Date:         Thu, 28 Feb 2008 10:42:49 -0500
Reply-To:     Chris Lambrecht <chrisl@INTELLMKT.COM>
Sender:       Georgia Birders Online <GABO-L@LISTSERV.UGA.EDU>
From:         Chris Lambrecht <chrisl@INTELLMKT.COM>
Subject:      Radar Images of Bird Migration
Content-type: text/plain; charset="US-ASCII"

I thought this message pulled from the Texas Listserv is worth repeating:

Texbird help file http://www.texbirds.org <---

As in the past several years I will be posting a daily, or nearly so,
analysis of spring bird migration as observed by NEXRAD radars along the
Gulf Coast and selected inland locations in the southern states. Migration
traffic is not significant enough to observe before about mid March. I often
get questions about how to analyze the NEXRAD images broadcast on the
Internet. If this really fascinates you (as it does me) I wrote the
following brief summary for a friend and I thought it would be worth
repeating here.

I would first direct you to the Clemson University Radar
Ornithology website http://virtual.clemson.edu/groups/birdrad/. They have a
great introduction to NEXRAD and how it can be used to observe migrating
birds.NEXRAD is available on the internet at a number of sites. The most
Useful ones for observing bird migration are http://www.weathertap.com, a
subscription site (about $75 a year) that I use mostly, and
http://www.rap.ucar.edu/weather/, a free site.

Since distinguishing birds from other targets requires knowing the wind
direction and speed in the UPPER atmosphere (not at the surface) you must
also consult http://weather.uwyo.edu/upperair/sounding.html. Click on the
nearest station to your location and check the 850 hP level direction and
speed. That is the most useful elevation for judging bird migration. Note
that the VAD wind profiles that can be observed as an option using NEXRAD
are NOT usable for judging the presence of birds although they can provide
other useful information About what is going on in the atmosphere. Birds,
bats, and other animals with powered flight will be moving significantly (at
least 10 kts.) faster than the wind speeds.Targets moving at observed wind
speeds will be dust, pollen, smoke, most insects, etc., that are being
passively carried on the winds.

I hope you find this information useful.

John C. Arvin
Research Coordinator
Gulf Coast Bird Observatory


Chris Lambrecht
Atlanta

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