[ncl-talk] Fwd: SPI values derived using Pearson 3

[Dawit Abebe]

Dear All

Kindly your help on errors with SPI using Pearson Type 3 described below

Dawit

---------- Forwarded message ----------
From: Dawit Abebe <dawit.kan at gmail.com>
Date: 8 June 2017 at 15:43
Subject: SPI values derived using Pearson 3
To: ncl-talk-request at ucar.edu, ncl-talk at ucar.edu, Mary Haley <haley at ucar.edu
>


Dear All,

Can any one help me understand the following error messages when
calculating SPI based on Pearson 3 option.

Part of my script related to this is:
=============================================
opt = True
opt at spi_type = 3
spi = new((/nrun, ntime, nlat, mlon/), typeof(prc), pmsg)

do nr=0, nrun-1
    spi(nr, :, :, :) = dim_spi_n(prc, run(r), opt, 0)
end do

However,
1. I get the an error message: "*** ERROR *** ROUTINE CDFPE3 : PARAMETERS
INVALID” , why and what does this mean? I cam across a similar problem
being reported but not responded to.

2. After the above error message, however, NCL has generated the SPI
values. However,  for months with consecutive zero precipitation values,
the corresponding SPI value is indicated as missing value (i.e. -999). The
fact that Pearson 3 is advantageous over Gama that where monthly and
seasonal precipitation of zero is common, it will give better results than
Gama (http://www.ncl.ucar.edu/Document/Functions/Built-in/dim_spi_n.shtml),
I'm unsure why missing values (-999) generated for months and seasons with
zero precipitation value.  This is observed mainly on SPI calculate over 1
and 3 months time scale.

I would very much appreciate if any me help me to understand and solve this
two issues.

Dawit
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