Project: A Reanalysis (ModE-RA) and a medium-size AGCM ensemble (ModE-Sim) to study climate variability in the modern era (1420 to 2009) - ModE is the output of the PALAEO-RA project hosted at the Oeschger Centre for Climate Change Research between 2018 to 2023, funded by the European Research Council through the H2020 program (ERC Grant PALAEO-RA 787574). The aim of PALAEO-RA was to create a monthly, 3-dimensional climate reconstruction of the past 600 years. Therefore sparse information on historical climate (including early instrumental data, documentary data, and proxy data) of that period were combined with additional physical constraints taken from a large ensemble of simulations with a state-of-the-art atmospheric general circulation model by using an offline data assimilation technique. For more information on the project, visit https://www.palaeo-ra.unibe.ch/. The project output provided here consists of two main products and an additional sensitivity experiment: • ModE-RA, the main reanalysis product, • ModE-Sim, the original AGCM ensemble prior to data assimilation. • ModE-RAclim, a version of the reanalysis product based on an alternative (experimental) covariance estimation (see experiment description for details). While ModE-RA should be the version used for regular analysis, ModE-RAclim should be more seen as a side product only to be used for sensitivity studies. Summary: Please note: ModE-RAclim is only a side product of the ModE project. ModE-RAclim does not contain centennial scale climate variability. For most users the main product ModE-RA therefore should be used for regular studies on past climate. ModE-RAclim is an alternative version of ModE-RA, the main reanalysis product of this project. ModE-RAclim can be used as a sensitivity study to investigate the effects of stationary covariances. Same as ModE-RA it is a monthly 3-dimensional reanalysis product covering the period from 1421 to 2008. It was created by combining information on historical climate - including early instrumental data, documentary data, and proxy data - with additional physical constraints from ModE-Sim (Modern Era Simulations, to be found within this WDC project as a separate experiment), a large ensemble of simulations with an atmospheric general circulation model. Observed anomalies were assimilated with an offline Ensemble Kalman filtering technique. One of the main differences between ModE-RAclim and ModE-RA is on the model side: ModE-RAclim uses 100 randomly picked years from ModE-Sim as a priori state for improved covariance estimation, but thereby assuming stationarity in the covariance structure and eliminating the externally forced signal in the model simulations. In contrast, ModE-RA uses 20 distinct transient members of ModE-Sim, retaining the externally forced signal. Reference for ModE-RA and ModE-RAclim: Veronika Valler, Franke. J. , Brugnara. Y. , Samakinwa, E., Hand, R. , Lundstad, E., Burgdorf, A., and Stefan Brönnimann, 2023 (in preparation): ModE-RA - A global monthly paleo-reanalysis of the modern era (1421 to 2008), to be submitted to Nature scientific data.
