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The GlobVapour project has been successfully ended on the 31st March 2012.



Retrieved TCWV from MERIS VIS/NIR




Project Manager:

Dr. Marc Schröder (DWD)


Technical Officer:

Dr. Bojan R. Bojkov (ESA)

User Help Desk

Data Request & Technical Support:

Dr. Marc Schröder (DWD)

April 2012

ESA DUE GlobVapour project

Executive summary

The European Space Agency (ESA) Data User Element (DUE) is an element of the Earth Observation Envelope Programme (EOEP), an optional programme of ESA. The DUE aims to bridge the gap between research projects, and the sustainable provision of Earth Observation products at an information level that fully responds to the operational needs of user communities. The ESA DUE GlobVapour project's main objective was to provide long-term coherent water vapour data sets allowing for improved accuracies and enhanced temporal and spatial sampling. The project successfully produced the total column water vapour (TCWV) data set based on SSM/I and MERIS observations. The product combines high quality ocean and land observations with 0.5° and 0.05° spatial resolution by keeping the uncertainty estimates and individual advantages. Daily composites and monthly mean with global coverage are provided for the period 2003-2008. The second product consists of a homogenised GOME, SCIAMACHY and GOME-2 time series. Weekly and monthly averages of TCWV with global coverage and in 0.5° spatial resolution have been produced for the years 1996-2008. The products are available in netCDF format following the CF standard. To ease utilisation the number of valid observations, the standard deviation, the retrieval uncertainty and useful masks such as land/sea/ice masks are included.

An essential aspect of the GlobVapour project was a direct involvement of the user community in the project. The formation of the GlobVapour user group began already prior to the project start. The user group strongly supported the definition of the requirements baseline and guided retrieval and processing development as well as product definition and validation. Furthermore, the project conducted three User Consultation Meetings in the course of the project in order to foster discussions between retrieval, climate and modelling scientists. In total 22 users registered as users of GlobVapour products. This is a remarkable success as the project run only for two years and the final products with reasonable temporal coverage were provided close to project end. At UCM2 and UCM3 results from first applications at user institutes have been presented. The project also compared GlobVapour products to output from sixteen models submitted to the Coupled Model Inter-comparison Project (CMIP) 5.

After gathering feedback from user community to define the requirements baseline the project concentrated on the development of various retrieval schemes and merging/combining techniques applicable to ESA and non-ESA sensors:

  • New development of a physical retrieval scheme for TCWV from MERIS.
  • Improvement of a 1D-Var retrieval scheme for TCWV from SSM/I.
  • New development of a combined SSM/I+MERIS product.
  • Development in support to a merged SEVIRI+IASI product.
  • Adaptation of the SSM/I 1D-Var to allow application to MWR on Envisat.
  • Improvement of the GOME/SCIAMACHY/GOME-2 retrieval scheme.
  • New development of the homogenisation of the GOME/SCIAMACHY/GOME-2 TCWV time series.

The retrieval schemes for the final GlobVapour products have been adapted to carry out the implementation into a single and stand alone processing system to foster operational application. At the end of the project the acceptance review test for the processing system was successfully passed.

Another essential part of the project was the intensive validation of the GlobVapour products. Various sources have been used as reference for the validation: ground-based, in-situ and other satellite observations, which comprise the Diagnostic Data Set, the basis for the validation. The validation results have been documented and together with algorithm theoretical basis documents and product user guides fully describe the GlobVapour products.

The validation was carried out using Level 3 data. The resulting uncertainties consist of radiance, retrieval, spatio-temporal mismatch, sampling, averaging and other uncertainties. In order to verify that GCOS requirements on TCWV are met it is at least needed to separate the sampling/averaging and spatio-temporal mismatch uncertainties from total uncertainty to finally assess compliance with GCOS requirements.

GlobVapour was in close contact to international activities. It supported the GEWEX Data Assessment Panel in its effort to initiate a water vapour and temperature profile assessment in a joint meeting hosted by ESA-ESRIN. The project conducted a IASI assessment and the experiences from GlobVapour validation activities can be beneficial for the GEWEX assessment. GlobVapour submitted an extended abstract on the combined SSM/I+MERIS product to one of the lead authors of IPCC AR5 in order to potentially get referenced in the AR5.

Finally, GlobVapour processors and products will most likely be transferred to sustained and operational environments at ESA and CM SAF. Examples are the MERIS 1D-Var retrieval for implementation into the MERIS reprocessing at ESA and the continuation of the SSM/I+MERIS products.

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Project Manager: Marc Schröder (DWD)   ·   Technical Officer: Bojan R. Bojkov (ESA)   ·   The web site is hosted at Brockmann Consult