zaphod
Level 3 Rank
Posts: 210
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Post by zaphod on Jul 22, 2013 1:06:11 GMT
Thanks, icefisher, I can find out more about that as well. It seemed such a regular oscillation there
had to be a reason.
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Post by sigurdur on Jul 22, 2013 1:56:33 GMT
DMI analysis:
An NWP analysis is based on vastly more information than available from any
single observing system. Data from ground, aircraft, bouys, ship, satellites,
radiosondes, etc. are all combined to adjust the first guess field. As a
consequence the quality of an analysis is much better than what can be obtained
from gridding, or treating in other ways, data from a single or a few observing
systems
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Post by sigurdur on Jul 22, 2013 1:57:38 GMT
zaphod:
I don't have time right now to do an analysis of your question. Like many others, I was hoping someone would make a stab at it.
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Post by cuttydyer on Jul 22, 2013 7:49:44 GMT
Would someone mind answering my question above? I'm trying to learn something... "A simple question, which hopefully one of the more knowledgeable members can answer. The DMI Daily Mean Temperatures graph, reproduced by Cuttydyer above and here ocean.dmi.dk/arctic/meant80n.uk.php shows a pretty regular fluctuation of temperature in terms of time rather than magnitude. It is particularly noticeable in the section of the graph above 273 Kelvin, perhaps because the fluctuations are less wild than elsewhere. I cannot work out the period of the oscillation (is it weekly?) and would like an explanation for the oscillation if someone can give one. Thanks!" Zaphod, Interesting question; I've emailed an enquiry to the DMI staff - currently awaiting a response. As mkelter has posted, the period is 3-4 days. CD. ______________________________________________________ Update: Palle Bo Nielsen of the DMI has forwarded your question to the specialist Jacob Høyer.  Unfortunately, he's on vacation until the 6th of August. I'll keep you posted... |
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Post by cuttydyer on Jul 22, 2013 11:21:03 GMT
Would someone mind answering my question above? I'm trying to learn something... "A simple question, which hopefully one of the more knowledgeable members can answer. The DMI Daily Mean Temperatures graph, reproduced by Cuttydyer above and here ocean.dmi.dk/arctic/meant80n.uk.php shows a pretty regular fluctuation of temperature in terms of time rather than magnitude. It is particularly noticeable in the section of the graph above 273 Kelvin, perhaps because the fluctuations are less wild than elsewhere. I cannot work out the period of the oscillation (is it weekly?) and would like an explanation for the oscillation if someone can give one. Thanks!" Zaphod, In the absense of Jacob Høyer, Gorm Dybkjær has kindly addressed my enquiry.  Email response by Gorm Dybkjær: Thanks for your interest in the data we put on our website.
I agree with you that the sawtooth-like temperature variation in the past month or so, looks very rhythmic, but I think it is coincidencial natural variations and not a 'product of temperature acquisition', as you also suggest. The data are based on model analysis data as you can read in the link to further information on the site.
I have put the bi-daily mslp and temperature plots for the past 3 weeks on my ftp site:
ftp.dmi.dk/pub/Users/Gorm.Dybkjaer/burville/
You can unpact and animate these data and you will see that there is no particular occillation in that period that explains the saw-tooth variations.
You can see our new satellite observation based Arctic surface temperature product here:
polarportal.dk/havisen-i-arktis/nbsp/havisens-temperatur/
Cheers
gorm |
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Post by mkelter on Jul 22, 2013 11:39:43 GMT
Would someone mind answering my question above? I'm trying to learn something... "A simple question, which hopefully one of the more knowledgeable members can answer. . . Zaphod, In the absense of Jacob Høyer, Gorm Dybkjær has kindly addressed my enquiry. . . Email response by Gorm Dybkjær: Thanks for your interest in the data we put on our website. . .
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zaphod
Level 3 Rank
Posts: 210
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Post by zaphod on Jul 22, 2013 11:57:19 GMT
Wow! Thanks, all. I do appreciate the responses. I thought it was a simple question but nothing in this science seems simple. I am still struck by the oscillations... The link Gorm provided polarportal.dk/en/arctic-sea-ice/nbsp/sea-ice-temperature/ is interesting and, I think, a new resource. zaphod |
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Post by numerouno on Jul 22, 2013 12:59:51 GMT
"The data are based on model analysis data as you can read in the link to further information on the site."
Most people seem to forget that the DMI Arctic temp is not a real measurement, but a product of a model of the Arctic into which the available sparse data are fed. The results reflect the fidelity of the model. Therefore, in an unforeseen behaviour of the Arctic, the results will likely be wrong.
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Post by cuttydyer on Jul 22, 2013 13:12:15 GMT
"The data are based on model analysis data as you can read in the link to further information on the site." Most people seem to forget that the DMI Arctic temp is not a real measurement, but a product of a model of the Arctic into which the available sparse data are fed. The results reflect the fidelity of the model. Therefore, in an unforeseen behaviour of the Arctic, the results will likely be wrong. Do you trust any of these measurements? GISS, five years:  GISS, ten years:  HadCRUT4, five years:  HadCRUt4, ten years:  NCDC, five years:  NCDC, ten years:  The mean of the anomalies on all three terrestrial datasets, five years:  The mean of the anomalies on all three terrestrial datasets, ten years:  I guess not... |
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Post by numerouno on Jul 22, 2013 13:20:23 GMT
"I guess not..."
Will you be trusting them if/when there is are no two points in the graph between which that you can cherry pick a decreasing trend any longer?
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Post by mkelter on Jul 22, 2013 14:11:47 GMT
"I guess not..." Will you be trusting them if/when there is are no two points in the graph between which that you can cherry pick a decreasing trend any longer? Do You Like Cherry-picked Hockey Sticks Better? |
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Post by mkelter on Jul 22, 2013 20:55:29 GMT
"The data are based on model analysis data as you can read in the link to further information on the site." Most people seem to forget that the DMI Arctic temp is not a real measurement, but a product of a model of the Arctic into which the available sparse data are fed. The results reflect the fidelity of the model. Therefore, in an unforeseen behaviour of the Arctic, the results will likely be wrong. Kinda like the IPCC Models, Huh? |
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zaphod
Level 3 Rank
Posts: 210
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Post by zaphod on Jul 22, 2013 21:23:44 GMT
"The data are based on model analysis data as you can read in the link to further information on the site." Most people seem to forget that the DMI Arctic temp is not a real measurement, but a product of a model of the Arctic into which the available sparse data are fed. The results reflect the fidelity of the model. Therefore, in an unforeseen behaviour of the Arctic, the results will likely be wrong. Numerouno: 1) Please identify where the DMI Arctic Temp graph is stated to be a model (I can't find that). 2) Are you suggesting that the present behaviour of the Arctic is unforeseen by the DMI model, if it is a model? If so, where is this substantiated? I respect your views and expertise, but you seem to be inviting readers to draw an inference which may not be intended by your statements. |
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Post by numerouno on Jul 22, 2013 21:53:04 GMT
"1) Please identify where the DMI Arctic Temp graph is stated to be a model (I can't find that)."
It's in the answer by the DMI staff if you read carefully. It is also, as the member of the staff explained in his answer, also stated on their web page. I can't unfortunately help you any further on this.
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Post by sigurdur on Jul 22, 2013 23:24:30 GMT
Zaphod:
The DMI temperature graph is an anomaly graph. It is based on a model of observations. It is explained on the DMI page where the temp chart is.
Calculation of the Arctic Mean Temperature
The daily mean temperature of the Arctic area north of the 80th northern parallel is estimated from the average of the 00z and 12z analysis for all model grid points inside that area. The ERA40 reanalysis data set from ECMWF, has been applied to calculate daily mean temperatures for the period from 1958 to 2002, from 2002 to 2006 data from the global NWP model T511 is used and from 2006 to 2010 T799 data are used and from 2010 to present the T1279 model data are used.
The ERA40 reanalysis data, has been applied to calculation of daily climate values that are plotted along with the daily analysis values in all plots. The data used to determine climate values is the full ERA40 data set, from 1958 to 2002.
More information can be found here.
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