The Beijing Climate Center Climate System Model (BCC-CSM): the main progress from CMIP5 to CMIP6

TLDR

The paper presents the key advancements of the BCC climate system model from CMIP5 to CMIP6, focusing on improved physical parameterizations and model performance. The study compares BCC-CSM1.1m (CMIP5) with BCC-CSM2-MR, BCC-CSM2-HR, and BCC-ESM1.0 (CMIP6) using historical simulations from 1851–2014 and evaluates them against energy budget, temperature, precipitation, circulation, SST, sea‑ice, AMOC, and climate variability metrics. BCC-CSM2-MR outperforms BCC-CSM1.1m, delivering notable gains in tropospheric temperature, circulation, and multi‑scale climate variability, including QBO, MJO, diurnal precipitation, equatorial Pacific SST, and long‑term surface temperature trends. Abstract.

Abstract

Abstract. The main advancements of the Beijing Climate Center (BCC) climate system model from phase 5 of the Coupled Model Intercomparison Project (CMIP5) to phase 6 (CMIP6) are presented, in terms of physical parameterizations and model performance. BCC-CSM1.1 and BCC-CSM1.1m are the two models involved in CMIP5, whereas BCC-CSM2-MR, BCC-CSM2-HR, and BCC-ESM1.0 are the three models configured for CMIP6. Historical simulations from 1851 to 2014 from BCC-CSM2-MR (CMIP6) and from 1851 to 2005 from BCC-CSM1.1m (CMIP5) are used for models assessment. The evaluation matrices include the following: (a) the energy budget at top-of-atmosphere; (b) surface air temperature, precipitation, and atmospheric circulation for the global and East Asia regions; (c) the sea surface temperature (SST) in the tropical Pacific; (d) sea-ice extent and thickness and Atlantic Meridional Overturning Circulation (AMOC); and (e) climate variations at different timescales, such as the global warming trend in the 20th century, the stratospheric quasi-biennial oscillation (QBO), the Madden–Julian Oscillation (MJO), and the diurnal cycle of precipitation. Compared with BCC-CSM1.1m, BCC-CSM2-MR shows significant improvements in many aspects including the tropospheric air temperature and circulation at global and regional scales in East Asia and climate variability at different timescales, such as the QBO, the MJO, the diurnal cycle of precipitation, interannual variations of SST in the equatorial Pacific, and the long-term trend of surface air temperature.