Contributors: Hans Gleisner (DMI)
History of modification
List of datasets covered by this document
Related documents
Acronyms
General definitions
Scope of the document
This document is the Algorithm Theoretical Basis Document (ATBD) for Tropospheric Water Vapour Profiles (product C3S_D312b_Lot1.3.3.9) based on GNSS Radio Occultation (RO) measurements. It describes the algorithms used to generate the water vapour product, outlines the chosen approach, and provides a description of the assumptions and limitations of the algorithms. The ATBD is valid for both the Climate Data Records (CDRs) and the corresponding Interim Climate Data Records (ICDRs)
The data products covered by this ATBD are provided as a brokered service from the EUMETSAT ROM SAF. The original ROM SAF ATBDs, to which the present document refers, are the "ROM SAF ATBD: Level 2B and 2C 1D-Var products [D1] and the "ROM SAF ATBD: Level 3 Gridded Data" [D2]. They are found at the ROM SAF web site http://www.romsaf.org.
Executive summary
The project C3S_312b_Lot1 includes brokering of tropospheric water vapour gridded monthly mean data from the EUMETSAT ROM SAF. This document refers to the ROM SAF documentation [D1], [D2] describing the methods and algorithms that are used by the ROM SAF to generate the water vapour data products.
The ROM SAF documentation covers both the CDR (ROM SAF product GRM-29-L3-H-R1) and the ICDR (ROM SAF product GRM-29-L3-H-I1). The CDR covers the time period December 2006 to December 2016, while the ICDR covers the time period from January 2017 and onward, being regularly updated with a two-month delay. The regularly updated ICDR has the same characteristics as the CDR, which has been generated in a ROM SAF reprocessing activity.
1. Instruments
1.1 GNSS Radio Occultation data
This is described in Section 2 of the EUMETSAT ROM SAF Level 3 ATBD [D2].
2. Input and auxiliary data
The input data to the ROM SAF processing, as well as the auxiliary data (ERA-Interim reanalysis short-term forecast data used as background in the 1D variational retrieval), are described in Section 3.2 of the ROM SAF Level 2B ATBD [D1] and in Section 2 of the ROM SAF Level 3 ATBD [D2].
3. Algorithms
The methods and algorithms that are used by the ROM SAF to generate the water vapour data products, which are provided by the C3S_312b_Lot1 as a brokered service, are described in Sections 2 and 3 of the ROM SAF Level 2B ATBD [D1] and in Section 5 of the ROM SAF Level 3 ATBD [D2].
4. Output data
The output data are only described very briefly by the ROM SAF ATBDs – in Section 4.5 of the ROM SAF Level 2B ATBD [D1] and in Section 6 of the ROM SAF Level 3 ATBD [D2]. More details are found in the ROM SAF Level 1B and 2 PUM [D3] and in the ROM SAF Level 3 PUM [D4].
References
References are found in Section 1.2 of the ROM SAF Level 3 ATBD [D2].
This document has been produced in the context of the Copernicus Climate Change Service (C3S).
The activities leading to these results have been contracted by the European Centre for Medium-Range Weather Forecasts, operator of C3S on behalf of the European Union (Delegation agreement signed on 11/11/2014). All information in this document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose.
The users thereof use the information at their sole risk and liability. For the avoidance of all doubt , the European Commission and the European Centre for Medium - Range Weather Forecasts have no liability in respect of this document, which is merely representing the author's view.
