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 Means Rules- help and advice 
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 Post subject: Means Rules- help and advice
PostPosted: Wed Dec 26, 2012 8:09 pm 
Professor
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There has been a thread running alongside November 2012 regards working out Mean temperatures - started a new thread to reflect the interest

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 Post subject: Re: Means Rules- help and advice
PostPosted: Wed Dec 26, 2012 8:10 pm 
Professor
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For Newton Rigg the Met'O website has slightly different figures:

Mean Max 8.3c
Mean Min 2.6c
AF's 6
Rain 108.2

What you tend to find with the Met'O site is that whilst the figures (back to June) are shown as 'provisional', is that when they are verified, the temp' figures remain the same but the rainfall amount differs from the provisional figure.
Why, who knows, but that 108.2 mm seems a little low for me, guess we will find out sometime in 2013.

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darren

I think its all in the rounding up of the data

True figure is for the Air Min is 2.55 - my spreadsheet auto rounds this up to 2.5

BUT - I understand that there is a rule about rounding up which Carl M told me many moons ago and I think Met O will show this as 2.6. Clearly this is open to debate I guess. When I compute the means at the end of the month I dont really have time to round up each one manually and I dont know how you would do this using a spreadsheet calculation

Means Table Rule

If the mean temp Mean Max or the Mean Min comes to for eg 15.35 it is rounded off to the even number so in this case it would be 15.3 but if the figure was 15.45 it would be rounded off to be one higher 15.5.

EG
15.05 change 15.1
15.15 leave at 15.1
15.25 change to 15.3
15.35 leave at 15.3
15.45 change to 15.5
15.55 leave at 15.5
15.65 change to 15.7
15.75 leave at 15.7
15.85 change to 15.9
15.95 leave at 15.9
16.05 change to 16.1

so the Mean for newton rigg is 5.5c - using my spreadsheet it would be 5.4c

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--------------------------------------------------------------------------------------------------------------------------------------------------------------
Paul C wrote:
Means Table Rule

If the mean temp Mean Max or the Mean Min comes to for eg 15.35 it is rounded off to the even number so in this case it would be 15.3 but if the figure was 15.45 it would be rounded off to be one higher 15.5.


Yep, that's it.

Paul C wrote:
so the Mean for newton rigg is 5.5c - using my spreadsheet it would be 5.4c


I don't fully rely on my spreadsheet, always use my hand calculator as a backup just to make sure
I've got the means right.

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Paul - I think that you mentioned this before.

however, when a mean works out at .05 I always round up, regardless of whether it is .15, .25, .35, etc.

i imagine the thinking of 'one up, one down' must simply be to compensate for the 'average' 6 occassions a year when you would have a mean of 0.05 - so that by average, 3 go up and 3 come down and eh a balanced figure - but would it really work like that.
Now writing and thinking at the same time, see I can multi-task, I do see an element of sense, but I guess that I won't change.
however, it also ignores the rounding up/down of the mean min/max and that will effect if the final mean is bang on 0.1 or a 0.05 - now I see less sense.

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Paul C
Post subject: Re: November 2012Posted: Wed Dec 19, 2012 11:35 am
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Those "rules" I understand are Met O rules - so they really should be used. Now whether they make a difference overall I dont know, stick to one method. But we should always follow the standard.

I enjoy recording the data more than I understand the actual weather, but as I am not that mathematically minded I dont really want to get to hung up on a 0.1c degree here and there . Am I right to think this way ?

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darrog
Post subject: Re: November 2012Posted: Tue Dec 25, 2012 7:47 pm
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So how do you work out seasonal and yearly averages then?

A - the sum of the mean temps divide by 12 and then apply those rules re 0.05, 0.15, etc or

B - the sum of the mean min/max divide by 2 and then apply the above rules?

i should add that all means in COL use A

i will give my yearly figures as an example of how this matters.

2009
using A above my yearly mean would = 8.83c (8.8c)
Using B above my yearly mean would = 8.85c - which then becomes 8.9c


2010
using A above my yearly mean would = 7.39c (7.4c)
Using B above my yearly mean would = 7.35c - which then becomes 7.3c

So it does matter and I know which I prefer (A), but I bet you tell me B

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Paul C
Post subject: Re: November 2012Posted: Wed Dec 26, 2012 12:10 pm
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In short YES - same rules apply

Would you not get the same result though using either A or B Method ?

Unless Carl has another take on it ?

I am now in a state of "what do I do" I think my means are a mixture of the "rule" the early years and then when my spreadsheet calculations take over

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darrog
Post subject: Re: November 2012Posted: Wed Dec 26, 2012 2:46 pm
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Paul - with the end of the year coming up that's why i asked.

I applied your system to my data and it changed a number of months - but then I thought about the years..

After making those changes using your system I then checked out the effect that they had on the years.

first I used A - this changed one year

then i used B - and this changed two of the years but not the year that A changed!!!!

It should not be this complicated

EDIT - just checked the Met'O site for historical averages at Newton Rigg
Mean yearly max' for 1981-10 - total of 12 max's = 148.1 divide by 12 = 12.34 - they show 12.4 !!!!!!!!
Mean yearly min for 1961-90 - total of 12 mins = 55.7 divide by 12 = 4.64 - they show 4.7 !!!!!!!!

can you explain?

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Paul C
Post subject: Re: November 2012Posted: Wed Dec 26, 2012 5:29 pm
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?
Is there Min 55.7c yours or there figure

Looks like on the evidence you put forward they have made a mistake then, cant round up 12.34 to 12.4, that would never work either in basic maths rules or Meto rules

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Carl M
Post subject: Re: November 2012Posted: Wed Dec 26, 2012 5:59 pm
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Always use your ''A'' rule.

Not sure how the Met O came to those figures, worth sending them
a cheeky email then

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darrog
Post subject: Re: November 2012Posted: Wed Dec 26, 2012 6:22 pm
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Carl - thanks and will e-mail the Met'O - may even ask them thi same Q.

I do think that for a yearly mean that A works best.

I have also put something on COL's forum to see the response from there.

paul - would it be worthwhile putting these few posts re mean temps onto a new topic of its own?

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 Post subject: Re: Means Rules- help and advice
PostPosted: Wed Dec 26, 2012 8:27 pm 
Professor
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Darren- I think you should buy "The Weather Observers Handbook" - its got quite abit about analysing your data avalanche

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Last edited by Paul C on Fri Dec 28, 2012 12:49 pm, edited 1 time in total.

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 Post subject: Re: Means Rules- help and advice
PostPosted: Wed Dec 26, 2012 9:10 pm 
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Paul - what does the WO handbook say?

Re those NR figures - The 55.7 is the sum of the 12 individual means.

55.7 /12 = 4.64c
rounded off will be 4.6c
But they show 4.7c

What is annoying is that they only show monthly+yearly mean mins+ maxes and not monthly+yearly means.

As for COL - it is simply sum of mean min+max divided by 2 and if it comes to a 0.05, round up.

Look at Paul's mean temp for November, Paul quotes 6.2c - COL have 6.3c - whilst both quote the same mean min/max

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 Post subject: Re: Means Rules- help and advice
PostPosted: Sat Dec 29, 2012 12:45 pm 
Professor
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After all that I can find anything in the book regards calculating means !

BUT - have found this download section- plenty of spreadsheets to get stuck into over the New Year !"!!!

http://measuringtheweather.com/downloads/

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 Post subject: Re: Means Rules- help and advice
PostPosted: Sat Dec 29, 2012 2:40 pm 
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I posted a message on uk sci weather group

They call it "throwing it to the odd"

Quote "The standard meteorological method is to "throw it to the odd". Therefore,
15.15 becomes 15.1 whereas 15.25 becomes 15.3. I believe the logic in this is
to eliminate systematic bias that would be caused if rounding was always up (or
down).

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 Post subject: Re: Means Rules- help and advice
PostPosted: Sun Dec 30, 2012 11:07 am 
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Paul - thanks.

The 'throw to the odd' definitely looks much the better way - I totally disliked the 'always round up' way, even though I used it and have now amended my own records.

I have added to your post on ukscire re then calculating seasonal/yearly means.

I guess everyone on this forum should be encouraged re the 'throw to the odd'

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 Post subject: Re: Means Rules- help and advice
PostPosted: Sun Dec 30, 2012 12:22 pm 
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I think we all a little odd anyway ! drl1

I have gone through all my mean max tables for the last 12 years and made the nesessary corrections. has made no difference at all the end result :x
BUT I did find a clerical error in the mean min where I had just put the wrong value and it was way out, so its been corrected and made a difference of 0.1c overall on the mean

So my overall Mean Max is 12.8c and Mean Min 5.8c up +0.1c

So thats 3 hours of my day gone already ESK

At least I know its right

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 Post subject: Re: Means Rules- help and advice
PostPosted: Sun Dec 30, 2012 12:40 pm 
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Paul - it changed a few things for myself.
Instead of two months sharing the warmest mean temp of 14.8c - I now have none on 14.8c, but one at 14.9 and the other at 14.7!!!
Changed 2011 from 9.2c to 9.1c and in the years 2010 only had 1 amended month and 2009, 2011 and 2012 had 4 each.

but re 'past mistakes' - easily done and always picking them up.

check this anomaly though for the month of May.

mean min of 5.7c
mean max of 14.7c
mean of 10.1c - not 10.2c

trust me on the maths, the 4 monthly means = 40.6 (divide by 4 = 10.15c) 'throw to the odd' =10.1c

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 Post subject: Re: Means Rules- help and advice
PostPosted: Mon Dec 31, 2012 10:39 am 
Professor
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I like the info on the uk sci weather thread - whole host of advice there

Not so sure I will be using the rather long excel code snippets

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