GRAS A Spot

New version of GRAS radio occultation processing

GRAS A Spot
GRAS A Spot

The GRAS data processing will be updated to version 5 on 14 September 2021.

Last Updated

08 September 2021

Published on

12 August 2021

Operational Radio Occultation products derived from the measurements of the Metop GRAS instruments will be updated on 14 September. In the new version of the operational processor (v5), the retrieval algorithms for bending angle data have been updated, solving a number of known issues in the GRAS level 1 data quality. In particular:

  • No non-physical oscillations (in the mesosphere) and spikes (in the troposphere), previously present in a small number of bending angle profiles.
  •  Existing asymmetry between tropical tropospheric bending angle biases for rising and setting occultations has been largely reduced.
  • Statistical properties of lower tropospheric bending angle data are now more consistent with those of other publicly available radio occultation data.
  • Standard deviations statistics improved, especially at high altitudes and in the mid- and lower troposphere.

The Product Validation Report will be made available soon.

Test data in BUFR format are available from EUMETSAT's ftp server at:
ftp://ftp.eumetsat.int/pub/OPS/out/test-data/GRAS_NRT/<sat>/bufr
where <sat> is one of metop_a, metop_b or metop_c.

The server contains a rolling archive of GRAS data generated on EUMETSAT's validation ground segment over the previous 24 hours.

Note: the BUFR data format has not changed compared to previous versions of the GRAS data.

We welcome any user feedback which can be sent to our User Service Helpdesk until 5 September 2021.

For more information, contact our User Service Helpdesk