Re: [ferret_users] Nino3.4 estimation

[Ryo Furue <furue@xxxxxxxxxx>]

Hi Akash,

On Sat, Feb 15, 2020 at 7:28 PM Akash. S <akash013akash@xxxxxxxxx> wrote:

I calculated the Nino3.4 area averaged SST anomaly (variable name = nino34 and l=1:372). I want to know which are the El Nino and La Nina years, (Condition is define El Nino and La Nina episodes as exceeding the threshold of ±0.5°C for a minimum of five consecutive overlapping seasons).

Since I don't know the details of your problem, I just outline one strategy.  It seems that you can achieve your goal by

1. creating a mask, which is 1 when the "event" occurs and 0 when not: LET mask = IF <condition> then 1 else 0.
2. summing the mask over the period:  if the sum is equal to the number of the time steps within the period, then you have consecutive events.

For the sum, the boxcar smoother (@SBX) over L may be convenient:

https://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/variables-xpressions/XPRESSIONS#_VPINDEXENTRY_460

Although it's called a "smoother", it just takes a simple average over an interval, so that you can use this relation to infer the sum

(sum) = (average) *  (number of data points).

Otherwise, you can use the @SUM operator over an interval of L.

Hope this helps.

Ryo