[ncl-talk] How "dim_spi_n" deal with zero precipitaion and maps cdf into spi values??

[Dennis Shea]

NCL uses a f77 subroutine based upon a code originally created by the USA's
National Climate Data Center (now known as the  National Centers for
Environmental Information
<https://en.wikipedia.org/wiki/National_Centers_for_Environmental_Information>
(NCEI). It contains the following code comments.

c       OUTPUT: par1,par2,par3    parameters (mean, s.d., skewness) of
c                                 Pearson Type III distribution used to
c                                 fit the input data > 0
c               xmom1,xmom2,xmom3 l-moments of the input data > 0
c               pzero             relative  frequency of input data = 0

So, without looking at the code in detail, I'd say 0s are ignored.

If you want to see the code, I have placed the code at

http://www.cgd.ucar.edu/~shea/spi3.f

Good luck

On Wed, Jun 29, 2016 at 7:39 AM, Kritanai Torsri (HAII User) <
kritanai at haii.or.th> wrote:

> Dear ALL,
>
> Can any one help me to clarify how "dim_spi_n" deals with zero
> precipitation for both fitting with 2-param Gamma distribution and Pearson
> Type 3?
>
> and how it maps cumulative distribution function (cdf) into SPI values?
>
> Thanks in advance.
>
> BRGs,
>
> Kritanai T.
>
>
>
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