[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

20001204: McIDAS-X GRDCOPY with MATH questions



>From: Mark Lilly <address@hidden>
>Organization: UVa
>Keywords: 200012042120.eB4LKHo05867 McIDAS-X 7.6 GRDCOPY MATH=

Mark,

>I am a graduate student for Jennie Moody at the University of Virginia.  I
>am working on a paper and trying to calculate Richardson #.  I have
>attached the batch.  Tony Wimmers told me to contact you.  I am simply
>multiplying to grids together but the output (the third grid) is not even
>close to what the product of the two grids should be.  I am really
>confused.  I was wondering if you might be able to take a quick look at my
>problem.

-------------------------- NEXT.BAT ----------------------------------------

REM Usage:  BATCH CONTINUE=YES "/p0/users/sm8f/mlilly/NEXT.BAT

REDIRECT REST PEL
REDIRECT ADD GRID9* "/p0/users/sm8f/mlilly

TE SOURCE "PEL/ETA.22

GRDCOPY #SOURCE MYDATA/GRIDS.9001 G1='PARAM T; FTIME 0; LEV 925' 
MATH='(9.8/G1)' NEWPAR=FP U 925 MB DEL=YES

GRDCOPY #SOURCE MYDATA/GRIDS.9001 G1='PARAM T; FTIME 0; LEV 950' G2='PARAM T; 
FTIME 0; LEV 900' G3='PARAM Z; FTIME 0; LEV 950' G4='PARAM Z; FTIME 0; LEV 900' 
MATH='(.0098-((G1-G2)/(G3-G4)))' NEWPAR=SP U 925 MB

GRDCOPY MYDATA/GRIDS.9001 MYDATA/GRIDS.9001 G1='PARAM FP' G2='PARAM SP' 
MATH='(G1*G2)' NEWPAR=ONE U 925 MB SUB=39 42 73 81

REM GRDCOPY #SOURCE MYDATA/GRIDS.9001 G1='PARAM U; FTIME 0; LEV 950' G2='PARAM 
U; FTIME 0; LEV 900' G3='PARAM Z; FTIME 0; LEV 950' G4='PARAM Z; FTIME 0; LEV 
900' G5='PARAM V; FTIME 0; LEV 950' G6='PARAM V; FTIME 0; LEV 900' 
MATH='(((((G1**2)+(G5**2))**.5)-(((G2**2)+(G6**2))**.5))/(G3-G4))' NEWPAR=TWO U 
925 MB

REM GRDCOPY MYDATA/GRIDS.9001 MYDATA/GRIDS.9001 G1='PARAM ONE; FTIME 0; LEV 
925' G2='PARAM TWO; FTIME 0; LEV 925' MATH='(G1/G2)' NEWPAR=RICH U 925 MB


EG B 1 3
GRDDISP MYDATA/GRIDS.9001 1 PAR=FP
GRDDISP MYDATA/GRIDS.9001 2 PAR=SP
GRDDISP MYDATA/GRIDS.9001 3 PAR=ONE

GRDLIST MYDATA/GRIDS.9001 NUM=ALL
GRDINFO MYDATA/GRIDS.9001 PAR=ONE

-------------------------- NEXT.BAT ----------------------------------------

I tried the above invocations in both McIDAS-X 7.6 and McIDAS-X 7.7 on
both a Solaris x86 and SPARC workstation.  In all three cases (for x86
I only had McIDAS-X 7.7), I, like you, did not get numbers that were
reasonable.  In particular, I was looking for numbers that were on the
order of the product of the mean values, which, given the STATistics of
the first two grids, would have been somehere on the order of 10**-4 to
10**-3.

This lead me to wonder if the parameters being used for doing the
internal math are not properly typed (e.g., they are mishandling the
results of floating point operations).  I even tried multiplying each
grid by 1000 (creating new grids) and then doing the multiplication
(divided by 10**6) (to see if there was some sort of calculation
errors), but that gave me the same results as the original test.

I finally decided to take a harder look at the actual grids used in the
various calculations.  Here is what I found:

DATALOC ADD PEL windfall.evsc.virginia.edu

GRDLIST PEL/ETA.1 PAR=T FTIME=0 LEV=925 FORM=ALL
Dataset position 1      Directory Title= Eta archive
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
T     925 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00   313 LAMB
Total pts= 23865 Num rows= 129  Num columns= 185    received:  2000181 021616Z
Temperature
GRIB ID numbers: Geographic =212; PAR = 11; Model ID = 84; Level type =100
Units of gridded variable are K    Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -226.67  Col num of pole=  105.00  Col spacing (m)= 40635.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
Number of grids listed = 1
GRDLIST - done

GRDLIST PEL/ETA.1 PAR=T FTIME=0 LEV=950 FORM=ALL
Dataset position 1      Directory Title= Eta archive
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
T     950 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00   107 LAMB
Total pts=  6045 Num rows=  65  Num columns=  93    received:  2000181 021238Z
Temperature
GRIB ID numbers: Geographic =211; PAR = 11; Model ID = 84; Level type =100
Units of gridded variable are K    Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -113.34  Col num of pole=   53.00  Col spacing (m)= 81270.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
Number of grids listed = 1
GRDLIST - done

GRDLIST PEL/ETA.1 PAR=T FTIME=0 LEV=900 FORM=ALL
Dataset position 1      Directory Title= Eta archive
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
T     900 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00   101 LAMB
Total pts=  6045 Num rows=  65  Num columns=  93    received:  2000181 021238Z
Temperature
GRIB ID numbers: Geographic =211; PAR = 11; Model ID = 84; Level type =100
Units of gridded variable are K    Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -113.34  Col num of pole=   53.00  Col spacing (m)= 81270.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
Number of grids listed = 1
GRDLIST - done

GRDLIST PEL/ETA.1 PAR=Z FTIME=0 LEV=950 FORM=ALL
Dataset position 1      Directory Title= Eta archive
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
Z     950 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00   105 LAMB
Total pts=  6045 Num rows=  65  Num columns=  93    received:  2000181 021238Z
Geopotential height
GRIB ID numbers: Geographic =211; PAR =  7; Model ID = 84; Level type =100
Units of gridded variable are GPM  Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -113.34  Col num of pole=   53.00  Col spacing (m)= 81270.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
Number of grids listed = 1
GRDLIST - done

GRDLIST PEL/ETA.1 PAR=Z LEV=900 FTIME=0 FORM=ALL
Dataset position 1      Directory Title= Eta archive
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
Z     900 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00    99 LAMB
Total pts=  6045 Num rows=  65  Num columns=  93    received:  2000181 021238Z
Geopotential height
GRIB ID numbers: Geographic =211; PAR =  7; Model ID = 84; Level type =100
Units of gridded variable are GPM  Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -113.34  Col num of pole=   53.00  Col spacing (m)= 81270.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
Number of grids listed = 1
GRDLIST - done

You can see from these lists that the first grid calculation that you did
was from and resulted in a grid on the 212 grid:

GRDLIST MYDATA/GRIDS.9001 GRID=1 FORM=ALL
Dataset position 9001   Directory Title=
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
FP    925 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00     1 LAMB
Total pts= 23865 Num rows= 129  Num columns= 185    received:  2000181 021616Z
GRIB ID numbers: Geographic =212; PAR = 11; Model ID = 84; Level type =100
Units of gridded variable are U    Scale of variable is:   7
Lambert Conformal Tangent Cone Projection
Row num of pole= -226.67  Col num of pole=  105.00  Col spacing (m)= 40635.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
Number of grids listed = 1
GRDLIST - done

The grids used in the second calculation are all on the 211 grid, so the
operation also resulted in a 211 grid projection:

GRDLIST MYDATA/GRIDS.9001 GRID=2 FORM=ALL
Dataset position 9001   Directory Title=
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
SP    925 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00     2 LAMB
Total pts=  6045 Num rows=  65  Num columns=  93    received:  2000181 021238Z
GRIB ID numbers: Geographic =211; PAR = 11; Model ID = 84; Level type =100
Units of gridded variable are U    Scale of variable is:   7
Lambert Conformal Tangent Cone Projection
Row num of pole= -113.34  Col num of pole=   53.00  Col spacing (m)= 81270.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
Number of grids listed = 1
GRDLIST - done

The third operation you were trying to do was, in fact, illegal:  you
were attempting to do a pointwise multiplication of grid points from
grids that do not have colocated points.  This is why my 7.7 GRDCOPY in
step three kept failing.  It should have since multiplying grids on
different projections does not make any sense.

A quich check of your input GRID file shows that there are no 925 mb T
grids on the same projection as the 900 mb T, 950 mb T, and 950 mb Z
grids:

GRDLIST PEL/ETA.1 PAR=T FHOUR=0 LEV=925 GPRO=LAMB NUM=ALL FORM=ALL
Dataset position 1      Directory Title= Eta archive
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
T     925 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00   313 LAMB
Total pts= 23865 Num rows= 129  Num columns= 185    received:  2000181 021616Z
Temperature
GRIB ID numbers: Geographic =212; PAR = 11; Model ID = 84; Level type =100
Units of gridded variable are K    Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -226.67  Col num of pole=  105.00  Col spacing (m)= 40635.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
Number of grids listed = 1
GRDLIST - done

There are, however, 900 mb T, 950 mb T, 900 mb Z, and 950 mb Z grids on
the projection of the 925 mb T grid:

GRDLIST PEL/ETA.1 PAR=T FTIME=0 LEV=950 FORM=ALL NUM=ALL
Dataset position 1      Directory Title= Eta archive
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
T     950 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00   107 LAMB
Total pts=  6045 Num rows=  65  Num columns=  93    received:  2000181 021238Z
Temperature
GRIB ID numbers: Geographic =211; PAR = 11; Model ID = 84; Level type =100
Units of gridded variable are K    Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -113.34  Col num of pole=   53.00  Col spacing (m)= 81270.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
T     950 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00   312 LAMB
Total pts= 23865 Num rows= 129  Num columns= 185    received:  2000181 021616Z
Temperature
GRIB ID numbers: Geographic =212; PAR = 11; Model ID = 84; Level type =100
Units of gridded variable are K    Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -226.67  Col num of pole=  105.00  Col spacing (m)= 40635.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
Number of grids listed = 2
GRDLIST - done

GRDLIST PEL/ETA.1 PAR=T FTIME=0 LEV=900 FORM=ALL NUM=ALL
Dataset position 1      Directory Title= Eta archive
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
T     900 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00   101 LAMB
Total pts=  6045 Num rows=  65  Num columns=  93    received:  2000181 021238Z
Temperature
GRIB ID numbers: Geographic =211; PAR = 11; Model ID = 84; Level type =100
Units of gridded variable are K    Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -113.34  Col num of pole=   53.00  Col spacing (m)= 81270.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
T     900 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00   314 LAMB
Total pts= 23865 Num rows= 129  Num columns= 185    received:  2000181 021616Z
Temperature
GRIB ID numbers: Geographic =212; PAR = 11; Model ID = 84; Level type =100
Units of gridded variable are K    Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -226.67  Col num of pole=  105.00  Col spacing (m)= 40635.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
Number of grids listed = 2
GRDLIST - done

GRDLIST PEL/ETA.1 PAR=Z FTIME=0 LEV=950 FORM=ALL NUM=ALL
Dataset position 1      Directory Title= Eta archive
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
Z     950 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00   105 LAMB
Total pts=  6045 Num rows=  65  Num columns=  93    received:  2000181 021238Z
Geopotential height
GRIB ID numbers: Geographic =211; PAR =  7; Model ID = 84; Level type =100
Units of gridded variable are GPM  Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -113.34  Col num of pole=   53.00  Col spacing (m)= 81270.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
Z     950 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00   286 LAMB
Total pts= 23865 Num rows= 129  Num columns= 185    received:  2000181 021554Z
Geopotential height
GRIB ID numbers: Geographic =212; PAR =  7; Model ID = 84; Level type =100
Units of gridded variable are GPM  Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -226.67  Col num of pole=  105.00  Col spacing (m)= 40635.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
Number of grids listed = 2
GRDLIST - done

GRDLIST PEL/ETA.1 PAR=Z LEV=900 FTIME=0 NUM=ALL FORM=ALL
Dataset position 1      Directory Title= Eta archive
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
Z     900 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00    99 LAMB
Total pts=  6045 Num rows=  65  Num columns=  93    received:  2000181 021238Z
Geopotential height
GRIB ID numbers: Geographic =211; PAR =  7; Model ID = 84; Level type =100
Units of gridded variable are GPM  Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -113.34  Col num of pole=   53.00  Col spacing (m)= 81270.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
Z     900 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00   291 LAMB
Total pts= 23865 Num rows= 129  Num columns= 185    received:  2000181 021604Z
Geopotential height
GRIB ID numbers: Geographic =212; PAR =  7; Model ID = 84; Level type =100
Units of gridded variable are GPM  Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -226.67  Col num of pole=  105.00  Col spacing (m)= 40635.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
Number of grids listed = 2
GRDLIST - done

Since the 'Geographic' (the grib projection number) is not one of the
selection keys you can use, you have to "manually" figure out which grids
you want to use and either specify them directly (using the 'GRID n' syntax)
or copy just the grids you want (i.e., the grids on the same grid projection)
to a destination file and work from there.  Here is an example of doing
the latter:

GRDCOPY PEL/ETA.1 MYDATA/GRIDS.9002 PAR=T LEV=925 FTIME=0 PRO=LAMB
GRDCOPY PEL/ETA.1 MYDATA/GRIDS.9002 GRID=312
GRDCOPY PEL/ETA.1 MYDATA/GRIDS.9002 GRID=314
GRDCOPY PEL/ETA.1 MYDATA/GRIDS.9002 GRID=286
GRDCOPY PEL/ETA.1 MYDATA/GRIDS.9002 GRID=291

This results in GRID9002 having all 5 grids _on the same projection_:

GRDLIST MYDATA/GRIDS.9002 NUM=ALL FORM=ALL
Dataset position 9002   Directory Title=
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO

---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
T     925 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00     1 LAMB
Total pts= 23865 Num rows= 129  Num columns= 185    received:  2000181 021616Z
Temperature
GRIB ID numbers: Geographic =212; PAR = 11; Model ID = 84; Level type =100
Units of gridded variable are K    Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -226.67  Col num of pole=  105.00  Col spacing (m)= 40635.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
Z     950 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00     2 LAMB
Total pts= 23865 Num rows= 129  Num columns= 185    received:  2000181 021554Z
Geopotential height
GRIB ID numbers: Geographic =212; PAR =  7; Model ID = 84; Level type =100
Units of gridded variable are GPM  Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -226.67  Col num of pole=  105.00  Col spacing (m)= 40635.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
T     900 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00     3 LAMB
Total pts= 23865 Num rows= 129  Num columns= 185    received:  2000181 021616Z
Temperature
GRIB ID numbers: Geographic =212; PAR = 11; Model ID = 84; Level type =100
Units of gridded variable are K    Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -226.67  Col num of pole=  105.00  Col spacing (m)= 40635.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
T     950 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00     4 LAMB
Total pts= 23865 Num rows= 129  Num columns= 185    received:  2000181 021616Z
Temperature
GRIB ID numbers: Geographic =212; PAR = 11; Model ID = 84; Level type =100
Units of gridded variable are K    Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -226.67  Col num of pole=  105.00  Col spacing (m)= 40635.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
PAR    LEVEL       DAY        TIME    SRC FHOUR     FDAY       FTIME  GRID  PRO
---- --------- ------------ -------- ---- ----- ------------ -------- ----- ----
Z     900 MB   29 JUN 00181 00:00:00  ETA     0 29 JUN 00181 00:00:00     5 LAMB
Total pts= 23865 Num rows= 129  Num columns= 185    received:  2000181 021604Z
Geopotential height
GRIB ID numbers: Geographic =212; PAR =  7; Model ID = 84; Level type =100
Units of gridded variable are GPM  Scale of variable is:   2
Lambert Conformal Tangent Cone Projection
Row num of pole= -226.67  Col num of pole=  105.00  Col spacing (m)= 40635.0
Standard Latitudes=   25.00     25.00   Standard Longitude=   95.00
Number of grids listed = 5
GRDLIST - done


Now, you can run the various GRDCOPYs in your BATCH file:

GRDCOPY MYDATA/GRIDS.9002 MYDATA/GRIDS.9001 G1='PARAM T; LEV 925; FHOUR 0' 
MATH='9.8/G1' NEWPAR=FP U 925 MB

GRDCOPY MYDATA/GRIDS.9002 MYDATA/GRIDS.9001 G1='PARAM T; FTIME 0; LEV 950' 
G2='PARAM T; FTIME 0; LEV 900' G3='PARAM Z; FTIME 0; LEV 950' G4='PARAM Z; 
FTIME 0; LEV 900' MATH='(.0098-((G1-G2)/(G3-G4)))' NEWPAR=SP U 925 MB

GRDCOPY MYDATA/GRIDS.9001 MYDATA/GRIDS.9001 G1='PARAM FP' G2='PARAM SP' 
MATH='(G1*G2)' NEWPAR=ONE U 925 MB SUB=39 42 73 81

This results in the expected results:

GRDINFO MYDATA/GRIDS.9001 STAT GRID=1 3
Statistics of
Parameter: FP
Units: U
Level of data: 925  MB
Time of data:      0 UTC
Day of data:   2000181
Data came from: ETA
0-hour forecast

Dataset: MYDATA/GRIDS

Minimum:   0.3131390E-01 occurred at [row,col]: [   74,   61]
                                   [lat,lon]: [  36.74, 114.70]
Maximum:   0.3620110E-01 first occurred at [row,col]: [   19,  137]
                                         [lat,lon]: [  55.63,  77.44]
                                          and     2 times thereafter
Mean:   0.3362913E-01
SD  :   0.8249292E-03
Number of points analyzed:  23865
Number of points missing:       0

Row range:     1 to   129
Col range:     1 to   185


Statistics of
Parameter: SP
Units: U
Level of data: 925  MB
Time of data:      0 UTC
Day of data:   2000181
Data came from: ETA
0-hour forecast

Dataset: MYDATA/GRIDS

Minimum:  -0.5392000E-03 occurred at [row,col]: [   34,   45]
                                   [lat,lon]: [  49.31, 125.67]
Maximum:   0.2193130E-01 occurred at [row,col]: [   44,   58]
                                   [lat,lon]: [  46.90, 118.31]
Mean:   0.1519655E-01
SD  :   0.3019999E-02
Number of points analyzed:  23865
Number of points missing:       0

Row range:     1 to   129
Col range:     1 to   185


Statistics of
Parameter: ONE
Units: U
Level of data: 925  MB
Time of data:      0 UTC
Day of data:   2000181
Data came from: ETA
0-hour forecast

Dataset: MYDATA/GRIDS

Minimum:   0.4518910E-03 occurred at [row,col]: [    7,   18]
                                   [lat,lon]: [  39.74,  73.34]
Maximum:   0.6364570E-03 occurred at [row,col]: [    5,    2]
                                   [lat,lon]: [  41.19,  80.55]
Mean:   0.5525933E-03
SD  :   0.6216484E-04
Number of points analyzed:    198
Number of points missing:       0

Row range:     1 to    11
Col range:     1 to    18
GRDINFO Done, Number of grids statistically analyzed=3
GRDINFO - done

It is obvious that there is something lacking in McIDAS' way of selecting
grids since grids in both the 212 and 211 projections list out as being
LAMB (which they are), but there is no way to ask for either one or the
other grid without resorting to finding out which grid in the GRID
file has the data you want.  I need to complain about this to SSEC.

>Thank you very much for your time, I greatly appreciate.  I
>should be here in the office for many more hours.  The number here is
>804-924-0576 or I could give you call.  Either thanks for your time.

I will touch base with SSEC about the inability to easily specify
one LAMBert Conformal grid projection from another.

Tom