[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[McIDAS #OXG-395498]: conversion of lac level1b to area format

Hi Marc,

re: assumption that McIDAS AREAs made from level 1b data work in McIDAS-X

> Yes, he also made IR and VIS images from it.

Very good.

re: McIDAS Lite can not read Level 1B "formatted" files directly

> > Ok, and I don't think it can read those leve 1b either.

re: do you have one or two examples of converted images that I could take
a look at
> Well I am still not able to read it in Mcidas V. I do have one file that
> he converted to AREA format but I am in the US right now without any FTP
> setup.


> I will be back in Switzerland next week but in the meantime, if you are
> there, would you have any way for me to send the file to you to check it?

Depending on the size, you could send me 1 image via email.  If you decide
to do this, please send the image to my personal email address,

re: What do you mean by "cloud information"?

> Well I mean cloud information as to retrieve the cloud-base-heights
> (or cloud-top-heights) from the images using Mcidas V. I am trying to
> retrieve these parameters to verify the height of the PBL and to infer the
> cloud rolls height. Actually, I am collaborating with a colleague and the 
> poster
> is due near the end of this Janurary.


> > My friend said that Mcidas cannot do this type of analysis. I would need an
> > algorithm to do this. Is this true?

The images themselves can not provide either cloud base/top height.  The IR
images simply provide the temperature of the layer of clouds being viewed.  In
order to interpret the values, one must understand use the weighting function
for the channel being viewed (e.g., 10.7 um for the BAND=4 images from GOES, 
and possibly have soundings that relate the thermal profile to height above
ground.  This, I believe, is what your friend was referring to.

> Ok, if there is a way to retrieve the cloud-base-heights from the AREA format
> files that would be great using Mcidas V. Let me know if this is possible.

It is not directly possible to infer the cloud base/top heights from satellite
imagery directly.  This is not a failing of McIDAS-X/-V, but, rather, a simple
fact.  Products that depict the cloud base/top heights are created using 
of images in multiple wavelength channels (which have different weighting 
and possibly temporally close sounding data or model output.

You may want to read through the web pages from the Cooperative Institute for
Meteorological Satellite Studies (CIMSS) of the Space Science an Engineering
Center (SSEC) at the University of Wisconsin-Madison for more information on
what is involved in creating products like cloud-top pressure:

CIMSS HomePage

  The CIMSS Realtime GOES Page

    Cloud Top Pressure

 "Cloud Products Derived from the GOES Sounders

  Combined GOES-East and GOES-West Cloud Top Pressure 

  Cloud top pressure (CTP) is derived from GOES-East and GOES-West Sounder
  radiance information routinely at hourly intervals. Calculations, using the
  CO2 Absorption Technique, are made at each field of view. The image is then
  color enhanced to display 50 hPa intervals where clouds have been identified.
  Due to the low-level atmospheric signal being dominated by surface emissions,
  this technique is less reliable for near surface clouds. For a more detailed
  explanation of this technique, see the CIMSS GOES Automated Service Observing
  System (ASOS) page. 

  A wider view of the CTP DPI is obtained using all available sectors observed
  from both the GOES-East and GOES-West Sounders."

> Thanks again for your help!

No worries.


Unidata User Support                                    UCAR Unidata Program
(303) 497-8642                                                 P.O. Box 3000
address@hidden                                   Boulder, CO 80307
Unidata HomePage                       http://www.unidata.ucar.edu

Ticket Details
Ticket ID: OXG-395498
Department: Support McIDAS
Priority: Normal
Status: Closed

NOTE: All email exchanges with Unidata User Support are recorded in the Unidata inquiry tracking system and then made publicly available through the web. If you do not want to have your interactions made available in this way, you must let us know in each email you send to us.