1987 Flagstaff Nighttime Cloudiness Summary


                 Jan  Feb  Mar  Apr  May  Jun  Jul  Aug  Sep  Oct  Nov  Dec  Yr
                              
                                        (nights)
           
Photometric        5    4    6    3    4   10    9    4    3    8    3    2   61
                                                                             5.1

Partial            5    2    4    3    5    3    4    3    8    4    9    6   56
                                                                             4.7

Spectroscopic      4    3    5   11    5    8    4    2    6    5    5    5   63
                                                                             5.2

Cloudy            17   19   16   13   17    9   14   22   13   14   13   18  185
                                                                            15.4

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Clear Hours       95   57   90   45   57   82   87   50   77  105   99   64  908
                                                                            75.7

Clear+Dark Hours  27   46   67   28   44   42   52   31   42   35   74   27  515
                                                                            42.9

Mean Consec      1.2  1.3  1.5  1.5  1.3  2.5  2.3  2.0  1.0  1.6  1.0  1.0   -
                                                                             1.5

Max Consec         2    2    2    2    2    4    4    3    1    3    1    1    4
                                                                             2.2

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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.