[AZ-Observing] Flagstaff 2004 nighttime cloudiness

  • From: Brian Skiff <Brian.Skiff@xxxxxxxxxx>
  • To: az-observing@xxxxxxxxxxxxx
  • Date: Fri, 31 Dec 2004 21:52:29 -0700 (MST)

     We had a pretty good year in Flagstaff as far as observing weather goes.
The total number of completely cloudfree nights, 102, was typical, but the
number of clear _hours_, about 1200 by my reckoning, was above average at
the +1-sigma level.
     I started keeping this record of the nighttime cloudiness in June 1978,
so this marks the twenty-sixth full year for which I have results.  In 18 of
the 26 years, May or June was our best month (or one or them), with around
15 clear nights.

\Brian

===============================================================================

2004 Flagstaff Nighttime Cloudiness Summary


                 Jan  Feb  Mar  Apr  May  Jun  Jul  Aug  Sep  Oct  Nov  Dec  Yr
                              
                                        (nights)
           
Photometric        5    6    7   10   14   12    5    7   11    8    6   11  102
                                                           Monthly Average:  8.5

Partial            7    3    5    2    4    3    1    5    5    3    0    4   42
                                                           Monthly Average:  3.5

Spectroscopic      3    1    6    5    5   11    6    0    0    4    3    3   47
                                                           Monthly Average:  3.9

Cloudy            16   19   13   13   18    4   19   19   14   16   21   13  185
                                                           Monthly Average: 15.4

-------------------------------------------------------------------------------

Clear Hours       91   86  100  102  129   96   39   83  127  100   68  162 1183
                                                           Monthly Average: 98.6

Clear+Dark Hours  38   27   49   72   53   61    1   27   62   49   27   85  551
                                                           Monthly Average: 45.9

Mean Consec      1.0  1.5  2.3  2.5  2.3  2.4  1.7  1.8  2.8  1.6  2.3  2.2
                                                           Monthly Average:  2.0

Max Consec         1    3    3    5    5    4    2    4    4    3    3    3
                                                           Monthly Average:  3.3
-------------------------------------------------------------------------------

Definitions:

Photometric  -  cloudfree dusk-to-dawn.
Partial  -  at least 3 consecutive cloudfree hours during the night.
Spectroscopic  -  less than about 1 mag. extinction throughout the night.
Cloudy  -  cloudy.

Clear+Dark Hours = photometric hours with moon absent.
Mean Consec = mean number of consecutive photometric nights during the month.
Max Consec = maximum number of consecutive photometric nights during the month.
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