caa a22 4500 605473102 CHVBK 20210128100341.0 cr unu---uuuuu 210128e20150201xx s 000 0 eng 10.1007/s00382-015-2468-6 doi (NATIONALLICENCE)springer-10.1007/s00382-015-2468-6 The double ITCZ bias in CMIP5 models: interaction between SST, large-scale circulation and precipitation [Elektronische Daten] [Boutheina Oueslati, Gilles Bellon] The double intertropical convergence zone (ITCZ) bias still affects all the models that participate to CMIP5 (Coupled Model Intercomparison Project, phase 5). As an ensemble, general circulation models have improved little between CMIP3 and CMIP5 as far as the double ITCZ is concerned. The present study proposes a new process-oriented metrics that provides a robust statistical relationship between atmospheric processes and the double ITCZ bias, additionally to the existing relationship between the sea surface temperature (SST) and the double ITCZ bias. The SST contribution is examined using the THR-MLT index (Bellucci et al. in J Clim 5:1127-1145, 2010), which combines biases on the representation of local SSTs and the SST threshold leading to the onset of ascent in the double ITCZ region. As a metrics of a model's bias in simulating the interaction between circulation and precipitation, we propose to use the Combined Precipitation Circulation Error (CPCE). It is computed as the quadratic error on the contribution of each vertical regime to the total precipitation over the tropical oceans. CPCE is a global measure of the circulation-precipitation coupling that characterizes the model physical parameterizations rather than the regional characteristics of the eastern Pacific. A linear regression analysis shows that most of the double ITCZ spread among CMIP5 coupled ocean-atmosphere models is attributed to SST biases, and that the precipitation large-scale dynamics relationship explains a significant fraction of the bias in these models, as well as in the atmosphere-only models. Springer-Verlag Berlin Heidelberg, 2015 Double ITCZ nationallicence Atmospheric dynamics nationallicence Coupled ocean-atmosphere feedbacks nationallicence Oueslati Boutheina Centre National de Recherches Météorologiques (CNRS)/Météo-France, 42, Avenue Gaspard Coriolis, 31057, Toulouse, France aut Bellon Gilles Centre National de Recherches Météorologiques (CNRS)/Météo-France, 42, Avenue Gaspard Coriolis, 31057, Toulouse, France aut Climate Dynamics Springer Berlin Heidelberg 44/3-4(2015-02-01), 585-607 0930-7575 44:3-4<585 2015 44 382 https://doi.org/10.1007/s00382-015-2468-6 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/s00382-015-2468-6 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Oueslati Boutheina Centre National de Recherches Météorologiques (CNRS)/Météo-France, 42, Avenue Gaspard Coriolis, 31057, Toulouse, France aut NATIONALLICENCE 700 1- Bellon Gilles Centre National de Recherches Météorologiques (CNRS)/Météo-France, 42, Avenue Gaspard Coriolis, 31057, Toulouse, France aut NATIONALLICENCE 773 0- Climate Dynamics Springer Berlin Heidelberg 44/3-4(2015-02-01), 585-607 0930-7575 44:3-4<585 2015 44 382