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Pacific Fisheries Environmental Laboratory

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NOI and the SOI* Computation

The indices are computed from NCEP sea level pressure anomalies (SLPA) (monthly sea level pressure minus climatology) of the North Pacific High (NPH) [35N,130W], South Pacific High (SPH) [30S,95W], Darwin [10S,130E], and Tahiti [18S,150W]. The NOI, SOI*, and SOI are created as follows:

NOI = SLPA_NPH - SLPA_DARWIN
SOI* = SLPA_SPH - SLPA_DARWIN
SOI = SLPA_TAHITI - SLPA_DARWIN

The definitions used to calculate the NOI and SOI* differ slightly from the traditional definition of the SOI (Chelliah 1990), in that neither the pressure series nor the indices are normalized. We compute a version of the SOI consistent with the NOI and SOI*. The base period we used for the climatologies is January 1948 to December 1997.

5-month smoothed NOI,  SOI*,  SOI


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View/Download NOI,SOI,SOI* timeseries Citing the NOI ERD home page

http://www.pfeg.noaa.gov/products/PFEL/modeled/indices/NOIx/compute.html




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