Modelled black carbon radiative forcing and atmospheric lifetime in AeroCom Phase II constrained by aircraft observations

Samset, B. H.; Myhre, Gunnar; Herber, Andreas; Kondo, Yutaka; Li, Shao-Meng; Moteki, Nobuhiro; Koike, M.; Oshima, Naga; Schwarz, J. P.; Balkanski, Yves; Bauer, Susanne E.; Bellouin, Nicolas; Berntsen, Terje; Bian, Huisheng; Chin, Mian; Diehl, Thomas; Easter, Richard C.; Ghan, Steven J.; Iversen, Trond; Kirkevåg, Alf; Lamarque, Jean‐François; Lin, Guang; Liu, Xiaohong; Penner, Joyce E.; Schulz, Mıchael; Seland, Øyvind; Skeie, Ragnhild Bieltvedt; Stier, Philip; Takemura, Toshihiko; Tsigaridis, Kostas; Zhang, Kai

doi:10.5194/acp-14-12465-2014

Cited by 165 publications

(200 citation statements)

References 42 publications

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“…For example, high bias of BC concentrations in the upper troposphere in the tropics and subtropics exists in almost all the global models participating in the AeroCom Phase I and Phase II intercomparison Schwarz et al, 2010;Samset et al, 2014), while low BC bias in the lower atmosphere by over a factor of 10 exists in the polar regions. The aerosol absorption optical depth also tends to be biased low in GCMs compared to satellite observations , although it compares better to ground-based Sun photometers .…”

Section: Liu Et Al: Four-mode Version Of Modal Aerosol Modulementioning

confidence: 99%

Description and evaluation of a new four-mode version of the Modal Aerosol Module (MAM4) within version 5.3 of the Community Atmosphere Model

et al. 2016

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Abstract. Atmospheric carbonaceous aerosols play an important role in the climate system by influencing the Earth's radiation budgets and modifying the cloud properties. Despite the importance, their representations in large-scale atmospheric models are still crude, which can influence model simulated burden, lifetime, physical, chemical and optical properties, and the climate forcing of carbonaceous aerosols. In this study, we improve the current three-mode version of the Modal Aerosol Module (MAM3) in the Community Atmosphere Model version 5 (CAM5) by introducing an additional primary carbon mode to explicitly account for the microphysical ageing of primary carbonaceous aerosols in the atmosphere. Compared to MAM3, the four-mode version of MAM (MAM4) significantly increases the column burdens of primary particulate organic matter (POM) and black carbon (BC) by up to 40 % in many remote regions, where in-cloud scavenging plays an important role in determining the aerosol concentrations. Differences in the column burdens for other types of aerosol (e.g., sulfate, secondary organic aerosols, mineral dust, sea salt) are less than 1 %. Evaluating the MAM4 simulation against in situ surface and aircraft observations, we find that MAM4 significantly improves the simulation of seasonal variation of near-surface BC concentrations in the polar regions, by increasing the BC concentrations in all seasons and particularly in cold seasons. However, it exacerbates the overestimation of modeled BC concentrations in the upper troposphere in the Pacific regions. The comparisons suggest that, to address the remaining model POM and BC biases, future improvements are required related to (1) in-cloud scavenging and vertical transport in convective clouds and (2) emissions of anthropogenic and biomass burning aerosols.

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Section: Liu Et Al: Four-mode Version Of Modal Aerosol Modulementioning

confidence: 99%

Description and evaluation of a new four-mode version of the Modal Aerosol Module (MAM4) within version 5.3 of the Community Atmosphere Model

et al. 2016

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“…For our analysis, we used model results from the Aerosol Comparisons between Observations and Models (AeroCom) project, an open international initiative aimed at understanding the global aerosol and its impact on climate (Samset et al, 2014;Myhre et al, 2013;Jiao et al, 2014;Tsigaridis et al, 2014). The project combines a large number of observations and outputs from fourteen global models to test, document, and compare state-of-the-art modelling of the global aerosol.…”

Section: Trends In Aod Over Greenlandmentioning

confidence: 99%

The darkening of the Greenland ice sheet: trends, drivers, and projections (1981–2100)

et al. 2016

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Abstract. The surface energy balance and meltwater production of the Greenland ice sheet (GrIS) are modulated by snow and ice albedo through the amount of absorbed solar radiation. Here we show, using space-borne multispectral data collected during the 3 decades from 1981 to 2012, that summertime surface albedo over the GrIS decreased at a statistically significant (99 %) rate of 0.02 decade −1 between 1996 and 2012. Over the same period, albedo modelled by the Modèle Atmosphérique Régionale (MAR) also shows a decrease, though at a lower rate (∼ −0.01 decade −1 ) than that obtained from space-borne data. We suggest that the discrepancy between modelled and measured albedo trends can be explained by the absence in the model of processes associated with the presence of light-absorbing impurities. The negative trend in observed albedo is confined to the regions of the GrIS that undergo melting in summer, with the drysnow zone showing no trend. The period 1981-1996 also showed no statistically significant trend over the whole GrIS. Analysis of MAR outputs indicates that the observed albedo decrease is attributable to the combined effects of increased near-surface air temperatures, which enhanced melt and promoted growth in snow grain size and the expansion of bare ice areas, and to trends in light-absorbing impurities (LAI) on the snow and ice surfaces. Neither aerosol models nor in situ and remote sensing observations indicate increasing trends in LAI in the atmosphere over Greenland. Similarly, an analysis of the number of fires and BC emissions from fires points to the absence of trends for such quantities. This suggests that the apparent increase of LAI in snow and ice might be related to the exposure of a "dark band" of dirty ice and to increased consolidation of LAI at the surface with melt, not to increased aerosol deposition. Albedo projections through to the end of the century under different warming scenarios consistently point to continued darkening, with albedo anomalies averaged over the whole ice sheet lower by 0.08 in 2100 than in 2000, driven solely by a warming climate. Future darkening is likely underestimated because of known underestimates in modelled melting (as seen in hindcasts) and because the model albedo scheme does not currently include the effects of LAI, which have a positive feedback on albedo decline through increased melting, grain growth, and darkening.

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“…However, the diversity in existing estimates of the climate effect of BC is large (Bond et al, 2013;Boucher et al, 2013;Myhre et al, 2013). The causes for the diversity in estimates are many, from emissions (Amann et al, 2013;Cohen and Wang, 2014;Lam et al, 2012;Stohl et al, 2013;Wang et al, 2014b), lifetime and abundance (Hodnebrog et al, 2014;Samset et al, 2014;Wang et al, 2014a) to radiative efficiency Zarzycki and Bond, 2010).…”

Section: Introductionmentioning

confidence: 99%

Standard climate models radiation codes underestimate black carbon radiative forcing

Myhre

Samset

2015

Atmos. Chem. Phys.

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Abstract. Radiative forcing (RF) of black carbon (BC) in the atmosphere is estimated using radiative transfer codes of various complexities. Here we show that the two-stream radiative transfer codes used most in climate models give too strong forward scattering, leading to enhanced absorption at the surface and too weak absorption by BC in the atmosphere. Such calculations are found to underestimate the positive RF of BC by 10 % for global mean, all sky conditions, relative to the more sophisticated multi-stream models. The underestimation occurs primarily for low surface albedo, even though BC is more efficient for absorption of solar radiation over high surface albedo.

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Modelled black carbon radiative forcing and atmospheric lifetime in AeroCom Phase II constrained by aircraft observations

Cited by 165 publications

References 42 publications

Description and evaluation of a new four-mode version of the Modal Aerosol Module (MAM4) within version 5.3 of the Community Atmosphere Model

Description and evaluation of a new four-mode version of the Modal Aerosol Module (MAM4) within version 5.3 of the Community Atmosphere Model

The darkening of the Greenland ice sheet: trends, drivers, and projections (1981–2100)

Standard climate models radiation codes underestimate black carbon radiative forcing

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