ROM SAF - NRT Notification Detail

NRT Notification Detail

Upgrade of the GRAS SAF refractivity product GRM-01

DATE: 2010-01-27 14:31
TYPE: NRT-GTS

Description

Dear GRAS SAF User Issued 2010-01-27 15:30 UTC We plan to upgrade the GRAS SAF operational processing software early next week. This upgrade should significantly reduce the current bias in the refractivity product (GRM-01) above about 30 km. However, 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 http://www.grassaf.org/product_archive.php soon after the upgrade). 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. Currently, the GRAS SAF refractivity product is having the status of pre-operational (version 1.2). After the upgrade the refractivity product will be declared operational (version 1.3). The upgraded refractivity product will be disseminated over the GTS and EUMETCast systems in BUFR format in NRT. It will also be archived at our website in both NetCDF and BUFR files for offline access. We will send out a reminder a few hours before the upgrade and an additional message after the upgrade. Kind Regards, The GRAS SAF Team

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