The vertical distribution of black carbon in CMIP5 models: Comparison to observations and the importance of convective transport

Allen, Robert J.; Landuyt, W.

doi:10.1002/2014jd021595

Cited by 57 publications

(74 citation statements)

References 92 publications

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“…This bias appears to be more significant in NorESM and CESM, while CanAM produces particularly reasonable agreement with the observations, especially during the spring season. Comparisons of model results with aircraft measurements do not provide any evidence for large systematic overestimates of simulated BC concentrations in the upper troposphere in the Arctic in the AMAP models, which is different from conclusions in several previous studies [e.g., Koch et al ., ; Kipling et al ., ; Wang et al ., ; Allen and Landuyt , ; Samset et al ., ]. Furthermore, Eckhardt et al .…”

Section: Resultsmentioning

confidence: 99%

“…Consequently, differences in upper tropospheric BC concentrations and burdens in simulations appear to be related to differences in simulated large‐scale lifting of air masses or convective transport of BC outside the Arctic. This is broadly consistent with Allen and Landuyt [] who found that Coupled Model Intercomparison Project Phase 5 climate models tend to produce higher concentrations of BC in the upper troposphere and lower stratosphere (UT/LS) than observed from aircraft. A modified version of one of the models in their study with reduced convective transport of BC produced lower concentrations and better agreement with observations in the UT/LS outside the Arctic.…”

Section: Resultsmentioning

confidence: 99%

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Seasonality of global and Arctic black carbon processes in the Arctic Monitoring and Assessment Programme models

et al. 2016

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This study quantifies black carbon (BC) processes in three global climate models and one chemistry transport model, with focus on the seasonality of BC transport, emissions, wet and dry deposition in the Arctic. In the models, transport of BC to the Arctic from lower latitudes is the major BC source for this region. Arctic emissions are very small. All models simulated a similar annual cycle of BC transport from lower latitudes to the Arctic, with maximum transport occurring in July. Substantial differences were found in simulated BC burdens and vertical distributions, with Canadian Atmospheric Global Climate Model (CanAM) (Norwegian Earth System Model, NorESM) producing the strongest (weakest) seasonal cycle. CanAM also has the shortest annual mean residence time for BC in the Arctic followed by Swedish Meteorological and Hydrological Institute Multiscale Atmospheric Transport and Chemistry model, Community Earth System Model, and NorESM. Overall, considerable differences in wet deposition efficiencies in the models exist and are a leading cause of differences in simulated BC burdens. Results from model sensitivity experiments indicate that convective scavenging outside the Arctic reduces the mean altitude of BC residing in the Arctic, making it more susceptible to scavenging by stratiform (layer) clouds in the Arctic. Consequently, scavenging of BC in convective clouds outside the Arctic acts to substantially increase the overall efficiency of BC wet deposition in the Arctic, which leads to low BC burdens and a more pronounced seasonal cycle compared to simulations without convective BC scavenging. In contrast, the simulated seasonality of BC concentrations in the upper troposphere is only weakly influenced by wet deposition in stratiform clouds, whereas lower tropospheric concentrations are highly sensitive.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Seasonality of global and Arctic black carbon processes in the Arctic Monitoring and Assessment Programme models

et al. 2016

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“…Another modeling problem may be excessive convective transport and underestimation of the associated wet scavenging in convective clouds, which can lead to model overestimates of BC in the upper troposphere and lower stratosphere (Allen and Landuyt, 2014;Wang et al, 2014). Despite remaining difficulties, simulations of Arctic aerosols with many models have improved considerably in the last few years by updating the model treatment of some or all of the above-mentioned processes (Fisher et al, 2011;Breider et al, 2014;Sharma et al, 2013;Lund and Berntsen, 2012;Allen and Landuyt, 2014).…”

Section: S Eckhardt Et Al: Current Model Capabilities For Simulatinmentioning

confidence: 99%

Current model capabilities for simulating black carbon and sulfate concentrations in the Arctic atmosphere: a multi-model evaluation using a comprehensive measurement data set

et al. 2015

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International audienceThe concentrations of sulfate, black carbon (BC) and other aerosols in the Arctic are characterized by high values in late winter and spring (so-called Arctic Haze) and low values in summer. Models have long been struggling to capture this seasonality and especially the high concentrations associated with Arctic Haze. In this study, we evaluate sulfate and BC concentrations from eleven different models driven with the same emission inventory against a comprehensive pan-Arctic measurement data set over a time period of two years (2008–2009). The set of models consisted of one Lagrangian particle dispersion model, four chemistry-transport models (CTMs), one atmospheric chemistry-weather forecast model and five chemistry-climate models (CCMs), of which two were nudged to meteorological analyses and three were running freely. The measurement data set consisted of surface measurements of equivalent BC (eBC) from five stations (Alert, Barrow, Pallas, Tiksi and Zeppelin), elemental carbon (EC) from Station Nord and Alert and aircraft measurements of refractory BC (rBC) from six different campaigns. We find that the models generally captured the measured eBC/rBC and sulfate concentrations quite well, compared to past comparisons. However, the aerosol seasonality at the surface is still too weak in most models. Concentrations of eBC and sulfate averaged over three surface sites are underestimated in winter/spring in all but one model (model means for January-March underestimated by 59 and 37% for BC and sulfate, respectively), whereas concentrations in summer are overestimated in the model mean (by 88 and 44% for July–September), but with over- as well as underestimates present in individual models. The most pronounced eBC underestimates, not included in the above multi-site average, are found for the station Tiksi in Siberia where the measured annual mean eBC concentration is three times higher than the average annual mean for all other stations. This suggests an underestimate of BC sources in Russia in the emission inventory used. Based on the campaign data, biomass burning was identified as another cause of the modelling problems. For sulfate, very large differences were found in the model ensemble, with an apparent anti-correlation between modeled surface concentrations and total atmospheric columns. There is a strong correlation between observed sulfate and eBC concentrations with consistent sulfate/eBC slopes found for all Arctic stations, indicating that the sources contributing to sulfate and BC are similar throughout the Arctic and that the aerosols are internally mixed and undergo similar removal. However, only three models reproduced this finding, whereas sulfate and BC are weakly correlated in the other models. Overall, no class of models (e.g., CTMs, CCMs) performed better than the others and differences are independent of model resolution

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“…In addition, in Fig. 5b-c, CCAM is within the range of estimates for total deposition, wet deposition fraction, burden, and lifetime of organic aerosols (OAs) and BC (Tsigaridis et al, 2014;Allen and Landuyt, 2014). CCAM modeled OC emissions and burden is converted to OA by multiplying by a factor of 1.4 for a consistent comparison (Tsigaridis et al, 2014).…”

Section: Southern African Aeronet Aod and α Ext Observationsmentioning

confidence: 59%

Evaluation of climate model aerosol seasonal and spatial variability over Africa using AERONET

et al. 2017

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Abstract. The sensitivity of climate models to the characterization of African aerosol particles is poorly understood. Africa is a major source of dust and biomass burning aerosols and this represents an important research gap in understanding the impact of aerosols on radiative forcing of the climate system. Here we evaluate the current representation of aerosol particles in the Conformal Cubic Atmospheric Model (CCAM) with ground-based remote retrievals across Africa, and additionally provide an analysis of observed aerosol optical depth at 550 nm (AOD 550 nm ) and Ångström exponent data from 34 Aerosol Robotic Network (AERONET) sites. Analysis of the 34 long-term AERONET sites confirms the importance of dust and biomass burning emissions to the seasonal cycle and magnitude of AOD 550 nm across the continent and the transport of these emissions to regions outside of the continent. In general, CCAM captures the seasonality of the AERONET data across the continent. The magnitude of modeled and observed multiyear monthly average AOD 550 nm overlap within ±1 standard deviation of each other for at least 7 months at all sites except the Réunion St Denis Island site (Réunion St. Denis). The timing of modeled peak AOD 550 nm in southern Africa occurs 1 month prior to the observed peak, which does not align with the timing of maximum fire counts in the region. For the western and northern African sites, it is evident that CCAM currently overestimates dust in some regions while others (e.g., the Arabian Peninsula) are better characterized. This may be due to overestimated dust lifetime, or that the characterization of the soil for these areas needs to be updated with local information. The CCAM simulated AOD 550 nm for the global domain is within the spread of previously published results from CMIP5 and AeroCom experiments for black carbon, organic carbon, and sulfate aerosols. The model's performance provides confidence for using the model to estimate largescale regional impacts of African aerosols on radiative forcing, but local feedbacks between dust aerosols and climate over northern Africa and the Mediterranean may be overestimated.

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The vertical distribution of black carbon in CMIP5 models: Comparison to observations and the importance of convective transport

Cited by 57 publications

References 92 publications

Seasonality of global and Arctic black carbon processes in the Arctic Monitoring and Assessment Programme models

Seasonality of global and Arctic black carbon processes in the Arctic Monitoring and Assessment Programme models

Current model capabilities for simulating black carbon and sulfate concentrations in the Arctic atmosphere: a multi-model evaluation using a comprehensive measurement data set

Evaluation of climate model aerosol seasonal and spatial variability over Africa using AERONET

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