id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
90	Refractivity below surface	frae	frcm	"When running ropp_fm/tools/ecmwf2ro_1d on a netCDF file that has a fixed e.g. 200m geopotential height levels resolution starting from the ground (given to the FM in geop_refrac) I get rather funny refractivity values when I do not provide any background data below let's say 1000m geopotential height since the surface is at 1000m. The FM seems to extrapolate the values below 1000m from the ones above 1000m. This is a behaviour I wasn't expecting, one might want to use a fixed geopotential altitude grid which sometimes is below the ground, in particular when combining several occultations in one netCDF file.

Here is a netCDF input file to ecmwf2ro_1d that shows this behaviour:

[ftp://sat.physik.uni-bremen.de/incoming/axel/fm_example.nc]

Am I missing something here? Is some other input required?"	defect	closed	normal	1.0	ropp_fm	0.9	wontfix		dave.offiler@… michael.rennie@…