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Re: bugs in gdprof and gdpoint

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Subject: Re: bugs in gdprof and gdpoint
Date: Mon, 23 Jan 2006 11:35:08 -0800
Hello,

I have been asked by another one of our group to follow up on this bug
report.  Have you been able to verify these errors?  Have these been
passed on to be worked on by anyone?  Is there any timeline
established for when they might be fixed? 

I realize that my original emails may not have stated the errors very
well.  In summary, wind direction calculations (and simple math
functions involving 2 wind components) at interpolated grid
points in gdprof and gdpoint are WRONG.  The reason is that wind
directions (and math involving 2 wind components) are calculated at
gridpoints first and are then interpolated without regard to vector
componets (see original email below for examples of the erroneous
output).  The correct way to do the calculation is to interpolate 
components and then do the all math on the interpolated values.
Though one could argue against this approach for something like 
  GFUNC = MUL(urel,urel)

you really cannot take the other approach for
  GFUNC = dirr(wnd)
  GFUNC = dirr(vecr(urel,vrel))

I have only made a quick, single point check in gdthgt and have not
tried gdtser.  The bug may exist in those as well.

Thanks for any info,

David


On Thu, Nov 24, 2005 at 11:56:12PM -0800, ovens wrote:
> Hello,
> 
> Turns out the math functions are occurring on the data BEFORE it is
> interpolated.  Hence, at point (x,y) = (8.458,92.63) even though 
>     UREL = -1.116
> GFUNC  = MUL(urel,urel) gives    
>     MUL(urel,urel) = 3.763 
> instead of 1.25 because the surrounding 4 gridpoints:
>      (x,y)                   UREL                  VREL
>  -------------    ------------------       --------------
>  (8,93) (9,93)     1.0634    -2.4366       0.379    1.129
>  (8,92) (9,92)    -1.8116    -2.4366       1.879   -0.371
> 
> are each being squared and THEN interpolated.  At an exact grid point,
> you get the correct/expected answer always.
> 
> Though I understand what is going on in the programs, I am still
> confused about the vector output.  For the same point (8.458,92.63),
> the  
>     UREL = UWND = -1.116
>     VREL = VWND =  0.769
> and the program says that 
>     GFUNC = dirn(wnd) =  159.70622
> instead of 124.6 degrees (which you get from urel and vrel by using 
> dirn = 270 - atan2(urel,vrel)*RTD).
> 
> What do you think the wind direction should be?
> 
> 
> David
> 
> 
> 
> On Thu, Nov 24, 2005 at 03:01:07AM -0800, ovens wrote:
> > Hello,
> > 
> > I have discovered the following bugs in GEMPAK 5.8.3a (Unidata binary
> > version and my compiled and patched versions).
> > 
> > In gdprof and gdpoint the use of MUL(urel,urel) and MAG(WND) and
> > DIRN(WND) are giving totally incorrect answers (for ECMWF, GFS, and
> > ETA 104 grids at least).  When I run MUL(urel,const) I get the
> > correct number.  This looks like some kind of memory error when both
> > arguments are the same item.
> > 
> > Here are the commands and results from gdprof, gdpoint results follow:
> > ====================  gdprof results ======================
> > GEMPAK-GDPROF>li
> >  GPOINT   = @8.458;92.63
> >  GDATTIM  = f0
> >  GVCORD   = hagl
> >  GVECT    = WND
> >  GDFILE   = /home/disk/data/gempak/model/ecmwf/2005112300_ecmwf.gem
> >  LINE     = 3
> >  MARKER   = 0
> >  BORDER   = 1
> >  PTYPE    = lin
> >  SCALE    = 0
> >  XAXIS    = 0
> >  YAXIS    = 0/10
> >  WIND     = BM1
> >  REFVEC   =  
> >  WINPOS   = 1
> >  FILTER   = YES
> >  TITLE    = 1
> >  PANEL    = 0
> >  CLEAR    = YES
> >  TEXT     = 1/21//hw
> >  DEVICE   = XW
> >  OUTPUT   = T
> >  THTALN   = 0
> >  THTELN   = 0
> >  MIXRLN   = 0
> >  GFUNC    = urel
> > r
> > 
> > 
> >  Grid function:             urel
> >  X,Y grid point:              8.46   92.63
> >  Lat/lon:                    47.44 -122.31
> >  Number of levels:            1
> >  Data range:                 -1.12   -1.12
> >  Scaling factor:             10** 0
> >        051123/0000V000  UREL   @8.458;92.63
> >        LATITUDE, LONGITUDE = (  47.44, -122.31 )
> >                   HAGL                  UREL
> >                   10.00               -1.116
> >                   HAGL        U         UREL   V         VREL
> >                   10.00               -1.116            0.769
> > 
> >  GEMPAK-GDPROF>gfunc = mul(urel,urel)
> >  GEMPAK-GDPROF>r
> >  GDPROF PARAMETERS
> >  Grid function:             mul(urel,urel)
> >  Grid vector function:      WND
> >  X,Y grid point:              8.46   92.63
> >  Lat/lon:                    47.44 -122.31
> >  Number of levels:            1
> >  Data range:                  3.76    3.76    ***** WRONG!!!!
> >  Scaling factor:             10** 0
> >  Wind display:            BM1                                               
> >                                                                             
> >   
> >        051123/0000V000  MULRELUREL   @8.458;92.63
> >        LATITUDE, LONGITUDE = (  47.44, -122.31 )
> >                   HAGL            MULRELUREL
> >                   10.00                3.763    ***** WRONG!!!!
> >                   HAGL        U         UREL   V         VREL
> >                   10.00               -1.116            0.769
> > 
> >  GEMPAK-GDPROF>gfunc = mul(urel,-1.116)
> >  GEMPAK-GDPROF>r
> >  Grid function:             mul(urel,-1.116)
> >  Data range:                  1.25    1.25
> >        051123/0000V000  MULREL-1.1   @8.458;92.63
> >        LATITUDE, LONGITUDE = (  47.44, -122.31 )
> >                   HAGL            MULREL-1.1
> >                   10.00                1.246
> >                   HAGL        U         UREL   V         VREL
> >                   10.00               -1.116            0.769
> > 
> > 
> > ====================  gdpoint results ======================
> >  GEMPAK-GDPOINT>li
> >  GDATTIM  = f0
> >  GDFILE   = /home/disk/data/gempak/model/ecmwf/2005112300_ecmwf.gem
> >  GLEVEL   = 10
> >  GPOINT   = @8.458;92.63
> >  GVCORD   = hagl
> >  GFUNC    = mul(urel,-1.116)
> >  SCALE    = 0
> >  GEMPAK-GDPOINT>gfun = urel
> >  GEMPAK-GDPOINT>r
> >  
> > GDFILE: /home/disk/data/gempak/model/ecmwf/2005112300_ecmw
> > GPOINT: @8.458;92.63                                      
> > GVCORD: hagl                                              
> > GLEVEL: 10                                                
> > GFUNC : urel                                              
> > SCALE : 0                                                 
> >      051123/0000F000 :     -1.11616
> > 
> >  GEMPAK-GDPOINT>gfu = mul(urel,urel)
> >  GEMPAK-GDPOINT>r
> > GDFILE: /home/disk/data/gempak/model/ecmwf/2005112300_ecmw
> > GPOINT: @8.458;92.63                                      
> > GVCORD: hagl                                              
> > GLEVEL: 10                                                
> > GFUNC : mul(urel,urel)                                    
> > SCALE : 0                                                 
> >      051123/0000F000 :      3.76344    ***** WRONG!!!!
> >  GEMPAK-GDPOINT>gfu = mul(urel,-1.11616)
> >  GEMPAK-GDPOINT>r
> >  
> > GDFILE: /home/disk/data/gempak/model/ecmwf/2005112300_ecmw
> > GPOINT: @8.458;92.63                                      
> > GVCORD: hagl                                              
> > GLEVEL: 10                                                
> > GFUNC : mul(urel,-1.11616)                                
> > SCALE : 0                                                 
> >      051123/0000F000 :      1.24581
> >  GEMPAK-GDPOINT>gfun = vrel
> >  GEMPAK-GDPOINT>r  
> >  
> > GDFILE: /home/disk/data/gempak/model/ecmwf/2005112300_ecmw
> > GPOINT: @8.458;92.63                                      
> > GVCORD: hagl                                              
> > GLEVEL: 10                                                
> > GFUNC : vrel                                              
> > SCALE : 0                                                 
> >      051123/0000F000 :      0.76872
> > 
> >  GEMPAK-GDPOINT>gfu = mag(wnd)
> >  GEMPAK-GDPOINT>r
> >  
> > GDFILE: /home/disk/data/gempak/model/ecmwf/2005112300_ecmw
> > GPOINT: @8.458;92.63                                      
> > GVCORD: hagl                                              
> > GLEVEL: 10                                                
> > GFUNC : mag(wnd)                                          
> > SCALE : 0                                                 
> >      051123/0000F000 :      2.10129    ***** WRONG!!!! s/b 1.355
> > 
> >  GEMPAK-GDPOINT>gfu = dirn(wnd)
> >  GEMPAK-GDPOINT>r
> > GFUNC : dirn(wnd)                                         
> >      051123/0000F000 :    159.70622    ***** WRONG!!!! s/b 124.6 degrees
> > 
> > 
> > And, lest you think this is confined to the ecmwf file, here's the
> > same bug with the 1-degree GFS file
> >  GEMPAK-GDPOINT>r
> > GDFILE: $HDS/gfs/2005112312_gfs.gem                       
> > GPOINT: @8.458;92.63                                      
> > GVCORD: hagl                                              
> > GLEVEL: 10                                                
> > GFUNC : urel                                              
> > SCALE : 0                                                 
> >      051123/1200F000 :     -0.83057
> >  GEMPAK-GDPOINT>gfu = mul(urel,-0.83057)
> >  GEMPAK-GDPOINT>r
> > GFUNC : mul(urel,-0.83057)                                
> >      051123/1200F000 :      0.68985
> >  GEMPAK-GDPOINT>gfu = mul(urel,urel)
> >  GEMPAK-GDPOINT>r
> > GFUNC : mul(urel,urel)                                    
> >      051123/1200F000 :      0.85965    ***** WRONG!!!! s/b 0.689
> > 
> > 
> > and with the eta104 grids:
> >  GEMPAK-GDPOINT>gdfi = $HDS/eta/2005112312_eta104.gem
> >  GEMPAK-GDPOINT>gfu = urel
> >  GEMPAK-GDPOINT>r
> > GDFILE: $HDS/eta/2005112312_eta104.gem                    
> > GPOINT: @8.458;92.63                                      
> > GVCORD: hagl                                              
> > GLEVEL: 10                                                
> > GFUNC : urel                                              
> > SCALE : 0                                                 
> >      051123/1200F000 :     -2.27911
> >  GEMPAK-GDPOINT>gfu= mul(urel,-2.27911)
> >  GEMPAK-GDPOINT>r
> > GFUNC : mul(urel,-2.27911)                                
> >      051123/1200F000 :      5.19433
> >  Parameters requested: GDATTIM,GDFILE,GLEVEL,GPOINT,GVCORD,GFUNC,SCALE.
> >  GEMPAK-GDPOINT>gfu = mul(urel,urel)
> >  GEMPAK-GDPOINT>r
> > GFUNC : mul(urel,urel)                                    
> >      051123/1200F000 :      5.28800    ***** WRONG!!!! s/b 5.194
> > 
> >  GEMPAK-GDPOINT>gfun = vrel
> >  GEMPAK-GDPOINT>r
> > GFUNC : vrel                                              
> >      051123/1200F000 :      2.67976
> > 
> >  GEMPAK-GDPOINT>gfu = mag(vecr(urel,vrel))
> >  GEMPAK-GDPOINT>r
> > GFUNC : mag(vecr(urel,vrel))                              
> >      051123/1200F000 :      3.58182    ***** WRONG!!!! s/b 3.518
> >                                              
> > ======================================================================
> > 
> > Thanks in advance for taking a look at this.
> > 
> > 
> > David
> > 
> > -- 
> > David Ovens          e-mail: address@hidden
> > Research Meteorologist    phone: (206) 685-8108
> > Dept of Atm. Sciences      plan: Real-time MM5 forecasting for the
> > Box 351640                        Pacific Northwest
> > University of Washington          http://www.atmos.washington.edu/mm5rt
> > Seattle, WA  98195               Weather Graphics and Loops
> >                                   
> > http://www.atmos.washington.edu/~ovens/loops
> 
> -- 
> David Ovens            e-mail: address@hidden
> Research Meteorologist    phone: (206) 685-8108
> Dept of Atm. Sciences      plan: Real-time MM5 forecasting for the
> Box 351640                        Pacific Northwest
> University of Washington          http://www.atmos.washington.edu/mm5rt
> Seattle, WA  98195               Weather Graphics and Loops
>                                   http://www.atmos.washington.edu/~ovens/loops

-- 
David Ovens              e-mail: address@hidden
Research Meteorologist    phone: (206) 685-8108
Dept of Atm. Sciences      plan: Real-time MM5 forecasting for the
Box 351640                        Pacific Northwest
University of Washington          http://www.atmos.washington.edu/mm5rt
Seattle, WA  98195               Weather Graphics and Loops
                                  http://www.atmos.washington.edu/~ovens/loops
References:
- bugs in gdprof and gdpoint
  - From: David Ovens
- Re: bugs in gdprof and gdpoint
  - From: David Ovens
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