Mean Temperatures

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NZstorm
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Mean Temperatures

Unread post by NZstorm »

How are mean temperatures computed these days? The traditional method is to Max + Min /2.
Just wondering whether the likes of NIWA have adopted a new method or not.
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Re: Mean Temperatures

Unread post by David »

I always use the traditional method but I notice some online weather stations average the temperature at many points of the day to give the days mean. Not to say these stations are necessarily using meteorological standards though.

Just sent an email to Jim Salinger asking this question, hopefully he can find the time to answer.
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Re: Mean Temperatures

Unread post by RWood »

It's still common for summarised reports to use (max+min)/2. The point is that if a consistent formula is used then trends and anomalies can still be assessed. Met Service many years ago drew up a table of monthly adjustments which could be applied to a small set of stations studied (about a dozen) to convert this measure to a mean based on hourly values averaged, or something like that.
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Re: Mean Temperatures

Unread post by NZstorm »

Thanks for the replies.
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Re: Mean Temperatures

Unread post by David »

Just wondering if any else in Auckland with soil thermometers could help me. My soil reading now is 18.7C, but I find that a bit strange for September. All other days in the last week the readings have been between 15-18C. Does this sound right?
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Re: Mean Temperatures

Unread post by southernthrash »

What do people here think about max + min / 2? Do you think this is sufficient? Especially for examining trends? Or would a mean or median of regular sample points be better? Could be an interesting project for a climatology/stats/geography student...

Obviously you can't really go changing standards if you want to use long records for data analysis, but all the same...
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Re: Mean Temperatures

Unread post by spwill »

What do people here think about max + min / 2?
If you have warm NW for an hour followed by cold southerly for 23 hours, would the average temp be a good reflection of the day ?

Also with higher dewpoint conditions over northern NZ temps tend to stay closer to the max longer as moist air is slower to release warmth.
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Re: Mean Temperatures

Unread post by NZstorm »

Yes, the 'traditional mean' has its weaknesses but I think for most days it works okay.

I would expect NIWA to be now developing/employing a finer model for future use.
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Re: Mean Temperatures

Unread post by spwill »

Yes, over the long term it would be close enough.
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Re: Mean Temperatures

Unread post by NZ Thunderstorm Soc »

I don't want to be silly or ask a stupid question, but what is the difference betwixt man and average temperature?
Is it the same formula?

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Re: Mean Temperatures

Unread post by David »

NZ Thunderstorm Soc wrote:I don't want to be silly or ask a stupid question, but what is the difference betwixt man and average temperature?
Is it the same formula?
By average they are referring to mean, so they are the same thing
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Re: Mean Temperatures

Unread post by NZ Thunderstorm Soc »

David wrote:
NZ Thunderstorm Soc wrote:I don't want to be silly or ask a stupid question, but what is the difference betwixt man and average temperature?
Is it the same formula?
By average they are referring to mean, so they are the same thing
OK then. I meant mean not man :oops:

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Re: Mean Temperatures

Unread post by David »

My email to J. Salinger of niwa:
> It has been brought up on the NZ weather forum how daily mean temps are
> recorded by metservice/niwa. Is the traditional method still used
> (max+min)/2 or is some other method used now?

His response:
You are correct - the (max+min)/2 is used. This has been used since
climate records began during the 19th century.


That solves the matter then :)
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Re: Mean Temperatures

Unread post by David »

http://www.niwascience.co.nz/__data/ass ... mp_650.jpg
This is interesting - one area had its warmest July to September period on record.
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