News Archive

The news listed below have previously been shown in the "News" column of the GRAS SAF Main page

Software Release
The GRAS SAF is pleased to announce the fifth full release for the software deliverable 'ROPP', Version 5.0.

The principal changes from the previous release, v4.1, are the inclusion of non-ideal gas effects (compressibility factors) in the forward model and 1D-Var modules, and support for the ECMWF BUFR library. Numerous bug-fixes and minor enhancements, particularly in the ropp_pp module, have also been included. All user documentation has been reviewed and updated. Details of all changes are available together with the updated software on the ROPP download website.

Users are recommended to update their applications to use this latest ROPP distribution.
[July 11 2011]

NRT Monitoring of SAC-C and C/NOFS Data
The GRAS SAF is pleased to announce that our NRT monitoring page now includes RO data from two more satellites: The Argentinian satellite SAC-C and the US satellite C/NOFS.

The data are processed and disseminated by UCAR and are now on the GTS, though data since February 2011 are provided.

Firefox users may have to do CTRL+SHIFT+R to refresh javascripts before viewing the data. Note that the matched occultations (RO-RO and RO-sonde) are not yet linked but this will happen soon.
[May 30 2011]

1D-Var Products Declared Operational
The GRAS SAF is pleased to announce, that the following 1D-Var products have been officially declared operational: GRM-02 (NRT temperature profile), GRM-05 (NRT surface pressure), and GRM-07 (Error covariance matrix for NRT products). The following 1D-Var products have been officially declared pre-operational: GRM-03 (NRT specific humidity profile) and GRM-04 (NRT pressure profile).
The products are expected to become available to users through dissemination and download in Q4 2011.
[May 3 2011]

NRT Monitoring of TerraSAR-X Data
The GRAS SAF is pleased to announce that our NRT monitoring page now includes RO data from the German TerraSAR-X satellite.

The data, processed and disseminated by the GFZ, have an improved stratospheric bias from October 21 onwards. Corresponding ECMWF statistics are available.

Firefox users may have to do ctrl+shift+R to refresh javascripts before viewing the data.
[October 26 2010]

Successful GRAS SAF Climate Workshop
On September 6-11, 2010, the GRAS SAF co-organized OPAC2010 (International Occultations for Probing Atmosphere and Climate Workshop) together with the University of Graz. OPAC2010 comprised the Joint OPAC-4, GRAS SAF Climate, and IROWG-1 workshops, and was held in Graz, Austria.

OPAC2010 was a successful forum for everybody interested in atmospheric remote sensing by occultation methods and/or the use of occultation data in atmospheric physics, chemistry, and meteorology, this time with special focus on climate applications.

For program, abstracts, and presentations, please visit the OPAC2010 web page.
[September 20 2010]

Software Update
The GRAS SAF is pleased to announce an update to the fourth full release for the software deliverable 'ROPP', Version 4.1.

The principle change from the previous release, Version 4.0, is an update to the radio occultation pre-processing module to provide more robust processing of open loop data. Additional functionality to process GRAS occultation phase and amplitude data has also been included. The 1DVar module has also been updated to provide improved support in defining observation and background error structures, and to output additional diagnostic information. All user documentation has been reviewed and updated. Details of all changes are available together with the updated software on the ROPP download website.

Users are recommended to update their applications to use this latest ROPP distribution.
[July 20 2010]

Climate Workshop
The GRAS SAF is co-organizing OPAC2010 (International Occultations for Probing Atmosphere and Climate Workshop) together with the University of Graz. OPAC2010 will comprise the Joint OPAC-4, GRAS SAF Climate, and IROWG-1 workshops, and will be held on September 6-11, 2010 in Graz, Austria.

OPAC2010 will be an attractive forum for everybody interested in atmospheric remote sensing by occultation methods and/or the use of occultation data in atmospheric physics, chemistry, and meteorology, this time with special focus on climate applications.

For more information please visit the OPAC2010 web page.
[April 23 2010]

NRT refractivity product operational
The GRAS SAF is pleased to announce that the GRAS SAF level 2 NRT refractivity product (GRM-01) has been declared operational. This is happening in connection with an upgrade of the GRAS SAF operational processing software, which will significantly reduce the current bias in GRM-01 above about 30 km. The standard deviation above 40 km will in general be a little larger than before. The influence on the data below 30 km should be insignificant.

The details of the change are described in the associated Validation Report (available at the Product Archive). The main thing is a shift from statistical optimization based on a 1-parameter background fit to a 2-parameter fit in combination with a global search in a library of climatological profiles. The statistical optimization used is known as optimal linear combination (OLC).

Due to the change of approach in processing the data at high altitudes, some profiles are dismissed as outliers above 40 km, and they are not further processed. As a consequence the number of refractivity profiles after the upgrade will on average be less than before (a reduction of about 5%).

Other minor changes:
NetCDF variables:
- time_offset [Time offset for georeferencing (since start of occ.)] is currently incorrect and will therefore be set to missing value.
- azimuth [GNSS->LEO line of sight angle (from True North) for the reference coordinate] will now be provided in 'atm' files.
BUFR variables:
Local Earth parameters:
- Time increment [data field 29; descriptor 0 04 016] is currently incorrect and will therefore be set to missing value.
- Bearing or azimuth [data field 36; descriptor 0 05 021] will now be provided.

Until today the GRAS SAF refractivity product had the status of pre-operational (version 1.2). After the upgrade the refractivity product is now declared operational (version 1.3).

The upgraded refractivity product is disseminated over the GTS and EUMETCast systems in BUFR format in NRT. It is also being archived at our website in both NetCDF and BUFR files for offline access.
[February 1 2010]

Software Release
The GRAS SAF is pleased to announce the fourth full release for the software deliverable 'ROPP', Version 4.0.

The principle change from the previous release, v3.0, is the addition of a new two-dimensional bending angle observation operator, together with the corresponding two-dimensional tangent linear and adjoint codes and I/O support. Additional functionality has been provided in the pre-processing of excess phase data to ionospheric corrected bending angle and refractivity profiles, including use of external navigation bit data (this algorithm has experimental status and is suitable for research use only), revised filtering algorithms and additional options for initialising the Abel transform. Output diagnostic and error information from any ROPP routine may now be controlled by the user. Dependence on the third-party udunits library has been removed. All user documentation has been reviewed and updated. Details of all changes are available together with the updated software on the ROPP download website.

Users are recommended to update their applications to use this latest ROPP distribution.
[January 11 2010]

New GRAS SAF user survey
The GRAS SAF is conducting a new user survey, the questionnaire can be found here. Initially, email invitations have been sent out to 574 recipients.
[December 15 2009]

GRAS SAF web site updated
The GRAS SAF web site has undergone a major update. Notable changes are a modified look, individual product pages, and merging of the two previously separated parts www.grassaf.org and garf.grassaf.org. Users, who previously logged in to access the garf.grassaf.org part, will notice that login is now only required to download product, software, and documents.
[November 17 2009]

New GRAS SAF Report (GSR 09)
A new GRAS SAF report addressing the issue of refractivity coefficients has been published. The report is written by Sean Healy, ECMWF, and has the name "Refractivity coefficients used in the assimilation of GPS radio occultation measurements"

Summary: The sensitivity of ECMWF numerical weather prediction analyses to the empirical refractivity coefficients and the introduction of non-ideal gas effects in the bending angle operator have been investigated. A review of the literature on the refractivity coefficients suggests that the uncertainty in the values is probably larger than has been recognised. The results reinforce the need for new measurements of the refractivity coefficients at radio frequencies.

The GSR 09 report can be viewed here.
[October 9 2009]

Software Release
The GRAS SAF is pleased to announce an update release for the software deliverable 'ROPP', Version 3.0.

The principle changes from the previous release, v2.0, is to provide functionality to process excess phase and amplitude time series to compute L1 and L2 channel bending angle profiles by geometric optics and wave optics methods. This complements existing functionality to compute ionospheric corrected bending angle and refractivity profiles from L1 and L2 channel bending angle data.

Users are recommended to update their applications to use this latest ROPP distribution.

Details of all the changes are available together with the updated software package on the ROPP download website.
[July 6 2009]

Feature on GRAS SAF
EUMETSATs web page has a feature on the GRAS SAF and our refractivity product this week.
[April 17 2009]

Data access on GARF
The GRAS SAF is pleased to announce that the product archive GARF is open for access to archived NRT data. Read more here.
[March 30 2009]

Refractivity (GRM-01) product via EUMETCast
The GRAS SAF is pleased to announce that the GRAS SAF level 2 NRT refractivity product (GRM-01) is being disseminated in trial mode via the EUMETCast at EUMETSAT. The dissemination started 30 March 2009, at about 11:00 UTC. For more information see EUMETSAT's announcement below:
[March 30 2009]

NRT refractivity product pre-operational
The GRAS SAF is pleased to announce that the GRAS SAF level 2 NRT refractivity product (GRM-01) has been declared pre-operational.

The product is disseminated in NRT via the GTS system and is in the final stages of being made available over the EUMETCast system; a separate announcement will be issued when this is ready. On Thursday this week we will open the GRAS SAF Archive and Retrieval Facility (GARF) where archived NRT data can be retrieved.

The current level 1b bending angle is obtained by GO and cannot be recommended for usage below about 8 km; this is also true for the refractivity. The quality of the refractivity product can be seen in the attached figure which shows the global O-B/B statistics compared to ECMWF. The figure shows the O-B/B mean and standard deviation and the product requirements accuracies: threshold (green) and target (red). We are currently improving on the standard deviation and the bias above 35 km and we expect to be able to provide an updated product within 1-2 months time.

On GARF we provide continuous NRT monitoring of the data quality and data flow. The monitoring does not only include MetOp/GRAS RO data from EUMETSAT and the GRAS SAF but also RO data from the following missions: FORMOSAT-3/COSMIC, CHAMP, and GRACE-A.

The BUFR file that is being disseminated via GTS contains in addition to the refractivity product a GRAS SAF produced thinnned version of EUMETSAT's NRT level 1b bending angle. The thinning is consistent with the thinning algorithm applied by EUMETSAT. In order to start receiving the GRAS SAF BUFR file please follow the normal procedures at your organization. The files are generated at DMI and carries the WMO bulletin headers: "IUT[A-L]14 EKMI". For more information about the BUFR files please read this document.

If you have questions please do not hesitate to ask us. Please address your questions directly to the GRAS SAF helpdesk by using this link: Helpdesk
[March 25 2009]

Software update
The GRAS SAF is pleased to announce an update release for the software deliverable 'ROPP', Version 2.0.

Details of the changes are available together with the updated software package on the ROPP download website.
[December 1 2008]

Software update
The GRAS SAF is pleased to announce an update release for the software deliverable 'ROPP', Version 1.2.

The principle changes from the previous release, v1.1, is to increase flexibility to support other than the ECMWF NWP model levels, significantly decrease dependencies on 3rd party code and to fix some reported bugs relating to the processing of Level 1 GRAS data.

Details of the changes are available together with the updated software on the ROPP download website.
[September 3 2008]

User workshop
A joint ECMWF/GRAS SAF workshop on the assimilation of GPS radio occultation measurements was held at ECMWF in Reading, UK, from 16 to 18 June 2008. Read more here.
[June 16-18 2008]

NRT monitoring
The GRAS SAF is pleased to announce NRT monitoring of level 2 demonstration products based on pre-operational level 1b GRAS bending angle data from EUMETSAT.
[April 11 2008]

Software update
The GRAS SAF is pleased to announce an update release for the software deliverable 'ROPP', Version 1.1. The principle change from the first release, v1.0 is to make the code in general much more robust to non- nominal data inputs and to support new forthcoming RO missions. The v1.1 code has also been successfully tested with a wider range of compilers, so portability is significantly enhanced.

Details of the changes are available together with the updated software on the ROPP download website.
[April 9 2008]

Software release
The GRAS SAF is pleased to announce the first full release of the Radio Occultation Processing Package (ROPP-1 v1.0).

The package provides software to support GRAS (and other RO missions such as COSMIC and CHAMP) data to be assimilated into NWP models, RO data file interfaces plus various stand-alone tools such as 1D-Var retrieval and BUFR encoding/decoding. Full documentation is provided. There are no charges for this downloading or using this package.

The ROPP-1 software, test data, documentation and supporting items can be downloaded from the GRAS SAF Product Archive, from where ialso an overview document describing ROPP can be freely downloaded. In order to download the package components, you will first need to register as an ROPP user via this website. This is an automatic process and very simple and quick to obtain the access details. Users who have previously registered for the Beta release will need to re-register for the full release.

When you have your access details, you will be able to log in and navigate to the ROPP downloads page where - for the first login only - you will be required to agree to the terms of a Software Licence. Please first look at the Release Notes which contain a description of the available files, the current status of the packages components and a quick installation guide.

We thank you for your interest in ROPP and we look forward to hearing of your experiences in using the package. If you have any comments or questions about ROPP, please use the Helpdesk facilities.
[April 11 2007]