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Add Spectral Nudging Option and Fix Nudging Behavior When Files Are Missing #1402

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Add Spectral Nudging Option and Fix Nudging Behavior When Files Are Missing #1402

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6fb95cb
Add Spectral Nudging Option
patcal Sep 30, 2025
2a4a281
Update Spectral Methods Usage
patcal May 22, 2026
9abc12a
Add revisions from review, Install capabilities for Ps nudging and us…
patcal Jun 23, 2026
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78 changes: 77 additions & 1 deletion bld/namelist_files/namelist_definition.xml
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Expand Up @@ -220,6 +220,53 @@
Default: FALSE
</entry>

<entry id="Nudge_SpectralFilter" type="logical" category="nudging"
group="nudging_nl" valid_values="" >
Toggle Spectral Filtering of Nudging Tendencies ON/OFF.

Nudge_SpectralFilter - LOGICAL Option to apply spherical harminic filtering to
the model state and target data so that nudging
tendencies are only applied to scales larger than
the specified truncation.
Default: FALSE
</entry>

<entry id="Nudge_SpectralNtrunc" type="integer" category="nudging"
group="nudging_nl" valid_values="" >
Set Horizonal Scale for Spectral Filtering

Nudge_SpectralNtrunc - INT The number of meridional spherical harmonic modes used
for spectral filtering. The nominal horizontal scale of
the filtering can be estimated as:

Hscale = PI*6350/Nudge_SpectralNtrunc

i.e. Nudge_SpectralNtrunc=40 corresponds to a horizontal
nudging scale Hscale~500km.
Default: -1
</entry>

<entry id="Nudge_SpectralNring" type="integer" category="nudging"
group="nudging_nl" valid_values="" >
Set size of local-area grid used to suppress Sampling Errors.

Nudge_SpectralNring - INT The number of sampling rings used for local area averaging
of spherical harmonic modes, to suppress sampling errors.
When initializing each basis, a local average of SH values
is computed for the area associated with each grid point.
SpectralNring set the number of rings of equal-area points
in this sampling domain.
Each ring (kk) contains 8*(kk-1) sample points.

Nudge_SpectralNring Number of Sampling Points
------------------- -------------------------
1 1 (DEFAULT SampleGrid NOT used)
2 9
3 25
4 49
Default: 1
</entry>

<entry id="Nudge_Path" type="char*256" input_pathname="abs" category="nudging"
group="nudging_nl" valid_values="" >
Full pathname of analyses data to use for nudging.
Expand Down Expand Up @@ -307,6 +354,9 @@
0 == OFF (No Nudging of this variable)
1 == CONSTANT (Spatially Uniform Nudging)
2 == HEAVISIDE WINDOW FUNCTION
3 == HEAVISIDE WINDOW FUNCTION IN VERTICAL
and USER SPECIFIED HORIZONAL DOMAIN
(Specified by user via Nudge_Bwindow_File)
Default: 0
</entry>

Expand All @@ -323,6 +373,9 @@
0 == OFF (No Nudging of this variable)
1 == CONSTANT (Spatially Uniform Nudging)
2 == HEAVISIDE WINDOW FUNCTION
3 == HEAVISIDE WINDOW FUNCTION IN VERTICAL
and USER SPECIFIED HORIZONAL DOMAIN
(Specified by user via Nudge_Bwindow_File)
Default: 0
</entry>

Expand All @@ -339,6 +392,9 @@
0 == OFF (No Nudging of this variable)
1 == CONSTANT (Spatially Uniform Nudging)
2 == HEAVISIDE WINDOW FUNCTION
3 == HEAVISIDE WINDOW FUNCTION IN VERTICAL
and USER SPECIFIED HORIZONAL DOMAIN
(Specified by user via Nudge_Bwindow_File)
Default: 0
</entry>

Expand All @@ -355,6 +411,9 @@
0 == OFF (No Nudging of this variable)
1 == CONSTANT (Spatially Uniform Nudging)
2 == HEAVISIDE WINDOW FUNCTION
3 == HEAVISIDE WINDOW FUNCTION IN VERTICAL
and USER SPECIFIED HORIZONAL DOMAIN
(Specified by user via Nudge_Bwindow_File)
Default: 0
</entry>

Expand All @@ -367,10 +426,12 @@

<entry id="Nudge_PSprof" type="integer" category="nudging"
group="nudging_nl" valid_values="" >
Profile index for PS nudging.
Profile index for PS nudging.(Horizontal Only)
0 == OFF (No Nudging of this variable)
1 == CONSTANT (Spatially Uniform Nudging)
2 == HEAVISIDE WINDOW FUNCTION
3 == USER SPECIFIED HORIZONAL DOMAIN
(Specified by user via Nudge_Bwindow_File)
Default: 0
</entry>

Expand All @@ -381,6 +442,14 @@
Default: 0.
</entry>

<entry id="Nudge_PSscal" type="real" category="nudging"
group="nudging_nl" valid_values="" >
Coeffcient controling the vertical influence function.
Nudge_PSscal < 1.0 : P'(n) = [ B(n) ]*(Target_Ps - Model_Ps)
Nudge_PSscal > 1.0 : P'(n) = [(Pref/P0)**scl]*(Target_Ps - Model_Ps)
Default: 0.
</entry>

<entry id="Nudge_Hwin_lat0" type="real" category="nudging"
group="nudging_nl" valid_values="" >
LAT0 center of Horizontal Window in degrees [-90.,90.].
Expand Down Expand Up @@ -461,6 +530,13 @@
Default: FALSE
</entry>

<entry id="Nudge_Bwindow_File" type="char*256" input_pathname="abs" category="nudging"
group="nudging_nl" valid_values="" >
Filename for the Horizonal Boundary Window to use for nudging with profile option 3.
(e.g. '/$DIN_LOC_ROOT/atm/cam/nudging/BoundaryWindowFile.nc')
Default: 'BoundaryWindowFile.nc'
</entry>

<entry id="Nudge_ZonalFilter" type="logical" category="nudging"
group="nudging_nl" valid_values="" >
Switch to turn on zonal mean filtering nudging. If TRUE, the nudging scheme
Expand Down
7 changes: 7 additions & 0 deletions cime_config/testdefs/testmods_dirs/cam/nudging/user_nl_cam
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Expand Up @@ -20,6 +20,11 @@
Nudge_TimeScale_Opt = 0
Nudge_Times_Per_Day=4
Model_Times_Per_Day=48
Nudge_ZonalFilter=.false.
Nudge_ZonalNbasis=-1
Nudge_SpectralFilter=.false.
Nudge_SpectralNtrunc=-1
Nudge_SpectralNring= 1
Nudge_Uprof =1
Nudge_Ucoef =1.00
Nudge_Vprof =1
Expand All @@ -30,6 +35,7 @@
Nudge_Qcoef =0.00
Nudge_PSprof =0
Nudge_PScoef =0.00
Nudge_PSscal =0.00
Nudge_Beg_Year =2008
Nudge_Beg_Month=12
Nudge_Beg_Day =16
Expand All @@ -48,5 +54,6 @@
Nudge_Vwin_Lindex =5.
Nudge_Vwin_Ldelta =1.0
Nudge_Vwin_Invert =.false.
Nudge_Bwindow_File='BoundaryWindowFile.nc'
/

8 changes: 6 additions & 2 deletions cime_config/testdefs/testmods_dirs/cam/outfrq3s_nudging_f10_L26/user_nl_cam
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Expand Up @@ -13,6 +13,9 @@
Nudge_TimeScale_Opt = 0
Nudge_Times_Per_Day=4
Model_Times_Per_Day=48
Nudge_SpectralFilter=.false.
Nudge_SpectralNtrunc=-1
Nudge_SpectralNring= 1
Nudge_Uprof =1
Nudge_Ucoef =1.00
Nudge_Vprof =1
Expand All @@ -21,8 +24,9 @@
Nudge_Tcoef =1.00
Nudge_Qprof =1
Nudge_Qcoef =1.00
Nudge_PSprof =1
Nudge_PScoef =1.00
Nudge_PSprof =0
Nudge_PScoef =0.00
Nudge_PSscal =0.00
Nudge_Beg_Year =0001
Nudge_Beg_Month=01
Nudge_Beg_Day =01
Expand Down
8 changes: 6 additions & 2 deletions cime_config/testdefs/testmods_dirs/cam/outfrq3s_nudging_ne5_L26/user_nl_cam
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,9 @@
Nudge_TimeScale_Opt = 0
Nudge_Times_Per_Day=4
Model_Times_Per_Day=48
Nudge_SpectralFilter=.false.
Nudge_SpectralNtrunc=-1
Nudge_SpectralNring= 1
Nudge_Uprof =1
Nudge_Ucoef =1.00
Nudge_Vprof =1
Expand All @@ -21,8 +24,9 @@
Nudge_Tcoef =1.00
Nudge_Qprof =1
Nudge_Qcoef =1.00
Nudge_PSprof =1
Nudge_PScoef =1.00
Nudge_PSprof =0
Nudge_PScoef =0.00
Nudge_PSscal =0.00
Nudge_Beg_Year =0001
Nudge_Beg_Month=01
Nudge_Beg_Day =01
Expand Down
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