id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
424	Problem with ropp_fm_bg2ro_2d	Ian Culverwell	Ian Culverwell	"Axel von Engeln (EUM) reports
{{{
I am just trying to run the ROPP with the 55 case profiles
generated in a DMI/RUAG/ECMWF study. For that I converted those 
background profiles into ROPP format and then ran it through ROPP8, 
either on the default 300 vertical levels, or the 247 ones. On the 
247 I get this for occultation 18 (index starts at 1):

FATAL ERROR (from set_obs_levels_refrac_247):  GPH iteration failed to converge in 100 iterations

The default run I do is:

ropp_fm_bg2ro_1d WOP_Study_Cases.nc -f -comp -new_op -o Output.nc

When adding the -247L levels in, I get the error above. When
removing ""-comp -new_op"", I already get the error at profile 3.

Any idea why that is? Or are you not having these issues with your
ROPP version?
}}}

I replied
{{{
This is not too surprising. The forward model generates
refractivities and bending angles on the corresponding 247L, and if 
you want the latter to match the standard 247 impact heights, then 
you need to do a bit of iterating on the refractivity levels.  I 
had some problems when developing this, but it finally seemed to 
work OK.  I'll look into it.
}}}

One thought: his levels are monotonically ''descending'', ECMWF-style, not ''ascending'' as I (probably) assumed. This might have something to do with it. "	defect	closed	major	9.0	ROPP (all)	8.0	fixed