[AZ-Observing] Flagstaff 2002 nighttime cloudiness
- From: Brian Skiff <Brian.Skiff@xxxxxxxxxx>
- To: amastro@xxxxxxxxxxxxxxx, avondale@xxxxxx,az-observing@xxxxxxxxxxxxx, janes@xxxxxxxxxxxxx, jorstad@xxxxxx,staff@xxxxxxxxxx
- Date: Wed, 1 Jan 2003 13:03:50 -0700 (MST)
Well, the numbers are in on local nighttime cloudiness. The number of
fully clear nights in 2002 was nearly identical to the long-term average
(94 +/- 21 nights over the last 24 years), but because of a large number of
what I call 'partial' nights, the total clear hours was +1 sigma above the
mean (which is 1087 +/- 134 hours). If we hadn't got 10 significant winter
trough passages in December, including one on New Year's Eve, the totals could
have been quite a bit better. May and June were the best months, as is
typically the case; the mid-September to mid-November dry season was not in
the running this year. July yielded a goose egg for the clear nights/hours
tally.
It is worth noting again that my reckoning is quite conservative.
A recent example is Dec 30/31: the night started out with cirrus thin enough
that I observed for several hours with the LONEOS camera, picking up close to
1500 asteroids; lower overcast came in later, and in my scheme I regard this
as a 'cloudy' night. The point all along has been to count the clear
nights/hours and not to finess degrees of cloudiness, such as having a category
for 'partly spectroscopic' nights as this night was. By summing the first
three categories you can get a good idea of the number of 'usable' nights for
different sorts of astronomy---over 200 this year---plenty of opportunity for
observing.
The nightly data in this summary (and the annual summaries, too) are
available at the Lowell Web site, starting at:
http://www.lowell.edu/cgi-bin/www/clouds/clouds.cgi
\Brian
================================================================================
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.
--
See message header for info on list archives or unsubscribing, and please
send personal replies to the author, not the list.
Other related posts:
