[ncl-talk] ENSO index

[Morteza Qadimi]

Hi dear admin(s), 

I need to classify ENSO different flavors (i.e. EP and CP El Ninos) by
the method mentioned in a paper (Short Communication A new method to
classify ENSO events into eastern and central Pacific types [1]). In the
methodology section, author has said: 

"Based on fundamental features associated with this concept, we first
carry out the EOF analysis using the monthly SSTA over the tropical
Pacific (20∘S-20∘N, 110∘E-70∘W) from 1982 to 2014, and obtain the first
and second EOF modes of monthly SSTAs as EP-type and CP-type ENSO modes
(figures notshown), respectively. The pattern correlation coefficients
(PCCs) between first two leading EOF modes and monthly mean SSTA are
then calculated for the period January 1982 through December 2014. To
smooth out short-term fluctuations such as intraseasonal variations, the
5-month running mean is applied to the above-mentioned PCCs. Finally, we
obtain the EOF-based pattern correlations for two EOF modes, which are
referred to as EPC1 and EPC2 for the first and second modes,
respectively (Figure 1). The EP (CP)-type El Niño is defined as the case
when the EPC1 (EPC2) index is equal to or greater than 0.79 (0.57),
which is significant at the 90% confidence level from the two-tailed
Student's t-test. According to this method, the EP (CP)-type La Niña
state is defined as the case when the EPC1 (EPC2) index is equal to or
less than -0.79 (-0.57)." 

I've done the first step, and now i need to calculate the Pattern
Correlation Coefficients. Does NCL has any function that i can use it
for this? I'm gratefully open for any ideas or suggestions.

Sincerely, 

Morteza 

Links:
------
[1] https://onlinelibrary.wiley.com/doi/full/10.1002/joc.4813
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