Climate Sensitivity of the Community Climate System Model, Version 4

Bitz, Cecilia M.; Shell, Karen M.; Gent, Peter R.; Bailey, David A.; Danabasoglu, Gökhan; Armour, Kyle C.; Holland, Marika M.; Kiehl, J. T.

doi:10.1175/jcli-d-11-00290.1

Cited by 223 publications

(270 citation statements)

References 35 publications

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“…The primary model used in our study is the NCAR AGCM, Community Atmospheric Model version 4 (CAM4) [Gent et al, 2011;Bitz et al, 2012;Meehl et al, 2013]. We also provide results from CAM5 (S1) [Neale et al, 2010].…”

Section: Methodsmentioning

confidence: 99%

The neglected Indo‐Gangetic Plains low‐level jet and its importance for moisture transport and precipitation during the peak summer monsoon

Acosta

Huber

2017

Geophysical Research Letters

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Accurately simulating the Indo‐Asian monsoon (IAM) using atmospheric general circulation models (AGCMs) is challenging but crucial. This study uses reanalysis products European Centre of Medium‐Range Forecast Interim reanalysis, Japanese Reanalysis year 55, and High Asia Reanalysis to highlight an easterly, low‐level barrier jet along the Indo‐Gangetic Plain (referred from here as IG LLJ), which we identify as the primary moisture transport mechanism for the northeastern branch of the IAM. We show that the NCAR family of AGCMs (Community Atmospheric Model (CAM)) does not capture this circulation until 1/2° or greater spatial horizontal resolution is used. The IG LLJ develops due to a persistent low‐pressure system centered over the Ganges basin and is enhanced by the Himalayas. Using diabatic heating rates and the moist Froude number as diagnostics, we find that in CAM, this branch of the IAM displays two different dynamical regimes as a function of resolution. At low resolution, the atmosphere near the Himalayas is statically unstable, diabatic heating is strong, and the moisture flow is southwesterly from the Arabian Sea and moves over the terrain (unblocked). At high resolution, the moist static stability near the Himalayan Mountains is stable, diabatic heating is weak, and the flow primarily enters easterly from the Bay of Bengal and moves parallel to the terrain (blocked). During the summer season, the low‐resolution CAM is locked into the unblocked mode, which has serious implications for interpreting topography‐monsoon interactions. For a broader context, we demonstrate that more than half of the CMIP5 models do not capture the IG LLJ, which further highlights model‐data mismatch across the IAM region.

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Section: Methodsmentioning

confidence: 99%

The neglected Indo‐Gangetic Plains low‐level jet and its importance for moisture transport and precipitation during the peak summer monsoon

Acosta

Huber

2017

Geophysical Research Letters

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“…This is consistent with Stohl (2006), who found a large portion of modeled BC transport from fires as opposed to industrial sources. In general, biomass combustion aerosol has a much higher fraction of light-absorbing organic carbon (relative to BC) than does fossil fuel combustion (Bond et al, 2004), so it is very likely that the non-BC absorption reported by Doherty et al (2010) is from organics. If the non-BC particle fraction is significantly absorbing due to greater mass or greater absorption efficiency than that which has been assumed, then the net absorption from combustion sources may be underestimated.…”

Section: Constraints On Particle Parametersmentioning

confidence: 99%

“…Ocean heat flux is prescribed based on the climatology of a long pre-industrial control integration. This particular model configuration is described more fully in Bitz et al (2012). All of the results presented are for at least 60-yr equilibrium simulations, for which the last 30 yr have been averaged to create a climatology.…”

Section: Model Experiments Designmentioning

confidence: 99%

“…Because this value is based on an experiment doubling CO 2 from an 1850 value, we must assume that climate sensitivity does not strongly depend on the mean climate (an assumption we evaluate more in the next section). The temperature difference due to doubling of CO 2 , from Bitz et al (2012), is T CO 2 = 3.13 K for the same slab ocean model configuration used here.…”

Section: Efficacy and Climate Feedbackmentioning

confidence: 99%

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Arctic climate response to forcing from light-absorbing particles in snow and sea ice in CESM

Goldenson

Doherty²,

Bitz

et al. 2012

Atmos. Chem. Phys.

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Abstract. The presence of light-absorbing aerosol particles deposited on arctic snow and sea ice influences the surface albedo, causing greater shortwave absorption, warming, and loss of snow and sea ice, lowering the albedo further. The Community Earth System Model version 1 (CESM1) now includes the radiative effects of light-absorbing particles in snow on land and sea ice and in sea ice itself. We investigate the model response to the deposition of black carbon and dust to both snow and sea ice. For these purposes we employ a slab ocean version of CESM1, using the Community Atmosphere Model version 4 (CAM4), run to equilibrium for year 2000 levels of CO 2 and fixed aerosol deposition. We construct experiments with and without aerosol deposition, with dust or black carbon deposition alone, and with varying quantities of black carbon and dust to approximate year 1850 and 2000 deposition fluxes. The year 2000 deposition fluxes of both dust and black carbon cause 1-2 • C of surface warming over large areas of the Arctic Ocean and subArctic seas in autumn and winter and in patches of Northern land in every season. Atmospheric circulation changes are a key component of the surface-warming pattern. Arctic sea ice thins by on average about 30 cm. Simulations with year 1850 aerosol deposition are not substantially different from those with year 2000 deposition, given constant levels of CO 2 . The climatic impact of particulate impurities deposited over land exceeds that of particles deposited over sea ice. Even the surface warming over the sea ice and sea ice thinning depends more upon light-absorbing particles deposited over land. For CO 2 doubled relative to year 2000 levels, the climate impact of particulate impurities in snow and sea ice is substantially lower than for the year 2000 equilibrium simulation.

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“…CESM (Bitz et al, 2011;Gent et al, 2011) has fully coupled atmosphere, ocean, land, and sea ice components. Within CESM, the Community Land Model v4.0 (CLM; Lawrence et al, 2011) receives the selected GLM outputs via a translator that converts these outputs to 16 CLM plant functional types (PFTs; eight forest, three grass, three shrub, one bare soil, and one crop) (Lawrence et al, 2012).…”

Section: Iesm Descriptionmentioning

confidence: 99%

From land use to land cover: restoring the afforestation signal in a coupled integrated assessment–earth system model and the implications for CMIP5 RCP simulations

et al. 2014

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Abstract. Climate projections depend on scenarios of fossil fuel emissions and land use change, and the Intergovernmental Panel on Climate Change (IPCC) AR5 parallel process assumes consistent climate scenarios across integrated assessment and earth system models (IAMs and ESMs). The CMIP5 (Coupled Model Intercomparison Project Phase 5) project used a novel "land use harmonization" based on the Global Land use Model (GLM) to provide ESMs with consistent 1500-2100 land use trajectories generated by historical data and four IAMs. A direct coupling of the Global Change Assessment Model (GCAM), GLM, and the Community ESM (CESM) has allowed us to characterize and partially address a major gap in the CMIP5 land coupling design: the lack of a corresponding land cover harmonization. For RCP4.5, CESM global afforestation is only 22 % of GCAM's 2005 to 2100 afforestation. Likewise, only 17 % of GCAM's 2040 afforestation, and zero pasture loss, were transmitted to CESM within the directly coupled model. This is a problem because GCAM relied on afforestation to achieve RCP4.5 climate stabilization. GLM modifications and sharing forest area between GCAM and GLM within the directly coupled model did not increase CESM afforestation. Modifying the land use translator in addition to GLM, however, enabled CESM to include 66 % of GCAM's afforestation in 2040, and 94 % of GCAM's pasture loss as grassland and shrubland losses. This additional afforestation increases CESM vegetation carbon gain by 19 PgC and decreases atmospheric CO 2 gain by 8 ppmv from 2005 to 2040, which demonstrates that CESM without additional afforestation simulates a different RCP4.5 scenario than prescribed by GCAM. Similar land cover inconsistencies exist in other CMIP5 model results, primarily because land cover information is not shared between models. Further work to harmonize land cover among models will be required to increase fidelity between IAM scenarios and ESM simulations and realize the full potential of scenario-based earth system simulations.

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Climate Sensitivity of the Community Climate System Model, Version 4

Cited by 223 publications

References 35 publications

The neglected Indo‐Gangetic Plains low‐level jet and its importance for moisture transport and precipitation during the peak summer monsoon

The neglected Indo‐Gangetic Plains low‐level jet and its importance for moisture transport and precipitation during the peak summer monsoon

Arctic climate response to forcing from light-absorbing particles in snow and sea ice in CESM

From land use to land cover: restoring the afforestation signal in a coupled integrated assessment–earth system model and the implications for CMIP5 RCP simulations

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