2003 Flagstaff Nighttime Cloudiness Summary Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Yr (nights) Photometric 6 4 8 6 5 13 7 2 14 10 4 5 84 Monthly Average: 7.0 Partial 8 4 7 12 3 6 1 5 1 8 2 5 62 Monthly Average: 5.2 Spectroscopic 4 0 4 4 10 7 2 4 3 4 6 4 52 Monthly Average: 4.3 Cloudy 12 20 12 8 13 4 21 20 12 9 18 17 162 Monthly Average: 13.5 ------------------------------------------------------------------------------- Clear Hours 124 76 117 121 47 120 49 41 138 143 58 84 1118 Monthly Average: 93 Clear+Dark Hours 56 45 90 68 23 67 26 34 73 61 44 36 623 Monthly Average: 52 Mean Consec 1.0 1.3 2.7 1.2 1.2 2.6 3.5 2.0 2.8 2.5 1.0 1.2 Monthly Average: 1.9 Max Consec 1 2 4 2 2 4 4 2 6 4 1 2 Monthly Average: 2.8 ------------------------------------------------------------------------------- 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.