Operational News

04.02.2010 Impacts on O-F/GDR and IGDR products due to changes in ECMWF model

Dear AVISO products users,

As you probably know, we use ECMWF atmospheric model pressure grids to derive dry troposphere and inverse barometer corrections for sea surface height measurements. Last week, on 26-Jan-2010, the ECMWF model was upgraded to a higher spatial resolution: www.ecmwf.int/publications/cms/get/ecmwfnews/251

We have since identified an impact on the O-F/GDR and IGDR products, due to interpolation of the new higher resolution surface pressure grid onto the lower resolution grid that is still being used operationally. This anomaly has impacts on Jason-1, Jason-2 and ENVISAT products.

The affected period for those missions are: 

For ENVISAT, FGDR and IGDR products have been affected by the ECMWF model resolution change from cycle 86 (pass 404) up to cycle 86 (pass 613).For Jason-1, OGDR and IGDR products have been affected by the ECMWF model resolution change from cycle 297 (pass 70) up to cycle298 (pass 3)For Jason-2, OGDR and IGDR products have been affected by the ECMWF model resolution change from cycle 57 (pass 197) up to cycle 58 (pass 130).

The largest impact is seen in the inverse barometer correction, which has static variations of up to 2 cm amplitude at a wavelength of ~ 50 km. This effect is most noticeable in regions within 200 km of the coast, but is not negligible outside those regions. The anomalous short-wavelength variations can be detected comparing IB values before and after the model evolution. The dry tropospheric correction is affected as well (~4 times smaller amplitude), but not the wet tropospheric correction.

The solution is to retain all the model's spectral information when interpolating from the high-resolution to low-resolution grids, which is an option when creating the operational grids. This change was implemented on 02-Feb-2010.

A smaller issue remains that the interpolation of the high-resolution ECMWF surface pressure grids to a lower resolution does not allow us to fully remove spectral leakage of land features onto the ocean. The remaining errors have a smaller amplitude (~20% of the short-wavelength features seen in the first figure), is also static in time, and almost exclusively affects regions within about 100 km of the coast. We are working on solving the remaining issue as well, and will keep you updated on our progress.

The affected IGDR files will be reprocessed for all missions. All issues related to the ECMWF model resolution change will be corrected prior to GDR production for this time period.

We would like to acknowledge our gratitude to Saleh Abdalla of ECMWF for his collaboration on this issue.

We thank you in advance for your understanding while we resolve these issues.

On behalf of the Jason-2 Measurement Systems Engineers[more]

25.01.2010 Increase in horizontal resolution of ECMWF model

Horizontal resolution of ECMWF model will be increased on the 26th January 2010. These meteo fields are used for altimetric corrections. Some impacts are expected.[more]

25.01.2010 [Jason-1 GDR-C] Reprocessing Complete

The reprocessing for the Jason-1 GDR-C is now complete. Jason-1 GDR-C products for cycles 1-283 are now available at the Aviso and Podaac ftp sites.[more]

21.01.2010 Version 3.0 of OGDR/IGDR/GDR processing software

Last week the Jason-2 OGDR near real-time processing software (TM-NRT) was upgraded to version 3.0 at both NOAA and EUMETSAT. This is a major system upgrade from the previous version (2.3), but has minimal impact on users. There are no format changes to the products. [more]

24.11.2009 Delay in GDR production for Jason-1 cycles 284 onwards

Due to a recalibration on the Jason-1 Microwave Radiometer, Jason-1 GDR production for cycle 284 onwards will be delayed.[more]

16.11.2009 [Jason-2] systematic validation reports available

All the Jason-2 systematic validation reports, including a series of quality controls and statistical analysis, have been published on the Aviso web site.[more]

09.11.2009 [Ssalto] Temporary Postponement for 10 cycles of new version C Jason-1 GDR

Reprocessing of Jason-1 GDR-C is still on going. Please note that cycles 131 to 140 have been temporarily removed from the Aviso ftp server, waiting for new products. See all the cycles currently available on ftp://avisoftp.cnes.fr/AVISO/pub/jason-1/gdr_c/ .

All the new version C Jason-1 GDR should be deliver until the end of the year.

[more]

18.02.2009 [Jason-2 IGDR] update of AMR and Poseidon3 characterisation files

AMR and Poseidon3 characterisation files used in the Jason-2 processing chains have been updated on the 18th of February 2009. Impact is expected on Jason-2 IGDR product quality beginning cycle 23.[more]

18.02.2009 Jason-1 on its new orbit

Jason-1 is on its new orbit since the 14 February 2009 at 20:51 UTC.

Nominal production of all data products is ongoing.

21.01.2009 Jason-2 IGDR products available

Jason-2 IGDR products are available on AVISO server from now.

These products are computed at CNES in NetCDF file format.

3 types of files are available :

- a IGDR native NetCDF formatted datasets ("standard product");

- a reduced 1Hz subset of the full dataset (IGDR-SSHA);

- an expert sensor product containing the full radar-echo waveforms (S-IGDR)