NavList:

   

Reply

As a mostly silent member of this list, I may eventualy add something
to this subject.

I'm interested in refraction near the horizon. For this I regularly
observe sunset events.

The amount of cloud cover depends to a large extend on the temperature
(and of course also on the atmospheric pressure). As higher the
temperature as more the air can absorb humidity and thus reduce the
number of clouds.

At my present location at about 40N the clouds mostly disappear during
summer days due to the high temperatures of around 30C. During this
time a lot of observations are therefore possible. This changes
drastically during the colder seasons where the number of days with
unobstructed sunsets become rare. This seasonal dependency is trivial,
we all know it from our own experience.

However, in addition to this seasonal cycle exists also the daily one,
i.e. the temperature has also a more or less pronounced diurnal cycle.
The highest temperature within a day occurs generally about 2 to 3
hours after the sun's transit. In the case of a circumpolar sun it's
about 1 hour. The lowest temperature within the diurnal cycle occurs
between about 0 to 1 hour before sunrise and about 1 hour after the
lower transit in case of the circumpolar sun.

The behaviour of the diurnal temperature cycle suggests that the
chances for finding a hole in a totally covered sky are probably best
in the afternoon.

Marcel

--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---

   

Reply