2002 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 5 12 7 5 16 18 0 7 9 7 9 1 96 Monthly Average: 8.0 Partial 8 4 7 5 6 0 0 5 6 6 5 9 61 Monthly Average: 5.1 Spectroscopic 2 4 5 4 4 7 9 5 2 2 4 3 51 Monthly Average: 4.3 Cloudy 16 8 12 16 5 5 22 14 13 16 12 18 157 Monthly Average: 13.1 ------------------------------------------------------------------------------- Clear Hours 121 148 105 71 153 126 0 81 116 105 108 81 1215 Monthly Average: 101 Clear+Dark Hours 74 63 53 26 86 80 0 34 37 76 40 50 619 Monthly Average: 52 Mean Consec 1.2 2.4 2.3 1.2 2.3 6.0 0 1.8 2.3 1.8 1.8 1.0 Monthly Average: 2.0 Max Consec 2 5 3 2 6 14 0 3 6 3 2 1 Monthly Average: 3.9 ------------------------------------------------------------------------------- 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.