[email protected] wrote:
> I've got a question about how best to average temperature readings.
> There is the simple arithmetic average, +50C and -50C then average to
> 0C. But, I've been thinking if radiation is dependent on T^4, then
> shouldn't the average instead be calculated by (((273-50)^4+(273+50)
> ^4)/2)^0.25-273, which works out as 12.9C?
Well it depends on what you are trying to do. If you are interested in
the outgoing radiation, then using 4th powers may be meaningful
(although even then one would have to be careful about what the
temperature data represent, since the surface does not lose heat through
radiation alone). A farmer may be more interested in the growth of his
crops over a season, in which case the integrated temperature above a
threshold may be more relevant than the arithmetic average (-5C and -1C
are the same to most crops, so long as they do not actually die).
So long as the deviations are small, the simple arithmetic average
(basically the direct integral of the temperature, with no exponent or
thresholding) will usually be close to what you might get from any more
convoluted but perhaps application-relevant calculation. IIRC Roger
Pielke Snr tried to make a noise about this wrt global average
temperatures and AGW a year or two ago on his blog, but even if he was
right in principle (I forget the exact point he was trying to make) the
numerical impact seemed pretty negligible.
James
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