Background
The ROM SAF has produced two climate reanalyses as part of its CDOP2 activities. These reanalyses were recommended by the IROWG climate subgroup (see recommendation 6 to CGMS, in section 4.2), where is was stated that:
"Encourage NWP centers to engage in reanalysis activities based only on data types that are not bias-corrected, especially RO. ECMWF, e.g., carries out such an activity as part of the ROM SAF CDOP-2 plans."
Two reanalyses that meet this recommendation have been completed, for the period 20070101 to 20151231. They have been run using the ERA5 system, but at low resolution (T159), and using a static B matrix rather than a flow-dependent version using the Ensemble of Data Assimilations approach. The first reanalysis assimilates just reprocessed GPS-RO data provided the ROM SAF and AMSUA channel 14 to constrain the upper stratosphere. The second reanalysis also includes conventional measurements (e.g., sondes, synop, ...) that are not bias corrected as part of the variational bias correction (VAR-BC) scheme. Notably, this excludes aircraft temperature measurements that are bias corrected in VAR BC.
The two reanalyses provide:
- gridded analysis files at the hours (00,03,06,09,12,15,18,21) for each day
- monthly mean fields from 20070201 to 20151201
- the observation departure statistics for the data assimilated in the reanalyses
The data availability
Access via web-api
The ROM SAF datasets can be retrieved using web-api from from the ECMWF public datasets service. web-api is a "programmatic approach" for data download with python scripts.
General information on downloading with web-api is given here:
https://confluence.ecmwf.int/display/WEBAPI/Web-API+Downloads
Specifically, follow the steps here to install the latest code version:
https://pypi.org/project/ecmwf-api-client/