The Global Atmosphere‐aerosol Model ICON‐A‐HAM2.3–Initial Model Evaluation and Effects of Radiation Balance Tuning on Aerosol Optical Thickness

Salzmann, Marc; Ferrachat, Sylvaine; Tully, Colin; Münch, Steffen; Watson-Parris, Duncan; Neubauer, David; Drian, Colombe Siegenthaler-Le; Rast, Sebastian; Heinold, Bernd; Crueger, Traute; Brokopf, Renate; Mülmenstädt, J.; Quaas, Johannes; Wan, Hui; Zhang, Kai; Lohmann, Ulrike; Stier, Philip; Tegen, Ina

doi:10.1029/2021ms002699

Cited by 10 publications

(6 citation statements)

References 121 publications

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“…The minimum CDNC threshold (10 cm −3 ) prevents the occurrence of clouds with nonzero cloud fraction but very few cloud droplets. This threshold is also used in ECHAM6.3 (Salzmann et al., 2022) and showed impacts on aerosol ERF and EffCS (Neubauer et al., 2019). The more negative autoconversion CDNC exponent enhances the sensitivity of autoconversion rate to a CDNC change, and the increased accretion enhancement factor increases the accretion rate of cloud droplets by rain.…”

Section: Physical Processes Contributing To Evolution Of Cloud Feedba...mentioning

confidence: 99%

Causes of Reduced Climate Sensitivity in E3SM From Version 1 to Version 2

Qin,

Zheng,

Klein

et al. 2024

J Adv Model Earth Syst

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The effective climate sensitivity in the Department of Energy's Energy Exascale Earth System Model (E3SM) has decreased from 5.3 K in version 1 to 4.0 K in version 2. This reduction is mainly due to a weaker positive cloud feedback that leads to a stronger negative radiative feedback. Present‐day atmosphere‐only experiments with uniform 4 K sea surface temperature warming are used to separate the contributions of individual model modifications to the reduced cloud feedback. We find that the reduced cloud feedback is mostly driven by changes over the tropical marine low cloud regime, mainly related to a new trigger function for the deep convection scheme and modifications in the cloud microphysics scheme. The new trigger function helps weaken the low cloud reduction by increasing the cloud water detrainment at low levels from deep convection under warming. Changes to the formula of autoconversion rate from liquid to rain and an introduced minimum cloud droplet number concentration threshold in cloud microphysical calculations help sustain clouds against dissipation by suppressing precipitation generation with warming. In the midlatitudes, the increased Wegener‐Bergeron‐Findeisen (WBF) efficiency strongly reduces present‐day liquid water and leads to a stronger negative cloud optical depth feedback. The reduced trade cumulus cloud feedback in v2 is closer to estimates from recent observational and large‐eddy modeling studies but might not be due to the right physical reasons. The reduced mid‐latitude cloud feedback may be more plausible because more realistic present‐day mixed‐phase clouds are produced through the change in the WBF efficiency.

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Section: Physical Processes Contributing To Evolution Of Cloud Feedba...mentioning

confidence: 99%

Causes of Reduced Climate Sensitivity in E3SM From Version 1 to Version 2

Qin,

Zheng,

Klein

et al. 2024

J Adv Model Earth Syst

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“…Salzmann et al. (2022) recently reported on the impact of moist convection parameter settings on wet deposition and as a result on AOD.…”

Section: Simulation Campaignmentioning

confidence: 99%

“…This might be an unintended consequence of intensive cloud and precipitation parameter tuning for EAMv2. Salzmann et al (2022) recently reported on the impact of moist convection parameter settings on wet deposition and as a result on AOD.…”

Section: Aerosolsmentioning

confidence: 99%

The DOE E3SM Model Version 2: Overview of the Physical Model and Initial Model Evaluation

Golaz

Roekel

Zheng

et al. 2022

J Adv Model Earth Syst

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This work documents version two of the Department of Energy's Energy Exascale Earth SystemModel (E3SM). E3SMv2 is a significant evolution from its predecessor E3SMv1, resulting in a model that is nearly twice as fast and with a simulated climate that is improved in many metrics. We describe the physical climate model in its lower horizontal resolution configuration consisting of 110 km atmosphere, 165 km land, 0.5° river routing model, and an ocean and sea ice with mesh spacing varying between 60 km in the mid-latitudes and 30 km at the equator and poles. The model performance is evaluated with Coupled Model Intercomparison Project Phase 6 Diagnosis, Evaluation, and Characterization of Klima simulations augmented with historical simulations as well as simulations to evaluate impacts of different forcing agents. The simulated climate has many realistic features of the climate system, with notable improvements in clouds and precipitation compared to E3SMv1. E3SMv1 suffered from an excessively high equilibrium climate sensitivity (ECS) of 5.3 K. In E3SMv2, ECS is reduced to 4.0 K which is now within the plausible range based on a recent World Climate Research Program assessment. However, a number of important biases remain including a weak Atlantic Meridional Overturning Circulation, deficiencies in the characteristics and spectral distribution of tropical atmospheric variability, and a significant underestimation of the observed warming in the second half of the historical period. An analysis of single-forcing simulations indicates that correcting the historical temperature bias would require a substantial reduction in the magnitude of the aerosol-related forcing.

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“…The modal aerosol module "HAM" that employs seven log-normal aerosol modes is used interactively in the ECHAM model since almost two decades (Zhang et al 2012 ;Tegen et al 2019). Recently it is also implemented in the successor of ECHAM, the ICON model (Salzmann et al 2022). The two models with profoundly different dynamical cores share the same physics package.…”

Section: Perspectivesmentioning

confidence: 99%

Incorporation of aerosols into the COSPv2 satellite lidar simulator for climate model evaluation

Bonazzola¹,

Chepfer²,

et al. 2022

Preprint

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Abstract. Aerosols have a large impact on climate, air quality, and biogeochemical cycles. Their concentrations are highly variable in space and time, and a key variability is in their vertical distribution, because it influences atmospheric heating profiles, aerosols life-time and, as a result, surface concentrations, and because it has an impact on aerosol-cloud interactions. On the side of model-oriented aerosols research, using a lidar aerosol simulator ensures consistent comparisons between the modeled aerosols and the observed aerosols. In the current study, we present the lidar aerosol simulator implemented within the COSPv2 satellite lidar simulator. We estimate the total attenuated backscattered signal (ATB) and the scattering ratios (SR) that would be observed at 532 nm by the lidar CALIOP overflying the atmosphere predicted by the E3SMv1 climate model. The simulator performs the computations at the same vertical resolution as the CALIOP lidar, making use of aerosol optics from the E3SMv1 model as inputs, and assuming that aerosols are uniformly distributed horizontally within each model grid-box. It applies a cloud masking and an aerosol detection threshold, to get the ATB and SR profiles that would be observed above clouds by CALIOP with its actual aerosol detection capability. Our comparison shows that the aerosol distribution simulated at a seasonal timescale is generally in good agreement with observations, with however a discrepancy in the Southern Hemisphere, as the observed SR maximum is not reproduced in simulations there. Comparison between cloud-screened and non cloud-screened computed SRs shows little differences, indicating that the cloud screening by potentially incorrect model clouds does not affect the mean aerosol signal averaged over a season. Consequently, the differences between observed and simulated SR values are not due to sampling errors, and allow to point out some weaknesses in the aerosol representation in models. The use of lidar observations at several wavelengths can give further indication on the nature of the aerosols that need to be improved.

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The Global Atmosphere‐aerosol Model ICON‐A‐HAM2.3–Initial Model Evaluation and Effects of Radiation Balance Tuning on Aerosol Optical Thickness

Cited by 10 publications

References 121 publications

Causes of Reduced Climate Sensitivity in E3SM From Version 1 to Version 2

Causes of Reduced Climate Sensitivity in E3SM From Version 1 to Version 2

The DOE E3SM Model Version 2: Overview of the Physical Model and Initial Model Evaluation

Incorporation of aerosols into the COSPv2 satellite lidar simulator for climate model evaluation

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