Global Climate Simulated by the Seoul National University Atmosphere Model Version 0 with a Unified Convection Scheme (SAM0-UNICON)

Abstract

As a contribution to phase 6 of the Coupled Model Intercomparison Project (CMIP6), the global climate simulated by an atmospheric general circulation model (GCM), the Seoul National University Atmosphere Model version 0 with a Unified Convection Scheme (SAM0-UNICON), is compared with observation and climates simulated by the Community Atmosphere Model version 5 (CAM5) and Community Earth System Model version 1 (CESM1), on which SAM0-UNICON is based. Both SAM0-UNICON and CESM1 successfully reproduce observed global warming after 1970. The global mean climate simulated by SAM0-UNICON is roughly similar to that of CAM5/CESM1. However, SAM0-UNICON improves the simulations of the double intertropical convergence zone, shortwave cloud forcing, near-surface air temperature, aerosol optical depth, sea ice fraction, and sea surface temperature (SST), but is slightly poorer for the simulation of tropical relative humidity, Pacific surface wind stress, and ocean rainfall. Two important biases in the simulated mean climate in both models are a set of horseshoe-shaped biases of SST, sea level pressure, precipitation, and cloud radiative forcings in the central equatorial Pacific and a higher sea ice fraction in the Arctic periphery and Southern Hemispheric circumpolar regions. Both SAM0-UNICON and CESM1 simulate the observed El Niño–Southern Oscillation (ENSO) reasonably well. However, compared with CAM5/CESM1, SAM0-UNICON performs better in simulating the Madden–Julian oscillation (MJO), diurnal cycle of precipitation, and tropical cyclones. The aerosol indirect effect (AIE) simulated by SAM0-UNICON is similar to that from CAM5 but the magnitudes of the individual shortwave and longwave AIEs are substantially reduced.

Impacts of ENSO and Madden–Julian oscillation on the genesis of tropical cyclones simulated by general circulation models and compared to observations

“…SAM0-UNICON is one of the international GCMs participating in the CMIP6 and is based on the Community Atmosphere Model Version 5 (CAM5; [41,42]), but CAM5ʼs shallow ( [43]) and deep convection schemes ( [44]) were replaced by UNICON ( [45,46]) with a revised treatment of convective detrainment processes ( [47]). Reference [31] demonstrated that the global mean climate and ENSO simulated by SAM0/SEM0 are similar to those simulated by CAM5/CESM1. However, SAM0/SEM0 substantially improves the simulation of MJO, the diurnal cycle of precipitation, and TG.…”

“…Daily outgoing longwave radiation (OLR) and horizontal wind vector at levels of 850 and 200 hPa, which are used for defining MJO, came from observations of the Advanced Very-High-Resolution Radiometer satellite ( [36]) and the NCEP-NCAR reanalysis product ( [37]), respectively. In terms of GCMs, we conducted 400 years of coupled simulations at a 0.95°latitude×1.25°longitude horizontal resolution (nominally, 1°) in the pre-industrial period with the CESM1 and SEM0-UNICON ( [31]) driven by the forcing data obtained from phase six of the Coupled Model Intercomparison Project (CMIP6; [38]). Although not sufficient for reproducing the observed strength of TCs, 1°GCM simulations have been used in previous studies to examine the interannual and intraseasonal variations of the genesis of tropical cyclones ( [26,39,40]).…”

“…Here, we investigate the impacts of ENSO and MJO on TG using a set of long-term coupled GCM simulations produced by the Community Earth System Model version 1 (CESM1; [30]) and Seoul National University Earth System Model Version 0 with a unified convection scheme (SEM0-UNICON; [31]). The results are then compared to observations.…”

“…The results are then compared to observations. SEM0-UNICON is one of the very few GCMs that simulates observed ENSO, MJO, and their teleconnections reasonably well ( [32,33]), as well as TG and the diurnal cycle of precipitation ( [31]). To the best of our knowledge, our study is one of the very few attempts to investigate the combined effects of ENSO and MJO on TG utilizing GCMs, which can contribute to improving short-term TC forecasting and understanding changes in TC activity in the future.…”

Enhancing ENSO Prediction Skill by Combining Model‐Analog and Linear Inverse Models (MA‐LIM)

“…We performed the analyses using monthly SST/SSH fields at 1° latitude 1° longitude horizontal resolution in the tropics (25°S to 25°N). For the perfect model analysis, we use 450 years from the preindustrial period simulated by the Seoul National University Atmosphere Model Version 0 with a Unified Convection Scheme (SAM0‐UNICON; Park et al, ). All model analyses are tenfold cross validation of the 10 subsets of the simulation data: each subset consists of a 45 year evaluation period (10% of the entire data) and the remaining 405 year population.…”