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[McIDAS #HUS-936607]: how to chose a combinations of params for sfcplot



Hi Zhou,

I apologize for the slow reply to your inquiry... I have been involved in
our series of training workshops, and have not had much time to attend to
support for the past week.

re:
> I'm brand new to McIDAS, now I want to use sfcplot.k to generate a
> surface plot.  I have a question about "param", the param PLOT combines
> some parameters to generate a sfc station plot.

Correct.

re:
> How do I chose different parameters and the positions surrounding to
> a station?  For example, windbar at center, T at topleft corner, dew at
> bottomleft, slp at topright and RH at bottom left,...

All parameters you mention _except_ RH are available for surface plotting:

T    - temperature
TD   - dew point temperature
PMSL - mean sea level pressure
WIND - wind barb

RH can be calculated and plotted individually, but I don't think it can
be included in a complex (more than one parameter) plot in a single
SFCPLOT invocation.

Here is how you would create a new plot parameter named MYPLOT.PMSL:

- create the file STNPLOT.USER in the $MCDATA directory of the user
  running McIDAS.  The contents of the file will be:

MYPLOT.PMSL  UNIT=AMERICAN METRIC \
             AMERICAN='F F MB KTS' METRIC='C C MB KTS' \
             COLOR='2 2 3 3' \
             FORMAT='I3 I3 K3 FLAG' \
             LSIZE='6 6 6 10' \
             MULTIPLY='1 1 10 1' \
             OFFSET='-8 -15 8 -15 -8 8 X X 8 8' \
             LOC=+ \
             TITLE=X 3 \
             FONT=' '\
             ISFC='T TD PRE WIND ' \
             SVCA='T TD PRE WIND ' \
             SYN= 'T TD PSL WIND ' \
             ISHP='T TD PSL WINDA'

Relative humidity can be plotted individually:

SFCPLOT RH WORLD

You could product the plot you want by running SFCPLOT twice: once for
MYPLOT.PMSL and once for RH.  To arrange the RH value to fit with the
custom station model plot, however, you would need to redefine RH by
adding the following definition to SFCPLOT.USER:

RH     UNIT=% \
       FORMAT=I3 \
       OFFSET='8 8'\
       MATH='EXP(5423*(1/P1-1/P2))*100'\
       ISFC='P1=T[K]' 'P2=TD[K]'\
       SVCA='P1=T[K]' 'P2=TD[K]'\
       SYN ='P1=T[K]' 'P2=TD[K]'\
       ISHP='P1=T[K]' 'P2=TD[K]'

The invocation sequence that will produce the desired plot (more or less)
is then:

ERASE;SFCPLOT MYPLOT.PMSL CO;SFCPLOT RH OLAY

re:
> Thank you in advance

No worries.

Please look through the file ~mcidas/data/SFCPLOT.CORE and the McIDAS User's
Guide to get more information/ideas on how to create complex parameter
plots using SFCPLOT.

Side comment:  You could create the plot you want using PTDISP (the low-level
program that SFCPLOT invokes to do its plots), but PTDISP is pretty complicated
and a bit messy.  If the two step process I outlined above does not work for
you, I will send along some guidelines on how to use PTDISP directly.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: HUS-936607
Department: Support McIDAS
Priority: Normal
Status: Closed


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