scholarly journals Sensitivity of black carbon concentrations and climate impact to aging and scavenging

2016 ◽  
Author(s):  
Marianne T. Lund ◽  
Terje K. Berntsen ◽  
Bjørn H. Samset
Keyword(s):  
Nitric Acid ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Mitigation Strategies ◽  
The Arctic ◽  
Climate Mitigation ◽  
Vertical Profiles ◽  
The Impact ◽  
Model Measurement ◽  
Global Mean

Abstract. Despite recent improvements, significant uncertainties in global modeling of black carbon (BC) aerosols persist, posing important challenges for the design and evaluation of effective climate mitigation strategies targeted at BC emission reductions. Here we investigate the sensitivity of BC concentrations in the chemistry-transport model OsloCTM2 with the microphysical aerosol parameterization M7 (OsloCTM2-M7) to parameters controlling aerosol aging and scavenging. We focus on Arctic surface concentrations and remote region BC vertical profiles, and introduce a novel treatment of condensation of nitric acid on BC. The OsloCTM2-M7 underestimates annual averaged BC surface concentrations, with a mean normalized bias of −0.55. The seasonal cycle and magnitude of Arctic BC surface concentrations is improved compared to previous OsloCTM2 studies, but model-measurement discrepancies during spring remain. High-altitude BC over the Pacific is overestimated compared with measurements from the HIPPO campaigns. We find that a shorter global BC lifetime improves the agreement with HIPPO, in line with other recent studies. Several processes can achieve this, including allowing for convective scavenging of hydrophobic BC and reducing the amount of soluble material required for aging. Simultaneously, the concentrations in the Arctic are reduced, resulting in poorer agreement with measurements in part of the region. A first step towards inclusion of aging by nitrate in OsloCTM2-M7 is made by allowing for condensation of nitric acid on BC. This results in a faster aging and reduced lifetime, and in turn to a better agreement with the HIPPO measurements. On the other hand, model-measurement discrepancies in the Arctic are exacerbated. Work to further improve this parameterization is needed. The impact on global mean radiative forcing (RF) and surface temperature response (TS) in our experiments is estimated. Compared to the baseline, decreases in global mean direct RF on the order of 10–30 % of the total pre-industrial to present BC direct RF is estimated for the experiments that result in the largest changes in BC concentrations. We show that globally tuning parameters related to BC aging and scavenging can improve the representation of BC vertical profiles in the OsloCTM2-M7 compared with observations. Our results also show that such improvements can result from changes in several processes and often depend on assumptions about uncertain parameters such as the BC ice nucleating efficiency and the change in hygroscopicity with aging. It is also important to be aware of potential tradeoffs in model performance between different regions. Other important sources of uncertainty, particularly for Arctic BC, such as model resolution has not been investigated here. Our results underline the importance of more observations and experimental data to improve process understanding and thus further constrain models.

scholarly journals Hindcasting and forecasting of regional methane from coal mine emissions in the Upper Silesian Coal Basin using the online nested global regional chemistry–climate model MECO(n) (MESSy v2.53)

2020 ◽  
Vol 13 (4) ◽  
pp. 1925-1943 ◽  
Author(s):  
Anna-Leah Nickl ◽  
Mariano Mertens ◽  
Anke Roiger ◽  
Andreas Fix ◽  
Axel Amediek ◽  
...  
Keyword(s):  
Coal Mining ◽  
Spatial Resolution ◽  
Radiative Forcing ◽  
Climate Model ◽  
Mitigation Strategies ◽  
Climate Mitigation ◽  
Coal Basin ◽  
Airborne Measurements ◽  
Upper Silesian Coal Basin ◽  
The Impact

Abstract. Methane is the second most important greenhouse gas in terms of anthropogenic radiative forcing. Since pre-industrial times, the globally averaged dry mole fraction of methane in the atmosphere has increased considerably. Emissions from coal mining are one of the primary anthropogenic methane sources. However, our knowledge about different sources and sinks of methane is still subject to great uncertainties. Comprehensive measurement campaigns and reliable chemistry–climate models, are required to fully understand the global methane budget and to further develop future climate mitigation strategies. The CoMet 1.0 campaign (May to June 2018) combined airborne in situ, as well as passive and active remote sensing measurements to quantify the emissions from coal mining in the Upper Silesian Coal Basin (USCB, Poland). Roughly 502 kt of methane is emitted from the ventilation shafts per year. In order to help with the flight planning during the campaigns, we performed 6 d forecasts using the online coupled, three-time nested global and regional chemistry–climate model MECO(n). We applied three-nested COSMO/MESSy instances going down to a spatial resolution of 2.8 km over the USCB. The nested global–regional model system allows for the separation of local emission contributions from fluctuations in the background methane. Here, we introduce the forecast set-up and assess the impact of the model's spatial resolution on the simulation of methane plumes from the ventilation shafts. Uncertainties in simulated methane mixing ratios are estimated by comparing different airborne measurements to the simulations. Results show that MECO(3) is able to simulate the observed methane plumes and the large-scale patterns (including vertically integrated values) reasonably well. Furthermore, we obtain reasonable forecast results up to forecast day four.

scholarly journals Black carbon in the atmosphere and snow, from pre-industrial times until present

2011 ◽  
Vol 11 (14) ◽  
pp. 6809-6836 ◽  
Author(s):  
R. B. Skeie ◽  
T. Berntsen ◽  
G. Myhre ◽  
C. A. Pedersen ◽  
J. Ström ◽  
...  
Keyword(s):  
Black Carbon ◽  
Radiative Forcing ◽  
Fossil Fuel ◽  
The Arctic ◽  
Slight Reduction ◽  
Snow Albedo ◽  
Aerosol Effect ◽  
Albedo Effect ◽  
Concentration Changes ◽  
Global Mean

Abstract. The distribution of black carbon (BC) in the atmosphere and the deposition of BC on snow surfaces since pre-industrial time until present are modelled with the Oslo CTM2 model. The model results are compared with observations including recent measurements of BC in snow in the Arctic. The global mean burden of BC from fossil fuel and biofuel sources increased during two periods. The first period, until 1920, is related to increases in emissions in North America and Europe, and the last period after 1970 are related mainly to increasing emissions in East Asia. Although the global burden of BC from fossil fuel and biofuel increases, in the Arctic the maximum atmospheric BC burden as well as in the snow was reached in 1960s, with a slight reduction thereafter. The global mean burden of BC from open biomass burning sources has not changed significantly since 1900. With current inventories of emissions from open biomass sources, the modelled burden of BC in snow and in the atmosphere north of 65° N is small compared to the BC burden of fossil fuel and biofuel origin. From the concentration changes radiative forcing time series due to the direct aerosol effect as well as the snow-albedo effect is calculated for BC from fossil fuel and biofuel. The calculated radiative forcing in 2000 for the direct aerosol effect is 0.35 W m−2 and for the snow-albedo effect 0.016 W m−2 in this study. Due to a southward shift in the emissions there is an increase in the lifetime of BC as well as an increase in normalized radiative forcing, giving a change in forcing per unit of emissions of 26 % since 1950.

scholarly journals Aircraft observations of enhancement and depletion of black carbon mass in the springtime Arctic

2010 ◽  
Vol 10 (6) ◽  
pp. 15167-15196
Author(s):  
J. R. Spackman ◽  
R. S. Gao ◽  
W. D. Neff ◽  
J. P. Schwarz ◽  
L. A. Watts ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Black Carbon ◽  
Biomass Burning ◽  
Boundary Layer Transition ◽  
Arctic Climate ◽  
The Arctic ◽  
Vertical Profiles ◽  
Free Troposphere ◽  
Air Mass ◽  
The Impact

Abstract. Understanding the processes controlling black carbon (BC) in the Arctic is crucial for evaluating the impact of anthropogenic and natural sources of BC on Arctic climate. Vertical profiles of BC mass were observed from the surface to near 7-km altitude in April 2008 using a Single-Particle Soot Photometer (SP2) during flights on the NOAA WP-3D research aircraft from Fairbanks, Alaska. These measurements were conducted during the NOAA-sponsored Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) project as part of POLARCAT, an International Polar Year (IPY) activity. In the free troposphere, the Arctic air mass was influenced by long-range transport from biomass-burning and anthropogenic source regions at lower latitudes especially during the latter part of the campaign. Maximum average BC mass loadings of 150 ng kg−1 were observed near 5.5-km altitude in the aged Arctic air mass. In biomass-burning plumes, BC was enhanced from near the top of the Arctic boundary layer (ABL) to 5.5 km compared to the aged Arctic air mass. At the bottom of some of the profiles, positive vertical gradients in BC were observed in the vicinity of open leads in the sea-ice. BC mass loadings increased by about a factor of two across the boundary layer transition in the ABL in these cases while carbon monoxide (CO) remained constant, evidence for depletion of BC in the ABL. BC mass loadings were positively correlated with O3 in ozone depletion events (ODEs) for all the observations in the ABL suggesting that BC was removed by dry deposition of BC on the snow or ice because molecular bromine, Br2, which photolyzes and catalytically destroys O3, is thought to be released near the open leads in regions of ice formation. We estimate the deposition flux of BC mass to the snow using a box model constrained by the vertical profiles of BC in the ABL. The open leads may increase vertical mixing in the ABL and entrainment of pollution from the free troposphere possibly enhancing the deposition of BC to the snow.

scholarly journals Black carbon in the atmosphere and snow, from pre-industrial times until present

2011 ◽  
Vol 11 (3) ◽  
pp. 7469-7534 ◽  
Author(s):  
R. B. Skeie ◽  
T. Berntsen ◽  
G. Myhre ◽  
C. A. Pedersen ◽  
J. Ström ◽  
...  
Keyword(s):  
Black Carbon ◽  
Radiative Forcing ◽  
Fossil Fuel ◽  
The Arctic ◽  
Slight Reduction ◽  
Snow Albedo ◽  
Aerosol Effect ◽  
Albedo Effect ◽  
Concentration Changes ◽  
Global Mean

Abstract. The distribution of black carbon (BC) in the atmosphere and the deposition of BC on snow surfaces since pre-industrial time until present are modelled with the Oslo CTM2 model. The model results are compared with observations including recent measurements of BC in snow in the Arctic. The global mean burden of BC from fossil fuel and biofuel sources increased during two periods. The first period, until 1920, is related to increases in emissions in North America and Europe, and the last period after 1970 are related mainly to increasing emissions in East Asia. Although the global burden of BC from fossil fuel and biofuel increases, in the Arctic the maximum atmospheric BC burden as well as in the snow was reached in 1960s, with a slight reduction thereafter. The global mean burden of BC from open biomass burning sources has not changed significantly since 1900. With current inventories of emissions from open biomass sources, the modelled burden of BC in snow and in the atmosphere north of 65° N is small compared to the BC burden of fossil fuel and biofuel origin. From the concentration changes radiative forcing time series due to the direct aerosol effect as well as the snow-albedo effect is calculated for BC from fossil fuel and biofuel. The calculated radiative forcing in 2000 for the direct aerosol effect is 0.35 W m−2 and for the snow-albedo effect 0.016 W m−2. Due to a southward shift in the emissions there is an increase in the lifetime of BC as well as an increase in normalized radiative forcing, giving a change in forcing per unit of emissions of 26% since 1950.

scholarly journals Vertical profiles of aerosol and black carbon in the Arctic: a seasonal phenomenology along two years (2011–2012) of field campaign

2016 ◽  
Author(s):  
Luca Ferrero ◽  
David Cappelletti ◽  
Maurizio Busetto ◽  
Mauro Mazzola ◽  
Angelo Lupi ◽  
...  
Keyword(s):  
Size Distribution ◽  
Black Carbon ◽  
High Arctic ◽  
Aerosol Concentration ◽  
The Arctic ◽  
Aerosol Size Distribution ◽  
Vertical Profiles ◽  
Anthropogenic Aerosol ◽  
Haze Pollution ◽  
The Impact

Abstract. In this paper we present results from a systematic study of vertical profiles of aerosol number size distribution and black carbon (BC) concentrations conducted in the Arctic, over Ny-Ålesund (Svalbard). The campaign lasted 2 years (2011–2012) and resulted in 200 vertical profiles measured during the spring and summer seasons. In addition, chemical analysis of filter samples, aerosol size distribution and a full set of meteorological parameters were determined at ground to put on a firmer grounds the analysis of the vertical profiles. The collected experimental data allowed a classification of the vertical profiles into different typologies which allowed to describe a seasonal phenomenology of vertical aerosol properties in the Arctic. During spring, four main types of profiles were found and their behaviour was related to the main aerosol and atmospheric dynamics occurring at the measuring site. Background conditions generated homogenous profiles. Transport events caused an increase of aerosol concentration with altitude. High Arctic haze pollution trapped below thermal inversions promoted a decrease of aerosol concentration with altitude. Finally, ground-based plumes of locally formed secondary aerosol determined profiles with decreasing aerosol concentration located at different altitude in function of size. During the summer season, the impact from shipping caused aerosol and BC pollution plumes constrained close to the ground, indicating that increasing shipping emissions in the Arctic could bring anthropogenic aerosol and BC in the summer Arctic affecting the climate.

scholarly journals Aircraft observations of enhancement and depletion of black carbon mass in the springtime Arctic

2010 ◽  
Vol 10 (19) ◽  
pp. 9667-9680 ◽  
Author(s):  
J. R. Spackman ◽  
R. S. Gao ◽  
W. D. Neff ◽  
J. P. Schwarz ◽  
L. A. Watts ◽  
...  
Keyword(s):  
Sea Ice ◽  
Black Carbon ◽  
Biomass Burning ◽  
Dry Deposition ◽  
Arctic Climate ◽  
The Arctic ◽  
Vertical Profiles ◽  
Free Troposphere ◽  
Air Mass ◽  
The Impact

Abstract. Understanding the processes controlling black carbon (BC) in the Arctic is crucial for evaluating the impact of anthropogenic and natural sources of BC on Arctic climate. Vertical profiles of BC mass loadings were observed from the surface to near 7-km altitude in April 2008 using a Single-Particle Soot Photometer (SP2) during flights on the NOAA WP-3D research aircraft from Fairbanks, Alaska. These measurements were conducted during the NOAA-sponsored Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) project. In the free troposphere, the Arctic air mass was influenced by long-range transport from biomass-burning and anthropogenic source regions at lower latitudes especially during the latter part of the campaign. Average BC mass mixing ratios peaked at about 150 ng BC (kg dry air )−1 near 5.5 km altitude in the aged Arctic air mass and 250 ng kg−1 at 4.5 km in biomass-burning influenced air. BC mass loadings were enhanced by up to a factor of 5 in biomass-burning influenced air compared to the aged Arctic air mass. At the bottom of some of the profiles, positive vertical gradients in BC were observed over the sea-ice. The vertical profiles generally occurred in the vicinity of open leads in the sea-ice. In the aged Arctic air mass, BC mass loadings more than doubled with increasing altitude within the ABL and across the boundary layer transition while carbon monoxide (CO) remained constant. This is evidence for depletion of BC mass in the ABL. BC mass loadings were positively correlated with O3 in ozone depletion events (ODEs) for all the observations in the ABL. Since bromine catalytically destroys ozone in the ABL after being released as molecular bromine in regions of new sea-ice formation at the surface, the BC–O3 correlation suggests that BC particles were removed by a surface process such as dry deposition. We develop a box model to estimate the dry deposition flux of BC mass to the snow constrained by the vertical profiles of BC mass in the ABL. Open leads in the sea-ice may increase vertical mixing and entrainment of pollution from the free troposphere possibly enhancing the deposition of BC aerosol to the snow.

scholarly journals Vertical profiles of aerosol and black carbon in the Arctic: a seasonal phenomenology along 2 years (2011–2012) of field campaigns

2016 ◽  
Vol 16 (19) ◽  
pp. 12601-12629 ◽  
Author(s):  
Luca Ferrero ◽  
David Cappelletti ◽  
Maurizio Busetto ◽  
Mauro Mazzola ◽  
Angelo Lupi ◽  
...  
Keyword(s):  
Size Distribution ◽  
Black Carbon ◽  
High Arctic ◽  
Aerosol Concentration ◽  
The Arctic ◽  
Aerosol Size Distribution ◽  
Vertical Profiles ◽  
Anthropogenic Aerosol ◽  
Haze Pollution ◽  
The Impact

Abstract. We present results from a systematic study of vertical profiles of aerosol number size distribution and black carbon (BC) concentrations conducted in the Arctic, over Ny-Ålesund (Svalbard). The campaign lasted 2 years (2011–2012) and resulted in 200 vertical profiles measured by means of a tethered balloon (up to 1200 m a.g.l.) during the spring and summer seasons. In addition, chemical analysis of filter samples, aerosol size distribution and a full set of meteorological parameters were determined at ground. The collected experimental data allowed a classification of the vertical profiles into different typologies, which allowed us to describe the seasonal phenomenology of vertical aerosol properties in the Arctic. During spring, four main types of profiles were found and their behavior was related to the main aerosol and atmospheric dynamics occurring at the measuring site. Background conditions generated homogenous profiles. Transport events caused an increase of aerosol concentration with altitude. High Arctic haze pollution trapped below thermal inversions promoted a decrease of aerosol concentration with altitude. Finally, ground-based plumes of locally formed secondary aerosol determined profiles with decreasing aerosol concentration located at different altitude as a function of size. During the summer season, the impact from shipping caused aerosol and BC pollution plumes to be constrained close to the ground, indicating that increasing shipping emissions in the Arctic could bring anthropogenic aerosol and BC in the Arctic summer, affecting the climate.

scholarly journals The Arctic response to remote and local forcing of black carbon

2012 ◽  
Vol 12 (7) ◽  
pp. 18379-18418 ◽  
Author(s):  
M. Sand ◽  
T. K. Berntsen ◽  
J. E. Kay ◽  
J. F. Lamarque ◽  
Ø. Seland ◽  
...  
Keyword(s):  
Sea Ice ◽  
Black Carbon ◽  
Temperature Response ◽  
Mitigation Strategies ◽  
Arctic Climate ◽  
The Arctic ◽  
Comprehensive Treatment ◽  
Model Calculations ◽  
The Impact ◽  
Ice Fraction

Abstract. Recent studies suggest that the Arctic temperature response to black carbon (BC) forcing depend on the location of the forcing. We investigate how BC in the mid-latitudes remotely influence the Arctic climate, and compare this with the response to BC located in the Arctic it self. In this study, idealized climate simulations are carried out with a fully coupled Earth System Model, which includes a comprehensive treatment of aerosol microphysics. In order to determine how BC transported to the Arctic and BC sources not reaching the Arctic impact the Arctic climate, forcing from BC aerosols is artificially increased by a factor of 10 in different latitude bands in the mid-latitudes (28° N–60° N) and in the Arctic (60° N–90° N), respectively. Estimates of the impact on the Arctic energy budget are represented by analyzing radiation fluxes at the top of the atmosphere, at the surface and at the lateral boundaries. Our calculations show that increased BC forcing in the Arctic atmosphere reduces the surface air temperature in the Arctic with a corresponding increase in the sea-ice fraction, despite the increased planetary absorption of sunlight. The analysis indicates that this effect may be due to a combination of a weakening of the northward heat transport caused by a reduction in the meridional temperature gradient and a reduction in the turbulent mixing of heat downward to the surface. The latter factor is explained by the fact that most of the BC is located in the free troposphere and causes a warming at higher altitudes which increases the static stability in the Arctic. On the other hand we find that BC forcing at the mid-latitudes warms the Arctic surface significantly and decreases the sea-ice fraction. Our model calculations indicate that atmospheric BC forcing outside the Arctic is more important for the Arctic climate change than the forcing in the Arctic itself. Although the albedo effect of BC on snow does show a more regional response to an Arctic forcing, these results suggest that mitigation strategies for the Arctic climate should also address BC sources in locations outside the Arctic even if they do not contribute much to BC in the Arctic.

scholarly journals Sensitivity of black carbon concentrations and climate impact to aging and scavenging in OsloCTM2–M7

2017 ◽  
Vol 17 (9) ◽  
pp. 6003-6022 ◽  
Author(s):  
Marianne T. Lund ◽  
Terje K. Berntsen ◽  
Bjørn H. Samset
Keyword(s):  
Nitric Acid ◽  
Surface Temperature ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Climate Models ◽  
Transport Model ◽  
Climate Impact ◽  
Climate Impacts ◽  
The Arctic ◽  
Effective Parameters

Abstract. Accurate representation of black carbon (BC) concentrations in climate models is a key prerequisite for understanding its net climate impact. BC aging and scavenging are treated very differently in current models. Here, we examine the sensitivity of three-dimensional (3-D), temporally resolved BC concentrations to perturbations to individual model processes in the chemistry transport model OsloCTM2–M7. The main goals are to identify processes related to aerosol aging and scavenging where additional observational constraints may most effectively improve model performance, in particular for BC vertical profiles, and to give an indication of how model uncertainties in the BC life cycle propagate into uncertainties in climate impacts. Coupling OsloCTM2 with the microphysical aerosol module M7 allows us to investigate aging processes in more detail than possible with a simpler bulk parameterization. Here we include, for the first time in this model, a treatment of condensation of nitric acid on BC. Using kernels, we also estimate the range of radiative forcing and global surface temperature responses that may result from perturbations to key tunable parameters in the model. We find that BC concentrations in OsloCTM2–M7 are particularly sensitive to convective scavenging and the inclusion of condensation by nitric acid. The largest changes are found at higher altitudes around the Equator and at low altitudes over the Arctic. Convective scavenging of hydrophobic BC, and the amount of sulfate required for BC aging, are found to be key parameters, potentially reducing bias against HIAPER Pole-to-Pole Observations (HIPPO) flight-based measurements by 60 to 90  %. Even for extensive tuning, however, the total impact on global-mean surface temperature is estimated to less than 0.04 K. Similar results are found when nitric acid is allowed to condense on the BC aerosols. We conclude, in line with previous studies, that a shorter atmospheric BC lifetime broadly improves the comparison with measurements over the Pacific. However, we also find that the model–measurement discrepancies can not be uniquely attributed to uncertainties in a single process or parameter. Model development therefore needs to be focused on improvements to individual processes, supported by a broad range of observational and experimental data, rather than tuning of individual, effective parameters such as the global BC lifetime.

scholarly journals The Arctic response to remote and local forcing of black carbon

2013 ◽  
Vol 13 (1) ◽  
pp. 211-224 ◽  
Author(s):  
M. Sand ◽  
T. K. Berntsen ◽  
J. E. Kay ◽  
J. F. Lamarque ◽  
Ø. Seland ◽  
...  
Keyword(s):  
Sea Ice ◽  
Black Carbon ◽  
Heat Transport ◽  
Mitigation Strategies ◽  
Arctic Climate ◽  
The Arctic ◽  
Comprehensive Treatment ◽  
Model Calculations ◽  
The Impact ◽  
Ice Fraction

Abstract. Recent studies suggest that the Arctic temperature response to black carbon (BC) forcing depend strongly on the location of the forcing. We investigate how atmospheric BC in the mid-latitudes remotely influence the Arctic climate, and compare this with the response to atmospheric BC located in the Arctic itself. In this study, idealized climate simulations are carried out with a fully coupled Earth System Model, which includes a comprehensive treatment of aerosol microphysics. In order to determine how BC transported to the Arctic and BC sources not reaching the Arctic impact the Arctic climate, atmospheric BC concentrations are scaled up in the mid-latitudes (28–60° N) and in the Arctic (60–90° N), respectively. Estimates of the impact on the Arctic energy budget are represented by analyzing radiation fluxes at the top of the atmosphere and at the surface, surface turbulent fluxes, and meridional heat transport in the atmosphere. Our calculations show that increased BC forcing in the Arctic atmosphere reduces the surface air temperature in the Arctic with a corresponding increase in the sea-ice fraction, despite the increased planetary absorption of sunlight. The analysis indicates that this effect is due to a combination of a weakening of the northward heat transport caused by a reduction in the meridional temperature gradient and a dimming at the surface. On the other hand we find that BC forcing at the mid-latitudes warms the Arctic surface significantly and decreases the sea-ice fraction. Our model calculations indicate that atmospheric BC forcing outside the Arctic may be more important for the Arctic climate change than the forcing in the Arctic itself. These results suggest that mitigation strategies for the Arctic climate should also address BC sources in locations outside the Arctic even if they do not contribute much to BC in the Arctic.

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