The objectives of the ALGOM: GOMOS Level 2 Algorithm Evolution Studies are:

• Analysis of GOMOS Level 2 data products and validation results to assess the retrieval performance
• Definition of corrections and improvements to the GOMOS Level 2 processing algorithms
• Data format harmonisation among GOMOS, MIPAS and SCIAMACHY
• Preparation of an evolution recommendation report for further product improvement

ALGOM addresses the following studies:

• Improvement of the algorithm for O3 and aerosol retrievals in the UTLS:

  A validation of IPF v6.01 against soundings at different NDACC stations was performed. GOMOS v6.01 ozone data values in the upper troposphere–lower stratosphere (UTLS) are largely overestimated and therefore very large bias is shown. Within ALGOM framework, optimization of GOMOS O3 retrievals in the UTLS using two-step and one-step retrieval approach has been performed.

• Improvement of the algorithm for H2O and O2 retrievals:

  The aim of this mini project is the development of a new H2O and O2 algorithm. This new algorithm is based on transmission spectrum fitting using a Levenberg Marquardt method.

• Design a new algorithm for minor species using averaged transmissions:

  In this study, a method is developed for the retrieval of minor species defined as "Virtualisation method". The principle of virtualisation is to combine several single measurements spatially and temporally collocated in a time–latitude bin to obtain a "virtual" measurement, which is representative of this bin. For each bin, a statistical analysis is performed to guarantee that all the GOMOS single measurements used to build the data set are representative of the same atmospheric conditions. The SNR of the virtual measurement is then sufficient to retrieve the minor species, such as Na and OClO.

• Improve the user-friendliness of GOMOS Level 2 data by creating quality screening algorithms and forming user-friendly data sets:

  The aim of this study is the development of a method for data screening and flagging of GOMOS Level 2 data, processed with the latest processor IPF v6.01, resulting in a "user friendly" Level 2 dataset in netCDF4 format.