We present an unprecedented set of high‐resolution climate simulations, consisting of a 500‐year pre‐industrial control simulation and a 250‐year historical and future climate simulation from 1850 to 2100. A high‐resolution configuration of the Community Earth System Model version 1.3 (CESM1.3) is used for the simulations with a nominal horizontal resolution of 0.25° for the atmosphere and land models and 0.1° for the ocean and sea‐ice models. At these resolutions, the model permits tropical cyclones and ocean mesoscale eddies, allowing interactions between these synoptic and mesoscale phenomena with large‐scale circulations. An overview of the results from these simulations is provided with a focus on model drift, mean climate, internal modes of variability, representation of the historical and future climates, and extreme events. Comparisons are made to solutions from an identical set of simulations using the standard resolution (nominal 1°) CESM1.3 and to available observations for the historical period to address some key scientific questions concerning the impact and benefit of increasing model horizontal resolution in climate simulations. An emerging prominent feature of the high‐resolution pre‐industrial simulation is the intermittent occurrence of polynyas in the Weddell Sea and its interaction with an Interdecadal Pacific Oscillation. Overall, high‐resolution simulations show significant improvements in representing global mean temperature changes, seasonal cycle of sea‐surface temperature and mixed layer depth, extreme events and in relationships between extreme events and climate modes.

The eddy energy sources and sinks in the South China Sea (SCS) are studied based on a high‐resolution ocean circulation model. Eddies are found to acquire their energy from barotropic instability (BT), the release of available potential energy (APE) associated with baroclinic instability (BC) and horizontal convergence from surrounding areas, while they lose energy due to turbulent processes. Both the eddy energy sources and sinks show western intensification with their maximum around the southwestern SCS where most of the wind‐input energy occurs, and the Luzon Strait where the Kuroshio intrudes the SCS in winter. Unlike that in the open ocean, the eddy energy in the inner SCS is confined to the upper layer. Besides, the eddy energy indicates clear seasonal variability, especially at the Luzon Strait where the eddy activity is much stronger in winter than in summer. Energy budget analysis suggests that APE releasing is found to be the most important eddy energy source, accounting for over 60% of the total, followed by energy convergence from surrounding areas in horizontal direction (around 20%) and energy released from BT (around 15%). Most of the generated energy is mainly balanced by the turbulent processes, while both of the downward energy flux and tendency term are negligible.

Using the Estimating Circulation and Climate of the Ocean Phase II product, this study investigates the eddy characteristics and energetics in two dynamical regimes within the Kuroshio Extension (KE) region. Based on the empirical orthogonal function analysis, it is found that the decadal evolution of eddy kinetic energy in the KE region is characterized by a delayed negative correlation between the upstream and downstream. Besides the out‐of‐phase change in eddy activity levels, eddy characteristics and energetics in the upstream KE are also different from those in the downstream. In the upstream region, eddies are stretched in the zonal direction and the unstable state is characterized by strong eddy‐shedding processes. During these processes, cyclonic eddies are found to be formed in the first quasi‐stationary meander and finally pinched off from the KE jet. Energy budget illustrates that the eddy shedding processes are triggered by baroclinic instability, while barotropic instability becomes the dominated energy source after the meander is fully developed. Accompanied by the generation of cyclonic eddies, significant inverse energy cascade is detected. When the upstream KE is stable, the eddy activity is dominated by baroclinic instability and the inverse energy cascade occurs similarly. Distinct from the upstream, eddies in the downstream KE tend to be stretched in the meridional direction and the decadal variability of eddy kinetic energy in this region is mainly regulated by the upstream through lateral advection.

Using the high-resolution Community Earth System Model (CESM) output, this study investigates air–sea interaction and its role in eddy energy dissipation in the Kuroshio Extension (KE) region. Based on an eddy energetics analysis, it is found that the baroclinic pathway associated with temperature variability is the main eddy energy source in this region. Both the air–sea heat flux and wind stress act as eddy killers that remove energy from oceanic eddies. Heat exchange between atmosphere and oceanic eddies dominates the dissipation of eddy temperature variance within the surface layer and accounts for 36% of the total dissipation in the upper 350-m layer. Compared to the heat exchange, the role of wind power in damping the eddy kinetic energy (EKE) is relatively small. Only 18% of EKE dissipation in the upper 350 m is attributed to eddy wind power. Misrepresentation of the damping role of mesoscale ocean–atmosphere interaction can result in an incorrect vertical structure of eddy energy dissipation, leading to an erroneous representation of vertical mixing in the interior ocean.

Air‐sea exchanges across oceanic fronts are critical in powering cloud formation, precipitation, and atmospheric storms. Oceanic submesoscale fronts of scales 1–10 km are characterized by strong sea surface temperature (SST) gradients. However, it remains elusive how submesoscale fronts affect the overlying atmosphere due to a lack of high‐resolution observations or models. Based on rare high‐resolution in situ observations in the Kuroshio Extension region, we quantify the air‐sea exchanges across an oceanic submesoscale front. The cross‐front SST and turbulent heat flux gradients reaches 2.4°C/km and 47 W/m²/km, respectively, far stronger than that typically found in mesoscale‐resolving products. The stronger SST gradient drives substantially stronger air‐sea fluxes and vertical mixing than mesoscale fronts, enhancing cloud formations. The intense air‐sea exchanges across submesoscale fronts are confirmed in idealized model simulations, but not resolved in mesoscale‐resolving climate models. Our finding provides essential knowledge for improving simulations of cloud formation, precipitation, and storms in climate models.