[meteorite-list] Multiple radar hits for 8 August 2011 Ohio bolide

From: Matson, Robert D. <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Fri, 26 Aug 2011 19:33:45 -0700
Message-ID: <9180F6B27399C541B10663E21C8BDE92029F4938_at_0461-its-exmb09.us.saic.com>

Hi All,

Not exactly a timely e-mail, but I thought I'd post my radar analysis of
the August 8th, 2011, Ohio bolide with the MetList. (On Tuesday I sent this
analysis to Peter Brown, Bill Cooke, Donald Yeomans, SpaceWeather.com and a
half dozen others, but since this potential fall is likely of more general
interest, I thought I'd repost it here.)

Marc Fries was quick to concur with Bill Cooke's initial radar analysis,
and augment it (off-list) with additional data showing the tell-tale
signs of upper atmospheric turbulence at the location of the fall. I
concur with Marc's and others' assessments that this likely did produce
meteorites on the ground, though it is not a significant fall like Park
Forest, Ash Creek (West, TX) or Mifflin. I was able to add some significant
new data that confirms Bill's original KCLE radar returns.

To recap, Bill's triplet of more-or-less linear returns was at the 10-degree
cut angle from the KCLE Doppler radar which began its scan at 5:21:25 UT.
The 10-degree cut angle was the 14th scan of 17 taken in that sequence, and
the returns are all at an azimuth (from the radar) of around 91 degrees. A
rough estimate of the timing of those specific returns is 5:24:43, or about
2 ? minutes after being recorded by All Sky cameras. So the radar and camera
data are in good agreement.

Here are approximate coordinates of the centers of those three returns:

KCLE, 10-degree cut angle, ~5:24:43 UT 8/8/2011
80.617 W, 41.400 N (18.8 km alt)
80.496 W, 41.396 N (20.7 km)
80.396 W, 41.375 N (22.3 km)

A single bolide-related return is ALSO visible during the 5:25:36, 4-degree
cut angle scan:

KCLE, 4-degree cut angle, ~5:27:58 UT 80.294W, 41.433N (10.2 km)

There are additional returns during the 5:29:54 scan, but they may be
spurious. One is at high altitude (20.3 km) in the 6.4-degree cut angle
_at_ around 79.872W, 41.461N. But given that this is around 10 minutes after
the fall, the most it could represent is meteoric dust.

I did find high-altitude returns in two additional radars: KILN (Cincinnati)
and KCCX (State College, PA):

KILN, 3.1-degree cut angle, scan start at 5:23:18, approx. hit time: 5:25:19
80.916 W, 41.461 N (25.5 km)

I've saved State College for last because it is the most impressive. It records
not only the earliest returns, but also the highest altitude one. It also shows
the greatest persistence, appearing in three separate scans:

KCCX, 4-degree cut angle, scan start at 5:19:58, approx. time of hits: 5:22:55
[EARLIEST HITS RECORDED BY RADAR]
80.978 W, 41.675 N (22.7 km)
80.706 W, 41.235 N (19.4 km)

6.4-degree cut angle, scan start at 5:19:58, approx. hit time: 5:23:31
80.528 W, 41.181 N (26.8 km = 88 kft) [HIGHEST ALTITUDE HIT]

3.1-degree cut angle, scan start at 5:23:35, approx. hit time: 5:26:13
80.398 W, 41.202 N (13.7 km)

The State College radar does occasionally show some noisiness that tends to be
isolated to a particular azimuth of a scan, so I'm not sure the following
returns are real or spurious. However, they are proximal to the Cleveland
returns, so I've included them here:

0.9-degree cut angle, scan start 5:27:11, approx. hit time: 5:28:01
80.650 W, 41.380 N, 6.8 km
80.624 W, 41.375 N, 6.7 km
80.596 W, 41.371 N, 6.6 km
80.574 W, 41.368 N, 6.5 km

It can be confusing trying to correlate all of these hits without first
computing the actual times that each return was detected, and then accounting
for upper atmospheric wind drift. I pulled the radiosonde data for Pittsburgh
at the closest times bracketing the time of the fall (0 UT and 12 UT). At the
early time, the peak winds were around 55 knots at 300 mbar coming out of
azimuth 260. So drift at that time would have been 10 degrees north of east.
At the later time, winds were noticeably higher at around 87 knots out of
azimuth 265. If anyone wants the full radiosonde data by altitude, just let
me know and I'll send it your way.

Cheers,
Rob Matson
Science Applications International Corp.
Seal Beach, CA
Received on Fri 26 Aug 2011 10:33:45 PM PDT