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

[McIDAS #CLT-967906]: update and some questions

Hi Ioan,

re:
> Thanks for correcting me here.

No worries.

re:
> I reviewed the
> https://www.goes-r.gov/products/ATBDs/baseline/Imagery_v2.0_no_color.pdf
> and, the  kappa can be used for the same purpose.

The kappa value can be used to calculate albedo from radiances
(albedo = kappa * radiance)for the VIS channels.

re:
> I might be asking too much but could you provide me with some hints on how
> does McIDAS X do the calibration ???.

My day today was consumed by trying to find a bug in a script that files
GOES-16 L2 products using information it gets by cracking (parsing 'ncdump -h')
the netCDF4 files that contain the product.  I think the problem is a bug in how
BASH does regular expression matching in strings...

re:
> I use the scale factor and offset to create radiances 

A quick look at the McIDAS calibration module shows that it does also.

re:
> and the  esun and
> earth_sun_distance_anomaly_in_AU to compute reflectance.

The McIDAS calibration module does not calculate reflectance.  The calibrated
values (from IMGPROBE) for pixels from VIS images (bands 1-6) are:

RAW, RAD, ALB, BRIT

How are you using esun and earth_sun_distance_anomaly_in_AU to calculate
reflectance?

re:
> I am now unsure if I do it correctly. According to my understanding (from
> the above doc) if I multiply radiances with kappa I get reflectances.

McIDAS is calling that product albedo (appropriately scaled to 0 - 100%).

re:
> Perhaps McIDAS X converts scaled radiances or counts to reflectance
> directly.

McIDAS converts raw values to radiances using the scale and offset
and then radiance to albedo for VIS channels and equation 3-5
to convert radiances to temperatures.

re:
> All the best

Does the above help at all?

Cheers,

Tom
--
****************************************************************************
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: CLT-967906
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.