## 2 Materials and Methods
### Datasets and Data Processing
#### 2.2.2 ERA-Interim and ERA5 Atmospheric Reanalyses  
ERA-Interim is a global atmospheric reanalysis produced by the ECMWF [34]. Reanalyses provide a numerical description of the recent climate by combining models with observations using data assimilation systems. ERA-Interim overlays the period from 1 January 1979 onward and continues to be extended forward in near-real time. It is based on the integrated forecast system (IFS) version 31r1 (more informations at [[https://www.ecmwf.int/en/forecasts/documentation-and-support/](https://www.ecmwf.int/en/forecasts/documentation-and-support/)]([https://www.ecmwf.int/en/forecasts/documentation-and-support/](https://www.ecmwf.int/en/forecasts/documentation-and-support/)), last  
Figure 4: Maps of correlation R (**a**) and ubRMSD (**b**) between incoming solar radiation time series from ERA5 and in situ measurements. (**c**,**d**) represent the difference between ERA5 and ERA- Interim in correlation and ubRMSD for 2017, respectively. For each station presenting significant R (\(p\) values < 0.05), the simulation that presents the better R values is represented.  
Figure 3: Maps of correlation (R) on precipitation time series (**a**) and ubRMSD (mm/month) on precipitation time series (**b**) between in situ measurements and both ERA-Interim and ERA5. For each station presenting significant R (\(p\) values < 0.05), the simulation that presents the better R values is represented. Triangle symbols indicate when ERA5 presents the best value and circles when it is ERA-Interim.  
access: November 2018) using approximately an 80 km (T255) spatial resolution and with analyses available for 00:00, 06:00, 12:00, and 18:00 UTC. A detailed explanation of the ERA-Interim product archive is provided in [34; 50].  
Recently, ERA5 [51], the latest version of ECMWF reanalyses, was released as the fifth generation produced. It is envisioned that ERA5 will replace the release of the current ERA-Interim reanalysis, from 1979 to the near real time period (on a regular basis). Regarding climate information, ERA5 has numerous improved characteristics compared to ERA-Interim reanalysis. It presents one of the most updated versions of the Earth System Model and data assimilation techniques used at ECMWF, which enables the use of more sophisticated parametrization of geophysical processes in comparison to the previous versions used in ERA-Interim. Moreover, ERA5 has two other important features, which are the improved temporal sampling and spatial resolution: From 6-hourly in ERA-Interim to hourly in ERA5, and from 79 km in the horizontal dimension and 60 vertical levels to 31 km and 137 levels in ERA5. Eight variables from ERA5 and ERA-Interim have been used to constrain LDAS-Monde, including the lowest model level (about 10-m above ground level), air temperature, wind speed, specific humidity and pressure, and the downwelling fluxes of shortwave and longwave radiation as well as precipitation partitioned in the liquid and solid phases (the latter being null over the considered domain).  
At the time of this study, ERA5 is a new product and to the best of our knowledge, only three other studies compared the performance of ERA5 and ERA-Interim. In [4], the authors assessed the two reanalysis ERA5 and ERA-Interim using them to force the ISBA LSM over North America. Better performances in the representation of evaporation, snow depth, soil moisture, and river discharge estimates were observed in the simulations forced by ERA5. They were attributed by the authors to the improved precipitation estimates. [PERSON] et al. [36] compared SW\({}_{\text{in}}\) estimates from ERA5 and ERA-interim at a global scale, and observed a better performance with ERA5. Finally, [PERSON] et al. [35] highlighted the good performance of ERA5 precipitation with respect to 26 gridded subdaily precipitation datasets using Stage-IV gauge-radar data for the evaluation over the continental United States of America.