[gradsusr] rainfall rate script

[Charles Seman - NOAA Federal]

Ben,

We have calculated WRF precip rates from variable RAINNC.

You can try using code like (caution, has not been tested):

*  Calculate the WRF precipitation rates from accumulated precip...
*  convert WRF model accumulated precipitation from [mm] to [mm/day]
*
*  note, we can only go to "nt-1" because we do forward-in-time finite
*  differences for the WRF model precipitation rate...

nt = 6578	;* or the # of time levels in your time series
dt = 0.5	;* 12 hours or 0.5 day
'set x 1'
'set y 1'
'set z 1'
'set t 1 'nt-1
'define pratec = (RAINC(t+1)-RAINC(t+0))/'dt
'define pratenc = (RAINNC(t+1)-RAINNC(t+0))/'dt

then you can use pratec and pratenc (or whatever you call them)...

you can plot the variables directly; try something like:

legends = 'RAINC  RAINNC'
colors  = ' 2     3'
marks   = ' 0     0'

while ( nv <= 2 )
  c.nv = subwrd(colors,nv)
  m.nv = subwrd(marks,nv)
  l.nv = subwrd(legends,nv)
  nv = nv + 1
endwhile

pmin = 1e6 ; pmax = -1e6

'set t 1 'nt-1
'set gxout stat'
'd pratec'
min_max = sublin(result,8)
minv = subwrd(min_max,4)
maxv = subwrd(min_max,5)
if( minv < pmin )
   pmin = minv
endif
if( maxv > pmax )
   pmax = maxv
endif
'd pratenc'
min_max = sublin(result,8)
minv = subwrd(min_max,4)
maxv = subwrd(min_max,5)
if( minv < pmin )
   pmin = minv
endif
if( maxv > pmax )
   pmax = maxv
endif

'set gxout line'
'set grads off'

'set vrange 'pmin' 'pmax

'set ccolor 'c.1
'set cmark  'm.1
'd pratec'

'set ccolor 'c.2
'set cmark  'm.2
'd pratenc'

'cbar_line -x 3 -y 6 -c 'c.1' 'c.2' -l 1 1 -m "'m.1'" "'m.2'" -t "'l.1'" 
"'l.2'" -p'

note, the above code hasn't been tested, but it should give you some 
ideas of how to plot the variables... cbar_line can be found at 
http://cola.gmu.edu/grads/gadoc/library.html

if you still want to write out a binary file, try adapting your code:

'set fwrite scm9yr12hr.daily.grads'
'set gxout fwrite'
i=2
while(i<nt)
      'set t 'i
      'd pratec'
      'd pratenc'
      i=i+1
endwhile
'disable fwrite’

see also http://cola.gmu.edu/grads/gadoc/aboutgriddeddata.html

Hope this helps,
Chuck


On 01/16/2016 12:15 AM, Ben Stephens wrote:
> Hi, I am writing a script that will take existing total accumulated
> rainfall data (units of mm) and output daily rainfall rates (mm/day) for
> both rainc and rainnc.  This is the single-column WRF model output so
> there is only one grid point with 20 levels and 12-hour time increment.
>   Here is the script I have so far:
>
> 'open scm9yr12hr.ctl'
> 'set fwrite scm9yr12hr.daily.grads'
> 'set gxout fwrite'
> i=2
> while(i<6578)
>     'set t 'i
>     'd rainc(t+2)-rainc'
>     'd rainnc(t+2)-rainc'
>     i=i+2
> endwhile
> 'disable fwrite’
>
> I am basically wondering what to do after running the script.  I open
> GrADS and execute the script with a run command, and it generates the
> given output file, but I have not been able to display the data,
> assuming it is working correctly.  I tried to create a new control file
> for the output, and it opens, and the data seem to be there but they are
> clearly wrong.  I am getting numbers with huge exponents and so on.  Any
> input on whether my script is written correctly or how to display my output?
>
> Thanks!
> Ben
>
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>
> _______________________________________________
> gradsusr mailing list
> gradsusr at gradsusr.org
> http://gradsusr.org/mailman/listinfo/gradsusr
>

-- 

Please note that Charles.Seman at noaa.gov should be considered my NOAA
email address, not cjs at gfdl.noaa.gov.

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  Charles Seman                                Charles.Seman at noaa.gov
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