This paper introduces the Flexible Global Ocean‐Atmosphere‐Land System Model: Grid‐Point Version 3 (FGOALS‐g3) and evaluates its basic performance based on some of its participation in the sixth phase of the Coupled Model Intercomparison Project (CMIP6) experiments. Our results show that many significant improvements have been achieved by FGOALS‐g3 in terms of climatological mean states, variabilities, and long‐term trends. For example, FGOALS‐g3 has a small (−0.015°C/100 yr) climate drift in 700‐yr preindustrial control (piControl) runs and smaller biases in climatological mean variables, such as the land/sea surface temperatures (SSTs) and seasonal soil moisture cycle, compared with its previous version FGOALS‐g2 during the historical period. The characteristics of climate variabilities, for example, Madden‐Julian oscillation (MJO) eastward/westward propagation ratios, spatial patterns of interannual variability of tropical SST anomalies, and relationship between the East Asian Summer Monsoon and El Niño–Southern Oscillation (ENSO), are well captured by FGOALS‐g3. In particular, the cooling trend of globally averaged surface temperature during 1940–1970, which is a challenge for most CMIP3 and CMIP5 models, is well reproduced by FGOALS‐g3 in historical runs. In addition to the external forcing factors recommended by CMIP6, anthropogenic groundwater forcing from 1965 to 2014 was incorporated into the FGOALS‐g3 historical runs.

The second version of Chinese Academy of Sciences Earth System Model (CAS‐ESM 2) is described with emphasis on the development process, strength and weakness, and climate sensitivities in simulations of the Coupled Model Intercomparison Project (CMIP6) DECK experiments. CAS‐ESM 2 was built as a numerical model to simulate both the physical climate system as well as atmospheric chemistry and carbon cycle. It is a newcomer in the international modeling community to provide sufficiently independent solutions of climate simulations from those of other models. Performances of the model in simulating the basic states of the radiation budget of the atmosphere and ocean, precipitation, circulations, variabilities, and the 20^th Century warming are presented. Model biases and their possible causes are discussed. Strength includes horizontal heat transport in the atmosphere and oceans, vertical profile of the Atlantic Meridional Overturning Circulation; weakness includes the double Inter‐Tropical Convergence Zone (ITCZ) and stronger amplitude of the El Niño‐Southern Oscillation (ENSO) that are also common in many other models. The simulated the 20^th Century warming shares a similar discrepancy with observations as in several other models—less warming in the 1920s and stronger cooling in the 1960s than in observation—at the time when there was a steep increase of anthropogenic aerosols. As a result, the 20^th Century warming is about 60% of the observed warming despite that the model simulated a similar slope of warming trend after 1980 to observation. The model has an equilibrium climate sensitivity of 3.4 K with a positive cloud feedback from the shortwave radiation.

A 61-year (1958–2018) global eddy-resolving dataset for phase 2 of the Ocean Model Intercomparison Project has been produced by the version 3 of Chinese Academy of Science, the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics (LASG/IAP) Climate system Ocean Model (CAS-LICOM3). The monthly and a part of the surface daily data in this study can be accessed on the Earth System Grid Federation (ESGF) node. Besides the details of the model and experiments, the evolutions and spatial patterns of large-scale and mesoscale features are also presented. The mesoscale features are reproduced well in the high-resolution simulation, as the mesoscale activities can contribute up to 50% of the total SST variability in eddy-rich regions. Also, the large-scale circulations are remarkably improved compared with the low-resolution simulation, such as the climatological annual mean SST (the RMSE is reduced from 0.59°C to 0.47°C, globally) and the evolution of Atlantic Meridional Overturning Circulation. The preliminary evaluation also indicates that there are systematic biases in the salinity, the separation location of the western boundary currents, and the magnitude of eddy kinetic energy. All these biases are worthy of further investigation.

A high-resolution ($\mathrm{1}/\mathrm{20}{}^{\circ }$ ) global ocean general circulation model with graphics processing unit (GPU) code implementations is developed based on the LASG/IAP Climate System Ocean Model version 3 (LICOM3) under a heterogeneous-compute interface for portability (HIP) framework. The dynamic core and physics package of LICOM3 are both ported to the GPU, and three-dimensional parallelization (also partitioned in the vertical direction) is applied. The HIP version of LICOM3 (LICOM3-HIP) is 42 times faster than the same number of CPU cores when 384 AMD GPUs and CPU cores are used. LICOM3-HIP has excellent scalability; it can still obtain a speedup of more than 4 on 9216 GPUs compared to 384 GPUs. In this phase, we successfully performed a test of $\mathrm{1}/\mathrm{20}{}^{\circ }$ LICOM3-HIP using 6550 nodes and 26 200 GPUs, and on a large scale, the model's speed was increased to approximately 2.72 simulated years per day (SYPD). By putting almost all the computation processes inside GPUs, the time cost of data transfer between CPUs and GPUs was reduced, resulting in high performance. Simultaneously, a 14-year spin-up integration following phase 2 of the Ocean Model Intercomparison Project (OMIP-2) protocol of surface forcing was performed, and preliminary results were evaluated. We found that the model results had little difference from the CPU version. Further comparison with observations and lower-resolution LICOM3 results suggests that the $\mathrm{1}/\mathrm{20}{}^{\circ }$ LICOM3-HIP can reproduce the observations and produce many smaller-scale activities, such as submesoscale eddies and frontal-scale structures.

Some mesoscale eddies intrude over the continental slope in the northern South China Sea, supporting cross‐shelf matter transport. We investigated the characteristics, the intruding tracks and formation mechanisms, of slope intrusion mesoscale eddies using satellite altimeter data and model outputs. In total, 36 and 22 slope intrusion anticyclonic and cyclonic eddies (SAEs/SCEs) are found, respectively. Slope intrusion eddies have longer lifetimes (~58 days), smaller size (~110 km), and greater eddy kinetic energy and vorticity compared to ordinary eddies but are more unstable and more easily deformed during their life cycles. The statistical results show that more slope intrusion eddies are generated during winter than other seasons. It is found that slope intrusion eddies mainly propagate westward/northwestward, and southwestward along the continental slope and shelf. Eddy intrusions occur mainly near the Dongsha Islands, east of Hainan, and north of the Xisha Islands. SAEs continue to propagate onshore after arrival at the continental slope, while SCEs dissipate more quickly. Using mooring data, we found that eddy‐ambient flow interaction could cause the differences between SAEs and SCEs around the Dongsha Islands. Energy conversion was analyzed in these three regions using numerical products. During intrusion, eddies lose eddy kinetic energy and ambient flows gain energy.

In the study, the responses of chlorophyll to decadal oscillations of Kuroshio Extension (KE) between two dynamical states are investigated using satellite data. Associated with the KE stable and unstable states, the surface chlorophyll south of 35°N also undergoes two different contrast patterns: low (high) chlorophyll (∼12% relative to multiyear mean) corresponding to strengthened (weakened) KE jet, i.e., stable (unstable) KE. Two distinct seesaw patterns exist on the north and south side of 35°N for both chlorophyll and sea level anomaly and on the east and west side of 153°E for both chlorophyll and eddy kinetic energy. Similarly, the magnitude of spring bloom was also modulated by decadal variations of KE. The spring bloom was suppressed (enhanced) relative to the magnitude of climatological spring bloom south of 35°N during the KE stable (unstable) period. This change is significant and can reach 35% in extreme years of 2006 and 2009. The decadal variation of chlorophyll in the KE is likely modulated by vertical nutrient supply induced by divergences (convergences) associated with the westward propagation of wind‐induced Rossby waves in the central and eastern North Pacific Ocean, which are dynamically modulated by the North Pacific Gyre Oscillations (NPGO) or PDO (Pacific Decadal Oscillations).