I’ve moved to WordPress. This post can now be found at Comparison of El Nino Modoki Index and NINO3.4 SST Anomalies
##############I’ve prepared this post for those who want to compare El Nino Modoki Index data to NINO3.4 SST anomalies. I did not standardize the El Nino Modoki Index data. Note also that I scaled the NINO3.4 SST anomaly data by a factor of 0.5 to bring it into line with the El Nino Modoki Index data.
Last, keep in mind that the El Nino Modoki Index is a calculated value. Ashok et al describe the calculation as follows:
“EMI= [SSTA]A-0.5*[SSTA]B-0.5*[SSTA]C (1)
“The square bracket in Equation (1) represents the area-averaged SSTA over each of the
regions A (165E-140W, 10S-10N), B (110W-70W, 15S-5N), and C (125E-145E, 10S-20N), respectively.”
Link to the Ashok et al (2007) paper “El Nino Modoki and its Possible Teleconnection.”
https://www.jamstec.go.jp/frcgc/research/d1/iod/publications/modoki-ashok.pdf
Figure 1 illustrates those regions used in the El Nino Modoki Index. Keep in mind that the declines in the SST anomalies in Regions B and C help raise the El Nino Modoki Index, and vice versa.
http://i31.tinypic.com/33xeziu.pngFigure 1
Figure 2 is a long-term comparison of El Nino Modoki Index data and NINO3.4 SST anomalies. In Figures 3 through 6, I’ve shortened the time spans. I have not attempted to provide the threshold for the El Nino Modoki events on the graphs. You’ll have to scale that value on your own. You can use Figures 2 and 3 and the accompanying dialogue in my post There Is Nothing New About The El Nino Modoki for reference, but remember that the threshold was established for the standardized data.
Here are the graphs without further commentary.
http://i25.tinypic.com/ilgml5.pngFigure 2
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http://i32.tinypic.com/2gvj8y8.pngFigure 3
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http://i32.tinypic.com/m7yf6w.pngFigure 4
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http://i30.tinypic.com/m833on.pngFigure 5
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http://i27.tinypic.com/2ezn2q9.pngFigure 6
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SOURCE
HADISST SST and SST anomaly data are available through the KNMI Climate Explorer.
http://climexp.knmi.nl/selectfield_obs.cgi?someone@somewhere
6 comments:
if there is nothing new in the modoki index, can we use this index rather than the conventional one?
OceanOne: How would you like to use the El Nino Modoki Index? Global temperatures also respond to central Pacific El Nino events.
Hi Bob,I'd like to use this index to see its relation with precipitation in the maritime continent, since many previous studies used NINO3.4 index
OceanOne: There are papers on central Pacific El Ninos that reference Ashok et al. Those papers have different methods of calculating central Pacific El Nino events, but I don't believe one method is favored yet.
thanks a lot Bob. I am just wondering, what are the primary large scale climate drivers that affected the tropical area?
OceanOne: You asked, "...what are the primary large scale climate drivers that affected the tropical area?"
If by "climate drivers" you are referring to natural cycles, I would have to think ENSO and the IOD.
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