On Wed, 23 Sep 2015 09:13:46 -0700 (PDT)
Len Wood wrote:
In the northern hemisphere, the maximum temperature occurs near the
end of the third week of July and the minimum near the third week of
January. These are only a few days from the mid-point of the
meteorological seasons.
If the astronomical calendar is used, the middle of summer would be
at the end of the first week of August with mid-winter's day being
at the end of the first week of February. Also, December would be
largely an Autumn month and March would be a Winter one. The
astronomical calendar just doesn't tally with climatological
reality.
'In the northern hemisphere, the maximum temperature occurs near the
end of the third week of July and the minimum near the third week of
January. These are only a few days from the mid-point of the
meteorological seasons.'
------------------------------------------------------------------------
I am not sure this statement is true in general for the N Hemisphere.
For example, Helsinki has on average its lowest temperatures in
February. Even more so the further north you go.
http://www.worldclimate.com/cgi-bin/...24+1102+02974W
Also, people's perception of the seasons varies greatly.
You try telling a Fin in Finland that Spring begins on 1st March or
21st March for that matter.
Those dates are correct (within plus or minus 5 days) as an average of
stations in the northern hemisphere which have at least one month per
year with a mean temperature near or below 0C. How do I know that?
Because it's those stations that I used when working out those dates
fifty years ago. Unless global warming has somehow added a delay
factor, I think they should still hold true. ;-)
The reason for +/-5 days is that the dates had to coincide with the last
day of ten-day periods beginning on 1st January. This means that the
date for July should have been the 19th and not the 20th. The reason
for calculating these dates was that we needed fixed dates for the
start of the positive degree-day season after mid-winter and the same
for the negative degree-day season after mid-summer.
--
Graham P Davis, Bracknell, Berks. [Retd meteorologist/programmer]
http://www.scarlet-jade.com/
I wear the cheese. It does not wear me.
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