RONI vs. ONI

[so_whats_happening]

Lets give this a shot I am not sure if this will be able to be downloaded and opened. In the Excel sheet I created a decade by decade side by side of RONI and ONI from CPC and charted them out to get an idea of how things sort of coincided with each other (RONI, ONI). These are trimonthly readings dating back from 1950 to present, I'll let the data speak for itself but please excuse the X-axis in the charts. The numbers are just place filler for the data to the left and it would have been rather tedious and clogged up to have date and trimonthly with the charts.

 

RONI vs. ONI.xlsx

[so_whats_happening]

On 11/13/2025 at 9:50 AM, so_whats_happening said:

Oh man I feel like we go through this every winter. Warmings occur all the time this is not a new occurrence by any means. I do like to see there is some connection through the layers to show maybe some extended connection as we go through time but anything past 240hr is typically a crapshoot call even with something like the stratosphere which doesn't tend to have too much change.

My biggest issue with the use of RONI being implemented what if for some reason this process does actually switch up and ONI does become more representative than RONI are we going to switch back to using ONI data as reliable indication of Nina/Nino severity?

To me RONI is like the equivalency of saying well if we take out the warming of the last 50-100 years in something like air temperature (just an example) to show that in fact temps would have been cooler during this time period to me means nothing. Ok we have deduced that it is warmer now than in the past.

The processes that are involved with ENSO/ IOD/ PDO/ AMO have not seemingly changed, they all still evolve in the same manner. Are we trying to say that RONI is showing enhancement of La Ninas specifically? Are you and bluewave stating that because RONI showed -1.12 last winter for DJF that the winter acted like a moderate La Nina versus cold neutral? I mean just taking a quick glance at years of similar ONI where we never officially hit Nina status by measurements (some awfully close like last year). I did not match scales so forgive me on that. Only difference I see is a slightly more poleward low position in the pacific. I feel this is more of a PDO situation.

 

 

On 11/13/2025 at 10:25 AM, donsutherland1 said:

I see your point. The argument for RONI is that the overall warming of the Pacific is not temporary or cyclical.

The use of traditional ENSO metrics i.e., R3.4 anomaly, ONI, etc., has beenb contaminated by the overall warming of the Pacific. In their present form, El Niño events are amplified while La Niña ones are shown as weaker. As the warming continues, La Niña events could even be obscured. Winter 2024-2025 is one such case. It showed up as neutral-cold on ONI, but was a La Niña case according to RONI.

Some useful literature on the use of a relative index: 

https://iopscience.iop.org/article/10.1088/1748-9326/abe9ed

https://journals.ametsoc.org/view/journals/clim/37/4/JCLI-D-23-0406.1.xml

Australia's Bureau of Meteorology (BOM) has already made the switch to RONI. 

Here's a table from the article concerning the BOM's shift:

These are two of the posts I wanted to bring over that sparked this conversation.

[so_whats_happening]

I do not have an issue with the idea of what RONI is to show, which is the impact we have seen from a warming world in response of increases with CO2 and others. My issue is say we get to a point where there is such a difference that is large enough to become an error in a way. An example would be if ONI reads -.5 but RONI reads it as moderate event so < -1 creating a difference of nearly 0.5 or more do we believe the RONI value to be more representative of the atmosphere or do we believe ONI has a better handle? I guess this is the million dollar question of course. I mean they even mention it towards the end themselvesThe cyclical aspect will be interesting to follow coming up here, AMO seems to be throwing some curveballs right now

I would have liked to have seen just how much difference does continue to show and maybe was used more in conjunction with seeing differences and the impact on atmospheric events in comparison to ONI values. BOM must know something more than we do in now using RONI versus ONI values.

@donsutherland1