[AZ-Observing] 2003 Flagstaff nighttime cloudiness
- From: Brian Skiff <Brian.Skiff@xxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Thu, 1 Jan 2004 12:13:37 -0700 (MST)
The table below shows the Flagstaff nighttime cloudiness summary for 2003.
It was about an average year, slightly low in total clear nights but close
to the long-term average for total clear hours (reckoned in minimum three-hour
chunks). Though May was poor, the other usually-good months (June, September,
October) were okay.
This is the 25th year for which I have complete data taken in what I hope
is a consistent manner. (And again I wish I'd started recording it the day I
arrived five years prior.) Just looking at the clear nights (viz. completely
cloudfree from dusk-to-dawn), the average is 93 such nights per year with
1-sigma scatter of +/- 20. For total clear hours, the figures are 1088 +/- 131.
By the more usual reckoning, you can sum the all photometric, partial, and
spectroscopic nights, plus some fraction of the nights I call 'cloudy' to get
the number of 'useable' nights---there really aren't very many nights where
you can't obtain data of some sort for a couple of hours. By way of example,
being ready to use short clear spells during the night, Lowell visitor
Mike Jerzykiewicz did photometry at the 21-inch on nearly 50 nights between
early September and late November, far more often than would be implied by
the numbers below. (He's also got what it takes to keep up that kind of pace!)
These annual summaries and the nightly data can be obtained from the Lowell
Web site starting at:
http://www.lowell.edu/cgi-bin/www/clouds/clouds.cgi
\Brian
================================================================================
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.
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