caa a22 4500 605471770 CHVBK 20210128105155.0 cr unu---uuuuu 210128e20150901xx s 000 0 eng 10.1007/s00382-014-2390-3 doi (NATIONALLICENCE)springer-10.1007/s00382-014-2390-3 Coupled atmosphere-ocean data assimilation experiments with a low-order model and CMIP5 model data [Elektronische Daten] [Robert Tardif, Gregory Hakim, Chris Snyder] Coupled atmosphere-ocean data assimilation (DA) experiments are performed for estimating the Atlantic meridional overturning circulation (AMOC). Recovery of the AMOC with an ensemble Kalman filter is assessed for a range of experiments over observation availability (atmosphere, upper and deep ocean) and for assimilating high-frequency observations compared to time averages. For an idealised low-order coupled climate model, the traditional DA approach using an ensemble of model trajectories to estimate covariances is compared to a simplified "no-cycling” approach involving climatological covariances derived from a single long model integration. Robustness of the no-cycling method is also tested on data from a millennial-scale simulation of a comprehensive coupled atmosphere-ocean climate model. Results show that the no-cycling approach provides a good approximation to the traditional approach, and that assimilation of time-averaged observations improves AMOC recovery using drastically smaller ensembles than would be required for the case of instantaneous observations. Even in the limit of no ocean observations, the no-cycling approach is capable of recovering the low-frequency AMOC with time-averaged observations; assimilation of noisy instantaneous atmospheric observations fails to recover decadal-scale AMOC variability. The Author(s), 2014 Cost-effective nationallicence Coupled atmosphere-ocean data assimilation nationallicence Atlantic meridional overturning circulation nationallicence Estimation nationallicence Tardif Robert Department of Atmospheric Sciences, University of Washington, Box 351640, 98195-1640, Seattle, WA, USA aut Hakim Gregory Department of Atmospheric Sciences, University of Washington, Box 351640, 98195-1640, Seattle, WA, USA aut Snyder Chris National Center for Atmospheric Research, Boulder, CO, USA aut Climate Dynamics Springer Berlin Heidelberg 45/5-6(2015-09-01), 1415-1427 0930-7575 45:5-6<1415 2015 45 382 https://doi.org/10.1007/s00382-014-2390-3 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00382-014-2390-3 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Tardif Robert Department of Atmospheric Sciences, University of Washington, Box 351640, 98195-1640, Seattle, WA, USA aut NATIONALLICENCE 700 1- Hakim Gregory Department of Atmospheric Sciences, University of Washington, Box 351640, 98195-1640, Seattle, WA, USA aut NATIONALLICENCE 700 1- Snyder Chris National Center for Atmospheric Research, Boulder, CO, USA aut NATIONALLICENCE 773 0- Climate Dynamics Springer Berlin Heidelberg 45/5-6(2015-09-01), 1415-1427 0930-7575 45:5-6<1415 2015 45 382 SWISSBIB 56045466X