scholarly journals Potential limitations of using a modal aerosol approach for sulfate geoengineering applications in climate models

2021 ◽  
Author(s):  
Daniele Visioni ◽  
Simone Tilmes ◽  
Charles Bardeen ◽  
Michael Mills ◽  
Douglas G. MacMartin ◽  
...  
Keyword(s):  
Climate Models ◽  
Stratospheric Aerosol ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Sulfate Aerosols ◽  
Ice Clouds ◽  
Surface Warming ◽  
Computationally Intensive ◽  
Microphysical Processes

Abstract. Simulating the complex aerosol microphysical processes in a comprehensive Earth System Model can be very computationally intensive and therefore many models utilize a modal approach, where aerosol size distributions are represented by observations-derived lognormal functions. This approach has been shown to yield satisfactory results in a large array of applications, but there may be cases where the simplification in this approach may produce some shortcomings. In this work we show specific conditions under which the current approximations used in modal approaches might yield some incorrect answers. Using results from the Community Earth System Model v1 (CESM1) Geoengineering Large Ensemble (GLENS) project, we analyze the effects in the troposphere of a continuous increasing load of sulfate aerosols in the stratosphere, with the aim of counteracting the surface warming produced by non-mitigated increasing greenhouse gases concentration between 2020–2100. We show that the simulated results pertaining to the evolution of sea salt and dust aerosols in the upper troposphere are not realistic due to internal mixing assumptions in the modal aerosol treatment, which in this case reduces the size, and thus the settling velocities, of those particles and ultimately changes their mixing ratio below the tropopause. The unnatural increase of these aerosol species affects, in turn, the simulation of upper tropospheric ice formation, resulting in an increase in ice clouds that is not due to any meaningful physical mechanisms. While we show that this does not significantly affect the overall results of the simulations, we point to some areas where results should be interpreted with care in modeling simulations using similar approximations: in particular, the evolution of upper tropospheric clouds when large amount of sulfate is present in the stratosphere, as after a large explosive volcanic eruption or in similar stratospheric aerosol injection cases. Finally, we suggest that this could be avoided if sulfate aerosols in the coarse mode, the predominant species in these situation, are treated separately from other aerosol species in the model.

scholarly journals Simulations of the Mid-Pliocene Warm Period using the NASA/GISS ModelE2-R Earth System Model

2012 ◽  
Vol 5 (3) ◽  
pp. 2811-2842 ◽  
Author(s):  
M. A. Chandler ◽  
L. E. Sohl ◽  
J. A. Jonas ◽  
H. J. Dowsett
Keyword(s):  
North Atlantic ◽  
Climate Models ◽  
Climate Model ◽  
Geographic Region ◽  
Earth System Model ◽  
Warm Period ◽  
System Model ◽  
Earth System ◽  
Intergovernmental Panel ◽  
Future Global Warming

Abstract. Climate reconstructions of the mid-Pliocene Warm Period (mPWP) bear many similarities to aspects of future global warming as projected by the Intergovernmental Panel on Climate Change. In particular, marine and terrestrial paleoclimate data point to high latitude temperature amplification, with associated decreases in sea ice and land ice and altered vegetation distributions that show expansion of warmer climate biomes into higher latitudes. NASA GISS climate models have been used to study the Pliocene climate since the USGS PRISM project first identified that the mid-Pliocene North Atlantic sea surface temperatures were anomalously warm. Here we present the most recent simulations of the Pliocene using the AR5/CMIP5 version of the GISS Earth System Model known as ModelE2-R. These simulations constitute the NASA contribution to the Pliocene Model Intercomparison Project (PlioMIP) Experiment 2. Many findings presented here corroborate results from other PlioMIP multi-model ensemble papers, but we also emphasize features in the ModelE2-R simulations that are unlike the ensemble means. We provide discussion of features that show considerable improvement compared with simulations from previous versions of the NASA GISS models, improvement defined here as simulation results that more closely resemble the ocean core data as well as the PRISM3D reconstructions of the mid-Pliocene climate. In some regions even qualitative agreement between model results and paleodata are an improvement over past studies, but the dramatic warming in the North Atlantic and Greenland-Iceland-Norwegian Sea in these new simulations is by far the most accurate portrayal ever of this key geographic region by the GISS climate model. Our belief is that continued development of key physical routines in the atmospheric model, along with higher resolution and recent corrections to mixing parameterizations in the ocean model, have led to an Earth System Model that will produce more accurate projections of future climate.

scholarly journals A comprehensive assessment of tropical stratospheric upwelling in the specified dynamics Community Earth System Model 1.2.2 – Whole Atmosphere Community Climate Model (CESM (WACCM))

2020 ◽  
Vol 13 (2) ◽  
pp. 717-734 ◽  
Author(s):  
Nicholas A. Davis ◽  
Sean M. Davis ◽  
Robert W. Portmann ◽  
Eric Ray ◽  
Karen H. Rosenlof ◽  
...  
Keyword(s):  
Climate Models ◽  
Climate Model ◽  
Earth System Model ◽  
System Model ◽  
Trace Gas ◽  
Earth System ◽  
Mean Meridional Circulation ◽  
Community Earth System Model ◽  
The Mean ◽  
Wave Momentum

Abstract. Specified dynamics (SD) schemes relax the circulation in climate models toward a reference meteorology to simulate historical variability. These simulations are widely used to isolate the dynamical contributions to variability and trends in trace gas species. However, it is not clear if trends in the stratospheric overturning circulation are properly reproduced by SD schemes. This study assesses numerous SD schemes and modeling choices in the Community Earth System Model (CESM) Whole Atmosphere Chemistry Climate Model (WACCM) to determine a set of best practices for reproducing interannual variability and trends in tropical stratospheric upwelling estimated by reanalyses. Nudging toward the reanalysis meteorology as is typically done in SD simulations does not accurately reproduce lower-stratospheric upwelling trends present in the underlying reanalysis. In contrast, nudging to anomalies from the climatological winds or anomalies from the zonal-mean winds and temperatures better reproduces trends in lower-stratospheric upwelling, possibly because these schemes do not disrupt WACCM's climatology. None of the schemes substantially alter the structure of upwelling trends – instead, they make the trends more or less AMIP-like. An SD scheme's performance in simulating the acceleration of the shallow branch of the mean meridional circulation from 1980 to 2017 hinges on its ability to simulate the downward shift of subtropical lower-stratospheric wave momentum forcing. Key to this is not nudging the zonal-mean temperature field. Gravity wave momentum forcing, which drives a substantial fraction of the upwelling in WACCM, cannot be constrained by nudging and presents an upper limit on the performance of these schemes.

scholarly journals Improving the representation of anthropogenic CO<sub>2</sub> emissions in climate models: impact of a new parameterization for the Community Earth System Model (CESM)

2018 ◽  
Vol 9 (3) ◽  
pp. 1045-1062 ◽  
Author(s):  
Andrés Navarro ◽  
Raúl Moreno ◽  
Francisco J. Tapiador
Keyword(s):  
Human Activities ◽  
Climate Models ◽  
Global Climate ◽  
Grid Point ◽  
Earth System Model ◽  
Population Projections ◽  
Pollutant Emissions ◽  
System Model ◽  
Earth System ◽  
Community Earth System Model

Abstract. ESMs (Earth system models) are important tools that help scientists understand the complexities of the Earth's climate. Advances in computing power have permitted the development of increasingly complex ESMs and the introduction of better, more accurate parameterizations of processes that are too complex to be described in detail. One of the least well-controlled parameterizations involves human activities and their direct impact at local and regional scales. In order to improve the direct representation of human activities and climate, we have developed a simple, scalable approach that we have named the POPEM module (POpulation Parameterization for Earth Models). This module computes monthly fossil fuel emissions at grid-point scale using the modeled population projections. This paper shows how integrating POPEM parameterization into the CESM (Community Earth System Model) enhances the realism of global climate modeling, improving this beyond simpler approaches. The results show that it is indeed advantageous to model CO2 emissions and pollutants directly at model grid points rather than using the same mean value globally. A major bonus of this approach is the increased capacity to understand the potential effects of localized pollutant emissions on long-term global climate statistics, thus assisting adaptation and mitigation policies.

scholarly journals Snowball Earth Bifurcations in a Fully-Implicit Earth System Model

2021 ◽  
Vol 31 (06) ◽  
pp. 2130017
Author(s):  
Thomas E. Mulder ◽  
Heiko Goelzer ◽  
Fred W. Wubs ◽  
Henk A. Dijkstra
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Ocean Model ◽  
Earth System Model ◽  
System Model ◽  
Snowball Earth ◽  
Earth System ◽  
Geological Evidence ◽  
Fully Implicit ◽  
Additional Support

There is now much geological evidence that the Earth was fully glaciated during several periods in the geological past (about 700[Formula: see text]Myr ago) and attained a so-called Snowball Earth (SBE) state. Additional support for this idea has come from climate models of varying complexity that show transitions to SBE states and undergo hysteresis under changes in solar radiation. In this paper, we apply large-scale bifurcation analyses to a novel, fully-implicit Earth System Model of Intermediate Complexity (I-EMIC) to study SBE transitions. The I-EMIC contains a primitive equation ocean model, a model for atmospheric heat and moisture transport, a sea ice component and formulations for the adjustment of albedo over snow and ice. With the I-EMIC, high-dimensional branches of the SBE bifurcation diagram are obtained through parameter continuation. We are able to identify stable and unstable equilibria and uncover an intricate bifurcation structure associated with the ice-albedo feedback. Moreover, large-scale linear stability analyses are performed near major bifurcations, revealing the spatial nature of destabilizing perturbations.

scholarly journals Coupling of a sediment diagenesis model (MEDUSA) and an Earth system model (CESM1.2): a contribution toward enhanced marine biogeochemical modelling and long-term climate simulations

2019 ◽  
Author(s):  
Takasumi Kurahashi-Nakamura ◽  
André Paul ◽  
Guy Munhoven ◽  
Ute Merkel ◽  
Michael Schulz
Keyword(s):  
Climate Models ◽  
Climate Model ◽  
Coupled Model ◽  
Earth System Model ◽  
System Model ◽  
Future Application ◽  
Coupling Scheme ◽  
Earth System ◽  
Climate Simulations

Abstract. We developed a coupling scheme for the Community Earth System Model version 1.2 (CESM1.2) and the Model of Early Diagenesis in the Upper Sediment of Adjustable complexity (MEDUSA), and explored the effects of the coupling on solid components in the upper sediment and on bottom seawater chemistry by comparing the coupled model's behaviour with that of the uncoupled CESM having a simplified treatment of sediment processes. CESM is a fully-coupled atmosphere-ocean-sea ice-land model and its ocean component (the Parallel Ocean Program version 2, POP2) includes a biogeochemical component (BEC). MEDUSA was coupled to POP2 in an off-line manner so that each of the models ran separately and sequentially with regular exchanges of necessary boundary condition fields. This development was done with the ambitious aim of a future application for long-term (spanning a full glacial cycle; i.e., ~ 105 years) climate simulations with a state-of-the-art comprehensive climate model including the carbon cycle, and was motivated by the fact that until now such simulations have been done only with less-complex climate models. We found that the sediment-model coupling already had non-negligible immediate advantages for ocean biogeochemistry in millennial-time-scale simulations. First, the MEDUSA-coupled CESM outperformed the uncoupled CESM in reproducing an observation-based global distribution of sediment properties, especially for organic carbon and opal. Thus, the coupled model is expected to act as a better bridge between climate dynamics and sedimentary data, which will provide another measure of model performance. Second, in our experiments, the MEDUSA-coupled model and the uncoupled model had a difference of 0.2‰ or larger in terms of δ13C of bottom water over large areas, which implied potential significant model biases for bottom seawater chemical composition due to a different way of sediment treatment. Such a model bias would be a fundamental issue for paleo model–data comparison often relying on data derived from benthic foraminifera.

scholarly journals Evaluation of the interactive stratospheric ozone (O3v2 module) for the E3SM version 2 Earth System Model

2020 ◽  
Author(s):  
Qi Tang ◽  
Michael J. Prather ◽  
Juno Hsu ◽  
Daniel J. Ruiz ◽  
Philip J. Cameron-Smith ◽  
...  
Keyword(s):  
Climate Models ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Heating Rates ◽  
Quasi Biennial Oscillation ◽  
Column Ozone ◽  
The University

Abstract. Stratospheric ozone affects climate directly as the predominant heat source in the stratosphere and indirectly through chemical feedbacks controlling other greenhouse gases. The U.S. Department of Energy's Energy Exascale Earth System Model version 1 (E3SMv1) implemented a new ozone chemistry module that improves the simulation of the sharp tropopause gradients, replacing a version based partly on long-term average climatologies that poorly represented heating rates in the lowermost stratosphere. The new O3v2 module extends seamlessly into the troposphere and preserves the naturally sharp cross-tropopause gradient, with 20-40% less ozone in this region. Additionally, O3v2 enables the diagnosis of stratosphere-troposphere exchange flux of ozone, a key budget term lacking in E3SMv1. Here, we evaluate key features in ozone abundance and other closely related quantities in atmosphere-only E3SMv1 simulations driven by observed sea surface temperatures (SSTs, years 1990-2014), comparing with satellite observations and the University of California, Irvine chemistry transport model (UCI CTM) using the same stratospheric chemistry scheme but driven by European Centre forecast fields for the same period. In terms of stratospheric column ozone, O3v2 shows improved mean bias and northern mid-latitude variability, but not quite as good as the UCI CTM. As expected, SST forcing does not match the observed quasi-biennial oscillation, which is mostly matched with the UCI CTM. This new O3v2 E3SM model retains mostly the same climate state and climate sensitivity as the previous version, and we recommend its use for other climate models that still use ozone climatologies.

scholarly journals Analysis of Secondary Organic Aerosol Simulation Bias in the Community Earth System Model (CESM2.1)

2020 ◽  
Author(s):  
Yaman Liu ◽  
Xinyi Dong ◽  
Minghuai Wang ◽  
Louisa K. Emmons ◽  
Yawen Liu ◽  
...  
Keyword(s):  
Climate Models ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
The United States ◽  
Earth System Model ◽  
Basis Set ◽  
System Model ◽  
Earth System ◽  
Model Version ◽  
Community Earth System Model

Abstract. Organic aerosol (OA) has been considered as one of the most important uncertainties in climate modeling due to the complexity in presenting its chemical production and depletion mechanisms. To better understand the capability of climate models and probe into the associated uncertainties in simulating OA, we evaluate the Community Earth System Model version 2.1 (CESM2.1) configured with the Community Atmosphere Model version 6 (CAM6) with comprehensive tropospheric and stratospheric chemistry representation (CAM6-Chem), through a long-term simulation (1988–2019) with observations collected from multiple datasets in the United States. We find that CESM generally reproduces the inter-annual variation and seasonal cycle of OA mass concentration at surface layer with correlation of 0.40 as compared to ground observations, and systematically overestimates (69 %) in summer and underestimates (−19 %) in winter. Through a series of sensitivity simulations, we reveal that modeling bias is primarily related to the dominant fraction of monoterpene-formed secondary organic aerosol (SOA), and a strong positive correlation of 0.67 is found between monoterpene emission and modeling bias in eastern US during summer. In terms of vertical profile, the model prominently underestimates OA and monoterpene concentrations by 37–99 % and 82–99 % respectively in the upper air (> 500 m) as validated against aircraft observations. Our study suggests that the current Volatility Basis Set (VBS) scheme applied in CESM might be parameterized with too high monoterpene SOA yields which subsequently result in strong SOA production near emission source area. We also find that the model has difficulty in reproducing the decreasing trend of surface OA in southeast US, probably because of employing pure gas VBS to represent isoprene SOA which is in reality mainly formed through multiphase chemistry, thus the influence of aerosol acidity and sulfate particle change on isoprene SOA formation has not been fully considered in the model. This study reveals the urgent need to improve the SOA modeling in climate models.

Higher Vertical Resolution for Select Physical Processes in the Energy Exascale Earth System Model (E3SM)

2020 ◽  
Author(s):  
Hsiang-He Lee ◽  
Peter Bogenschutz ◽  
Takanobu Yamaguchi
Keyword(s):  
Boundary Layer ◽  
Climate Models ◽  
Computational Cost ◽  
Earth System Model ◽  
Global Climate Models ◽  
Computational Method ◽  
System Model ◽  
Vertical Resolution ◽  
Earth System ◽  
Low Cloud

&lt;p&gt;The low cloud bias in atmospheric models for climate and weather remains an unsolved problem. Coarse vertical resolution in the current global climate models (GCM) may be a significant cause of low cloud bias because planetary boundary layer (PBL) parameterizations, including higher-order turbulence closure (HOC), cannot resolve sharp temperature and moisture gradients often found at the top of subtropical stratocumulus layers. The aim of this work is to implement a new computational method, the Framework for Improvement by Vertical Enhancement (FIVE) into the Energy Exascale Earth System Model (E3SM) and its single column model. Three physics schemes are interfaced to vertically enhanced physics (VEP), which allows for these schemes to be computed on a higher vertical resolution grid compared to rest of the E3SM model.&amp;#160; In this presentation we use VEP for turbulence, microphysics, and radiation parameterizations and demonstrate better representation of subtropical boundary layer clouds while limiting additional computational cost from the increased number of levels.&amp;#160; We will also briefly discuss future plans for an adaptive vertical grid for VEP, which will allow for additional layers to be added only when/where they are needed.&lt;/p&gt;

Evaluation of Organized Convection Parameterization in Global Climate Models

2020 ◽  
Author(s):  
Chih-Chieh Chen ◽  
Changhai Liu ◽  
Mitch Moncrieff ◽  
Yaga Richter
Keyword(s):  
Climate Models ◽  
Global Climate ◽  
Earth System Model ◽  
Global Climate Models ◽  
System Model ◽  
Moist Convection ◽  
Earth System ◽  
Mesoscale Convective ◽  
Convective Organization ◽  
Organized Convection

&lt;p&gt;The importance of convective organization on the global circulation has been recognized for a long time, but parameterizations of the associated processes are missing in global climate models. Contemporary convective parameterizations commonly use a convective plume model (or a spectrum of plumes). This is perhaps appropriate for unorganized convection but the assumption of a gap between the small cumulus scale and the large-scale motion fails to recognize mesoscale dynamics manifested in mesoscale convective systems (MCSs) and multi-scale cloud systems associated with the MJO. Organized convection is abundant in environments featuring vertical wind shear, and significantly modulates the life cycle of moist convection, the transport of heat and momentum, and accounts for a large percentage of precipitation in the tropics. Mesoscale convective organization is typically associated with counter-gradient momentum transport, and distinct heating profiles between the convective and stratiform regions.&lt;/p&gt;&lt;p&gt;Moncrieff, Liu and Bogenschutz (2017) recently developed a dynamical based parameterization of organized moisture convection, referred to as multiscale coherent structure parameterization (MCSP), for global climate models. A prototype version of MCSP has been implemented in the NCAR Community Earth System Model (CESM) and the Energy Exascale Earth System Model (E3SM), positively affecting the distribution of tropical precipitation, convectively coupled tropical waves, and the Madden-Julian oscillation. We will show the further development of the MCSP and its impact on the simulation of mean precipitation and variability in the two global climate models.&lt;/p&gt;

scholarly journals Evaluation of CMIP5 Global Climate Models over the Volta Basin: Precipitation

2018 ◽  
Vol 2018 ◽  
pp. 1-24 ◽  
Author(s):  
Jacob Agyekum ◽  
Thompson Annor ◽  
Benjamin Lamptey ◽  
Emmannuel Quansah ◽  
Richard Yao Kuma Agyeman
Keyword(s):  
Climate Models ◽  
Global Climate ◽  
Earth System Model ◽  
Global Climate Models ◽  
System Model ◽  
Earth System ◽  
Climate System Model ◽  
Model Version ◽  
Volta Basin ◽  
Ensemble Mean

A selected number of global climate models (GCMs) from the fifth Coupled Model Intercomparison Project (CMIP5) were evaluated over the Volta Basin for precipitation. Biases in models were computed by taking the differences between the averages over the period (1950–2004) of the models and the observation, normalized by the average of the observed for the annual and seasonal timescales. The Community Earth System Model, version 1-Biogeochemistry (CESM1-BGC), the Community Climate System Model Version 4 (CCSM4), the Max Planck Institute Earth System Model, Medium Range (MPI-ESM-MR), the Norwegian Earth System Model (NorESM1-M), and the multimodel ensemble mean were able to simulate the observed climatological mean of the annual total precipitation well (average biases of 1.9% to 7.5%) and hence were selected for the seasonal and monthly timescales. Overall, all the models (CESM1-BGC, CCSM4, MPI-ESM-MR, and NorESM1-M) scored relatively low for correlation (<0.5) but simulated the observed temporal variability differently ranging from 1.0 to 3.0 for the seasonal total. For the annual cycle of the monthly total, the CESM1-BGC, the MPI-ESM-MR, and the NorESM1-M were able to simulate the peak of the observed rainy season well in the Soudano-Sahel, the Sahel, and the entire basin, respectively, while all the models had difficulty in simulating the bimodal pattern of the Guinea Coast. The ensemble mean shows high performance compared to the individual models in various timescales.

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