I’ve moved to WordPress: http://bobtisdale.wordpress.com/

Monday, May 3, 2010

NINO3.4 SST Anomalies In Neutral Territory

I’ve moved to WordPress.  This post can now be found at NINO3.4 SST Anomalies In Neutral Territory
Just a quick post. The weekly OI.v2 NINO3.4 SST anomalies dropped out of El Niño range last week, the week centered on Wednesday April 28th. They are presently at ~0.47 deg C.
Weekly NINO3.4 SST Anomalies

I’ll provide the monthly update for April on Monday when the monthly data is official.


OI.v2 SST data is available through the NOAA NOMADS website:


crashex said...

I find your plots and maps fascinating. Keep up the good work.

What is the source of the temperature measurements plotted as SST? Satellite, bouy??

Comparing the SST map with the Arctic Ice Extent maps usually leaves me with a bit of a paradox. For example, the current map shows the Bering Sea as a negative anomaly. And that region still has significant ice extent, only slightly greater in area than the "average" or "normal" ice cover. Since ice melt is isothermal, why would a sea surface temperature anomaly exist? Shouldn't the areas that are ice covered, when they are normally ice covered, simply have a zero anomoly?

The orange bit in the Canadian Arch. is the same issue, only in reverse. How can an area that remains ice covered have a positive SST anomoly?

I am not being critical of your plots and maps. I just want to understand why these apparent paradoxes exist. How is my reasoning erroneous?

Bob Tisdale said...

Crashex: You asked, “What is the source of the temperature measurements plotted as SST? Satellite, bouy??”

The NOAA OI.v2 SST data is primarily satellite, supplemented with buoy and ship readings:

You wrote, “Comparing the SST map with the Arctic Ice Extent maps usually leaves me with a bit of a paradox.”

Me too. They often show SST anomalies where ice exists.

I can understand how they arrive at anomalies for areas with annual ice melt, but in the years when areas of sea water are being exposed for the first time (example 2007), how can those temperatures be anomalous. Since there is no base from which to calculate anomalies there, NOAA prepared a climatology for what they believe the temperature of Arctic ocean should be for a given month. When the water is exposed for the first time, they can then subtract the climatology from the SST to create the anomalies.

Why do they sometimes show SST anomalies where there clearly is only ice? Dunno. That’s why I try to stay away from the Arctic in discussions. The data is too noisy and it’s questionable.


D Kelly O'Day said...


I track the weekly Nino34 index using this NOAA data page link.

NOAA reports a Nino34 of 0.5 for week of 4/28 compared to your 0.47 value. While this is probably a rounding issue, I'd like to compare both data sets to make sure they are the same.

Can you walk me through how you get your data set from the nomad3 site, I can't seem to find the data set you use.



Bob Tisdale said...

Kelly: Four quick steps after going to…

Step 1:

Step 2:

Step 3:

Step 4:

Oh, BTW, it is the same data.

jorgekafkazar said...

I'd rather not see 'approximately' abbreviated here by (~). The latter is way too close to a minus sign (-). It took me a while to realize the anomaly wasn't supposed to fall below the x-axis.

Bob Tisdale said...

jorgekafkazar: Sorry for the confusion. I'll try not to use it.


Tips are now being accepted.

Comment Policy, SST Posts, and Notes

Comments that are political in nature or that have nothing to do with the post will be deleted.
The Smith and Reynolds SST Posts DOES NOT LIST ALL SST POSTS. I stopped using ERSST.v2 data for SST when NOAA deleted it from NOMADS early in 2009.

Please use the search feature in the upper left-hand corner of the page for posts on specific subjects.
NOTE: I’ve discovered that some of the links to older posts provide blank pages. While it’s possible to access that post by scrolling through the history, that’s time consuming. There’s a quick fix for the problem, so if you run into an absent post, please advise me. Thanks.
If you use the graphs, please cite or link to the address of the blog post or this website.