[ncl-talk] SPI based on Pearson 3 distribution

[Dawit Abebe]

Dear All,

I tried to calculate SPI based on Pearson 3 option. The SPI values are generated but I see two issues which I am need to be clear about. 
1. an error return "*** ERROR *** ROUTINE CDFPE3 : PARAMETERS INVALID” before returning the SPI values. 
2. zero precipitation values are considered as missing (for example for 1-month SPI if the precipitation is 0 then the corresponding SPI is indicated as -999.0. Similarly, where three consecutive monthly precipitation was 0 the corresponding 3-month SPI is give as -999.0).

I kindly ask your comment on these two issues.

Thanks

Dawit 
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