id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
233	Lat/Lon and azimuth differences between ROPP & UCAR	Dave Offiler	cburrows	"Ali Sam reports in Helpdesk ID 72:
{{{
The GRAS SAF Helpdesk has received a question from ali sam

The helpdesk subject is:

corrupted output of ropp_pp_occ_tool  compare with COSMIC atmprf data.

The helpdesk description is:

Dear GRAS SAF Team,

1. I used one COSMIC atmphs profile as input of ucar2ropp tool 
and set it's output as input of ropp_pp_occ_tool in directory 
that I run this tools, MSIS_coeff.nc,egm96.dat and corrcoeff.dat
data files were peresent. I compared   lat_tp and lon_tp
parameters (Variable in output file of ropp_pp_occ_tool ) with 
lat and lon parameters (Variable in COSMIC atmprf netcdf file that
was correspond to  used COSMIC atmphs file). result of my work
showed this two sets of parameters did'nt match and phase_qual
(variable in output file of ropp_pp_occ_tool) in many data points
equal -99999000. also bangle_qual, refrac_quality and other
quality  variable in ropp_pp_occ_tool output file had -99999000
values. 

Would you please inform me if it's reasonable or any other
auxilliary data is needed?

2. also I want to know, is input file of ropp_pp_invert_tool and
ropp_pp_spectra_tool, similar to input file of ropp_pp_occ_tool?
if no, please help me.

Regards and thanks.

In order to reply to this helpdesk enquiry please use the link below:

http://www.grassaf.org/helpdesk_answer.php?id=72

This message is sent to the following email addresses: 

oliveras@ieec.fcr.es, grasadm@dmi.dk, grassaf@metoffice.gov.uk 
}}}

Our initial reply was:

{{{
Dear Ali,

Thanks for your Helpdesk feedback.

1) atmPhs profiles

a) You don't say whether the lat/lon differences are close 
(e.g. within a tenth of a degree) or completely different, 
so it's not possible to give an answer immediately. 
If the values are quite close, it's likely to be because the 
ROPP and UCAR algorithms generate samples on different Impact
Parameter heights - are the IP and BA values different too? 
If they are very different, them we'd need to look at the 
ECF/ECI calculations. Note that ROPP is not required to 
reproduce UCAR's values exactly, though they should be
statistically similar.

In order to investigate further, could you please email us the following:

- an indication of the size of differences in lat/lon that you are finding;
- the pair of UCAR/CDAAC atmPhs and atmPrf files (or their names
  so we can download them from the CDAAC server);
- your configuration file for ropp_pp_occ_tool;
- logs of the output from the ucar2ropp and ropp_pp_occ_tool commands.

For the latter, please use the -d switch to output additional
debug/diagnostic information. We will then try to reproduce and
explain (and if necessary, correct) the differences.

Please email directly to grassaf@metoffice.gov.uk - there is no
need to use the Helpdesk system (unless you have a new issue to
raise).

b) ROPP does not (yet) calculate any of the *_quality parameters,
so these are set to the default value for 'missing data'. 
The method of calculating these quality parameters, and from what
inputs, has yet to be defined. We could consider setting them to a
nominal 100 (percent), but for the present, they cannot be used 
for quality control purposes.

2) Yes, the input to ropp_pp_spectra_tool should be a ROPP
netCDF file converted from - for instance - a UCAR atmPhs file
by ucar2ropp, since this tool requires phase and amplitude data.

But ropp_pp_invert_tool requires L1 & L2 bending angle data, so
the input would be - for instance - a file output by ropp_pp_occ_tool.

I hope this is useful, and if yo can send us the requested files
and other information, we'll investigate the lat/lon issue. 

Best regards,
Dave Offiler
ROPP Development Team
grassaf@metoffice.gov.uk
}}}

Awaiting reply from Ali, but in the mean time an arbitrary atmPhs/atmPrf file pair will be investigated (by Chris)."	defect	closed	normal	6.0	ropp_pp	4.1	fixed	latitude, longitude, atmPhs, atmPrf