<p><b>xinzhang</b> 2009-04-03 09:23:29 -0600 (Fri, 03 Apr 2009)</p><p>Save for some of Xiaoyan's changes for Chap 6.<br>
</p><hr noshade><pre><font color="gray">Modified: trunk/wrf/UsersGuide/users_guide_chap6.doc
===================================================================
--- trunk/wrf/UsersGuide/users_guide_chap6.doc 2009-04-02 22:25:35 UTC (rev 169)
+++ trunk/wrf/UsersGuide/users_guide_chap6.doc 2009-04-03 15:23:29 UTC (rev 170)
@@ -1,5 +1,6 @@
-ࡱ
-
+
+
HYPERLINK \l "_Description_of_Namelist_1" Description of Namelist Variables
Introduction
-Data assimilation is the technique by which observations are combined with an 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.
+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.
MMM Division of NCAR supports a unified (global/regional, multi-model, 3/4D-Var) model-space variational data assimilation system (WRF-Var) 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 WRF-Var web-page HYPERLINK "http://www.mmm.ucar.edu/wrf/users/docs/user_guide_V3/users_guide_chap6.htm" http://www.mmm.ucar.edu/wrf/users/docs/user_guide_V3/users_guide_chap6.htm.
Various
components of the WRF-Var system are shown in blue in the s!
ketch be
low, together with their relationship with rest of the WRF system.
@@ -494,7 +495,7 @@
A file called namelist.output (which contains the complete namelist settings) will be generated after a successful da_wrfvar.exe run. Those settings appear in namelist.output that are not specified in your namelist.input are the default values from WRFDA/Registry/Registry.wrfvar.
After successful completion of job, wrfvar_output (the WRF-Var 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 (HYPERLINK \l "_WRF-Var_Diagnostics_1"WRF-Var Diagnostics).
In order to understand the role of various important WRF-Var options, try re-running WRF-Var by changing different namelist options. For example, making WRF-Var convergence criteria more stringent by reducing the value of EPS to e.g. 0.0001 by adding "EPS=0.0001" in namelist.input record &wrfvar6. Last section of this tutorial deals with
many such WRF-Var additional exercises.
-b. Run The Case4D-Var
+b. Run the Case4D-Var
To run WRF-4DVar, create a working directory, WRFDA/var/test/4dvar is a sample,
Assume the working shell is C shell;
Assume the directories for WRFDA , WRFNL and WRFPLUS are :
@@ -513,7 +514,7 @@
ob/2008020518
rc/2008020512
be
-Note: Currently, WRF-4DVar can only run with the observation data processed by OBSPROC, cannot work with PREPBUFR format data; WRF-4DVar can work with satellite radiance BUFR data, but the this capability is still under testing.
+Note: Currently, WRF-4DVar can only run with the observation data processed by OBSPROC, not work with PREPBUFR format data; 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:
@@ -606,7 +607,7 @@
> 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 difficulty to define a generic way to run the WRF 4D-Var parallel. Here, an example command to run WRF 4D-Var on a cluster with 16 processors is:
+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. Here, an example command to run WRF 4D-Var on a cluster with 16 processors is:
> mpirun np 4 da_wrfvar.exe: -np 8 ad/wrfplus.exe: -np 4 nl/wrf.exe
There are 4 processors are assigne
d to run WRFDA, 4 processors are assigned to run WRFNL and 8 processors for WRFPLUS due to high computational cost in adjoint code.
wrfda.log (or rsl.out.0000 if running in parallel mode) contains important WRF-4DVar runtime log. Always check the log after a WRF-4DVar run.
@@ -665,7 +666,7 @@
d. Channel Selection
-Channel selection in WRF-Var is controlled by some 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 WRF-Var to control if assimilating corresponding channel. Channels with the value -1 indicates 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 WRF-Var to set the observation error for each channel. Other columns are not used by WRF-Var. It should be mentioned that these error values are not necessarily optimal for your applications, it is users responsibility to obtain the optimal error statistics for your own applications.
+Channel selection in WRF-Var is controlled by some 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 WRF-Var to control if assimilating corresponding channel. Channels with the value -1 indicates 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 WRF-Var to set the observation error for each channel. Other columns are not used by WRF-Var. It should be mentioned that these error values are not necessarily optimal for your applications; it is users 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
@@ -695,7 +696,7
@@
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 WRF-Var cost function.
+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 WRF-Var 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, th
e predictors can evolve without any constraint.
@@ -1072,7 +1073,7 @@
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 4DVARnum_slots_pastthe number of time slots before time_analysisnum_slots_aheadthe number of time slots after time_analysiswrite_synopIf keep synop obs in obs_gts (ASCII) files.write_shipIf keep ship obs in obs_gts (ASCII) files.write_metarIf keep metar obs in obs_gts (ASCII) files.write_buoyIf keep buoy obs in obs_gts (ASCII) files.write_pilotIf keep pilot obs in obs_gts (ASCII) files.write_soundIf keep sound obs in obs_gts (ASCII) files.write_amdarIf keep amdar obs in obs_gts (ASCII) files.write_satemIf keep satem obs in obs_gts (ASCII) files.write_satobIf keep satob obs in obs_gts (ASCII) files.write_airepIf keep airep obs in obs_gts (ASCII) files.write_gpspwIf keep gpspw obs in obs_gts (ASCII) files.write_gpsztdIf keep gpsztd obs in obs_gts (ASCII) files.write_gpsrefIf keep gpsre
f obs in obs_gts (ASCII) files.write_gpsephIf keep gpseph obs in obs_gts (ASCII) files.write_ssmt1If keep ssmt1 obs in obs_gts (ASCII) files.write_ssmt2If keep ssmt2 obs in obs_gts (ASCII) files.write_ssmiIf keep ssmi obs in obs_gts (ASCII) files.write_tovsIf keep tovs obs in obs_gts (ASCII) files.write_qscatIf keep qscat obs in obs_gts (ASCII) files.write_proflIf keep profile obs in obs_gts (ASCII) files.write_bogusIf keep bogus obs in obs_gts (ASCII) files.write_airsIf keep airs obs in obs_gts (ASCII) files.
-
+
* Current release is RTTOV9, while there is no plan to incorporate RTTOV9 into WRF-Var.
@@ -1090,10 +1091,10 @@
-WRF-ARW V3: Users Guide 6- PAGE 24
+WRF-ARW V3: Users Guide 6- PAGE 52
-WRF-ARW V3: Users Guide 6- PAGE 49
+WRF-ARW V3: Users Guide 6- PAGE 53
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