MESCAN precipitation analysis as part of the CERRA reanalysis, for near real time and back extension production.

The atmospheric Copernicus European Regional Reanalysis (CERRA) and its land component CERRA-Land, including the MESCAN daily precipitation analysis, were produced from September 1984 to June 2021 and are available through the Copernicus Climate Data Store (CDS). A new service contract, currently underway and funded by the Copernicus Climate Change Service (C3S) under the Copernicus program, has been established to continue producing the existing reanalysis and extend it back in time. The three-hourly output from the CERRA reanalysis, based on the Harmonie-ALADIN 3D-VAR at 5.5 km, is used to generate hourly forcing files - including precipitation analyses using MESCAN - for the CERRA-Land surface reanalysis, an offline simulation of the SURFEX land surface modeling platform. Production of CERRA and CERRA-Land has resumed, reaching near real time, and the back extension production from September 1960 to August 1984 is ongoing.

This work focuses on the MESCAN precipitation analysis, which aims to improve total precipitation estimates from CERRA by assimilating in situ observations. MESCAN assimilates around 8,000 surface observations per day for the present period and around 6,500 observations at the start of the back-extension period. These observations come from the ECA&D, MARS and national databases. Their temporal variability and spatial distribution can impact long-term studies that use this product. That is why we strive to document changes and maintain consistency wherever possible. The quality control measures and characteristics of the CERRA-Land product will be presented. Furthermore, the added value compared to CERRA and its comparison with ERA5 for precipitation will be presented.