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#1428601 - 21/07/2017 20:00 Re: Observations of climate variation [Re: Surly Bond]
Surly Bond Offline
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Registered: 23/08/2003
Posts: 2097
Loc: Manilla, near Tamworth NSW




Explained here.
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#1428648 - 22/07/2017 11:38 Re: Observations of climate variation [Re: Surly Bond]
Surly Bond Offline
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Registered: 23/08/2003
Posts: 2097
Loc: Manilla, near Tamworth NSW
I fitted a bimodal curve to a distribution curve for all historical annual rainfalls in the post above.
Has anyone ever done that before?
I cannot find such a thing on the internet.

Searching using "bimodal rainfall" with other added terms gives results that, so far as I can see, ALL refer to the time-distribution of rainfall throughout the year. They report that many places have a seasonal rainfall pattern that is bimodal, with two distinct peaks of rainfall in a year. I made such a model myself for my town of Manilla a few years ago.

For all I know, there may be dozens of studies of bimodal distributions of annual rainfall, or of the rainfall in specific months of the year. It is important to find out. I don't see any way of narrowing my search to avoid being absolutely swamped by studies of the seasonal rainfall pattern.

Can anyone help?
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#1428653 - 22/07/2017 14:47 Re: Observations of climate variation [Re: Surly Bond]
Knot Offline
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Registered: 01/05/2014
Posts: 2560
Loc: Toronto N.S.W
I could help you out with bimodality in music but not statistical stuff I'm afraid. I managed to avoid all statistics lessons during a course I did to gain my HSC equivalent uni entry score.
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#1428661 - 22/07/2017 18:16 Re: Observations of climate variation [Re: Surly Bond]
Surly Bond Offline
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Registered: 23/08/2003
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Loc: Manilla, near Tamworth NSW
Thanks knot, but I can't even tell a major from a minor key!

I have found that Salt Lake City has a bimodal distribution of annual rainfalls, but no analysis of the fact. Just "there are wet times and dry times". Really?
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#1428664 - 22/07/2017 19:51 Re: Observations of climate variation [Re: Surly Bond]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7419
Loc: Adelaide Hills.
Originally Posted By: Surly Bond
For all I know, there may be dozens of studies of bimodal distributions of annual rainfall, or of the rainfall in specific months of the year.

"Origins of the Caribbean Rainfall Bimodal Behavior"
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 115, D11106, doi:10.1029/2009JD012990, 2010.

Is one smile .

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#1428668 - 22/07/2017 21:06 Re: Observations of climate variation [Re: Surly Bond]
Surly Bond Offline
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Registered: 23/08/2003
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Loc: Manilla, near Tamworth NSW
Sorry, Seira. That is one of the thousands of references to seasonal bimodality.
I have observed bimodality in the distribution of annual rainfall totals in the whole rainfall record.
I am planning to check for bimodality in the distribution of all rainfall records for the month of January, then of February, and so on.
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#1428680 - 22/07/2017 23:08 Re: Observations of climate variation [Re: Surly Bond]
Seira Offline
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Registered: 27/08/2003
Posts: 7419
Loc: Adelaide Hills.
Originally Posted By: Surly Bond
Sorry, Seira. That is one of the thousands of references to seasonal bimodality.
I have observed bimodality in the distribution of annual rainfall totals in the whole rainfall record.
I am planning to check for bimodality in the distribution of all rainfall records for the month of January, then of February, and so on.

Ok smile , sure.
I noticed:

Originally Posted By: Surly Bond
I fitted a bimodal curve to a distribution curve for all historical annual rainfalls

And:

Originally Posted By: Surly Bond
I have found that Salt Lake City has a bimodal distribution of annual rainfalls, but no analysis of the fact.

On the first, my impression is that is a fairly specific thing to do, and I am not sure how much success you’ll have finding much literature which gives certain examples (with mathematical descriptions of the processes involved), around specific geographic regions, or climate zones. You may need a combination of studies/sources to make more in-roads. I myself am not overly familiar with mathematics/processes involved, however if you are pioneering in this area, good on you smile !

On the second, with regard to an “analysis of the fact” – that I would be more interested in (the very fact of why and how bimodal distributions form and evolve).

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#1430574 - 14/08/2017 10:44 Re: Observations of climate variation [Re: Surly Bond]
Surly Bond Offline
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Registered: 23/08/2003
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Loc: Manilla, near Tamworth NSW
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#1431729 - 26/08/2017 10:51 Re: Observations of climate variation [Re: Surly Bond]
Surly Bond Offline
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Registered: 23/08/2003
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Loc: Manilla, near Tamworth NSW
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#1432017 - 28/08/2017 11:01 Re: Observations of climate variation [Re: Surly Bond]
Surly Bond Offline
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Registered: 23/08/2003
Posts: 2097
Loc: Manilla, near Tamworth NSW


Edited by Surly Bond (28/08/2017 11:03)
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#1441298 - 16/11/2017 09:54 Re: Observations of climate variation [Re: Surly Bond]
Surly Bond Offline
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Registered: 23/08/2003
Posts: 2097
Loc: Manilla, near Tamworth NSW
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#1442120 - 23/11/2017 17:10 Re: Observations of climate variation [Re: Surly Bond]
Seira Offline
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Registered: 27/08/2003
Posts: 7419
Loc: Adelaide Hills.
I think -- from reading through climate-zone dynamics and geography -- that bimodal annual rainfall would mean there is an overlap of sorts between climate zones smile , or, alternatively, a micro-climatic effect wherein the location in question experiences air streams coming from different directions, which also overlap. This is a very rough understanding though.

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#1442165 - 23/11/2017 23:37 Re: Observations of climate variation [Re: Surly Bond]
Surly Bond Offline
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Registered: 23/08/2003
Posts: 2097
Loc: Manilla, near Tamworth NSW
Thanks, Seira.
Rainfall here varies, both in the seasonal bimodality and the bimodality in the total frequency distribution, as well as the independent variation in the four moments of it. I suspect that all of them may relate to the sub-tropical high pressure belt. That is, the relative and absolute effect of its north and south movement from time to time.
But that could be entirely too simplistic.
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#1442272 - 24/11/2017 21:19 Re: Observations of climate variation [Re: Surly Bond]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7419
Loc: Adelaide Hills.
Originally Posted By: Surly Bond
I suspect that all of them may relate to the sub-tropical high pressure belt. That is, the relative and absolute effect of its north and south movement from time to time.

I agree smile .

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#1442496 - 27/11/2017 20:24 Re: Observations of climate variation [Re: Surly Bond]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 432
Loc: Pinjarra Hills, Qld
Originally Posted By: Surly Bond
Thanks, Seira.
Rainfall here varies, both in the seasonal bimodality and the bimodality in the total frequency distribution, as well as the independent variation in the four moments of it. I suspect that all of them may relate to the sub-tropical high pressure belt. That is, the relative and absolute effect of its north and south movement from time to time.
But that could be entirely too simplistic.


This topic of bimodality and different characteristics such as skew mean kurtosis etc is complex. A key issue with rainfall data is that analysis of point rainfall such as a specific location or gauge will include a mix of local influences out of sync with a broader region and in sync with a broader region.
That would need an analysis of rainfall over different spatial scale magnitudes of local to perhaps climate zone scale to identify consistency or otherwise. There are data sets such as AWAP and others that could support such analysis ..... But that would be a big effort to do that. I mean a computer with grunt together with clever programming.
Averaging period over 21 years may help bring local to regional scale closer but could also mask some characteristics variation over time.
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#1445538 - 22/12/2017 10:50 Re: Observations of climate variation [Re: Surly Bond]
Surly Bond Offline
Weatherzone Addict

Registered: 23/08/2003
Posts: 2097
Loc: Manilla, near Tamworth NSW


Edited by Surly Bond (22/12/2017 10:52)
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#1448242 - 10/01/2018 08:57 Re: Observations of climate variation [Re: Surly Bond]
Petros Offline
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Registered: 30/12/2002
Posts: 6922
Loc: Maffra, Central Gippsland, Vi...
ABC Media are today saying that 2017 was the third hottest year on record.


........"BOM annual climate statement shows 2017 was Australia's third warmest year on record
07:07 EDT

The Bureau of Meteorology (BOM) confirms 2017 was Australia's third warmest year on record with temperatures almost a degree above the 1961 to 1990 average".......


What does the above statement mean? - I take it that the "record" was last years average temperature versus the average temperatures in the dataset '61 - '90 - a period that ceased 17 years ago!

Hope I'm wrong, as that could easily be interpreted as a misleading attempt to ignore the 15 year pause in global temperature rise?????

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#1448255 - 10/01/2018 10:15 Re: Observations of climate variation [Re: Surly Bond]
Mike Hauber Offline
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Registered: 13/07/2007
Posts: 3059
Loc: Buderim


3rd hottest year after 2013 and 2005.

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#1448256 - 10/01/2018 10:19 Re: Observations of climate variation [Re: Surly Bond]
DaveM Offline
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Registered: 21/05/2001
Posts: 10129
Loc: Bathurst NSW about 700 m asl
That's a nasty looking trend.

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#1448260 - 10/01/2018 10:45 Re: Observations of climate variation [Re: Mike Hauber]
Kino Online   content
Weatherzone Addict

Registered: 10/08/2017
Posts: 2021
Loc: Wollongong, NSW, Aus
Originally Posted By: Mike Hauber


3rd hottest year after 2013 and 2005.


This topic forbidden. And one thing failed to be pointed out is the rider "Based on a 30-year climatology 1961-1990). So that graph is rubbish?

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