[Dart-dev] DART/branches Revision: 11397

[dart at ucar.edu]

jla at ucar.edu
2017-03-24 14:52:41 -0600 (Fri, 24 Mar 2017)
39
Documentation for the bgrid model_mod.



Modified: DART/branches/rma_trunk/models/bgrid_solo/model_mod.html
===================================================================
--- DART/branches/rma_trunk/models/bgrid_solo/model_mod.html	2017-03-24 17:38:33 UTC (rev 11396)
+++ DART/branches/rma_trunk/models/bgrid_solo/model_mod.html	2017-03-24 20:52:41 UTC (rev 11397)
@@ -36,15 +36,45 @@
 <H2>Overview</H2>
 
 <P>
-JEFF - you fill in as much information here as you want.
-Look at the <a href="../lorenz_96/model_mod.html">lorenz_96 model_mod.html</a>
-for a feel of what might be useful. Also - if there are more references you want
-me to put in, Lili's? etc., just let me know.
+DART interface module for the dynamical core of the GFDL AM2 Bgrid model. This model is subroutine callable
+from DART and can be run in a similar fashion to low-order models that produce diagnostic output files
+with multiple assimilation times per file. 
 <br />
 <br />
-This part should also mention that this model is subroutine callable ... usage notes on
-ancillary programs (ps_rand_local.f90, ps_id_stdin.f90, id_set_def_stdin.f90, column_rand.f90)
-all those need at least a brief mention for completeness.
+The Bgrid model was originally
+configured as a comprehensive atmospheric model (Anderson et al. 2004). All of that code remains in the directories under the
+models/bgrid_solo directory, however, much of the capability has been disabled by code modification. What is
+left is a dry dynamical core for a model with no dirunal cycle at equinox with Held-Suarez forcing (Held and
+Suarez 1994). The default
+settings are for a model with a 60x30 horizontal grid and 5 vertical levels. This is close to the smallest 
+version that has somewhat realistic baroclinic instability resulting in mid-latitude 'storm tracks'. The 
+model resolution can be changed with the entries in the bgrid_cold_start_nml. It may be necessary to change
+the model time step to maintain stability for larger model grids. The model state variables are the gridded
+surface pressure, temperature, and u and v wind components. 
+<br />
+<br />
+Some examples of ways in which this model can be configured and modified to test DART assimilation capabilities
+are documented in Anderson et al. (2005).
+<br />
+<br />
+Several programs that generate interesting observation sequences are available in the models/bgrid_solo directory. 
+These programs take interactive user input and create a text file that can be piped into program 
+create_obs_sequence to create obs_sequence files. These can serve as examples for users who are interested
+in designing their own custom obs_sequence files.
+<br />
+Program column_rand creates an obs_sequence with randomly located columns of observations (essentially
+synthetic radiosondes) that observe surface pressure along with temperature and wind components at all model 
+levels.
+<br />
+Program id_set_def_stdin generates an obs_sequence file that observes every state variable with error variance
+of 10000 for surface pressure and 1.0 for temperature and wind components.
+<br />
+Program ps_id_stdin generates an obs_sequence that observes every surface pressure variable for the default 
+model size (30x60) with an error variance of 100.
+<br />
+Program ps_rand_local generates a set of randomly located surface pressure observations with an interactively
+specified error variance. It also allows the observations to be confined to a rectangular subdomain.
+
 </P>
 
 <!--=====================================================================-->
@@ -146,31 +176,43 @@
 
 <TR><TD>current_time(4)</TD>
     <TD>integer</TD>
-    <TD> JEFF
+    <TD> Specifies the initial time of the Bgrid model internal clock. The four integer 
+         values are the day, hour, minutes, and seconds. The default version of the Bgrid
+         model has neither a diurnal or seasonal cycle, so these can all be set to 0, the
+         default value.
         </TD>
 </TR>
 
 <TR><TD>override</TD>
     <TD>logical</TD>
-    <TD> JEFF
+    <TD> If true, then the initial model date is taken from namelist entry current_time,
+         even if an atmos_model.res file is found in directory INPUT. For most DART 
+         applications, atmospheric restart values are coming from DART files and no
+         INPUT directory is used.
         </TD>
 </TR>
 
 <TR><TD>dt_atmos</TD>
     <TD>integer</TD>
-    <TD> JEFF
+    <TD> Model timestep in seconds.
         </TD>
 </TR>
 
 <TR><TD>noise_sd</TD>
     <TD>real(r8)</TD>
-    <TD> JEFF
+    <TD> Standard deviation of random perturbations to the time tendency of temperature applied
+         at each timestep. Each gridpoint value of the computed temperature tendency is multiplied
+         by 1+N(0, noise_sd) before the updated values of temperature are computed.
         </TD>
 </TR>
 
 <TR><TD>dt_bias</TD>
     <TD>integer</TD>
-    <TD> JEFF
+    <TD> Allows a simple mechanism to simulate model error. If dt_bias is non-zero, the assimilation 
+         programs believe that each model advance changes the time by dt_bias. However, internally the
+         bgrid model is moving things forward by dt_atmos. By running perfect_model_obs with