[gradsusr] How to Calculate and Plot Percentile Thresold for Rainfall in GrADS

[Jeff Duda]

Hiren,
First, prepare to use a lot of loops.

For each grid point, you'll have to collect all the precipitation values
using code that looks like this

'set x 'xx
'set y 'yy
'd precip'
precip_value = subwrd(result,4)
precip_xx.n = precip_value

where xx and yy are looping index values for your grid points, and n is an
integer index to represent the number of values in your precipitation
distribution at each grid point.  Note that you may have to include the
line 'line = sublin(result,2)' if your display command doesn't result in
text the way I assumed it would here.  TO check it, just type 'd precip' at
the command prompt with the previous settings already applied and see what
the output is.  Then adjust your code accordingly.  NOTE: your actual
precipitation grid name may not be "precip".  Change that as well to suit
your specific data.

After that's done, you'll have to sort the data so you can define the 90th
and 99th percentiles.  There are a number of ways to do that.

Finally, you'll have to define a domain sized grid.  Call it whatever you
want, but make sure it has the same size as the domain.  Then, at each grid
point, use the command 'set defval ....' to redefine the value of your new
field with that of the 90th or 99th percentile of precip.

Jeff Duda

On Wed, Nov 28, 2012 at 6:00 AM, hiren dave <hiren_dave85 at yahoo.com> wrote:

> Dear all
>         I am having gridded rainfall data set for 40 years. I want to
> know how to find out 90th and 99th percentile of daily rainfall series at
> each grid cell, considering days with only nonzero rainfall  for the whole
> period of 40 year.
>
> Hiren Dave
> Research Schoolar
> Gujarat University
> Ahmedabad-India
>
>
>
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>


-- 
Jeff Duda
Graduate research assistant
University of Oklahoma School of Meteorology
Center for Analysis and Prediction of Storms
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