This work documents the first version of the U.S. Department of Energy (DOE) new EnergyExascale Earth System Model (E3SMv1). We focus on the standard resolution of the fully coupled physical model designed to address DOE mission-relevant water cycle questions. Its components include atmosphere and land (110-km grid spacing), ocean and sea ice (60 km in the midlatitudes and 30 km at the equator and poles), and river transport (55 km) models. This base configuration will also serve as a foundation for additional configurations exploring higher horizontal resolution as well as augmented capabilities in the form of biogeochemistry and cryosphere configurations. The performance of E3SMv1 is evaluated by means of a standard set of Coupled Model Intercomparison Project Phase 6 (CMIP6) Diagnosis, Evaluation, and Characterization of Klima simulations consisting of a long preindustrial control, historical simulations (ensembles of fully coupled and prescribed SSTs) as well as idealized CO 2 forcing simulations. The model performs well overall with biases typical of other CMIP-class models, although the simulated Atlantic Meridional Overturning Circulation is weaker than many CMIP-class models. While the E3SMv1 historical ensemble captures the bulk of the observed warming between preindustrial (1850) and present day, the trajectory of the warming diverges from observations in the Key Points: • This work documents E3SMv1, the first version of the U.S. DOE Energy Exascale Earth System Model • The performance of E3SMv1 is documented with a set of standard CMIP6 DECK and historical simulations comprising nearly 3,000 years • E3SMv1 has a high equilibrium climate sensitivity (5.3 K) and strong aerosol-related effective radiative forcing (-1.65 W/m 2 ) Correspondence to: Chris Golaz, golaz1@llnl.gov Citation: Golaz, J.-C., Caldwell, P. M., Van Roekel, L. P., Petersen, M. R., Tang, Q., Wolfe, J. D., et al. (2019). The DOE E3SM coupled model version 1: Overview and evaluation at standard resolution. second half of the twentieth century with a period of delayed warming followed by an excessive warming trend. Using a two-layer energy balance model, we attribute this divergence to the model's strong aerosol-related effective radiative forcing (ERF ari+aci = −1.65 W/m 2 ) and high equilibrium climate sensitivity (ECS = 5.3 K). Plain Language Summary The U.S. Department of Energy funded the development of a new state-of-the-art Earth system model for research and applications relevant to its mission. The Energy Exascale Earth System Model version 1 (E3SMv1) consists of five interacting components for the global atmosphere, land surface, ocean, sea ice, and rivers. Three of these components (ocean, sea ice, and river) are new and have not been coupled into an Earth system model previously. The atmosphere and land surface components were created by extending existing components part of the Community Earth System Model, Version 1. E3SMv1's capabilities are demonstrated by performing a set of standardized simulation experiments described by...

This study provides an overview of the coupled high‐resolution Version 1 of the Energy Exascale Earth System Model (E3SMv1) and documents the characteristics of a 50‐year‐long high‐resolution control simulation with time‐invariant 1950 forcings following the HighResMIP protocol. In terms of global root‐mean‐squared error metrics, this high‐resolution simulation is generally superior to results from the low‐resolution configuration of E3SMv1 (due to resolution, tuning changes, and possibly initialization procedure) and compares favorably to models in the CMIP5 ensemble. Ocean and sea ice simulation is particularly improved, due to better resolution of bathymetry, the ability to capture more variability and extremes in winds and currents, and the ability to resolve mesoscale ocean eddies. The largest improvement in this regard is an ice‐free Labrador Sea, which is a major problem at low resolution. Interestingly, several features found to improve with resolution in previous studies are insensitive to resolution or even degrade in E3SMv1. Most notable in this regard are warm bias and associated stratocumulus deficiency in eastern subtropical oceans and lack of improvement in El Niño. Another major finding of this study is that resolution increase had negligible impact on climate sensitivity (measured by net feedback determined through uniform +4K prescribed sea surface temperature increase) and aerosol sensitivity. Cloud response to resolution increase consisted of very minor decrease at all levels. Large‐scale patterns of precipitation bias were also relatively unaffected by grid spacing.

Aerosol acidity plays an important role in atmospheric chemistry. China emits large amounts of SO2, NOx, and NH3 into the atmosphere, but aerosol acidity is poorly characterized. In this study, simultaneous 1 h measurements of particulate and gaseous compositions along with the ISORROPIA‐II thermodynamic equilibrium model were used to study aerosol acidity during severe haze episodes in northern China. The summed concentration of sulfate, nitrate, and ammonium was 135 ± 51 μg/m3 with a maximum of 250 μg/m3, and the gas‐phase NH3 mixing ratio was 22 ± 9 ppb. Fine particles were moderately acidic, with a pH range of 3.0–4.9 and an average of 4.2, which was higher than those in the United States and Europe. Excess NH3 and high aerosol water content are responsible for the relatively lower aerosol acidity. These results suggest that the new pathways for sulfate production in China proposed by recent studies should be revisited.

25Emissions from biomass burning contribute significantly to water-soluble organic carbon (WSOC) 26 and light-absorbing organic carbon (brown carbon). Ambient atmospheric samples were collected at an 27 urban site in Beijing during winter and summer, along with source samples from residential crop straw 28 burning. Carbonaceous aerosol species, including organic carbon (OC), elemental carbon (EC), WSOC and 29 multiple saccharides as well as water-soluble potassium (K + ) in PM 2.5 (fine particulate matter with size less 30 than 2.5µm) were measured. Chemical signatures of atmospheric aerosols in Beijing during winter and 31 summer days with significant biomass burning influence were identified. Meanwhile, light absorption by 32 WSOC was measured and quantitatively compared to EC at ground level. The results from this study 33 indicated that levoglucosan exhibited consistently high concentrations (209±145 ng m -3 ) in winter. Ratios 34 of levoglucosan/mannosan (L/M) and levoglucosan/galacosan (L/G) indicated that residential biofuel use 35is an important source of biomass burning aerosol in winter in Beijing. Light absorption coefficient per 36 unit ambient WSOC mass calculated at 365 nm is approximately 1.54±0.16 m 2 g -1 in winter and 0.73±0.15 37 m 2 g -1 in summer. Biomass burning derived WSOC accounted for 23±7% and 16±7% of total WSOC 38 mass, and contributed to 17±4% and 19±5% of total WSOC light absorption in winter and summer, 39 respectively. It is noteworthy that, up to 30% of total WSOC light absorption was attributed to biomass 40 burning in significant biomass-burning-impacted summer day. Near-surface light absorption (over the 41 range 300-400 nm) by WSOC was about ~40% of that by EC in winter and ~25% in summer. 42 Keywords: Biomass burning, WSOC, saccharides, levoglucosan, light absorption 43 44 4 / 21 2. Methodology 83 2.1 Sampling of ambient and source samples 84 PM 2.5 (fine particulate matter with size less than 2.5 µm) was collected in the campus of Peking 85 University (39°59′21″N, 116°18′25″E) in the northwestern area of Beijing city, with no obvious emission 86 sources around except two major roads (150 m to the east and 200 m to the south). Situated in a mixed 87 district of teaching, residential and commercial areas, the sampling site is representative of the Beijing 88 urban area. 89 A high volume sampler (VFC-PM 2.5 , Thermo Fisher Scientific Co., U.S., 1.13 m 3 min -1 , 8＂×10＂quartz 90 filter) and a four-channel sampler (TH-16A, Tianhong, China, 16.7 L min -1 , 47 mm i.d. Teflon and quartz 91 filters) were co-located at the site, mounted on the rooftop of a building approximately 20 m above ground 92 level. Particles less than 2.5 micron in aerodynamic diameter were collected by both samplers. Quartz 93 filters (Pallflex, Tissuquartz, 2500 QAT-UP) were used for EC and OC analysis and Teflon filters 94 (Whatman Inc. Clifton, NJ, USA) were used for ion analysis. All quartz filters were pre-baked in a furnace 95 at 550℃ for 6 hours. After sampling, all filter samples were kept frozen at ...