Using a process-based dendroclimatic proxy system model in a data assimilation framework: a test case in the Southern Hemisphere over the past centuries

Abstract

Abstract. Currently available data-assimilation-based reconstructions of past climate variations have only used statistical proxy system models to make the link between climate model outputs and indirect observations from tree rings. However, the linearity and stationarity assumptions of the statistical approach may have limitations. In this study, we incorporate the process-based dendroclimatic model MAIDEN into a data assimilation procedure using the reconstruction of near-surface air temperature, precipitation and winds in the midlatitudes of the Southern Hemisphere over the past 400 years as a test case. We compare our results with a data assimilation approach including a linear regression as a proxy system model for tree-ring width proxies. Overall, when compared to instrumental data, the reconstructions using MAIDEN as a proxy system model offer a skill equivalent to the experiment using the regression model. However, knowing the advantages that a process-based model can bring and the improvements that can still be made with MAIDEN, those results are promising.

An Unprecedented Sea Ice Retreat in the Weddell Sea Driving an Overall Decrease of the Antarctic Sea‐Ice Extent Over the 20th Century

“…The method is based on a particle filter (Dubinkina et al., 2011), with an implementation identical to several recent studies (Dalaiden et al., 2021; Klein et al., 2019; Rezsöhazy et al., 2022). In the offline version of the particle filter, all the years of the model simulations constitute our prior as the years are assumed to be independent (referred to as particles), which is a reasonable assumption for the variables of interest (Brennan et al., 2020; Hakim et al., 2016; Matsikaris et al., 2015; Okazaki et al., 2021; Steiger et al., 2017).…”