Abstract. BCC-CSM2-HR is a high-resolution version of the Beijing Climate Center (BCC)
Climate System Model (T266 in the atmosphere and 1/4∘
latitude × 1/4∘ longitude in the ocean). Its development is on the
basis of the medium-resolution version BCC-CSM2-MR (T106 in the atmosphere
and 1∘ latitude × 1∘ longitude in the ocean) which is the
baseline for BCC participation in the Coupled Model Intercomparison Project
Phase 6 (CMIP6). This study documents the high-resolution model, highlights
major improvements in the representation of atmospheric dynamical core and
physical processes. BCC-CSM2-HR is evaluated for historical climate
simulations from 1950 to 2014, performed under CMIP6-prescribed historical
forcing, in comparison with its previous medium-resolution version
BCC-CSM2-MR. Observed global warming trends of surface air temperature from
1950 to 2014 are well captured by both BCC-CSM2-MR and BCC-CSM2-HR.
Present-day basic atmospheric mean states during the period from 1995 to
2014 are then evaluated at global scale, followed by an assessment on
climate variabilities in the tropics including the tropical cyclones (TCs),
the El Niño–Southern Oscillation (ENSO), the Madden–Julian
Oscillation (MJO), and the quasi-biennial oscillation (QBO) in the
stratosphere. It is shown that BCC-CSM2-HR represents the global energy
balance well and can realistically reproduce the main patterns of atmospheric temperature and wind, precipitation, land surface air temperature, and sea
surface temperature (SST). It also improves the spatial patterns of sea ice
and associated seasonal variations in both hemispheres. The bias of the double
intertropical convergence zone (ITCZ), obvious in BCC-CSM2-MR, almost
disappears in BCC-CSM2-HR. TC activity in the tropics is increased with
resolution enhanced. The cycle of ENSO, the eastward propagative feature and
convection intensity of MJO, and the downward propagation of QBO in BCC-CSM2-HR
are all in a better agreement with observations than their counterparts in
BCC-CSM2-MR. Some imperfections are, however, noted in BCC-CSM2-HR, such as
the excessive cloudiness in the eastern basin of the tropical Pacific with
cold SST biases and the insufficient number of tropical cyclones in the
North Atlantic.