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

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.

Improvement of the simulation of the summer East Asian westerly jet from CMIP5 to CMIP6

“…The present study shows the improvements in the simulation of the EAJ in the CMIP6 models, with an improved description of the intensity and longitudinal location as well as reduced uncertainty. The improvements are likely induced by the improved AOGCMs in the CMIP6, for example, the higher resolutions in the atmosphere and ocean, improved representations of physical processes (Wu et al 2019) and improved representation of aerosols (Wyser et al 2019). However, how the changes in the AOGCMs improve the simulation of the EAJ in the CMIP6 models is unclear.…”

“…Compared to the earlier versions of AOGCMs used in the CMIP5, the CMIP6 models have been improved in many aspects, such as higher resolutions in the atmosphere and ocean, an improved representation of physics (e.g. Wu et al 2019), and improved representation of aerosols (e. g. Wyser et al 2019). Therefore, the output data provide an opportunity to estimate the abilities of these new AOGCMs to simulate the EAJ, which is the motivation for the present study.…”

Development of the global atmospheric general circulation-chemistry model BCC-GEOS-Chem v1.0: model description and evaluation

“…In this study we use the default horizontal spectral resolution of T42 (approximately 2.8° latitude × 2.8° longitude). The dynamical core and physical processes of the BCC-AGCM3 have been described comprehensively in Wu et al (2008Wu et al ( , 2010 with recent updates documented in Wu et al (2012Wu et al ( , 2019. Wu et al (2019) showed that the BCC-CSM2 (BCC-AGCM3 as the atmospheric model) well captured the global patterns of temperature, precipitation, and atmospheric energy budget.…”

“…BCC-GEOS-Chem is built on the coupling of the GEOS-Chem chemical module to the BCC Atmospheric General Circulation Model (BCC-AGCM), the atmospheric component of the BCC-CSM2. BCC-CSM2 is a fully coupled global CSM in which the atmosphere, land, ocean, and sea-ice components interact with each other through the exchange of momentum, energy, water, and carbon (Wu et al, 2008(Wu et al, , 2013(Wu et al, , 2019. The earlier version of BCC-CSM (v1.1 and v1.1m) was enrolled in CMIP5 and has been widely applied on weather and climate research (e.g., Wu et al, 2013Wu et al, , 2014Xin et al, 2013;Zhao and He, 2015).…”

“…The earlier version of BCC-CSM (v1.1 and v1.1m) was enrolled in CMIP5 and has been widely applied on weather and climate research (e.g., Wu et al, 2013Wu et al, , 2014Xin et al, 2013;Zhao and He, 2015). It has been recently updated to BCC-CSM2 and is being used in that configuration for the Coupled Model Intercomparison Project Phase 6 (CMIP6) (Wu et al, 2019). GEOS-Chem (http://geos-chem.org), originally described by Bey et al (2001) is a global three-dimensional chemical transport model (CTM) which includes detailed state-of-science gas-aerosol chemistry, is used by a large international community for a broad range of research on atmospheric chemistry, is continually updated with scientific innovations from users, is rigorously benchmarked, and is openly accessible on the cloud (Zhuang et al, 2019).…”