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. 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
- the observation departure statistics for the data assimilated in the reanalyses
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. The basic web-api documentation for accessing the data is given here.
General information related to downloading the data via web-api, is described 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/