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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
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Just a quick post. The weekly OI.v2 NINO3.4 SST anomalies dropped out of El NiƱo range last week, the week centered on Wednesday April 28th. They are presently at ~0.47 deg C.
http://i44.tinypic.com/sv1d8w.png
Weekly NINO3.4 SST Anomalies
http://i41.tinypic.com/zyhkw7.png
Map

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

SOURCE

OI.v2 SST data is available through the NOAA NOMADS website:
http://nomad3.ncep.noaa.gov/cgi-bin/pdisp_sst.sh?lite=

6 comments:

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:
http://www.emc.ncep.noaa.gov/research/cmb/sst_analysis/

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.

Regards

D Kelly O'Day said...

Bob
Bob:

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.

Thanks

Kelly

Bob Tisdale said...

Kelly: Four quick steps after going to…
http://nomad3.ncep.noaa.gov/cgi-bin/pdisp_sst.sh?lite=

Step 1:
http://i42.tinypic.com/34pxpgw.png

Step 2:
http://i44.tinypic.com/2lt50kk.png

Step 3:
http://i44.tinypic.com/2rztjx5.png

Step 4:
http://i44.tinypic.com/2dwb5o1.png

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.

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