GOMOS

Global Ozone Monitoring by Occultation of Stars

IMPORTANT: New GOPR 6.0a prototype and new product format. For some explanation concerning the distribution of the products, please read this!

To follow the status of the reprocessing task, please click here!

GOMOS product disclaimer is available (PDF)

News

The CAL/VAL data has been reprocessed using GOPR 6.0a. The products are available on our ftp server. See the Products page for more details concerning the data distribution.
The GOMOS daily and monthly reports are available on-line
The reprocessing of the 2002-2003 mission is under progress. GOPR 6.0a is used for this purpose.
An animation showing the split of the Southern polar vortex last fall as seen by GOMOS assimilated data is here (still using GOPR 5.4 data).

GOPR processor version

Last stable version is lv1b 6.0a - lv2 6.0a
Click here to have more information about the GOPR prototype version used to generate the products in the frame of the 2002-2003 mission reprocessing task

Reference data set

Old data sets are no more available on the ftp server.

Specific data

Format change of the GOMOS products since GOPR 6.0a
For the old list of data sets, please look at News/History

Occultation classification versus limb illumination conditions

Since GOPR 6.0a, the illumination condition is included as a PCD information in both GOMOS level 1b and level 2 products. In the distribution directories, the classification between dark/twilight/daylight occultations has been introduced as a new directory level (e.g. twilight/Rxxxxx/Sxxx).

* dark observations can be used for validation. The observations occurred in dark limb conditions with no or only a very small level of straylight. The SNR is very good for these occultations.
* twilight observations should be carefully used for validation. A new algorithm directly based on the satellite/earth/sun configuration has been implemented in the level 1b processing. The ratio U/C previously used to discreminate between the illumination conditions is also available in the level 1b product and the minimum altitude where this ratio is lower than 25% is available in the level 2 product. As previously, concentrations above this altitude may be used for validation if no other data is available.
* daylight observations should be avoided for validation. The background signal removal algorithm is still under improvement. The current correction algorithm leads to noisy transmission spectra at high altitude and wrong transmission spectra at low altitude.

Discremination algorithm:

Bright condition if: SZA_TGP < 97° for all ALT_TGP < 50 km
Twilight condition if: not bright condition and SZA_TGP < 110° for all ALT_TGP < 100 km or if SZA_SAT < 120°
Full dark condition if: not bright and not twilight.

SZA_TGP is the sun zenith angle at tangent point. ALT_TGP is the altitude of the tangent point, SZA_SAT is the sun zenith angle at the satellite location. The sun zenith angle at a specified location is the angle between the nadir and the sun direction.