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The Radio Occultation Processing Package

GRAS-SAF Team (Axel von Engeln), August 2005

GPSRO2, Lansdowne, Virginia

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Introduction

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ROPP Objectives

To provide users with a comprehensive software package, containing all necessary functions to pre-process RO data from CGS Level 1b files or GRAS SAF Level 2 files, plus RO-specific components to assist with the assimilation of these data.

Implemented as a set of pick’n’mix modules. Some 3rd party freeware support libraries required (e.g. netCDF, udunits, Lapack)

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ROPP Background

Partly follows the AAPP idea (ATOVS and AVHRR Pre-processing Package / NWP-SAF)

Developed within the GRAS-SAF at the Met Office

Aims at Operational Meteorological Centers

Also allows stand alone processing

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ROPP Context

GRAS Level 1b (CGS)

PFS netCDFpfs2ropp

GRAS Level 2 (SAF)

ropp2bufrBUFR

ropp_1dvar

ropp_fm

NWP VAR system

NWP User

netCDFropp_preproc

ropp_qc

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ROPP Facts

Portability built-in (tested with several Unix/Linux compilers)

Installation uses standard configure, make, make install sequence

Maintained under SVN version control ROPP is NOT a black box, standalone,

end-to-end processor but a modular system providing the required (possibly distributed) functions.

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Modules

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ROPP Modules (1)

ropp_tools Utility Library (unit conversions, interfaces etc)

ropp_io IO Library (bufr, netCDF, conversions)

ropp_fm Forward Library, T/L & Adjoints for bending angles

or refractivity (hybrid, pressure & height based)

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ROPP Modules (2)

ropp_1dvar 1DVar Library (Minimiser, Q/C)

ropp_ug User Guide

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ROPP Future Modules

ropp_preproc Pre-processing Library from Level 1b to Level 2

(Version2: Abel transform, thinning, coordinate transforms, Version3: FSI)

ropp_qc Quality control Libraries

ropp_fm 2-D Bending Angle (hybrid, pressure & height

based)

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ROPP Examples

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ROPP Examples: Information content

Tropical profile, w/ and w/o inflated background errors above 5 hPa, for various uncorrelated bending angle noise levels

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ROPP Examples: 1K Altitude

One order of magnitude in noise reduction ~ 15 km in altitude.

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ROPP: Surface Pressure Retrieval

Surface pressure retrieval increments. Small inconsistency in altitude reference (top) and modified (bottom).

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Acknowledgments / Contacts

Acknowledgments:

•Met Office (Dave Offiler)•Met Office / EUMETSAT (Christian Marquardt)•Met Office / ECMWF (Sean Healy)

Contacts:

•Email: grassaf@metoffice.gov.uk•Web: http://www.metoffice.gov.uk/research/interproj/grassaf/index.html

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Questions & Answers