Newsgroup: it.scienza.fisica
Titolo: Risonanza siderale nella temperatura

Ho fatto un lavoro che sembra mostrare una risonanza della temperatura
con il giorno siderale. E' basato su due anni di raccolta dati.
Scusatemi se posto il messagio in inglese, ed in un rozzo inglese, ma
se dovessi riscriverlo in italiano forse non lo posterei. Ma si
capisce.
Saluti,
Antonio Iovane
A two year test on temperature, made in my lab, would show an apparent
resonance
of temperature with the sideral day, as important as 0.06 degrees
centigrade
peak to peak.
As a control measurement for a primary test, I' ve been collecting
temperature
data in my lab for two years (from april 23 2002 to april 17 2004).
The
data points are 10 seconds spaced, and the two year file contains
about
6,530,000 data points. Moreover, for noise reduction, each data point
results
from 100 samples taken in about 2 seconds, and only the average is
stored
every 10 seconds.
I' ve made some exercises on the above data using a method of
reduction
described below, and found the surprising curves shown in
http://xoomer.virgilio.it/iovane
 (there select the proper link).
The method I' ve used seeks for specific resonances, and cancels
dramaticly
the noise and unwanted periodicities. The resulting plots are quite
clean.
In practice, for any examined periodicities, I' ve segmented the input
file
in n files, each being long the specified period (as an example, solar
day,
sideral day, random periods).
Reference being made to the plots, the shown time scale (hours)
represents
UT solar time for curve D, and local sideral time for curves A B and
C.
Notice that the lab (in the basement) is mostly unattended, and the
daily
fluctuation of temperature is limited between a few tenths of °C peak
to
peak including noise.
Let's start with a comment on curve D. It has been obtained dividing
the
input file in about 720 files each being one solar day long. The files
have
been superimposed, averaged and plotted. So, each point in the curve
is
the average of 720 data points taken at the same time in the solar
day.
This curve shows the average daily cycle of temperature in the lab in
two
years.
The Y axis covers 0.14 °C and the standard dev is 0.040211 °C. The
negative
peak denotes the average sunrise. Notice that for me (UT+1) 06:00
means
07:00 local, and this confirms me that I have some mountains at East
and
no nearby buildings. The time of the positive peak instead confirms
that
I have a nearby building at West.
Running the exercise with the same input file and a period of a
sideral
day (23h56m04s(see note)), skipping some initial records to get phased
with
the sideral day, the resulting curve is the black one in C. It is
phased
with the Local Sideral Time.
The Y axis covers 0.1 °C, the peak to peak variation is about 0.06 °C
and
the std dev is 0.022289.
The colored curves will be explained below.
Then I divided the input file in two one-year files, keeping the
phasing
with the sideral time. The exercise, made on year 1 and year 2, gives
the
curves A and B respectively.
In both curves the Y axis covers again 0.1 °C, the peak to peak
variation
is again about 0.06 °C and the std dev is respectively 0.023185 and
0.022295
°C.
Let' s come to the colored curves in C.
I' ve made the exercise with some random periodicities, obtaining
quite
flat curves. The shown colored curves rely on periodicities close to
the
sideral and solar day.
The RED curve is for a period of one sideral day minus 2 minutes. The
std
dev is 0.004911.
The GREEN curve is for a period of a sideral day plus 2 minutes, or,
if
you want, a solar day minus 2 minutes. The std dev is 0.007576.
The BLUE curve is for a period of a sideral day minus 2m40s. It is
quite
flat. The std dev is 0.002492.
In summary, the std dev peaks at the sideral day and solar day with
quite
clean curves.
The orientation of the peaks in A B and C is given in right ascension
directly
by the time scale shown between C and D.
(note): given the 10 seconds spacing, in the sideral exercise a datum
has
been skipped every 2.5 days in order to compensate for the extra 4
seconds
of the sideral day.
I' m not still shure that this work may have any value, and would like
to
read your comments.
Regards,
Antonio Iovane

 capisce.
Direi che si tratta semplicemente di un effetto di "aliasing".
Certamente c'e' un andamento stagionale della temperatura, col periodi
di un anno.
Con la tua tecnica di analisi questo periodo non lo puoi vedere, ma lo
vedi trasferito in un'altra regione dello spettro.
La cosa si capisce bene parlando di frequenze anziche' di periodi: se
f1 e' la frequenza corrispondente a un forno solare, f2 quella per un
giorno siderale, f3 quella per un anno, c'e' la relazione f2 = f1 +
f3.
Tu non puoi vedere f3, ma vedi f2.
Puoi convincertene, senza calcoli teorici, costruendo una serie
artificiale di dati, che abbiano solo la variazione annua, e
analizzandoli come hai fatto.
------------------------------
Elio Fabri
Dip. di Fisica - Univ. di Pisa
------------------------------
From 

 analizzandoli come hai fatto.
Non dovrebbe bastare, forse dovrei costruire una serie artificiale
contenente due frequenze, e' cosi? I calcoli comunque li ho fatti, ed
hai ragione.
Tuttavia non vorrei gia' buttare via questa serie di dati di due anni.
Se si volesse cercare una incidenza siderale nella temperatura, ben
sotto il rumore, non si potrebbe fare la misura in un ambiente
controllato, e si dovrebbe necessariamente soffrire la variazione
annuale e giornaliera.
Vorrei poter rimuovere dai dati almeno una delle due frequenze.
Conosci qualche metodo, almeno concettualmente? Ho pensato di
sottrarre i valori della curva giornaliera mediata dai corrispondenti
valori di ciascun giorno solare. Secondo te puo' funzionare?
Grazie anticipatamente e cordialita'.
Antonio Iovane