

Run tutorial case with

&wrfvar6

max_ext_its = 2,

With this setting “outer loop” for the minimization procedure will get activated. You may like to compare various diagnostics with earlier run.

Note: Maximum permissible value for “MAX_EXT_ITS” is 10

(f) Response of suppressing particular types of data in WRFDA:

The types of observations that WRFDA gets to use actually depend on what is included in the observation file and the WRFDA namelist settings. For example, if you have SYNOP data in the observation file, you can suppress its usage in WRFDA by setting use_synopobs=false in record &wrfvar4 of namelist.input. It is OK if there is no SYNOP data in the observation file and use_synopobs=true.

Turning on and off of certain types of observations are widely used for assessing impact of observations on data assimilations.

Note: It is important to go through the default “use_*” settings in record &wrfvar4 in WRFDA/Registry/Registry.wrfvar to know what observations are activated in default.

Hybrid Data Assimilation in WRFDA

The WRFDA system also includes a hybrid data assimilation technique, which is based on the existing 3DVAR. The difference between hybrid and 3DVAR schemes is that 3DVAR relies solely on a static covariance model to specify the background errors, while the hybrid system uses a combination of 3DVAR static error covariances and ensemble-estimated error covariances to incorporate a flow-dependent estimate of the background error statistics. Please refer to Wang et al. (2008a,b) for a detailed description of the methodology used in the WRF hybrid system. The following section will give a brief introduction of various aspects of using the hybrid system.

a. Source Code

There are three executables that are used in the hybrid system. If you have successfully compiled the WRFDA system, you will see the following:

WRFDA/var/build/gen_be_ensmean.exe

WRFDA/var/build/gen_be_ep2.exe

WRFDA/var/build/da_wrfvar.exe

gen_be_ensmean.exe is used to calculate the ensemble mean, while gen_be_ep2.exe is used to calculate the ensemble perturbations. As with 3DVAR/4DVAR, da_wrfvar.exe is the main WRFDA program. However, in this case, da_wrfvar.exe will run in the hybrid mode.

b. Running The Hybrid System

The procedure is the same as running 3DVAR/4DVAR with the exception of some extra input files and namelist settings. The basic input files for WRFDA are LANDUSE.TBL, ob.ascii or ob.bufr (depending on which observation format you use), and be.dat (static background errors). Additional input files required by the hybrid are a single ensemble mean file (used as the fg for the hybrid application) and a set of ensemble perturbation files (used to represent flow-dependent background errors).

Before the hybrid application can be started, a set of initial ensemble members must be prepared. These ensembles can be obtained from other ensemble model outputs or you can generate them yourself, for example, adding random noise to the initial conditions at a previous time and integrating each member to the desired time. Once you have the initial ensembles, the ensemble mean and perturbations can be calculated following the steps below.

1) Calculate ensemble mean

Copy or link the ensemble forecasts to your working directory. In this example, the time is 2006102712.

< ln -sf /wrfhelp/DATA/VAR/Hybrid/fc/2006102712.e0* .

Next, copy the directory that contains two template files (ensemble mean and variance files) to your working directory. In this case, the directory name is 2006102712, which contains the template ensemble mean file (wrfout_d01_2006-10-28_00:00:00) and the template variance file (wrfout_d01_2006-10-28_00:00:00.vari). These template files will be overwritten by the program that calculates the ensemble mean and variance as discussed below.

< cp -r /wrfhelp/DATA/VAR/Hybrid/fc/2006102712 .

Edit gen_be_ensmean_nl.nl (or copy it from /wrfhelp/DATA/VAR/Hybrid/gen_be_ensmean_nl.nl). You will need to set the following information in this script as follows:

< vi gen_be_ensmean_nl.nl

&gen_be_ensmean_nl
directory = './2006102712'
filename = 'wrfout_d01_2006-10-28_00:00:00'
num_members = 10
nv = 7
cv = 'U', 'V', 'W', 'PH', 'T', 'MU', 'QVAPOR'
/

Here,

“directory” is the folder you just copied,

“filename” is the name of the ensemble mean file,

“num_members” is the number of ensemble members you are using,

“nv” is the number of variables, which must be consistent with the next “cv” option, and

“cv” is the name of variables used in the hybrid system.

Next, link gen_be_ensmean.exe to your working directory and run it.

< ln –sf WRFDA/var/build/gen_be_ensmean.exe .
< ./ gen_be_ensmean.exe

Check the output files.

2006102712/wrfout_d01_2006-10-28_00:00:00 is the ensemble mean

2006102712/wrfout_d01_2006-10-28_00:00:00.vari is the ensemble variance

2) Calculate ensemble perturbations

Create another sub-directory in which you will be working to create ensemble perturbations.

< mkdir -p 2006102800/ep
< cd 2006102800/ep

Next, run gen_be_ep2.exe.

gen_be_ep2.exe requires four command-line arguments (DATE, NUM_MEMBER, DIRECTORY, FILENAME) as shown below:

< ln –sf WRFDA/var/build/gen_be_ep2.exe .
< ./gen_be_ep2.exe 2006102800 10 ../../2006102712 wrfout_d01_2006-10-28_00:00:00

Check the output files.

A list of binary files will be created under the 2006102800/ep directory. Among them, tmp.e* are temporary scratch files that can be removed.

3) Run WRFDA in hybrid mode

In your hybrid working directory, link all the necessary files and directories as follows:

< ln -fs 2006102800/ep ./ep (ensemble perturbation files should be under the ep subdirectory)
< ln -fs 2006102712/wrfout_d01_2006-10-28_00:00:00 ./fg (first guess is the ensemble mean)
< ln -fs WRFDA/run/LANDUSE.TBL .
< ln -fs /wrfhelp/DATA/VAR/Hybrid/ob/2006102800/ob.ascii ./ob.ascii (or ob.bufr)
< ln -fs /wrfhelp/DATA/VAR/Hybrid/be/be.dat ./be.dat
< ln –fs WRFDA/var/build/da_wrfvar.exe .
< cp /wrfhelp/DATA/VAR/Hybrid/namelist.input .

Edit namelist.input and pay special attention to the following hybrid-related settings:

&wrfvar7
je_factor = 2.0
/
&wrfvar16
ensdim_alpha = 10
alphacv_method = 2
alpha_corr_type=3
alpha_corr_scale = 1500.0
alpha_std_dev=1.000
/

Next, run hybrid in serial mode (recommended for initial testing of the hybrid system), or in parallel mode

< ./da_wrfvar.exe >&! wrfda.log

Check the output files.

The output file lists are the same as when you run WRF 3D-Var.

c. Hybrid namelist options

1) je_factor : ensemble covariance weighting factor. This factor controls the weighting component of ensemble and static covariances. The corresponding jb_factor = je_factor/(je_factor - 1).

2) ensdim_alpha: the number of ensemble members. Hybrid mode is activated when ensdim_alpha is larger than zero.

3) alphacv_method: 1=perturbations in control variable space (“psi”,”chi_u”,”t_u”,”rh”,”ps_u”); 2=perturbations in model space (“u”,”v”,”t”,”q”,”ps”). Option 2 is extensively tested and recommended to use.

4) alpha_corr_type: correlation function. 1=Exponential; 2=SOAR; 3=Gaussian.

5) alpha_corr_scale: hybrid covariance localization scale in km unit. Default value is 1500.

6) alpha_std_dev: alpha standard deviation. Default value is 1.0

Description of Namelist Variables

WRFDA namelist variables.

Variable Names	Default Value	Description
&wrfvar1
write_increments	false	.true.: write out a binary analysis increment file
var4d	false	.true.: 4D-Var mode
multi_inc	0	> 0: multi-incremental run
var4d_coupling	2	1: var4d_coupling_disk_linear, 2: var4d_coupling_disk_simul
print_detail_radar	false	print_detail_xxx: output extra (sometimes can be too many) diagnostics for debugging; not recommended to turn them on for production runs
print_detail_xa	false
print_detail_xb	false
print_detail_obs	false
print_detail_grad	false	the purpose of print_detail_grad is changed as of V3.1. .true.: to print out detailed gradient of each observation type at each iteration and write out detailed cost function and gradient into files called cost_fn and grad_fn
check_max_iv_print	true	obsolete (only used by Radar)
&wrfvar2
analysis_accu	900	seconds, if time difference between namelist setting (analysis_date) and date info read in from first guess is larger than analysis_accu, WRFDA will issue a warning message ("=======> Wrong xb time found???"), but won't abort.
calc_w_increment	false	.true.: the increment of the vertical velocity W will be diagnosed based on the increments of other fields. If there is information of the W from observations assimilated, such as the Radar radial velocity, the W increments are always computed, no matter calc_w_increment=true. or .false. .false.: the increment of the vertical velocity W is zero if no W information assimilated.
dt_cloud_model	false	Not used
&wrfvar3
fg_format	1	1: fg_format_wrf_arw_regional (default) 2: fg_format_wrf_nmm_regional 3: fg_format_wrf_arw_global 4: fg_format_kma_global
ob_format	2	1: ob_format_bufr (NCEP PREPBUFR), read in data from ob.bufr (not fully tested) 2: ob_format_ascii (output from obsproc), read in data from ob.ascii (default) 3: ob_format_madis (not tested)
num_fgat_time	1	1: 3DVar > 1: number of time slots for FGAT and 4DVAR
&wrfvar4
thin_conv	true	for ob_format=1 (NCEP PREPBUFR) only. thining is mandatory for ob_format=1 as time-duplicate data are "thinned" within thinning routine, however, thin_conv can be set to .false. for debugging purpose.
thin_mesh_conv	20. (max_instruments)	for ob_format=1 (NCEP PREPBUFR) only. km, each observation type can set its thinning mesh and the index/order follows the definition in WRFDA/var/da/da_control/da_control.f90
use_synopobs	true	use_xxxobs - .true.: assimilate xxx obs if available .false.: not assimilate xxx obs even available
use_shipsobs	true
use_metarobs	true
use_soundobs	true
use_pilotobs	true
use_airepobs	true
use_geoamvobs	true
use_polaramvobs	true
use_bogusobs	true
use_buoyobs	true
use_profilerobs	true
use_satemobs	true
use_gpspwobs	true
use_gpsrefobs	true
use_qscatobs	true
use_radarobs	false
use_radar_rv	false
use_radar_rf	false
use_airsretobs	true
; use_hirs2obs, use_hirs3obs, use_hirs4obs, use_mhsobs ; use_msuobs, use_amsuaobs, use_amsubobs, use_airsobs, ; use_eos_amsuaobs, use_hsbobs, use_ssmisobs are ; radiance-related variables that only control if reading ; in corresponding BUFR files into WRFDA or not, but ; do not control if assimilate the data or not. ; Some more variables have to be set in &wrfvar14 in order ; to assimilate radiance data.
use_hirs2obs	fasle	.true.: to read in data from hirs2.bufr
use_hirs3obs	false	.true.: to read in data from hirs3.bufr
use_hirs4obs	false	.true.: to read in data from hirs4.bufr
use_mhsobs	false	.true.: to read in data from mhs.bufr
use_msuobs	false	.true.: to read in data from msu.bufr
use_amsuaobs	false	.true.: to read in data from amsua.bufr
use_amsubobs	false	.true.: to read in data from amsub.bufr
use_airsobs	false	.true.: to read in data from airs.bufr
use_eos_amsuaobs	false	.true.: to read in data from airs.bufr
use_hsbobs	false	.true.: to read in data from hsb.bufr
use_ssmisobs	false	.true.: to read in data from ssmis.bufr
use_obs_errfac	false	.true.: apply obs error tuning factors if errfac.dat is available for conventional data only
&wrfvar5
check_max_iv	true	.true.: reject the observations whose innovations (O-B) are larger than a maximum value defined as a multiple of the observation error for each observation. i.e., inv > (obs_errorfactor) --> fails_error_max; the default maximum value is 5 times the observation error ; the factor of 5 can be changed through max_error_ settings.
max_error_t	5.0	maximum check_max_iv error check factor for t
max_error_uv	5.0	maximum check_max_iv error check factor for u and v
max_error_pw	5.0	maximum check_max_iv error check factor for precipitable water
max_error_ref	5.0	maximum check_max_iv error check factor for gps refractivity
max_error_q	5.0	maximum check_max_iv error check factor for specific humidity
max_error_p	5.0	maximum check_max_iv error check factor for pressure
max_error_thickness		maximum check_max_iv error check factor for thickness
max_error_rv		maximum check_max_iv error check factor for radar radial velocity
max_error_rf		maximum check_max_iv error check factor for radar reflectivity
&wrfvar6
max_ext_its	1	number of outer loops
ntmax	200	maximum number of iterations in an inner loop
eps	0.01 (max_ext_its)	minimization convergence criterion (used dimension: max_ext_its); minimization stops when the norm of the gradient of the cost function gradient is reduced by a factor of eps. inner minimization stops either when the criterion is met or when inner iterations reach ntmax.
&wrfvar7
cv_options	5	3: NCEP Background Error model 5: NCAR Background Error model (default)
as1(3)	-1.0	tuning factors for variance, horizontal and vertical scales for control variable 1 = stream function. For cv_options=3 only. The actual default values are 0.25, 1.0, 1.5.
as2(3)	-1.0	tuning factors for variance, horizontal and vertical scales for control variable 2 - unbalanced potential velocity. For cv_options=3 only. The actual default values are 0.25, 1.0, 1.5.
as3(3)	-1.0	tuning factors for variance, horizontal and vertical scales for control variable 3 - unbalanced temperature. For cv_options=3 only. The actual default values are 0.25, 1.0, 1.5.
as4(3)	-1.0	tuning factors for variance, horizontal and vertical scales for control variable 4 - pseudo relative humidity. For cv_options=3 only. The actual default values are 0.25, 1.0, 1.5.
as5(3)	-1.0	tuning factors for variance, horizontal and vertical scales for control variable 5 - unbalanced surface pressure. For cv_options=3 only. The actual default values are 0.25, 1.0, 1.5.
rf_passes	6	number of passes of recursive filter.
var_scaling1	1.0	tuning factor of background error covariance for control variable 1 - stream function. For cv_options=5 only.
var_scaling2	1.0	tuning factor of background error covariance for control variable 2 - unbalanced velocity potential. For cv_options=5 only.
var_scaling3	1.0	tuning factor of background error covariance for control variable 3 - unbalanced temperature. For cv_options=5 only.
var_scaling4	1.0	tuning factor of background error covariance for control variable 4 - pseudo relative humidity. For cv_options=5 only.
var_scaling5	1.0	tuning factor of background error covariance for control variable 5 - unbalanced surface pressure. For cv_options=5 only.
len_scaling1	1.0	tuning factor of scale-length for stream function. For cv_options=5 only.
len_scaling2	1.0	tuning factor of scale-length for unbalanced velocity potential. For cv_options=5 only.
len_scaling3	1.0	tuning factor of scale-length for unbalanced temperature. For cv_options=5 only.
len_scaling4	1.0	tuning factor of scale-length for pseudo relative humidity. For cv_options=5 only.
len_scaling5	1.0	tuning factor of scale-length for unbalanced surface pressure. For cv_options=5 only.
je_factor	1.0	ensemble covariance weighting factor
&wrfvar8 ;not used
&wrfvar9		for program tracing. trace_use=.true. gives additional performance diagnostics (calling tree, local routine timings, overall routine timings, memory usage) It does not change results, but does add runtime overhead.
stdout	6	unit number for standard output
stderr	0	unit number for error output
trace_unit	7	Unit number for tracing output note that units 10 and 9 are reserved for reading namelist.input and writing namelist.output respectively.
trace_pe	0	Currently, statistics are always calculated for all processors, and output by processor 0.
trace_repeat_head	10	the number of times any trace statement will produce output for any particular routine. This stops overwhelming trace output when a routine is called multiple times. Once this limit is reached a 'going quiet' message is written to the trace file, and no more output is produced from the routine, though statistics are still gathered.
trace_repeat_body	10	see trace_repeat_head description
trace_max_depth	30	define the deepest level to which tracing writes output
trace_use	true	.true.: activate tracing
trace_use_frequent	false
trace_use_dull	false
trace_memory	true	.true.: calculate allocated memory using a mallinfo call. On some platforms (Cray and Mac), mallinfo is not available and no memory monitoring can be done.
trace_all_pes	false	.true.: tracing is output for all pes. As stated in trace_pe, this does not change processor statistics.
trace_csv	true	.true.: tracing statistics are written to a xxxx.csv file in CSV format
use_html	true	.true.: tracing and error reporting routines will include HTML tags.
warnings_are_fatal	false	.true.: warning messages that would normally allow the program to continue are treated as fatal errors.
&wrfvar10 ; for code developer
&wrfvar11
cv_options_hum	1	do not change
check_rh		0 --> No supersaturation check after minimization. 1 --> supersaturation (rh> 100%) and minimum rh (rh<10%) check, and make the local adjustment of q. 2 --> supersaturation (rh> 95%) and minimum rh (rh<11%) check and make the multi-level q adjustment under the constraint of conserved column integrated water vapor
sfc_assi_options	1	1 --> surface observations will be assimilated based on the lowest model level first guess. Observations are not used when the height difference of the elevation of the observing site and the lowest model level height is larger than 100m. 2 --> surface observations will be assimilated based on surface similarity theory in PBL. Innovations are computed based on 10-m wind, 2-m temperature and 2-m moisture.
calculate_cg_cost_fn	false	the purpose of calculate_cg_cost_fn is changed. use print_detail_grad=.true. to dump cost function and gradient of each iteration to cost_fn and grad_fn. conjugate gradient algorithm does not require the computation of cost function at every iteration during minimization..true.: cost function is printed out and is directly derived from the gradient using the fully linear properties inside the inner-loop..false.: Only the initial and final cost functions are computed
lat_stats_option	false	do not change
&wrfvar12
balance_type	1	obsolete
&wrfvar13
vert_corr	2	do not change
vertical_ip	0	obsolete
vert_evalue	1	do not change
max_vert_var1	99.0	specify the maximum truncation value (in percentage) to explain the variance of stream function in eigenvector decomposition
max_vert_var2	99.0	specify the maximum truncation value (in percentage) to explain the variance of unbalanced potential velocity in eigenvector decomposition
max_vert_var3	99.0	specify the maximum truncation value (in percentage) to explain the variance of the unbalanced temperature in eigenvector decomposition
max_vert_var4	99.0	specify the maximum truncation value (percentage) to explain the variance of pseudo relative humidity in eigenvector decomposition
max_vert_var5	99.0	for unbalanced surface pressure, it should be a non-zero positive numer. set max_vert_var5=0.0 only for offline VarBC applications.
&wrfvar14
the following 4 variables (rtminit_nsensor, rtminit_platform, rtminit_satid, rtminit_sensor) together control what sensors to be assimilated.
rtminit_nsensor	1		total number of sensors to be assimilated
rtminit_platform	-1 (max_instruments)		platforms IDs array (used dimension: rtminit_nsensor); e.g., 1 for NOAA, 9 for EOS, 10 for METOP and 2 for DMSP
rtminit_satid	-1.0 (max_instruments)		satellite IDs array (used dimension: rtminit_nsensor)
rtminit_sensor	-1.0 (max_instruments)		sensor IDs array (used dimension: rtminit_nsensor); e.g., 0 for HIRS, 3 for AMSU-A, 4 for AMSU-B, 15 for MHS, 10 for SSMIS, 11 for AIRS
rad_monitoring	0 (max_instruments)		integer array (used dimension: rtminit_nsensor); 0: assimilating mode; 1: monitoring mode (only calculate innovations)
thinning_mesh	60.0 (max_instruments)		real array (used dimension: rtminit_nsensor); specify thinning mesh size (in KM) for different sensors.
thinning	false		.true.: perform thinning on radiance data
qc_rad	true		.true.: perform quality control. always .true.
write_iv_rad_ascii	false		.true.: output radiance Observation minus Background files, which are in ASCII format and separated by sensors and processors.
write_oa_rad_ascii	false		.true.: output radiance Observation minus Analysis files (Observation minus Background information is also included), which are in ASCII format and separated by sensors and processors.
use_error_factor_rad	false		.true.: use a radiance error tuning factor file "radiance_error.factor", which can be created with empirical values or generated using variational tuning method (Desroziers and Ivanov, 2001)
use_antcorr	false (max_instruments)		.true.: perform Antenna Correction in CRTM
rtm_option	1		what RTM (Radiative Transfer Model) to use 1: RTTOV (WRFDA needs to compile with RTTOV) 2: CRTM (WRFDA needs to compile with CRTM)
only_sea_rad	false		.true.: assimilate radiance over water only
use_varbc	false		.true.: perform Variational Bias Correction. A parameter file in ASCII format called VARBC.in (a template is provided with the source code tar ball) is required.
freeze_varbc	false		.true: together with use_varbc=.false., keep the VarBC bias parameters constant in time. In this case, the bias correction is read and applied to the innovations, but it is not updated during the minimization.
varbc_factor	1.0		for scaling the VarBC preconditioning
varbc_nobsmin	10		defines the minimum number of observations required for the computation of the predictor statistics during the first assimilation cycle. If there are not enough data (according to "VARBC_NOBSMIN") on the first cycle, the next cycle will perform a coldstart again.
airs_warmest_fov	false		.true.: uses the observation brightness temperature forAIRS Window channel #914 as criterion for GSI thinning (with a higher amplitude than the distance from the observation location to the nearest grid point).
crtm_atmosphere	0		climatology reference profile used above model top for CRTM Radiative Transfer Model (up to 0.01hPa 0: Invalid (default, use U.S. Standard Atmosphere) 1: Tropical 2: Midlatitude summer 3: Midlatitude winter 4: Subarctic summer 5: Subarctic winter 6: U.S. Standard Atmosphere
use_crtm_kmatrix	false		.true. use CRTM K matrix rather than calling CRTM TL and AD routines for gradient calculation, which reduces runtime noticeably.
&wrfvar15 (needs to be set together with &wrfvar19)
num_pseudo	0	Set the number of pseudo observations, either 0 or 1 (single ob)
pseudo_x	1.0	Set the x-position (I) of the OBS in unit of grid-point.
pseudo_y	1.0	Set the y-position (J) of the OBS in unit of grid-point.
pseudo_z	1.0	Set the z-position (K) of OBS with the vertical level index, in bottom-up order.
pseudo_val	1.0	Set the innovation of the ob; wind in m/s, pressure in Pa, temperature in K, specific humidity in kg/kg
pseudo_err	1.0	set the error of the pseudo ob. Unit the same as pseudo_val.; if pseudo_var="q", pseudo_err=0.001 is more reasonable.
&wrfvar16 (for hybrid WRFDA/ensemble)
alphacv_method	2	1: ensemble perturbations in control variable space 2: ensemble perturbations in model variable space
ensdim_alpha	0	ensemble size
alpha_corr_type	3	1: alpha_corr_type_exp 2: alpha_corr_type_soar 3: alpha_corr_type_gaussian (default)
alpha_corr_scale	1500.0	km
&wrfvar17
analysis_type	“3D-VAR”	"3D-VAR": 3D-VAR mode (default); "QC-OBS": 3D-VAR mode plus extra filtered_obs output; "VERIFY": verification mode. WRFDA resets check_max_iv=.false. and ntmax=0; "RANDOMCV": for creating ensemble perturbations
&wrfvar18 (needs to set &wrfvar21 and &wrfvar22 as well if ob_format=1 and/or radiances are used)
analysis_date	“2002-08-03_00:00:00.0000”	specify the analysis time. It should be consistent with the first guess time. However, if time difference between analysis_date and date info read in from first guess is larger than analysis_accu, WRFDA will issue a warning message ("=======> Wrong xb time found???"), but won't abort.
&wrfvar19 (needs to be set together with &wrfvar15)
pseudo_var	“t”	Set the name of the OBS variable: 'u' = X-direction component of wind, 'v' = Y-direction component of wind, 't' = Temperature, 'p' = Prerssure, 'q' = Specific humidity "pw": total precipitable water "ref": refractivity "ztd": zenith total delay
&wrfvar20
documentation_url	“http://www.mmm.ucar.edu/people/wrfhelp/wrfvar/code/trunk”
&wrfvar21
time_window_min	"2002-08-02_21:00:00.0000"	start time of assimilation time window used for ob_format=1 and radiances to select observations inside the defined time_window. Note: Start from V3.1, this variable is also used for ob_format=2 to double-check if the obs are within the specified time window.
&wrfvar22
time_window_max	"2002-08-03_03:00:00.0000"	end time of assimilation time window used for ob_format=1 and radiances to select observations inside the defined time_window. Note: Start from V3.1, this variable is also used for ob_format=2 to double-check if the obs are within the specified time window.
&wrfvar23 (settings related to the 4D-Var penalty term option, which controls the high-frequency gravity waves using a digital filter)
jcdfi_use	false	.true.: Include JcDF term in cost function. .False.: Ignore JcDF term in cost function.
jcdfi_io	false	.true.: Read JcDF output from WRF+. Even jcdfi_use= false. Used for diagnosis. .False.: Ignore the JcDF output from WRF+
jcdfi_tauc	10800	seconds, filter time window second.
jcdfi_gama	1.0	Scaling number used to tune the weight of JcDF term
jcdfi_error_wind	3.0	m/s, wind error used in JcDF
jcdfi_error_t	1.0	K, temperature error used in JcDF
jcdfi_error_q	0.001	kg/kg, specific humidity error used in JcDF
jcdfi_error_mu	1000.	Pa, perturbation pressure (mu) error used in JcDF

OBSPROC namelist variables.

Variable Names	Description
&record1
obs_gts_filename	name and path of decoded observation file
fg_format	'MM5' for MM5 application, 'WRF' for WRF application
obserr.txt	name and path of observational error file
first_guess_file	name and path of the first guess file
&record2
time_window_min	The earliest time edge as ccyy-mm-dd_hh:mn:ss
time_analysis	The analysis time as ccyy-mm-dd_hh:mn:ss
time_window_max	The latest time edge as ccyy-mm-dd_hh:mn:ss ** Note : Only observations between [time_window_min, time_window_max] will kept.
&record3
max_number_of_obs	Maximum number of observations to be loaded, ie in domain and time window, this is independent of the number of obs actually read.
fatal_if_exceed_max_obs	.TRUE.: will stop when more than max_number_of_obs are loaded .FALSE.: will process the first max_number_of_obs loaded observations.
&record4
qc_test_vert_consistency	.TRUE. will perform a vertical consistency quality control check on sounding
qc_test_convective_adj	.TRUE. will perform a convective adjustment quality control check on sounding
qc_test_above_lid	.TRUE. will flag the observation above model lid
remove_above_lid	.TRUE. will remove the observation above model lid
domain_check_h	.TRUE. will discard the observations outside the domain
Thining_SATOB	.FALSE.: no thinning for SATOB data. .TRUE.: thinning procedure applied to SATOB data.
Thining_SSMI	.FALSE.: no thinning for SSMI data. .TRUE.: thinning procedure applied to SSMI data.
Thining_QSCAT	.FALSE.: no thinning for SATOB data. .TRUE.: thinning procedure applied to SSMI data.
&record5
print_gts_read	TRUE. will write diagnostic on the decoded obs reading in file obs_gts_read.diag
print_gpspw_read	.TRUE. will write diagnostic on the gpsppw obs reading in file obs_gpspw_read.diag
print_recoverp	.TRUE. will write diagnostic on the obs pressure recovery in file obs_recover_pressure.diag
print_duplicate_loc	.TRUE. will write diagnostic on space duplicate removal in file obs_duplicate_loc.diag
print_duplicate_time	.TRUE. will write diagnostic on time duplicate removal in file obs_duplicate_time.diag
print_recoverh	.TRUE will write diagnostic on the obs height recovery in file obs_recover_height.diag
print_qc_vert	.TRUE will write diagnostic on the vertical consistency check in file obs_qc1.diag
print_qc_conv	.TRUE will write diagnostic on the convective adjustment check in file obs_qc1.diag
print_qc_lid	.TRUE. will write diagnostic on the above model lid height check in file obs_qc2.diag
print_uncomplete	.TRUE. will write diagnostic on the uncompleted obs removal in file obs_uncomplete.diag
user_defined_area	.TRUE.: read in the record6: x_left, x_right, y_top, y_bottom, .FALSE.: not read in the record6.
&record6
x_left	West border of sub-domain, not used
x_right	East border of sub-domain, not used
y_bottom	South border of sub-domain, not used
y_top	North border of sub-domain, not used
ptop	Reference pressure at model top
ps0	Reference sea level pressure
base_pres	Same as ps0. User must set either ps0 or base_pres.
ts0	Mean sea level temperature
base_temp	Same as ts0. User must set either ts0 or base_temp.
tlp	Temperature lapse rate
base_lapse	Same as tlp. User must set either tlp or base_lapse.
pis0	Tropopause pressure, the default = 20000.0 Pa
base_tropo_pres	Same as pis0. User must set either pis0 or base_tropo_pres
tis0	Isothermal temperature above tropopause (K), the default = 215 K.
base_start_temp	Same as tis0. User must set either tis0 or base_start_temp.
&record7
IPROJ	Map projection (0 = Cylindrical Equidistance, 1 = Lambert Conformal, 2 = Polar stereographic, 3 = Mercator)
PHIC	Central latitude of the domain
XLONC	Central longitude of the domain
TRUELAT1	True latitude 1
TRUELAT2	True latitude 2
MOAD_CEN_LAT	The central latitude for the Mother Of All Domains
STANDARD_LON	The standard longitude (Y-direction) of the working domain.
&record8
IDD	Domain ID (1=< ID =< MAXNES), Only the observations geographically located on that domain will be processed. For WRF application with XLONC /= STANDARD_LON, set IDD=2, otherwise set 1.
MAXNES	Maximum numbe of domains as needed.
NESTIX	The I(y)-direction dimension for each of the domains
NESTJX	The J(x)-direction dimension for each of the domains
DIS	The grid size for each of the domains. For WRF application, always set NESTIX(1),NESTJX(1), and DIS(1) based on the infomation in wrfinput.
NUMC	The mother domain ID number for each of the domains
NESTI	The I location in its mother domain of the nest domain's low left corner -- point (1,1)
NESTI	The J location in its mother domain of the nest domain's low left corner -- point (1,1). For WRF application, NUMC(1), NESTI(1), and NESTJ(1) are always set to be 1.
&record9
prepbufr_output_filename	Name of the prebufr OBS file.
prepbufr_table_filename	'prepbufr_table_filename' ; not change
output_ob_format	output 1, prebufr OBS file only; 2, ASCII OBS file only; 3, Both prebufr and ASCII OBS files.
use_for	'3DVAR' obs file, same as before, default 'FGAT ' obs files for FGAT '4DVAR' obs files for 4DVAR
num_slots_past	the number of time slots before time_analysis
num_slots_ahead	the number of time slots after time_analysis
write_synop	If keep synop obs in obs_gts (ASCII) files.
write_ship	If keep ship obs in obs_gts (ASCII) files.
write_metar	If keep metar obs in obs_gts (ASCII) files.
write_buoy	If keep buoy obs in obs_gts (ASCII) files.
write_pilot	If keep pilot obs in obs_gts (ASCII) files.
write_sound	If keep sound obs in obs_gts (ASCII) files.
write_amdar	If keep amdar obs in obs_gts (ASCII) files.
write_satem	If keep satem obs in obs_gts (ASCII) files.
write_satob	If keep satob obs in obs_gts (ASCII) files.
write_airep	If keep airep obs in obs_gts (ASCII) files.
write_gpspw	If keep gpspw obs in obs_gts (ASCII) files.
write_gpsztd	If keep gpsztd obs in obs_gts (ASCII) files.
write_gpsref	If keep gpsref obs in obs_gts (ASCII) files.
write_gpseph	If keep gpseph obs in obs_gts (ASCII) files.
write_ssmt1	If keep ssmt1 obs in obs_gts (ASCII) files.
write_ssmt2	If keep ssmt2 obs in obs_gts (ASCII) files.
write_ssmi	If keep ssmi obs in obs_gts (ASCII) files.
write_tovs	If keep tovs obs in obs_gts (ASCII) files.
write_qscat	If keep qscat obs in obs_gts (ASCII) files.
write_profl	If keep profile obs in obs_gts (ASCII) files.
write_bogus	If keep bogus obs in obs_gts (ASCII) files.
write_airs	If keep airs obs in obs_gts (ASCII) files.

* Current release is RTTOV9, while there is no plan to incorporate RTTOV9 into WRFDA.

Chapter 6: WRF Data Assimilation

Table of Contents

Introduction

Installing WRFDA

Installing WRFNL and WRFPLUS (For 4D-Var only)

Running Observation Preprocessor (OBSPROC)

Running WRFDA

a. Download Test Data

b. Run the Case—3D-Var

c. Run the Case—4D-Var

Radiance Data Assimilations in WRFDA

WRFDA Diagnostics

Updating WRF boundary conditions

Running gen_be

Additional WRFDA Exercises:

Hybrid Data Assimilation in WRFDA

Description of Namelist Variables