caa a22 4500 605473951 CHVBK 20210128100345.0 cr unu---uuuuu 210128e20150301xx s 000 0 eng 10.1007/s00382-014-2161-1 doi (NATIONALLICENCE)springer-10.1007/s00382-014-2161-1 Strategies for reducing the climate noise in model simulations: ensemble runs versus a long continuous run [Elektronische Daten] [Damien Decremer, Chul Chung, Petri Räisänen] Climate modelers often integrate the model with constant forcing over a long time period, and make an average over the period in order to reduce climate noise. If the time series is persistent, as opposed to rapidly varying, such an average does not reduce noise efficiently. In this case, ensemble runs, which ideally represent independent runs, can reduce noise more efficiently. We quantify the noise reduction gain by using ensemble runs over a long continuous run in constant‐forcing simulations. We find that in terms of the amplitude of the noise, a continuous simulation of 30years may be equivalent to as few as five 3-year long ensemble runs in a slab ocean-atmosphere coupled model and as few as two 3-year long ensemble runs in a fully coupled model. The outperformance of ensemble runs over a continuous run is strictly a function of the persistence of the time series. We find that persistence depends on model, location and variable, and that persistence in surface air temperature has robust spatial structures in coupled models. We demonstrate that lag-1year autocorrelation represents persistence fairly well, but the use of lag-1year-lag-5years autocorrelations represents the persistence far more sufficiently. Furthermore, there is more persistence in coupled model output than in the output of a first-order autoregressive model with the same lag-1 autocorrelation. Springer-Verlag Berlin Heidelberg, 2014 Internal variability nationallicence Ensemble simulation nationallicence Climate noise nationallicence Coupled model nationallicence Autocorrelation nationallicence Persistence nationallicence Decremer Damien Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea aut Chung Chul Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea aut Räisänen Petri Finnish Meteorological Institute, Helsinki, Finland aut Climate Dynamics Springer Berlin Heidelberg 44/5-6(2015-03-01), 1367-1379 0930-7575 44:5-6<1367 2015 44 382 https://doi.org/10.1007/s00382-014-2161-1 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/s00382-014-2161-1 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Decremer Damien Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea aut NATIONALLICENCE 700 1- Chung Chul Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea aut NATIONALLICENCE 700 1- Räisänen Petri Finnish Meteorological Institute, Helsinki, Finland aut NATIONALLICENCE 773 0- Climate Dynamics Springer Berlin Heidelberg 44/5-6(2015-03-01), 1367-1379 0930-7575 44:5-6<1367 2015 44 382