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20010403: 850 Mixing ratio plots/contours have incorrect values

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  • Subject: 20010403: 850 Mixing ratio plots/contours have incorrect values
  • Date: Wed, 04 Apr 2001 13:34:17 -0600
>From: "Paul L. Sirvatka" <address@hidden>
>Organization: College of DuPage
>Keywords: 200104032011.f33KBiL13131 McIDAS-X RAOBPLOT RAOBCON PTDISP PTCON 
>RAOBCON.CORE RAOBPLOT.CORE

Paul,

>I ran the command RAOBCON MIX 850 USA and it gave me all the wrong mixing
>ratios. Any idea why? See

You are correct, the MIX values contoured from your invocation are bogus.
The problem can also be seen in a RAOBPLOT:

RAOBPLOT MIX 850 USA 

The problem turned out to be typos in the context files for RAOBPLOT and
RAOBCON (RAOBPLOT.CORE and REAOBCON.CORE, respectively).  The formulas
for MIX were specifying use of T instead of TD in the calculation of
mixing ratio:

MIX    UNIT=G/KG \
       FORMAT=F5.2 \
       MATH='RMIX(P1,P2)'\
       IRAB='P1=T[K]' 'P2=P[HPA]' \
       RAOB='P1=T[K]' 'P2=P[HPA]'

These should be changed to be:

MIX    UNIT=G/KG \
       FORMAT=F5.2 \
       MATH='RMIX(P1,P2)'\
       IRAB='P1=TD[K]' 'P2=P[HPA]' \
       RAOB='P1=TD[K]' 'P2=P[HPA]'

in both context files:

<login as 'mcidas'>
cd data
<edit RAOBPLOT.CORE and REAOBCON.CORE and change the MIX entry to specify
use of TD instead of T>

After making the change to the context files, the plots/contours of MIX
will agree with the values that are listed in UALIST output.

I will include fixed context files in an upcoming addendum.  For now, you
should make the change to your local context files as I indicate above.

Tom