[Cosmic_announce] (no subject)

[Doug Hunt]

Greetings:

Recently it was found (thanks to Christian Marquardt from EUMETSAT)
that the filtering used in our inversion software produces a bias
in retrieved bending angles. This bias is seen mainly above 10-20km
and its magnitude is of order of 0.1-0.2%. This bias is due to second
derivative of the excess phase as a function of time. This bias
propagates into the retrieved refractivity and, subsequently, into
other retrieved profiles. We will be replacing the filtering which
reduces the bias by several decimal orders of magnitude.

Concurrently we will be making another change by fixing the transition
height between geometric optics and radio holographic processings
to ~20 km (currently this height is determined individually for each
occultation and can be anywhere between ~10 and ~20 km). The purpose
of this change is to aid studies of the structure of tropopause by
providing the vertical resolution of about ~0.1 km below 20 km for
all occultations.

Both these changes are not yet included in our real time processing.
The data, BUFR files for November-December 2008, processed with
these changes are available at:

http://www.cosmic.ucar.edu/~dhunt/BUFR_with_new_filtering/

for testing in data assimilation systems. We would appreciate your
feedback. We would like to include these changes in our real time
processing in about 2 weeks. Later, we will re-process all our data
for all missions.

Best Regards,

   Doug Hunt

dhunt at ucar.edu
Software Engineer IV
UCAR - COSMIC, Tel. (303) 497-2611