2011-04-18 17:26:55New MEI analysis system
Alex C


NOAA has apparently implemented, as of the end of last month, a new observational record/system for their Multivariate ENSO Index.  They only discuss changes in the 1994-2010 period, though it seems like, based on the index they give above, the past record has been altered as per a new analysis too.


Notably, and I found this very interesting: the 2010 El Nino was pretty weak.  Well, is now.  Does anyone have any more info on what they are doing new exactly, and what implications this has for ENSO's role in year-to-year temperature fluctuations, especially past years?  Is this a better record with more data, or a whole new process?

2011-04-19 02:37:19
Julian Brimelow

Thanks Alex, I'll have to have a look at that.

2011-04-19 04:06:09
Alex C


I had asked a similar question on Yahoo! Answers and wasn't getting much feedback, so I posted here.  I did recently get a detailed answer - it seems that NOAA is now using a wider range of data from a variety of sources, as well as historic records.

The other answerer had speculated that this would result in a general smoothing of the data, but I am not sure this is correct as NOAA says that the expanded source has resulted in El Ninos being generally shifted more positive and La Ninas more negative.  It's likely not an across the board trend shift though, and I also think that they are using a new method of representing anomalies, besides just recalculating them with more data points.

In case anyone is interested about said question....