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[McIDAS #QBR-849370]: (No Subject)



Hi Boris,

Sorry for the silence on your previous inquiry.  I am involved in something 
that has
a very short deadline (end of Wednesday), and I don't have the time to answer
questions in the depth that they deserve.

re:
> I have a case where an image has been deployed using data from bright (0-255) 
> and
> I selected a shade to tell me the regions of CAPE (Convective Available 
> Potential
> Energy) like in attached. My question is: how I can adjust these brightness 
> values
> ??to actual values ?? of CAPE.

FYI: your email did not include an attachment.

The calculation of CAPE is not simple -- it requires use of several image
sounder channels in a full physical retrieval.

Unfortunately I do not know how to create a CAPE product from the sounder
channels available on GOES.

The folks at SSEC/CIMSS, on the other hand, do know how to create CAPE products
using sounder channels from GOES in a physical retrieval.  Their website shows
examples of CAPE products that they create:

http://cimss.ssec.wisc.edu/goes/rt/viewdata.php?product=ce_us

The description that is available in the link at the bottom of the
above page refers in general terms to the process used by CIMSS
to create CAPE displays:

 "A look at the Convective Available Potential Energy (CAPE) as derived
  from the GOES-East and GOES-West Sounders is provided each hour. This
  is a new experimental feature in the suite of DPI displays. Recall that
  the nominal GOES Sounder field-of-view (fov) is 10 km at the satellite
  sub-point. Spatial averaging over a 3x3 fov box is currently employed
  to increase the signal-to-noise. This image is derived from the full
  physical retrieval algorithm.

  However, please note that this image is a "pseudo" DPI, having been
  re-created after the fact in a image format from the CAPE values available
  from the 3x3 retrievals, along with use of the 11um window channel (for
  those areas where no retrievals were made). The CAPE product displayed is
  an atmospheric stability parameter for a given vertical thermodynamic profile,
  which indicates the amount of positive (buoyant) energy available to an
  idealized parcel, ascending from the Level of Free Convection (LFC) to the
  Equilibrium Level (EL). The larger the value (or the "positive-energy area"
  under the parcel curve on a thermodynamic diagram), the more unstable would
  the atmosphere be. A CAPE of 1500 J/kg would indicate a modestly unstable
  airmass. The values are color-coded with brown/beige>blue>yellow at the more
  stable end while red>magenta/purple would indicate considerably more potential
  instability. (Note that transitions between colors 
beige/blue/yellow/red/magenta
  occur at CAPE values of 1000, 2000, 3000, and 4000 J/kg respectively). This
  enhancement table is experimental and suggestions for improvement are welcome.
  A time sequence of the images remains the best way to monitor stability 
trends."

re:
> If there is any formula, can guide me to convert the brightness values ??
> to units of CAPE?

Since there was not image attached to your email, I don't know if you
have created a CAPE product from multiple GOES sounder channels, or if
you are thinking that one can identify/quantify CAPE values directly
from satellite images (you can't, it is unfortunately not that easy).

I suggest doing some web searches to see if you can find documentation
on how to create CAPE (and other) products using information from
satellite sounders.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: QBR-849370
Department: Support McV
Priority: Normal
Status: Closed


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