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20020108: handling MIXR with grid diagnostics in gempak




Clint,

This is the quick answer...

You are right in that the display of MIXR is scaled by 1000 to
produce g/kg (see $GEMPAK/source/gemlib/dg/dgscal.f). Calculations
are done in the dimensionless MKS units.

However, once you perform a calculation on the data (in MKS units),
and store the output for a different name (other than the recognized MIXR
name), your display will not be scaled to g/kg. So, you will have to
take that into acount when you SCALE the output for display.

I believe that is the gist of your message below. That is, when you
specify GRDNAM as MIXR_MOD for copying the data, the display output
will not be scaled to g/kg as MIXR would. You may also notice some
small roundoff changes due to the packing (PACK=grib/16) if the original
data used more precision.

If you want me to look into a specific calculation and how
to carry forth the MKS units let me know.


Chiz


Steve Chiswell
Unidata User Support



>From: Clint Rowe <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200201081709.g08H91N04033

>Chiz,
>
>I'm finding some strange behavior when trying to do some grid computations 
>in gempak.  I'm trying to compare two MM5 model runs and am creating a three-
>panel display (the two fields and their difference) using version 5.6e.  I've
>written a script that does this for whatever field I'm interested in.  
>Everything seemed to be working okay until Mark noticed that when plotting
>2m mixing ratios, the difference map were all blank, even though there are
>noticable differences in the two model runs.  If I run GDLIST on the two
>files and look at mixr, mixr+2 and sub(mixr, mixr+2), I get strange results.
>The reported mins and maxs look okay for the two runs and show differences
>as seen in the plots.  However, the results of the subtraction seems to
>yield zeros across the entire domain (i.e., the min and max are both zero).
>
>
>papagayo% gdlist
> GDATTIM   Grid date/time                    860731/1200
> GLEVEL    Grid level                        2
> GVCORD    Grid vertical coordinate          zagl
> GFUNC     Scalar grid                       mixrdiff
> GDFILE    Grid file                         test.gem
> GAREA     Graphics area                     dset
> PROJ      Map projection/angles/margins|dr  MER
> SCALE     Scalar scale / vector scale       0
> OUTPUT    Output device/filename            T
> Parameters requested: GDATTIM,GLEVEL,GVCORD,GFUNC,GDFILE,GAREA,PROJ,SCALE,
> OUTPUT.
> 
>GEMPAK-GDLIST>gdfil=../CTL/1986073100/1986073100_mm5_domain3.gem+../MOD/198607
> 31
>00/1986073100_mm5_domain3.gem
> GEMPAK-GDLIST>gfunc=mixr
> GEMPAK-GDLIST>r
>
>
> GDLIST PARAMETERS: 
>
> Grid file: 
>../CTL/1986073100/1986073100_mm5_domain3.gem+../MOD/1986073100/1986073100_mm5_
> do
>main3.gem                                       
> GRID IDENTIFIER:
>    TIME1             TIME2         LEVL1 LEVL2   VCORD PARM
>860731/1200                             2          ZAGL MIXR        
>
> GAREA:    dset                                            
> SCALE FACTOR : 10** 0
> OUTPUT:    TERM/              
>
> MINIMUM AND MAXIMUM VALUES     5.58    13.44
>Enter <cr> to accept parameters or type EXIT:ex
> Parameters requested: GDATTIM,GLEVEL,GVCORD,GFUNC,GDFILE,GAREA,PROJ,SCALE,
> OUTPUT.
> GEMPAK-GDLIST>gfun=mixr+2
> GEMPAK-GDLIST>r
>
>
> GDLIST PARAMETERS: 
>
> Grid file: 
>../CTL/1986073100/1986073100_mm5_domain3.gem+../MOD/1986073100/1986073100_mm5_
> do
>main3.gem                                       
> GRID IDENTIFIER:
>    TIME1             TIME2         LEVL1 LEVL2   VCORD PARM
>860731/1200                             2          ZAGL MIXR        
>
> GAREA:    dset                                            
> SCALE FACTOR : 10** 0
> OUTPUT:    TERM/              
>
> MINIMUM AND MAXIMUM VALUES     5.52    13.43
>Enter <cr> to accept parameters or type EXIT:ex
> Parameters requested: GDATTIM,GLEVEL,GVCORD,GFUNC,GDFILE,GAREA,PROJ,SCALE,
> OUTPUT.
> GEMPAK-GDLIST>gfun=sub(mixr,mixr+2)
> GEMPAK-GDLIST>r
>
>
> GDLIST PARAMETERS: 
>
> Grid file: 
>../CTL/1986073100/1986073100_mm5_domain3.gem+../MOD/1986073100/1986073100_mm5_
> do
>main3.gem                                       
> GRID IDENTIFIER:
>    TIME1             TIME2         LEVL1 LEVL2   VCORD PARM
>860731/1200                             2          ZAGL SUBMIXR     
>
> GAREA:    dset                                            
> SCALE FACTOR : 10** 0
> OUTPUT:    TERM/              
>
> MINIMUM AND MAXIMUM VALUES     0.00     0.00
>Enter <cr> to accept parameters or type EXIT:ex
> Parameters requested: GDATTIM,GLEVEL,GVCORD,GFUNC,GDFILE,GAREA,PROJ,SCALE,
> OUTPUT.
> GEMPAK-GDLIST>ex
>papagayo% 
>
>
>Okay, so if that wasn't a big enough problem, when I started putting together
>something to send you, I found even more strangeness.  I copied the mixing 
>ratio fields from the two files into a new file that I could send to you.  I
>also calculated the deifference to add to that file.  Then, when I began to 
>check my efforts, I found that the grids I had copied were different than
>what I expected. The raw fields had been multipled by 1000 and now there are 
>small differences (but smaller than implied by the fields themselves).
>
>
>papagayo% gdcfil
> GDOUTF    Output grid file                  test.gem
> PROJ      Map projection/angles/margins|dr  MER
> GRDAREA   Area covered by grid               
> KXKY      Number of grid points in x;y      10;10
> MAXGRD    Maximum number of grids           200
> CPYFIL    Grid file whose navigation is to  
>../CTL/1986073100/1986073100_mm5_domain3.gem
> ANLYSS    Grid analysis block               4/2;2;2;2
> Parameters requested: GDOUTF,PROJ,GRDAREA,KXKY,MAXGRD,CPYFIL,ANLYSS.
> GEMPAK-GDCFIL>r
>
> GDCFIL PARAMETERS: 
>
> New grid file:         test.gem                                              
>                                                                           
> File copied:           ../CTL/1986073100/1986073100_mm5_domain3.gem          
>                                                                           
> Grid projection:       LCC                     
> Lower left corner:         40.51  -104.66
> Upper right corner:        43.65   -96.77
> KX, KY:                      156       90
> DELTAN =     4.000       EXTEND =   2;  2;  2;  2
> Maximum number of grids that can be added to file  200
>Enter <cr> to accept parameters or type EXIT:
> Parameters requested: GDOUTF,PROJ,GRDAREA,KXKY,MAXGRD,CPYFIL,ANLYSS.
> GEMPAK-GDCFIL>ex
>papagayo% gddiag
> GDFILE    Grid file                         
>../CTL/1986073100/1986073100_mm5_domain3.gem+../MOD/1986073100/1986073100_mm5_
> do
>main3.gem
> GDOUTF    Output grid file                  test.gem
> GFUNC     Scalar grid                       sub(mixr,mixr+2)
> GDATTIM   Grid date/time                    860731/1200
> GLEVEL    Grid level                        2
> GVCORD    Grid vertical coordinate          zagl
> GRDNAM    Grid parameter name               mixr_mod
> GPACK     Packing type/number of bits       grib/16
> Parameters requested: GDFILE,GDOUTF,GFUNC,GDATTIM,GLEVEL,GVCORD,GRDNAM,
> GPACK.
> GEMPAK-GDDIAG>gfunc=mixr+2
> GEMPAK-GDDIAG>r
>
>
>    TIME1             TIME2         LEVL1 LEVL2   VCORD PARM
>860731/1200                             2          ZAGL MIXR_MOD    
>Enter a new grid parameter name, <cr> to accept or type EXIT:
> Parameters requested: GDFILE,GDOUTF,GFUNC,GDATTIM,GLEVEL,GVCORD,GRDNAM,
> GPACK.
> GEMPAK-GDDIAG>gfunc=mixr
> GEMPAK-GDDIAG>grdnam=mixr_ctl
> GEMPAK-GDDIAG>r
>
>
>    TIME1             TIME2         LEVL1 LEVL2   VCORD PARM
>860731/1200                             2          ZAGL MIXR_CTL    
>Enter a new grid parameter name, <cr> to accept or type EXIT:
> Parameters requested: GDFILE,GDOUTF,GFUNC,GDATTIM,GLEVEL,GVCORD,GRDNAM,
> GPACK.
> GEMPAK-GDDIAG>l
> GDFILE   = 
>../CTL/1986073100/1986073100_mm5_domain3.gem+../MOD/1986073100/1986073100_mm5_
> do
>main3.gem
> GDOUTF   = test.gem
> GFUNC    = mixr
> GDATTIM  = 860731/1200
> GLEVEL   = 2
> GVCORD   = zagl
> GRDNAM   = mixr_ctl
> GPACK    = none
> GEMPAK-GDDIAG>gfunc=sub(mixr,mixr+2)
> GEMPAK-GDDIAG>l
> GDFILE   = 
>../CTL/1986073100/1986073100_mm5_domain3.gem+../MOD/1986073100/1986073100_mm5_
> do
>main3.gem
> GDOUTF   = test.gem
> GFUNC    = sub(mixr,mixr+2)
> GDATTIM  = 860731/1200
> GLEVEL   = 2
> GVCORD   = zagl
> GRDNAM   = mixr_ctl
> GPACK    = none
> GEMPAK-GDDIAG>grdnam=mixrdiff
> GEMPAK-GDDIAG>r
>
>
>    TIME1             TIME2         LEVL1 LEVL2   VCORD PARM
>860731/1200                             2          ZAGL MIXRDIFF    
>Enter a new grid parameter name, <cr> to accept or type EXIT:
> Parameters requested: GDFILE,GDOUTF,GFUNC,GDATTIM,GLEVEL,GVCORD,GRDNAM,
> GPACK.
> GEMPAK-GDDIAG>ex
>papagayo% 
>papagayo% gdinfo
> GDFILE    Grid file                         
>../CTL/1986073100/1986073100_mm5_domain3.gem+../MOD/1986073100/1986073100_mm5_
> do
>main3.gem
> LSTALL    Full list flag                    YES
> OUTPUT    Output device/filename            T
> GDATTIM   Grid date/time                    860731/1200
> GLEVEL    Grid level                        2
> GVCORD    Grid vertical coordinate          zagl
> GFUNC     Scalar grid                       sub(mixr,mixr+2)
> Parameters requested: GDFILE,LSTALL,OUTPUT,GDATTIM,GLEVEL,GVCORD,GFUNC.
> GEMPAK-GDINFO>gdfil=test.gem
> GEMPAK-GDINFO>gfunc=all
> GEMPAK-GDINFO>r
>
> GRID FILE: test.gem                                                          
>                                                               
>
> GRID NAVIGATION: 
>     PROJECTION:          LCC                 
>     ANGLES:                30.0  -103.0    60.0
>     GRID SIZE:          156  90
>     LL CORNER:              40.51   -104.66
>     UR CORNER:              43.65    -96.77
>
> GRID ANALYSIS BLOCK: 
>     ANALYSIS TYPE:        BARNES
>     DELTAN:               4.000
>     DELTAX:           -9999.000
>     DELTAY:           -9999.000
>     GRID AREA:            39.00 -106.00   45.00  -96.00
>     EXTEND AREA:          39.00 -106.00   45.00  -96.00
>     DATA AREA:            39.00 -106.00   45.00  -96.00
>
> Number of grids in file:     3
>
> Maximum number of grids in file:    200
>
>  NUM       TIME1              TIME2           LEVL1 LEVL2  VCORD PARM
>    1     860731/1200                              2         ZAGL MIXR_MOD    
>    2     860731/1200                              2         ZAGL MIXR_CTL    
>    3     860731/1200                              2         ZAGL MIXRDIFF    
> Parameters requested: GDFILE,LSTALL,OUTPUT,GDATTIM,GLEVEL,GVCORD,GFUNC.
> GEMPAK-GDINFO>ex
>papagayo% gdlist
> GDATTIM   Grid date/time                    860731/1200
> GLEVEL    Grid level                        2
> GVCORD    Grid vertical coordinate          zagl
> GFUNC     Scalar grid                       all
> GDFILE    Grid file                         test.gem
> GAREA     Graphics area                     dset
> PROJ      Map projection/angles/margins|dr  MER
> SCALE     Scalar scale / vector scale       999
> OUTPUT    Output device/filename            T
> Parameters requested: GDATTIM,GLEVEL,GVCORD,GFUNC,GDFILE,GAREA,PROJ,SCALE,
> OUTPUT.
> GEMPAK-GDLIST>gfun=mixr_ctl
> GEMPAK-GDLIST>scal=0
> GEMPAK-GDLIST>r
>
>
> GDLIST PARAMETERS: 
>
> Grid file: test.gem                                                          
>                                                               
> GRID IDENTIFIER:
>    TIME1             TIME2         LEVL1 LEVL2   VCORD PARM
>860731/1200                             2          ZAGL MIXR_CTL    
>
> GAREA:    dset                                            
> SCALE FACTOR : 10** 0
> OUTPUT:    TERM/              
>
> MINIMUM AND MAXIMUM VALUES  5578.01 13438.01
>Enter <cr> to accept parameters or type EXIT:ex
> Parameters requested: GDATTIM,GLEVEL,GVCORD,GFUNC,GDFILE,GAREA,PROJ,SCALE,
> OUTPUT.
> GEMPAK-GDLIST>gfunc=mixr_mod
> GEMPAK-GDLIST>r
>
>
> GDLIST PARAMETERS: 
>
> Grid file: test.gem                                                          
>                                                               
> GRID IDENTIFIER:
>    TIME1             TIME2         LEVL1 LEVL2   VCORD PARM
>860731/1200                             2          ZAGL MIXR_MOD    
>
> GAREA:    dset                                            
> SCALE FACTOR : 10** 0
> OUTPUT:    TERM/              
>
> MINIMUM AND MAXIMUM VALUES  5519.52 13429.52
>Enter <cr> to accept parameters or type EXIT:ex
> Parameters requested: GDATTIM,GLEVEL,GVCORD,GFUNC,GDFILE,GAREA,PROJ,SCALE,
> OUTPUT.
> GEMPAK-GDLIST>gfunc=mixrdiff
> GEMPAK-GDLIST>r
>
>
> GDLIST PARAMETERS: 
>
> Grid file: test.gem                                                          
>                                                               
> GRID IDENTIFIER:
>    TIME1             TIME2         LEVL1 LEVL2   VCORD PARM
>860731/1200                             2          ZAGL MIXRDIFF    
>
> GAREA:    dset                                            
> SCALE FACTOR : 10** 0
> OUTPUT:    TERM/              
>
> MINIMUM AND MAXIMUM VALUES    -0.55     0.95
>Enter <cr> to accept parameters or type EXIT:ex
> Parameters requested: GDATTIM,GLEVEL,GVCORD,GFUNC,GDFILE,GAREA,PROJ,SCALE,
> OUTPUT.
> GEMPAK-GDLIST>ex
>papagayo% 
>
>
>
>Can you explain what's happening?
>
>Clint
>
>
>
>====================================================================
>Clinton M. Rowe
>Associate Professor 
>Meteorology/Climatology Program                  phone:(402)472-1946
>Department of Geosciences                          fax:(402)472-4917
>University of Nebraska-Lincoln                        address@hidden
>
>