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#3764 - 13/08/2009 21:45 Re: Observations of climate variation
Arnost Offline
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Registered: 10/02/2007
Posts: 3908
Maybe that explains why the winter months are almost a degree C cooler at the AWS... which is not really negligible.
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#3765 - 13/08/2009 21:49 Re: Observations of climate variation
Surly Bond Offline
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Registered: 23/08/2003
Posts: 2065
Loc: Manilla, near Tamworth NSW
>>>OK – here’s how I did it, so if anyone wants they can replicate…<<<.... says Arnost.

I am really keen to see some others replicating.

How big a region does the Manilla and Tamworth data represent? Certainly the NW Slopes, but how about New England? The North Coast? Brisbane? Even Sydney?
Melboune must be different, as they have had a drought. :evillaugh:
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#3766 - 13/08/2009 21:50 Re: Observations of climate variation
Keith Offline
Meteorological Motor Mouth

Registered: 16/12/2001
Posts: 6453
Loc: Kings Langley, NSW
Quote:
Originally posted by Surly Bond:
BTW Arnost, I believe the new Tamworth AWS is some kilometres from the old airport site.
The AWS is a "blasted heath" (without the witches). wink
I trust I won't see three old hags near the AWS chanting magic words about global warming (and no, I'm not a Macbeth, though I think some scientists practise rhabdomancy).

Thanks Arnost for the calculation notes. I did indeed get that part wrong (in how I understood the process, not the calculation in principle), so I'll try again.

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#3767 - 13/08/2009 21:58 Re: Observations of climate variation
Arnost Offline
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Registered: 10/02/2007
Posts: 3908
rhabdomancy... well you learn something every day!
_________________________
“No. Not even in the face of Armageddon. Never compromise” ...

And this of course applies to scientific principles. Never compromise these. Never! [Follow the science and you will be shown correct in the end...]

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#3768 - 14/08/2009 11:00 Re: Observations of climate variation
Keith Offline
Meteorological Motor Mouth

Registered: 16/12/2001
Posts: 6453
Loc: Kings Langley, NSW
This is a plot of my data from 1999 to 2008:



The traces are self-explanatory. The anomalies were calculated with reference to the average for 1970-2008, the longest period of complete years for which data aren't missing. The period up to 1978 from which I calculated the anomalies, actually covers the former official BOM station about 3 km southwest of here but for all intents and purposes the maxima would have been the same here (minima were much lower as the elevation was 30 metres or so lower).

There appears to be a cycle of about 1.75 years.

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#3769 - 14/08/2009 14:31 Re: Observations of climate variation
Keith Offline
Meteorological Motor Mouth

Registered: 16/12/2001
Posts: 6453
Loc: Kings Langley, NSW
Just for the heck of it more or less, I plotted this chart of my rainfall data:



The same criteria apply to data pre-1978 as with the temperature plot previously posted, with the added proviso that the averages are taken from 1950, the first year of record.

Again there appear to be cycles, but rather more variable than with the temperatures.

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#3770 - 17/08/2009 15:10 Re: Observations of climate variation
Surly Bond Offline
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Registered: 23/08/2003
Posts: 2065
Loc: Manilla, near Tamworth NSW
Good stuff, Keith! :cheers:
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#3771 - 17/08/2009 15:31 Re: Observations of climate variation
Surly Bond Offline
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Registered: 23/08/2003
Posts: 2065
Loc: Manilla, near Tamworth NSW
I hadn't finished, but the program decided I had.

Yes, I count six peaks and six troughs on your 10-year temp anom graph. That would be 5/3 year cycle.
BTW, your 1:2:1 smoothing trace is lagged behind the raw trace. I think the weighting should be centred on the raw data point. That would agree with what Arnost said.
Our data seem to agree on the highest peak and lowest trough. My highest peak is spring 2002. I am not sure we have used the same convention for x-axis labels. Your high peak (raw) is three grid lines after the one labelled "2002". Which season would that be?
My lowest trough is summer 2007-8. Yours is on the "2008" grid line.

"Lucia" has designed a mug that has the 5/3-year cycle on it, but I don't know what she is quoting. I can't read the legend:
http://www.cafepress.com.au/luciablackboard

The Indian Ocean Dipole Dipole Mode Index seems to have this cycle:
http://www.jamstec.go.jp/frcgc/research/d1/iod/HTML/Dipole%20Mode%20Index.html
I am surprised ROM didn't mention it.
:wave:
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#3772 - 17/08/2009 15:42 Re: Observations of climate variation
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2065
Loc: Manilla, near Tamworth NSW
Keith, I intend to try the spectral analysis to substantiate the cycle. I see that Excel Add-Ins includes Fast Fourier Transform. With Excel Help and various blogs I should be able to manage it.

I reckon the 5/3-year cycle should be called the "Surly Cycle". :nerd:
However, if phenomena such as the IOD show it, surely there must be a cacophony of discussion of it out there by now.
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#3773 - 17/08/2009 15:54 Re: Observations of climate variation
mobihci Offline
Weather Freak

Registered: 09/05/2009
Posts: 486
Loc: Brisbane
here is an odd one for you-

at spencers creek
http://www.snowyhydro.com.au/snowDepth.asp?pageID=46&parentID=6&mode=submitted

practically every even year has higher snow falls than the odd years.

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#3774 - 17/08/2009 18:16 Re: Observations of climate variation
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2065
Loc: Manilla, near Tamworth NSW
mobihci
Thanks for that. The internet seems full of such calculators. Unfortunately for me, the question that they answer is never the one I am asking.
I thought of laboriously copying the series of peak winter values into a list to look at the pattern. Then I realised that Harry Nyquist's folding frequency was in the way. Using annual data points, only cycles longer than two years can be resolved.
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#3775 - 17/08/2009 18:19 Re: Observations of climate variation
Surly Bond Offline
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Registered: 23/08/2003
Posts: 2065
Loc: Manilla, near Tamworth NSW
Keith, I just noticed that your graph shows maximum temperature, not mean temperature. I also have graphs of maxima and minima, which are not quite ready. Maxima and minima graphs differ quite a bit.
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#3776 - 17/08/2009 18:29 Re: Observations of climate variation
Surly Bond Offline
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Registered: 23/08/2003
Posts: 2065
Loc: Manilla, near Tamworth NSW
Keith, For my plot of smoothed data, I used the option in Excel Charts to format the "line" as "Smoothed". I think this is a logical thing to do, as we are trying to make the trace less jumpy. I believe one can also legitimately use the smooth line to estimate whether a peak is nearer to one season or the next, or just half-way between.
Perhaps you used a different program for the rainfall: the lines are smooth.
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#3777 - 17/08/2009 18:41 Re: Observations of climate variation
Surly Bond Offline
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Registered: 23/08/2003
Posts: 2065
Loc: Manilla, near Tamworth NSW
I compared the major peaks and troughs on the Dipole Mode Index with those on the Tamworth temperature plot that Arnost posted.
If there is a relation it is cryptic. Major peaks and troughs on one coincide with quiet times on the other.
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#3778 - 17/08/2009 19:56 Re: Observations of climate variation
Keith Offline
Meteorological Motor Mouth

Registered: 16/12/2001
Posts: 6453
Loc: Kings Langley, NSW
Hi Surly,

Seems i was suffering dyslexia in regard to what you had plotted; I was trying to just get things going and must have overshot the platform. laugh Anyway it at least had something to show.

Best of British with Excel's Fourier analysis..I've used it before but it's a bit of a dinosaur. One thing that's needed is exact multiples of 2^2 data (eg 4,16,32,64,128,256 etc)...though I understand most Fourier stuff requires that. There are some free downloads around the traps (not necessarily Excel, though).

I have separate signal processing software which will also generate wavelets..might try and post something with that. I struggle a bit with the outputs of some of the routines.

My charts were both done in Excel 97; I forgot to smooth the lines in the first graph. I did wonder why one trace was behind the other; although the calculation is centred on the middle value it's likely due to the way I've laid out the final data in the sheet (using pivot tables).

I've used plain years to describe the X-axis to avoid cluttering the legend, but eg 2008 is summer 2007-08 and lines in between each year are autumn, winter and spring in that order. I probably could have been a bit more inventive but wasn't feeling like it.

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#3779 - 17/08/2009 21:10 Re: Observations of climate variation
Keith Offline
Meteorological Motor Mouth

Registered: 16/12/2001
Posts: 6453
Loc: Kings Langley, NSW
OK, here we go again (having trouble with sizing images for some reason but I'm very tired and don't want to fiddle further with them):





The top image is a recast of the earlier graph to bring the data into correct alignment with each other.

The other chart is the 1:2:1 seasonally filtered data plotted against a wavelet reconstruction of the raw seasonal data with cycles <2 years removed.

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#3780 - 17/08/2009 22:38 Re: Observations of climate variation
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2065
Loc: Manilla, near Tamworth NSW
In NSW the North West Slopes and the Sydney Basin have had very similar seasonal temperature anomalies in the last 10 years.
So far, I have simply plotted Keith's Kings Langley figures for mean maxima on my graph for Manilla. The absolute anomaly values differ, but the peaks and troughs mostly occur at the same time in both places, and the trends up and down generally match.
This is information that I don't think has ever been documented before.
Thanks very much, Keith! :cheers:
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#3781 - 09/09/2009 13:19 Re: Observations of climate variation
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2065
Loc: Manilla, near Tamworth NSW
A picture is worth a thousand words. (I just made that up .)


I think there is no doubt that the temperature anomalies form a sine wave.
The period of the wave is a good deal longer than a year.

This replaces my post of 11-08-2009 15:41 (links broken).
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#3782 - 09/09/2009 13:33 Re: Observations of climate variation
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2065
Loc: Manilla, near Tamworth NSW
At Manilla, the traces of season temperature anomalies for daily maxima and daily minima differ, as these two graphs show. The convention is the same as for the earlier graph of daily mean temperature.



The peaks and troughs are different in height and date. Furthermore, the linear trend lines differ: that for maxima slopes down and that for minima slopes more steeply up. (This has been found before in climatic temperature change.)
In the above graphs the 1:2:1 smoothing does not extend to the two end points of the trace. The final data points, for winter 2009, do not include the last 12 days of the season. They, and the last smoothed point can be expected to rise a little with complete data.
The two traces are compared in the following graph:


The max and min traces tend to coincide when the temperature anomalies are small, as in climate years 1999,2000, 2001, 2003 and 2004.
In 2002, the max anomaly is much higher than the min, and the min lags by a whole season.
In 2006-7, the min anomaly is higher than the max and lags it by more than a whole season. The same happens at the 2007-8 trough, which is the deepest for both max and min.
I have found that, in the Manilla annual temperature cycle, daily minima lag daily maxima by almost a week. This lag of min temperature anomaly peaks and troughs by several months is in the same sense but very much longer.
I suspect the cause is related: daily maxima are caused fairly directly by received solar radiation. Daily minima are not. Perhaps they relate to a term I have just discovered: OLR (outgoing longwave radiation)?

This replaces the post of 18-08-2009 22:05 (broken links).
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#3783 - 09/09/2009 13:43 Re: Observations of climate variation
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2065
Loc: Manilla, near Tamworth NSW
Since the time series for anomalies in daily maxima and daily minima differ in magnitude and in phase, the difference between them, the daily temperature range anomaly, can be shown like this:



The graph is a log of seasonal anomalies in daily temperature range at Manilla for the last 42 seasons. Manilla has the extremely wide daily temperature range of 15.5 degrees. It varies little though the year.
There was a peak positive anomaly in winter 2002. The mean anomaly for that season was 2.14 degrees. That is, the mean daily range that winter was over 17.6 degrees. In the year beginning March 2002 more than 50 days had daily temperature ranges wider than 20 degrees. The same was true for 2006. The graph shows that th 2006 peak anomaly was lower but broader.
There are three troughs lower than -1.5 degrees in the daily temperature range anomaly. They correspond to mean seasonal daily temperature rangesof less than 14 degrees. All are very recent: winter '07, summer '07-08, and spring '08.
The linear trend line shows a fairly convincing decline in daily temperature range. The variation explained is low, however: R-squared is 0.06! A sixth-order polynomial trend recognises that the major change is a dip that comes in the last two years.

Wide daily temperature ranges generally relate to lack of cloud. I have observed amount of morning cloud in Octas. The log of the anomaly follows:



Clearly, the two graphs are almost mirror reversed, even in the trend lines.

This replaces my post of 23-08-2009 20:32 (broken links).
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