[meteorite-list] More exact information about the norwegian fall

From: Chris Peterson <clp_at_meteoritecentral.com>
Date: Wed Jun 14 18:26:43 2006
Message-ID: <038e01c69001$88a639c0$fd01a8c0_at_bellatrix>

Hi Bj?rn-

The important wind data is for higher altitudes. I don't have a good source
for this information in Norway- maybe the weather service? For the American
events I investigate I use radiosonde data produced or collected by NOAA.
This provides wind speed and direction up to 30km height twice daily. It is
usually possible using one or two datasets to get a good estimate of winds
even in remote locations far from active monitoring.

I've only seen one image of the fireball- are there more? That one appeared
to show only luminous trail- nothing like you describe. There doesn't seem
to be a terminal explosion, but rather a large disruption in the middle
(which IMO reduces the likelihood of meteorites). Unless the object makes it
to the ground carrying cosmic velocity, there is always a retardation point
and it isn't possible for any material to continue much beyond this with
much speed. The atmospheric drag forces are simply too large. The point of
retardation is usually where the drag forces are greatest, and material is
decelerating very rapidly- sometimes the forces are greater than the
material strength of the parent body. Forward motion is rapidly lost and the
fall becomes vertical, typically through zones of high wind speed (30-50 kts
or more). So while the fractured material may move one or two kilometers
forward of the retardation point, the winds are sufficient to move it ten
kilometers or more during dark flight. Of course, the higher the point of
retardation, the more effect the wind will have on the position of a strewn
field. So you really do need to have a good handle on the high altitude
winds when investigating these things, especially if you are searching in a
sparsely inhabited mountainous area.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message -----
From: "Bjorn Sorheim" <astrogeo_at_online.no>
To: "Chris Peterson" <clp_at_alumni.caltech.edu>;
<meteorite-list_at_meteoritecentral.com>
Sent: Wednesday, June 14, 2006 3:27 PM
Subject: Re: [meteorite-list] More exact information about the norwegian
fall


Hello Chris,
I just checked some weather charts from that day and time.
It seems at ground level there would be not much more than
5 m/s from southwest blowing at the outskirts of a Low
near Jan Mayen in the Northermost Atlantic.

With winds aloft I have no experience. Any easy way to come up
with a wind profile for that location and time, that is up to 30 k m?

I see on the best meteor photos of this event, that there is a thin line
going completly straight out forward of the big event. Meaning those
particles that
survived continued without retardation. (There seems also to be a small
event
forward of the big one.)
Wouldn't that mean in this and in the general case that some travel (forward
(would like to know the average) is the norm?

Bj?rn S?rheim
Received on Wed 14 Jun 2006 06:26:08 PM PDT