scholarly journals Combining atmospheric and snow radiative transfer models to assess the solar radiative effects of black carbon in the Arctic

2020 ◽  
Vol 20 (13) ◽  
pp. 8139-8156
Author(s):  
Tobias Donth ◽  
Evelyn Jäkel ◽  
André Ehrlich ◽  
Bernd Heinold ◽  
Jacob Schacht ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Arctic Ocean ◽  
Black Carbon ◽  
Heating Rate ◽  
Radiative Forcing ◽  
Mass Concentration ◽  
Early Summer ◽  
The Arctic ◽  
Snow Layer ◽  
Surface Snow

Abstract. The magnitude of solar radiative effects (cooling or warming) of black carbon (BC) particles embedded in the Arctic atmosphere and surface snow layer was explored on the basis of case studies. For this purpose, combined atmospheric and snow radiative transfer simulations were performed for cloudless and cloudy conditions on the basis of BC mass concentrations measured in pristine early summer and more polluted early spring conditions. The area of interest is the remote sea-ice-covered Arctic Ocean in the vicinity of Spitsbergen, northern Greenland, and northern Alaska typically not affected by local pollution. To account for the radiative interactions between the black-carbon-containing snow surface layer and the atmosphere, an atmospheric and snow radiative transfer model were coupled iteratively. For pristine summer conditions (no atmospheric BC, minimum solar zenith angles of 55∘) and a representative BC particle mass concentration of 5 ng g−1 in the surface snow layer, a positive daily mean solar radiative forcing of +0.2 W m−2 was calculated for the surface radiative budget. A higher load of atmospheric BC representing early springtime conditions results in a slightly negative mean radiative forcing at the surface of about −0.05 W m−2, even when the low BC mass concentration measured in the pristine early summer conditions was embedded in the surface snow layer. The total net surface radiative forcing combining the effects of BC embedded in the atmosphere and in the snow layer strongly depends on the snow optical properties (snow specific surface area and snow density). For the conditions over the Arctic Ocean analyzed in the simulations, it was found that the atmospheric heating rate by water vapor or clouds is 1 to 2 orders of magnitude larger than that by atmospheric BC. Similarly, the daily mean total heating rate (6 K d−1) within a snowpack due to absorption by the ice was more than 1 order of magnitude larger than that of atmospheric BC (0.2 K d−1). Also, it was shown that the cooling by atmospheric BC of the near-surface air and the warming effect by BC embedded in snow are reduced in the presence of clouds.

scholarly journals Combining atmospheric and snow layer radiative transfer models to assess the solar radiative effects of black carbon in the Arctic

2020 ◽  
Author(s):  
Tobias Donth ◽  
Evelyn Jäkel ◽  
André Ehrlich ◽  
Bernd Heinold ◽  
Jacob Schacht ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Black Carbon ◽  
Heating Rate ◽  
Mass Concentration ◽  
Early Spring ◽  
Early Summer ◽  
The Arctic ◽  
Radiative Effect ◽  
Snow Layer ◽  
Surface Snow

Abstract. Solar radiative effects (cooling or warming) of black carbon (BC) particles suspended in the Arctic atmosphere and surface snow layer were explored by radiative transfer simulations on the basis of BC mass concentrations measured in pristine early summer and polluted early spring conditions under cloudless and cloudy conditions. To account for the radiative interactions between the black carbon containing snow surface layer and the atmosphere, a snow layer and an atmospheric radiative transfer model were coupled iteratively. For pristine summer conditions (no atmospheric BC) and a representative BC particle mass concentration of 5 ng g−1 in the surface snow layer, a positive solar radiative effect of +0.2 W m−2 was calculated for the surface radiative budget. Contrarily, a higher load of atmospheric BC representing springtime conditions, results in a slightly negative radiative effect of about −0.05 W m−2, even when the same BC mass concentration is suspended in the surface snow layer. This counteracting of atmospheric BC and BC suspended in the snow layer strongly depends on the snow optical properties determined by the snow specific surface area. However, it was found, that the atmospheric heating rate by water vapor or clouds is one to two orders of magnitude larger than that by atmospheric BC. Similarly, the total heating rate (6 K day−1) within a snow pack due to absorption by the ice water, was found to be more than one order of magnitude larger than the heating rate of suspended BC (0.2 K day−1). The role of clouds in the estimation of the combined direct radiative BC effect (BC in snow and in atmosphere) was analyzed for the pristine early summer and the polluted early spring BC conditions. Both, the cooling effect by atmospheric BC, as well as the warming effect by BC suspended in snow are reduced in the presence of clouds.

scholarly journals Variability in black carbon mass concentration in surface snow at Svalbard

2021 ◽  
Vol 21 (16) ◽  
pp. 12479-12493
Author(s):  
Michele Bertò ◽  
David Cappelletti ◽  
Elena Barbaro ◽  
Cristiano Varin ◽  
Jean-Charles Gallet ◽  
...  
Keyword(s):  
Black Carbon ◽  
Mass Concentration ◽  
Multiple Linear Regression Model ◽  
The Arctic ◽  
Snow Layer ◽  
Physico Chemical ◽  
Surface Snow ◽  
Carbon Mass ◽  
Precipitation Events ◽  
Observation Period

Abstract. Black carbon (BC) is a significant forcing agent in the Arctic, but substantial uncertainty remains to quantify its climate effects due to the complexity of the different mechanisms involved, in particular related to processes in the snowpack after deposition. In this study, we provide detailed and unique information on the evolution and variability in BC content in the upper surface snow layer during the spring period in Svalbard (Ny-Ålesund). A total of two different snow-sampling strategies were adopted during spring 2014 (from 1 April to 24 June) and during a specific period in 2015 (28 April to 1 May), providing the refractory BC (rBC) mass concentration variability on a seasonal variability with a daily resolution (hereafter seasonal/daily) and daily variability with an hourly sampling resolution (hereafter daily/hourly) timescales. The present work aims to identify which atmospheric variables could interact with and modify the mass concentration of BC in the upper snowpack, which is the snow layer where BC particles affects the snow albedo. Atmospheric, meteorological and snow-related physico-chemical parameters were considered in a multiple linear regression model to identify the factors that could explain the variations in BC mass concentrations during the observation period. Precipitation events were the main drivers of the BC variability during the seasonal experiment; however, in the high-resolution sampling, a negative association has been found. Snow metamorphism and the activation of local sources (Ny-Ålesund was a coal mine settlement) during the snowmelt periods appeared to play a non-negligible role. The statistical analysis suggests that the BC content in the snow is not directly associated to the atmospheric BC load.

scholarly journals Variability of Black Carbon mass concentration in surface snow at Svalbard

2021 ◽  
Author(s):  
Michele Bertò ◽  
David Cappelletti ◽  
Elena Barbaro ◽  
Cristiano Varin ◽  
Jean-Charles Gallet ◽  
...  
Keyword(s):  
Black Carbon ◽  
Mass Concentration ◽  
The Arctic ◽  
Sampling Strategies ◽  
Snow Layer ◽  
Physico Chemical ◽  
Surface Snow ◽  
Carbon Mass ◽  
Precipitation Events ◽  
Substantial Uncertainty

Abstract. Black Carbon (BC) is a significant forcing agent in the Arctic, but substantial uncertainty remains to quantify its climate effects due to the complexity of the different mechanisms involved, in particular related to processes in the snow-pack after deposition. In this study, we provide detailed and unique information on the evolution and variability of BC content in the upper surface snow layer during the spring period in Svalbard (Ny-Ålesund). Two different snow-sampling strategies were adopted during spring 2014 and 2015, providing the refractory BC (rBC) mass concentration variability on a seasonal/daily and daily/hourly time scales. The present work aims to identify which atmospheric variables could interact and modify the mass concentration of BC in the upper snowpack, the snow layer which BC particles affects the snow albedo. Despite the low BC mass concentrations, a relatively high daily variability was observed. Atmospheric, meteorological, and snow-related physico-chemical parameters were considered in a multiple statistical model to separate the factors determining observations. Precipitation events were the main drivers of the BC variability. Snow metamorphism and activation of local sources during the snow melting periods appeared to play a non-negligible role (wind resuspension in specific Arctic areas where coal mines were present). The BC content in the snow resulted in being statistically decoupled from the atmospheric BC load.

scholarly journals Biases in modeled surface snow BC mixing ratios in prescribed-aerosol climate model runs

2014 ◽  
Vol 14 (21) ◽  
pp. 11697-11709 ◽  
Author(s):  
S. J. Doherty ◽  
C. M. Bitz ◽  
M. G. Flanner
Keyword(s):  
Black Carbon ◽  
Radiative Forcing ◽  
Climate Model ◽  
Aerosol Deposition ◽  
Deposition Flux ◽  
Snow Layer ◽  
Mixing Ratios ◽  
Mass Fluxes ◽  
Surface Snow ◽  
Snow Water

Abstract. Black carbon (BC) in snow lowers its albedo, increasing the absorption of sunlight, leading to positive radiative forcing, climate warming and earlier snowmelt. A series of recent studies have used prescribed-aerosol deposition flux fields in climate model runs to assess the forcing by black carbon in snow. In these studies, the prescribed mass deposition flux of BC to surface snow is decoupled from the mass deposition flux of snow water to the surface. Here we compare prognostic- and prescribed-aerosol runs and use a series of offline calculations to show that the prescribed-aerosol approach results, on average, in a factor of about 1.5–2.5 high bias in annual-mean surface snow BC mixing ratios in three key regions for snow albedo forcing by BC: Greenland, Eurasia and North America. These biases will propagate directly to positive biases in snow and surface albedo reduction by BC. The bias is shown be due to coupling snowfall that varies on meteorological timescales (daily or shorter) with prescribed BC mass deposition fluxes that are more temporally and spatially smooth. The result is physically non-realistic mixing ratios of BC in surface snow. We suggest that an alternative approach would be to prescribe BC mass mixing ratios in snowfall, rather than BC mass fluxes, and we show that this produces more physically realistic BC mixing ratios in snowfall and in the surface snow layer.

scholarly journals High–Arctic aircraft measurements characterising black carbon vertical variability in spring and summer

2018 ◽  
Author(s):  
Hannes Schulz ◽  
Heiko Bozem ◽  
Marco Zanatta ◽  
W. Richard Leaitch ◽  
Andreas B. Herber ◽  
...  
Keyword(s):  
Black Carbon ◽  
Radiative Forcing ◽  
Mass Concentration ◽  
Potential Temperature ◽  
Particle Diameter ◽  
High Arctic ◽  
The Arctic ◽  
Transport Pathways ◽  
Vertical Coordinate ◽  
Back Trajectories

Abstract. The vertical distribution of black carbon (BC) particles in the Arctic atmosphere is one of the key parameters controlling its radiative forcing. Hence, this work investigates the presence and properties of BC over the high Canadian Arctic. Airborne campaigns were performed as part of the NETCARE project and provided insights into the variability of the vertical distributions of BC particles in summer 2014 and spring 2015. The observation periods covered evolutions of cyclonic disturbances to the polar dome that caused and changed transport of air pollution into the High–Arctic, as otherwise the airmass boundary largely impedes entrainment of pollution from lower latitudes. A total of 48 vertical profiles of refractory BC (rBC) mass concentration and particle size, extending from 0.1 to 5.5 km altitude, were obtained with a Single–Particle Soot Photometer (SP2). Generally, the rBC mass concentration decreased from spring to summer by a factor 10. Such depletion was associated with a decrease of the mean rBC particle diameter, from approximately 200 nm to 130 nm at low altitude. Due to the very low number fraction, rBC particles did not substantially contribute to the total aerosol population in summer. Profiles analysed with potential temperature as vertical coordinate revealed characteristic variability patterns due to different balances of supply and removal of rBC in specific levels of the stable atmosphere. Kinematic back–trajectories were used to investigate transport pathways into these levels. The lower polar dome was influenced by low–level transport from sources within the cold central and marginal Arctic. During the spring campaign, a cold air outbreak over eastern Europe additionally caused northward transport of air from a corridor over western Russia to Central Asia that was affected by emissions from gas flaring, industrial activity and wildfires. This caused rBC concentrations between about 500 to 1800 m altitude to gradually increase from 32 to 49 ng m−3. The temporal development of transport to the level above, at around 2500 m, caused the initially low concentration to increase from

scholarly journals High Arctic aircraft measurements characterising black carbon vertical variability in spring and summer

2019 ◽  
Vol 19 (4) ◽  
pp. 2361-2384 ◽  
Author(s):  
Hannes Schulz ◽  
Marco Zanatta ◽  
Heiko Bozem ◽  
W. Richard Leaitch ◽  
Andreas B. Herber ◽  
...  
Keyword(s):  
Air Pollution ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Mass Concentration ◽  
Potential Temperature ◽  
Particle Diameter ◽  
Canadian Arctic ◽  
Polar Front ◽  
The Arctic ◽  
Low Level

Abstract. The vertical distribution of black carbon (BC) particles in the Arctic atmosphere is one of the key parameters controlling their radiative forcing and thus role in Arctic climate change. This work investigates the presence and properties of these light-absorbing aerosols over the High Canadian Arctic (>70∘ N). Airborne campaigns were performed as part of the NETCARE project (Network on Climate and Aerosols: Addressing Key Uncertainties in Remote Canadian Environments) and provided insights into the variability of the vertical distributions of BC particles in summer 2014 and spring 2015. The observation periods covered evolutions of cyclonic disturbances at the polar front, which favoured the transport of air pollution into the High Canadian Arctic, as otherwise this boundary between the air masses largely impedes entrainment of pollution from lower latitudes. A total of 48 vertical profiles of refractory BC (rBC) mass concentration and particle size, extending from 0.1 to 5.5 km altitude were obtained with a Single-Particle Soot Photometer (SP2). Generally, the rBC mass concentration decreased from spring to summer by a factor of 10. Such depletion was associated with a decrease in the mean rBC particle diameter, from approximately 200 to 130 nm at low altitude. Due to the very low number fraction, rBC particles did not substantially contribute to the total aerosol population in summer. The analysis of profiles with potential temperature as vertical coordinate revealed characteristic variability patterns within specific levels of the cold and stably stratified, dome-like, atmosphere over the polar region. The associated history of transport trajectories into each of these levels showed that the variability was induced by changing rates and efficiencies of rBC import. Generally, the source areas affecting the polar dome extended southward with increasing potential temperature (i.e. altitude) level in the dome. While the lower dome was mostly only influenced by low-level transport from sources within the cold central and marginal Arctic, for the mid-dome and upper dome during spring it was found that a cold air outbreak over eastern Europe caused intensified northward transport of air from a corridor over western Russia to central Asia. This sector was affected by emissions from gas flaring, industrial activity and wildfires. The development of transport caused rBC concentrations in the second lowest level to gradually increase from 32 to 49 ng m−3. In the third level this caused the initially low rBC concentration to increase from <15 to 150 ng m−3. A shift in rBC mass-mean diameter, from above 200 nm in the lower polar dome dominated by low-level transport to <190 nm at higher levels, may indicate that rBC was affected by wet removal mechanisms preferential to larger particle diameters when lifting processes were involved during transport. The summer polar dome had limited exchange with the mid-latitudes. Air pollution was supplied from sources within the marginal Arctic as well as by long-range transport, but in both cases rBC was largely depleted in absolute and relative concentrations. Near the surface, rBC concentrations were <2 ng m−3, while concentrations increased to <10 ng m−3 towards the upper boundary of the polar dome. The mass mean particle diameter of 132 nm was smaller than in spring; nonetheless the summer mean mass size distribution resembled the spring distribution from higher levels, with depletion of particles >300 nm. Our work provides vertical, spatial and seasonal information of rBC characteristics in the polar dome over the High Canadian Arctic, offering a more extensive dataset for evaluation of chemical transport models and for radiative forcing assessments than those obtained before by other Arctic aircraft campaigns.

scholarly journals Effects of mixing state on optical and radiative properties of black carbon in the European Arctic

2018 ◽  
Vol 18 (19) ◽  
pp. 14037-14057 ◽  
Author(s):  
Marco Zanatta ◽  
Paolo Laj ◽  
Martin Gysel ◽  
Urs Baltensperger ◽  
Stergios Vratolis ◽  
...  
Keyword(s):  
Black Carbon ◽  
Radiative Forcing ◽  
Mass Concentration ◽  
Arctic Region ◽  
The Arctic ◽  
Absorption Enhancement ◽  
Mixing State ◽  
Aerosol Radiative Forcing ◽  
Internal Mixing ◽  
The Arctic Region

Abstract. Atmospheric aging promotes internal mixing of black carbon (BC), leading to an enhancement of light absorption and radiative forcing. The relationship between BC mixing state and consequent absorption enhancement was never estimated for BC found in the Arctic region. In the present work, we aim to quantify the absorption enhancement and its impact on radiative forcing as a function of microphysical properties and mixing state of BC observed in situ at the Zeppelin Arctic station (78∘ N) in the spring of 2012 during the CLIMSLIP (Climate impacts of short-lived pollutants in the polar region) project. Single-particle soot photometer (SP2) measurements showed a mean mass concentration of refractory black carbon (rBC) of 39 ng m−3, while the rBC mass size distribution was of lognormal shape, peaking at an rBC mass-equivalent diameter (DrBC) of around 240 nm. On average, the number fraction of particles containing a BC core with DrBC>80 nm was less than 5 % in the size range (overall optical particle diameter) from 150 to 500 nm. The BC cores were internally mixed with other particulate matter. The median coating thickness of BC cores with 220 nm < DrBC< 260 nm was 52 nm, resulting in a core–shell diameter ratio of 1.4, assuming a coated sphere morphology. Combining the aerosol absorption coefficient observed with an Aethalometer and the rBC mass concentration from the SP2, a mass absorption cross section (MAC) of 9.8 m2 g−1 was inferred at a wavelength of 550 nm. Consistent with direct observation, a similar MAC value (8.4 m2 g−1 at 550 nm) was obtained indirectly by using Mie theory and assuming a coated-sphere morphology with the BC mixing state constrained from the SP2 measurements. According to these calculations, the lensing effect is estimated to cause a 54 % enhancement of the MAC compared to that of bare BC particles with equal BC core size distribution. Finally, the ARTDECO radiative transfer model was used to estimate the sensitivity of the radiative balance to changes in light absorption by BC as a result of a varying degree of internal mixing at constant total BC mass. The clear-sky noontime aerosol radiative forcing over a surface with an assumed wavelength-dependent albedo of 0.76–0.89 decreased, when ignoring the absorption enhancement, by −0.12 W m−2 compared to the base case scenario, which was constrained with mean observed aerosol properties for the Zeppelin site in Arctic spring. The exact magnitude of this forcing difference scales with environmental conditions such as the aerosol optical depth, solar zenith angle and surface albedo. Nevertheless, our investigation suggests that the absorption enhancement due to internal mixing of BC, which is a systematic effect, should be considered for quantifying the aerosol radiative forcing in the Arctic region.

Estimation of radiative forcing and heating rate based on vertical observation of black carbon in Nanjing, China

2021 ◽  
Vol 756 ◽  
pp. 144135
Author(s):  
Shuangshuang Shi ◽  
Bin Zhu ◽  
Wen Lu ◽  
Shuqi Yan ◽  
Chenwei Fang ◽  
...  
Keyword(s):  
Black Carbon ◽  
Heating Rate ◽  
Radiative Forcing
Sign in / Sign up

Export Citation Format

Share Document