[ncl-talk] SPI value for zero precipitation value based on Gamma vis-a-vis Pearson3 distribution

[Dawit Abebe]

Dear NCL-Talk participant

I am trying to assess the performance of the gamma and Pearson3 distribution in specific climatic region. The SPI value from Pearson3 returned two things I am not confident about and need your comment. These are
1. A long list of error message:
 *** ERROR *** ROUTINE SAMLMR : PARAMETER NMOM INVALID
 *** ERROR *** ROUTINE CDFPE3 : PARAMETERS INVALID
 *** ERROR *** ROUTINE CDFPE3 : PARAMETERS INVALID
 *** ERROR *** ROUTINE CDFPE3 : PARAMETERS INVALID

2. Pearson3 returns an SPI missing value(-999) for SPI-monthly and SPI-3 where monthly precipitation values are zero for SPI-monthly and three consecutive months for SPI-3. 

I kindly seek your view explaining these observations. 

Thank you so much

Dawit 
.

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