DMI Daily Mean Temperatures North of 80 degrees North

[Alphabet Hotel]

 I was wondering if the lines would cross but so far it appears not.  ;-)

[Alphabet Hotel]

still going

http://ocean.dmi.dk/arctic/meant80n.uk.php

[The Walrus]

It is not uncommon to remain above the mean for the first 100+ days.  In 2106, the temperature did not cross until day 150!

[oren]

The old normal.

[ms]

I like Nico Suns version from
https://cryospherecomputing.com/

[interstitial]

From the looks of those charts the baseline cold temperature in winter moved up about 7 or 8 degrees.

[I’M IN LOVE WITH A RAGER]

7-8 degrees Celsius is no small amount, that's actually somewhat surprising in magnitude to me, even considering the observed changes in the system

[The Walrus]

When you add up a roughly 8 degrees temperature rise in winter with 1 degree rise in spring and fall, the 10-degree total averaged throughout the year amounts to the 2.5 degree rise measured.

[oren]

For anyone who has DMI's temps North of 80 bookmarked, I recommend to replace with Zack Labe's version which uses the same data but with the correct averaging method.

[Niall Dollard]

For anyone who has DMI's temps North of 80 bookmarked, I recommend to replace with Zack Labe's version which uses the same data but with the correct averaging method.

Zach's charts are great.

However I can see very little difference between his and the dmi version. Is  there really a difference in the averaging, or am I looking at the same chart ?

[oren]

DMI averages weirdly by latitude, Zach averages properly by area. I guess the differences are not that large when the temperatures are nearly uniform between the Pole and the 80 line, but I'm sure there should be a difference somewhere. Or I have misunderstood the weighting methods.

[weatherdude88]

DMI averages weirdly by latitude, Zach averages properly by area. I guess the differences are not that large when the temperatures are nearly uniform between the Pole and the 80 line, but I'm sure there should be a difference somewhere. Or I have misunderstood the weighting methods.

It's the same graph and uses same data. The only difference is the colors.

Daily 2 m surface air temperature for the Arctic averaged above 80°N. Individual years from 1958-2021 are shown by the sequential blue/purple to yellow lines. 2022 is indicated by the red line. ERA40 has been applied for the 1958-2002 climatology (white line), while the operational ECMWF is used for the current year.

There are other graphs that show 70 N and regional area of temps in the Arctic.

https://zacklabe.com/arctic-temperatures/

[oren]

DMI are quite clear that their averaging method is by latitude, smaller but more northern grid cells
 (e.g. latitude 89) get the same weighting as much larger but more southern cells (e.g. latitude 80), so the result is not physical.

http://ocean.dmi.dk/arctic/documentation/arctic_mean_temp_data_explanation_newest.pdf

Plus 80N Temperatures - explanation.
The temperature graphs are made from numerical weather prediction (NWP)
"analysis" data. Analyses are the model fields used to start NWP models. They
represent the statistically most likely state of the atmosphere, given the
information available to make the analysis. Since the data are gridded, it is
straight forward to deduce the average temperature North of 80 degree North.
However, since the model is gridded in a regular 0.5 degree grid, the mean
temperature values are strongly biased towards the temperature in the most
northern part of the Arctic! Therefore, do NOT use this measure as an actual
physical mean temperature of the arctic. The 'plus 80 North mean temperature'
graphs can be used for comparing one year to an other.

The proper method to calculate the average is to give each cell its weight according to its area.

This is what I understood Zack Labe is doing. I will pm him to make sure I got it right.

Excellent, thank you Zack.
Just making sure, is temperature averaging N of 70 or 80 weighted by area (as it should be), or by latitude (as DMI does)?

weighted by area

[FishOutofWater]

Zach's temperature graph is a little bit smoother because it does not give one point - the pole - more weight than the points at 80ºN. DMI enhances anomalies at and around 90ºN.

[oren]

Sorry for sowing confusion, I got detailed information from Zack (many thanks!).
Indeed Zack's N of 80 chart data is identical to the DMI chart. Zack does use the correct averaging method in all other charts.

To clarify, I am simply reproducing the DMI graphic using their same data. Unfortunately, the raw real-time ECMWF model data is behind a paywall, which I do not have access to. So I can't create my own averaging technique.

Otherwise, every other graphic I produce on Twitter and my website uses the area-weighted averaging method.

My personal view is that while it's useful to to get an "approximate" idea of the current temperature at 80°N+ on the DMI graphic, it's a bit overrated (especially during summer) and not as useful from a historical long-term trend perspective. They are concatenating several different datasets together, which I would advise against doing in the scientific literature.

My monthly visualizations on my website are temporally and spatially consistent and are using the most up-to-data (strictly ERA5) - so I would stick with them for getting a better idea of long-term trends, ranks, and monthly mean anomalies.

[Blizzard92]

Hi all,

I just added a spatial view of the monthly mean temperatures and anomalies across the Arctic: https://zacklabe.com/arctic-temperatures/. The 80°N contour line is dashed. Please let me know what other near real-time visuals can be useful for these pages. Thanks!

[kassy]

It´s nice to have the absolute temperatures and the anomalies side by side. I would love to have this as a standard for anomaly maps (just a general wish, not a suggestion for you).

[Niall Dollard]

DMI N80 figure is showing below zero now (finally).

Although I notice Nico Sun's equivalent chart has flatlined at +0.5°C.

Normally the two are the same. Both are dated 30/08/23. There must be some delayed update on Nico's version.

[Niall Dollard]

At the middle of October the DMI N80 daily mean briefly dipped below the 1958-2002 mean. This was the first time in 10 years it dipped below the 1958-2002 mean, during the month of October.

However quickly followed by a steady rise. Normal service resumed it seems.

[Niall Dollard]

The recent Atlantic storms have sent the DMI N80 skyrocketing.

Have to go back to January 2006 to find an earlier similar rise of this magnitude.

[Niall Dollard]

DMI have posted an update to the chart which now brings it up to 31/10/24.

But still no improvement in the cold temperatures since Gero last posted this chart in the other thread.

It is truly a Halloween horror show. Unprecedented to see this almost flatlining through the month of October.

I wondered is it possible the algorothm/method of calulation is somehow malfunctioning ? (but I don't think so)

I have heard it said that the DMI N80 data is more weighted towards the pole than being a spatial average across the whole circle north of 80°.

And going by the current GFS temperatures on Nullschool, near the pole the temperatures are still relatively warm.

I tried to do a very rough estimate of the 4 qaudrants shown, based on this GFS snapshot. Very roughly  my estimate (averaged over each quadrant and reduced to near sea level) is as follows:

0 to 90 E = -2°

90E to 180E = -12°

0 to 90W = -14°

90W to 180W = -16°

Giving a four quadrant average of -11°.

The current DMI N80 figure stands at approx -7°. We have noticed before that GFS tends to be a bit cooler than the actual 2m temp,  so all in all there isnt much difference between these two "estimates".

Basically we are in unprecedented territory. How long before we see some decent cold over the CAB ? The ice is missing out on serious freezing time over the pole.

[gerontocrat]

I have heard it said that the DMI N80 data is more weighted towards the pole than being a spatial average across the whole circle north of 80°.

Somewhere or other in the ASIF there are posts that show weighting skewed towards the pole is a definite fact.

GFS temperature anomalies from climate reanalyser indicate high +ve  temp anomalies persisting for the near future.

[Phil.]

This is DMI's explanation:
Plus 80N Temperatures - explanation.
The temperature graphs are made from numerical weather prediction (NWP) "analysis" data. Analyses are the model fields used to start NWP models. They represent the statistically most likely state of the atmosphere, given the information available to make the analysis. Since the data are gridded, it is straight forward to deduce the average temperature North of 80 degree North. However, since the model is gridded in a regular 0.5 degree grid, the mean temperature values are strongly biased towards the temperature in the most northern part of the Arctic! Therefore, do NOT use this measure as an actual physical mean temperature of the arctic. The 'plus 80 North mean temperature' graphs can be used for comparing one year to an other.

https://ocean.dmi.dk/arctic/documentation/arctic_mean_temp_data_explanation_newest.pdf