<p><b>duda</b> 2013-04-01 11:51:03 -0600 (Mon, 01 Apr 2013)</p><p>BRANCH COMMIT<br>
<br>
Add code to scale by a constant value the divergence gradient component <br>
of the computation of del4 for the u field. The scaling is controlled by<br>
a new namelist option, config_del4u_div_factor, whose default value is<br>
1.0 (i.e., no scaling, or no change to what was previously being computed).<br>
<br>
In our testing on the 7.5-km grid, we've been setting <br>
config_del4u_div_factor = 10.0 with config_visc4_2dsmag = 0.05.<br>
<br>
No effect on results unless config_del4u_div_factor is set to something <br>
other than its default.<br>
<br>
<br>
M    src/core_nhyd_atmos/mpas_atm_time_integration.F<br>
M    src/core_nhyd_atmos/Registry.xml<br>
</p><hr noshade><pre><font color="gray">Modified: branches/atmos_physics/src/core_nhyd_atmos/Registry.xml
===================================================================
--- branches/atmos_physics/src/core_nhyd_atmos/Registry.xml        2013-04-01 17:46:03 UTC (rev 2686)
+++ branches/atmos_physics/src/core_nhyd_atmos/Registry.xml        2013-04-01 17:51:03 UTC (rev 2687)
@@ -49,6 +49,7 @@
                 &lt;nml_option name=&quot;config_h_theta_eddy_visc4&quot;         type=&quot;real&quot;          default_value=&quot;0.0&quot;/&gt;
                 &lt;nml_option name=&quot;config_v_theta_eddy_visc2&quot;         type=&quot;real&quot;          default_value=&quot;0.0&quot;/&gt;
                 &lt;nml_option name=&quot;config_visc4_2dsmag&quot;               type=&quot;real&quot;          default_value=&quot;0.0&quot;/&gt;
+                &lt;nml_option name=&quot;config_del4u_div_factor&quot;           type=&quot;real&quot;          default_value=&quot;1.0&quot;/&gt;
                 &lt;nml_option name=&quot;config_number_of_sub_steps&quot;        type=&quot;integer&quot;       default_value=&quot;4&quot;/&gt;
                 &lt;nml_option name=&quot;config_w_adv_order&quot;                type=&quot;integer&quot;       default_value=&quot;3&quot;/&gt;
                 &lt;nml_option name=&quot;config_theta_adv_order&quot;            type=&quot;integer&quot;       default_value=&quot;3&quot;/&gt;

Modified: branches/atmos_physics/src/core_nhyd_atmos/mpas_atm_time_integration.F
===================================================================
--- branches/atmos_physics/src/core_nhyd_atmos/mpas_atm_time_integration.F        2013-04-01 17:46:03 UTC (rev 2686)
+++ branches/atmos_physics/src/core_nhyd_atmos/mpas_atm_time_integration.F        2013-04-01 17:51:03 UTC (rev 2687)
@@ -2308,7 +2308,9 @@
                ! Compute diffusion, computed as </font>
<font color="black">abla divergence - k \times </font>
<font color="red">abla vorticity
                !                    only valid for h_mom_eddy_visc4 == constant
                !
-               u_diffusion =  rho_edge(k,iEdge) * (  ( delsq_divergence(k,cell2)  - delsq_divergence(k,cell1) ) / dcEdge(iEdge)  &amp;
+               ! Here, we want to scale the diffusion on the divergence part a factor of config_del4u_div_factor 
+               !    more than the rotational part
+               u_diffusion =  rho_edge(k,iEdge) * ( config_del4u_div_factor * ( delsq_divergence(k,cell2)  - delsq_divergence(k,cell1) ) / dcEdge(iEdge)  &amp;
                            -( delsq_vorticity(k,vertex2) - delsq_vorticity(k,vertex1) ) / max(dvEdge(iEdge), 0.25*dcEdge(iEdge)) &amp;
                                                   )
 

</font>
</pre>