[Rhodes22-list] Radar FAQs

[Mark Kaynor]

Bob,

I think it's a bit different than your binocular analogy. Not so much "close
vs. long range" as <some other analogy I haven't come up w/ yet>. The
following is from the web site:

"Base reflectivity only shows reflected energy at a single elevation scan of
the radar. Composite reflectivity displays the highest reflectivity of ALL
elevations scans. So, if heavier precipitation is higher in the atmosphere
over an area of lighter precipitation (the heavier rain that has yet to
reach the ground), the composite reflectivity image will display the
stronger dBZ level."

"This occurs often with severe thunderstorms. The updraft, which feeds the
thunderstorm with moist air, is strong enough to keep a large amount of
water aloft. Once the updraft can no longer support the weight of suspended
water then the rain intensity at the surface increases as the rain falls
from the cloud."

So, it seems to me that base reflectivity is like looking at a single slice
of atmospheric info, generally near the ground, from the radar source to
about 5 degrees above the horizon.

Composite reflectivity, on the other hand, shows the highest reflectivities
from several slices at several elevations. Also from the web site: "When
compared with Base Reflectivity, the Composite Reflectivity can reveal
important storm structure features and intensity trends of storms."

This is pretty cool stuff - I've never really thought what those nifty radar
images are actually showing before.

Mark



-----Original Message-----
From: rhodes22-list-bounces at rhodes22.org
[mailto:rhodes22-list-bounces at rhodes22.org]On Behalf Of Bob Weber
Sent: Friday, September 05, 2003 11:35 AM
To: rhodes22-list at rhodes22.org
Subject: Re: [Rhodes22-list] Radar FAQs


Mark, thanks for the oppertunity to learn.  From reading the article it is
my understanding that the Base / Composite Reflectivity are on opposite ends
of the radar return attenuation.  Kinda like the knob on your binacullars.
On one setting you see the close up things best on the oppisite setting you
see the outer limits of the lenses'.  Probably overly simplistic but "simple
is as simple does".  Bob Weber


>From: "Mark Kaynor" <mark at kaynor.org>
>Reply-To: The Rhodes 22 mail list <rhodes22-list at rhodes22.org>
>To: <rhodes22-list at rhodes22.org>
>Subject: [Rhodes22-list] Radar FAQs
>Date: Fri, 5 Sep 2003 10:32:25 -0400
>
>I was looking at our local weather radar on the NOAA site this morning and
>got to thinking "What does 'base reflectivity' mean?"
>
>I clicked around the site and found a pretty good explanation about weather
>radar and radar in general in fairly easy to understand layman's terms - I
>found it very helpful, being a complete radar novice myself, and figured
>I'd
>share it.
>
>http://www.srh.noaa.gov/radar/radinfo/radinfo.html
>
>Mark Kaynor
>
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