More exact monthly means...
By Eco Guy
5:19am 23rd April 2010
Following up with more data set pairs showing the difference in accuracy between min/max daily monthly means and taking the mean of all hourly measurements in that month..
For details of the method employed see What exactly is a monthly mean?
Data Pairs used
The following data pairs from the GCHN and SCRAM records were usedSanta Barbara/FAA Airport CA23190 -> 42574606001
Red Bluff/Municipal Airport CA24216 -> 42572591000
Fresno/Air Terminal CA93193 -> 42572389000
Scottsbluff/Country Airport NE24028 -> 42572566002
ISLIP/Long Island NY04781 -> 42572501001
Memphis/Intl Airport TN13893 -> 42572334000
Yakima/Air Terminal WA24243 -> 42572781000
Lander/Hunt Field WY24021 -> 42572576000
Lexington/Bluegrass Field KY93820 -> 42572422000
Chicago/O'Hare Int'l Arpt IL94846 -> 42572530000
ResultsPlease see this page for the results
This is purely done to allow me to better present the results, than trying to force them through the post mark-up.
Conclusions that can be drawn
The larger set of results show some interesting commonalities:
- The previous assertion, namely:
Looks to be holding up well across all the data set pairs. This indicates to me something significant is occurring.
- "The exact mean value is able to often 'stray' by greater than 0.2 away
from the GHCN data set value whilst the derived value remains in scope
(i.e a * in the fair right column, but none in the third). To me this
indicates the daily min/max mean approach is often incorrectly
representing the real distribution of temperatures in the month; which
is not that much of a surprise as the daily min/max only uses a maximum
of 62 contributing data points, compared to the exact mean that uses up
to 744 contributing data points (or 10x plus the effective resolution)."
- The 'Net temp diff' looks to be trending up from the beginning of the samples to the end, I will have to extract and plot to confirm - but looks like there is a 'warming' baked in some how; perhaps the min/max method fixates too much on the daily limits compared to the total temp frequency over the day??
Basically, more food for thought; need to extend this to a larger data set and codify for significance.
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