(meteorobs) CCNet on meteors

[RainerArlt]

> SCIENTISTS USE METEORS TO INVESTIGATE CLIMATE CHANGE
> ----------------------------------------------------

Thanks for forwarding this very interesting article.
One comments though:

> The mesosphere has been called the miner's canary for climate change; 
> meaning that it is very sensitive and the changes there may be larger 
> than in any other part of the atmosphere. Evidence of these changes 
> comes from sightings of noctilucent clouds, very unusual clouds seen 
> only in polar regions and known to be in the mesosphere.

Visually, these clouds are seen between 45 deg and 60 deg 
northern latitude. They are NOT SEEN above 60 deg because
it does not get dark enough during the summer, and only
during the summer, the temperature of the mesosphere
drops to low enough temperatures. Noctilucent clouds can
be detected at higher latitudes by other means - the
text was a bit misleading. I don't think we live in a
polar region, and we see them every summer (Berlin) ;-)

There has been a long discussion about whether the number
of NLC changes over decades. In a talk on our March meeting
of the German meteor grous, Prof Ulf von Zahn gave a talk on
that topic and came to the conclusion that there is no
statistically profound evidence for a change in NLC
occurrence rate. I think the period covered was ~30-40 years.
Prof von Zahn was the director of the Institute of Atmospheric 
Physics (http://www.iap-kborn.de/index_e.htm), Germany. They
have conducted mesosphere observations by radar and LIDAR 
(laser beam element detection and ranging) for ~10 years now.


Rainer


-- 
Rainer Arlt  --  Astrophysikalisches Institut Potsdam -- www.aip.de
Visual Commission - International Meteor Organization -- www.imo.net
rarlt at aip.de --  phone: +49-331-7499-354  --  fax: +49-331-7499-526