Fountains under combined temperature and salinity effect are common in environmental and industrial settings. The behavior of weak axisymmetric fountains under combined temperature and salinity effect is studied with two-dimensional direct numerical simulations over 0.25 ≤ FrT ≤ 2.0 and −0.75 ≤ N ≤ 5.0, where FrT is the Froude number based on temperature only and N is the buoyancy ratio quantifying the ratio of salinity to temperature contributed to density. The results show that for each FrT, both the initial and time-average maximum fountain heights decrease when N increases as the combined negative buoyancy due to both temperature and salinity is strengthened, whereas as FrT increases, they increase as the overall negative buoyancy reduces. If the overall Froude number, Fr, which is based on density due to the combined temperature and salinity contributions, is used instead of FrT, the existing scaling relations for weak axisymmetric fountains with density coming from temperature only are also applicable for the weak axisymmetric fountains under the combined temperature and salinity effect when Fr ≲ 2.0, although there are slight differences in their quantified correlations due to the extra effect from the co-existing salinity. It is further shown that the effect from the co-existing salinity shifts the scaling relation for intermediate fountains with 2.0 ≲ Fr ≲ 4.0 with density from only one contributor to the scaling relation for weak fountains with Fr ≲ 2.0 with density coming from both temperature and salinity, further showing the additional effect of salinity.

Abstract Quantification of dust aerosols in Earth System Models (ESMs) has important implications for water cycle and biogeochemistry studies. This study examines the global life cycle and direct radiative effects (DREs) of dust in the U.S. Department of Energy's Energy Exascale Earth System Model version 1 (E3SMv1), and the impact of increasing model resolution both horizontally and vertically. The default 1° E3SMv1 captures the spatial and temporal variability in the observed dust aerosol optical depth (DAOD) reasonably well, but overpredicts dust absorption in the shortwave (SW). Simulations underestimate the dust vertical and long‐range transport, compared with the satellite dust extinction profiles. After updating dust refractive indices and correcting for a bias in partitioning size‐segregated emissions, both SW cooling and longwave (LW) warming of dust simulated by E3SMv1 are increased and agree better with other recent studies. The estimated net dust DRE of −0.42 Wm−2 represents a stronger cooling effect than the observationally based estimate −0.2 Wm−2 (−0.48 to +0.2), due to a smaller LW warming. Constrained by a global mean DAOD, model sensitivity studies of increasing horizontal and vertical resolution show strong influences on the simulated global dust burden and lifetime primarily through the change of dust dry deposition rate; there are also remarkable differences in simulated spatial distributions of DAOD, DRE, and deposition fluxes. Thus, constraining the global DAOD is insufficient for accurate representation of dust climate effects, especially in transitioning to higher‐ or variable‐resolution ESMs. Better observational constraints of dust vertical profiles, dry deposition, size, and LW properties are needed.

The mantled solar heat storage (MSHS) tank can separate water utilization and heat collection, and its structure is not only conducive to the formation of temperature stratification, but also easy to be combined with the building, which has a wide range of application value. However, when it is in the simultaneous charging/discharging mode (CD-Mode), the mixing in the inner tank is affected by the heat transfer of the mantle exchanger, and the mixing mechanism and the development law need to be further explored. In this paper, the mixing mechanism of negative buoyancy jet at the inlet and the variation trend of thermocline in the tank under different operating modes were explored numerically and experimentally. As well as its influence on the overall thermal performance of the tank, a simple and feasible way to optimize the diffuser is discussed as well. It is found that in the CD-Mode, the mixing inside the water tank becomes more severe in the early stage of water use, and the thermocline thickness shows a trend of thickening first and then thinning over time. However, the mixing state is relatively stable during the whole water use period, and the change rate of thermocline thickness is smaller. But it is more affected by the inlet negative buoyancy jet than that in the discharging mode (D-mode), especially when the Rei number is large. Under the two operation modes, when the dimensionless time t* = 0.4-0.8, it enters the stable water use process, and the thermocline is in the stable development stage. The thickness of thermocline changes less in the CD-mode, which makes it easier for users to obtain longer hot water service time, reflecting the advantages of mantled heat exchange water tank in maintaining thermal stratification. For the working conditions studied, after optimized the diffuser, the hot water output rate can be 109.9% higher than the straight tube with the same tube length, and the hot water service time can be prolonged by 90.2%, which has practical application value.

The behavior of weak axisymmetric fountains in homogeneous fluid with coexistent temperature and concentration effects is studied numerically over 0.25 ≤ FrT ≤ 2.0, − 0.75 ≤ N ≤ 5.0, and 20 ≤ Re ≤ 300, where FrT is the Froude number defined with temperature only, N is the buoyancy ratio representing the relative contribution of concentration to density compared to that of temperature, and Re is the Reynolds number. For each FrT, the maximum fountain height, fountain upflow width, and whole fountain width reduce with increasing N, as the combined negative buoyancy from temperature and concentration becomes stronger, while as FrT becomes larger, they increase due to the reduced overall negative buoyancy. Re has strong effects on these parameters, with a larger Re value leading to increased values of these parameters. If the overall Froude number, Fr, which is defined with combined temperature and concentration, is used instead of FrT, the existing scaling relations for the maximum fountain height for weak axisymmetric fountains with density coming from temperature only, are also applicable for the weak axisymmetric fountains with density coming from both temperature and concentration, when Fr ≲ 2.0. The quantified correlations for the characteristic parameters under the combined effects of Re and Fr have also been obtained with the numerical results.

Abstract Mesoscale organization of convection is typically not represented in global circulation models, and hence its influence on the global circulation is not accounted for. The heating component of a parameterization that represents the dynamical and physical effects of circulations associated with organized convection, referred to as the multiscale coherent structure parameterization (MCSP), is implemented in the Energy Exascale Earth System Model version 1 (E3SMv1). Numerical simulations are conducted to assess its impact on the simulated climate. Besides E3SMv1 simulations, we performed high‐resolution (2 km) simulations using the Weather Research and Forecasting (WRF) Model to determine the temperature tendencies induced by mesoscale convective systems embedded in deep convection. We tuned the free parameters of the MCSP based on the WRF simulations. MCSP heating enhances Kevin wave spectra in E3SMv1, improves the representation of the Madden‐Julian Oscillation, and reduces precipitation biases over the tropical Pacific.

This paper describes the first implementation of the Δx = 3.25 km version of the Energy Exascale Earth System Model (E3SM) global atmosphere model and its behavior in a 40‐day prescribed‐sea‐surface‐temperature simulation (January 20 through February 28, 2020). This simulation was performed as part of the DYnamics of the Atmospheric general circulation Modeled On Non‐hydrostatic Domains (DYAMOND) Phase 2 model intercomparison. Effective resolution is found to be ∼6× the horizontal dynamics grid resolution despite using a coarser grid for physical parameterizations. Despite this new model being in an immature and untuned state, moving to 3.25 km grid spacing solves several long‐standing problems with the E3SM model. In particular, Amazon precipitation is much more realistic, the frequency of light and heavy precipitation is improved, agreement between the simulated and observed diurnal cycle of tropical precipitation is excellent, and the vertical structure of tropical convection and coastal stratocumulus look good. In addition, the new model is able to capture the frequency and structure of important weather events (e.g., tropical cyclones, extratropical cyclones including atmospheric rivers, and cold air outbreaks). Interestingly, this model does not get rid of the erroneous southern branch of the intertropical convergence zone nor the tendency for strongest convection to occur over the Maritime Continent rather than the West Pacific, both of which are classic climate model biases. Several other problems with the simulation are identified, underscoring the fact that this model is a work in progress.

The U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program User Facility produces ground-based long-term continuous unique measurements for atmospheric state, precipitation, turbulent fluxes, radiation, aerosol, cloud, and the land surface, which are collected at multiple sites. These comprehensive datasets have been widely used to calibrate climate models and are proven to be invaluable for climate model development and improvement. This article introduces an evaluation package to facilitate the use of ground-based ARM measurements in climate model evaluation. The ARM data-oriented metrics and diagnostics package (ARM-DIAGS) includes both ARM observational datasets and a Python-based analysis toolkit for computation and visualization. The observational datasets are compiled from multiple ARM data products and specifically tailored for use in climate model evaluation. In addition, ARM-DIAGS also includes simulation data from models participating the Coupled Model Intercomparison Project (CMIP), which will allow climate-modeling groups to compare a new, candidate version of their model to existing CMIP models. The analysis toolkit is designed to make the metrics and diagnostics quickly available to the model developers.

This paper presents a process-oriented evaluation of precipitating stratocumulus and its transition to cumulus in version 1 of the Energy Exascale Earth System Model (E3SMv1) using comprehensive case-study observations from a field campaign of the Atmospheric Radiation Measurement program (ARM). The E3SMv1 single-column model (SCM) of the marine boundary layer and its low clouds and precipitation are compared to observations including subcloud drizzle retrievals from a combination of Doppler radar and lidar backscatter measurements. The SCM is also compared to a large-eddy simulation (LES) of the same case. The combination of advanced remote sensing observations and LES is a powerful framework to evaluate the physical parameterizations of large-scale models. Given the observed large-scale environment, the E3SMv1 SCM realistically represents the evolution of clouds and boundary layer structure during the stratocumulusto-cumulus transition. The model well simulates the liquid water path and its diurnal cycle in the stratocumulus period as well as the two-layer vertical thermodynamic structure and lower cloud fraction in the transition period. E3SMy1's success in simulating the cloud in the stratocumulus period permitted examination of its precipitation processes. Here problems were identified with E3SMv1 producing an unrealistically small subcloud precipitation fraction, an unrealistic double peak in the vertical profiles of precipitation mass, and drizzle that evaporates too close to the surface. Further model diagnostics determined that these unrealistic characteristics resulted from an overly long microphysics time step and an unrealistic parameterization of the precipitation fraction. These results imply that careful consideration of these issues is needed in order to better simulate precipitation processes in marine stratocumulus.

This study analyzes the summertime precipitation bias over the Central United States and its relationship to the simulated large‐scale environment and the convection scheme in the Energy Exascale Earth System Model Atmosphere Model version 1. This relationship is mainly examined in a set of short‐term hindcasts initialized with realistic large‐scale conditions for the summer of 2011. Besides the uniform 1° model resolution, we adopt Regionally Refined Meshes to increase the model resolution to 0.25° over the contiguous United States. Additional five‐year Atmospheric Model Intercomparison Project simulations are conducted to confirm that the results from the hindcasts are consistent with the climate runs. We find that the summertime dry precipitation bias over the Great Plains and the wet bias over the Rockies cannot be reduced simultaneously by changing resolution or tuning parameters. As for the diurnal cycle, Energy Exascale Earth System Model Atmosphere Model version 1 captures the general diurnal variation of the large‐scale moisture transport and the large‐scale upward motion over the Central United States. However, the diurnal cycle of precipitation over the Great Plains is out of phase with the diurnal variation of the large‐scale environment because the convective precipitation dominates the total precipitation and its diurnal cycle, and it does not directly respond to the local moisture convergence and the large‐scale upward motion. These results reemphasize the importance of improving the coupling of the convection to the large‐scale environment in reducing the summer precipitation bias over the Central United States in climate models with the resolution of ~0.25°.

Abstract The Energy Exascale Earth System Model Atmosphere Model version 1, the atmospheric component of the Department of Energy's Energy Exascale Earth System Model is described. The model began as a fork of the well‐known Community Atmosphere Model, but it has evolved in new ways, and coding, performance, resolution, physical processes (primarily cloud and aerosols formulations), testing and development procedures now differ significantly. Vertical resolution was increased (from 30 to 72 layers), and the model top extended to 60 km (~0.1 hPa). A simple ozone photochemistry predicts stratospheric ozone, and the model now supports increased and more realistic variability in the upper troposphere and stratosphere. An optional improved treatment of light‐absorbing particle deposition to snowpack and ice is available, and stronger connections with Earth system biogeochemistry can be used for some science problems. Satellite and ground‐based cloud and aerosol simulators were implemented to facilitate evaluation of clouds, aerosols, and aerosol‐cloud interactions. Higher horizontal and vertical resolution, increased complexity, and more predicted and transported variables have increased the model computational cost and changed the simulations considerably. These changes required development of alternate strategies for tuning and evaluation as it was not feasible to “brute force” tune the high‐resolution configurations, so short‐term hindcasts, perturbed parameter ensemble simulations, and regionally refined simulations provided guidance on tuning and parameterization sensitivity to higher resolution. A brief overview of the model and model climate is provided. Model fidelity has generally improved compared to its predecessors and the CMIP5 generation of climate models.