[gembud] GDDIAG - MASK FUNCTION BUG?

• To: <gembud@xxxxxxxxxxxxxxxx>
• Subject: [gembud] GDDIAG - MASK FUNCTION BUG?
• From: "Evan Lowery" <elowery@xxxxxxxxxxxx>
• Date: Fri, 8 Oct 2010 08:20:31 -0400

Hello all,

 

I've found a possible bug (or user error) with GDDIAG and the MASK grid
function, but wanted to check with everyone here before sending out an
official support request.

 

Within a GEMPAK grid file (test.grd), I have a temperature field (TEMPA)
which needs to be masked to only show values between a certain temperature
range (>=80F).  I run this process daily, and have never had a problem up
until this point.  When NO temperatures in TEMPA are >=80F, the MASK
function generates an erroneously large number rather than -9999.00
(RMISSD).

 

Dataset:                                               test.grd

 

gdlist

GDATTIM=101007/0000F001

GLEVEL=0

GVCORD=NONE

GFUNC=TEMPA

 

Using GDLIST (tempa.dat) I see that TEMPA:

MINIMUM AND MAXIMUM VALUES     1.03    60.00

 

Goal: only keep temperatures  >=80F

 

gddiag

GDATTIM=101007/0000F001

GLEVEL=0

GVCORD=NONE

GFUNC=MASK(TEMPA,SGE(TEMPA,80))

GRDNAM=TEMPB

GRDTYP=S

GPACK=

GRDHDR=

PROJ=

GRDAREA=

KXKY=

MAXGRD=

CPYFIL=

ANLYSS=

 

Using GDLIST (tempb.dat) I see that TEMPB:

MINIMUM AND MAXIMUM
VALUES9999999848243207295109594873856.009999999848243207295109594873856.00

 

I would expect all TEMPB values to be -9999.00 (RMISSD) since no
temperatures are greater than 80F, but instead it blows up and returns a
very large value.

 

http://www.unidata.ucar.edu/cgi-bin/gempak/manual/apxB_index

MASK  Masking function        MASK (S1, S2) = RMISSD IF S2 = RMISSD

                                            = S1 otherwise

 

In this example TEMPA had no values >=80F, but my csh scripts are constantly
mining through temperature grids, and "usually" there are values >=80F.

 

Has anyone ever experienced this type of result?  If yes, do you know a work
around to get the grid (TEMPB) with all values = -9999.00 (RMISSD) rather
than erroneously large values?

 

Regards,

Evan Lowery

Attachment: test.grd
Description: Binary data

Attachment: tempa.dat
Description: Binary data

Attachment: tempb.dat
Description: Binary data

• Follow-Ups:
  • Re: [gembud] GDDIAG - MASK FUNCTION BUG?
    • From: Kevin R. Tyle