“…Iterative forms of EnKF and ES, usually denoted by IEnKF (Gu and Oliver, 2007;Sakov et al, 2012;Gharamti et al, 2015;Luo, 2014) and IES (Chen and Oliver., 2013;Emerick and Reynolds, 2013;Luo et al 2015;Chang et al, 2017;Li et al, 2018), have been developed to improve assimilation performance in scenarios characterized by strongly nonlinear behaviors. A variety of studies investigate challenges linked to such (ensemble) data assimilation algorithms, including, e.g., the possibility of coping with non-Gaussian model parameter distributions (Zhou et al, 2011;Li et al, 2018), physical inconsistency/unphysical results stemming from the estimation workflow (Wen and Chen, 2006;Song et al, 2015), or spurious correlations (Panzeri et al, 2013;Bauser et al, 2018;Luo et al, 2018;Soares et al, 2019). All of these works contribute to improve the robustness of these algorithms for parameter estimation in complex environmental systems.…”