Predicting the severity of spurious "double ITCZ" problem in CMIP5 coupled models from AMIP simulations. Issue 3 (13th February 2017)

• Record Type: Journal Article
• Authors: Xiang, Baoqiang; Zhao, Ming; Held, Isaac M.; Golaz, Jean‐Christophe
• Is Part Of: Geophysical research letters. Volume 44:Issue 3(2017)
• Page Start: 1520
• Page End: 1527
• Publication Date: 2017-02-13
• Subjects: double ITCZ -- CMIP5 -- SST bias -- surface heat flux bias -- precipitation asymmetry index; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2016GL071992
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The severity of the double Intertropical Convergence Zone (DI) problem in climate models can be measured by a tropical precipitation asymmetry index (PAI), indicating whether tropical precipitation favors the Northern Hemisphere or the Southern Hemisphere. Examination of 19 Coupled Model Intercomparison Project phase 5 models reveals that the PAI is tightly linked to the tropical sea surface temperature (SST) bias. As one of the factors determining the SST bias, the asymmetry of tropical net surface heat flux in Atmospheric Model Intercomparison Project (AMIP) simulations is identified as a skillful predictor of the PAI change from an AMIP to a coupled simulation, with an intermodel correlation of 0.90. Using tropical top‐of‐atmosphere (TOA) fluxes, the correlations are lower but still strong. However, the extratropical asymmetries of surface and TOA fluxes in AMIP simulations cannot serve as useful predictors of the PAI change. This study suggests that the largest source of the DI bias is from the tropics and from atmospheric models. Key Points: The double ITCZ problem in CMIP5 models is tightly linked to the tropical SST bias The severity of the double ITCZ problem in coupled models can be predicted by using the tropical net surface heat flux in AMIP simulations The largest source of the DI bias is from the tropics and from atmospheric models