scholarly journals Factors Controlling Black Carbon Distribution in the Arctic

2016 ◽  
Author(s):  
Ling Qi ◽  
Qinbin Li ◽  
Yingrui Li ◽  
Cenlin He
Keyword(s):  
Black Carbon ◽  
Dry Deposition ◽  
Model Simulation ◽  
Deposition Velocity ◽  
Mixed Phase ◽  
The Arctic ◽  
Dry Deposition Velocity ◽  
Mixed Phase Clouds ◽  
Scavenging Efficiency ◽  
Snow And Ice

Abstract. We investigate the sensitivity of black carbon (BC) in the Arctic, including BC in snow (BCsnow, ng g−1) and surface air (BCair, μg m−3), to emissions, dry deposition and wet scavenging using a global 3-D chemical transport model (CTM) GEOS-Chem. We find that the model underestimates BCsnow in the Arctic by 40 % on average (median = 11.8 ng g−1). Natural gas flaring substantially increases total BC emissions in the Arctic (by ~ 70 %). The flaring emissions lead to up to 49 % increases (0.1–8.5 ng g−1) in Arctic BCsnow, dramatically improving model comparison with observations (50 % reduction in discrepancy) near flaring source regions (Western Extreme North of Russia). Ample observations suggest that BC dry deposition velocities over snow and ice in current CTMs (0.03 cm s−1 in GEOS-Chem) are exceedingly small. We apply the resistance-in-series method to compute the dry deposition velocity that varies with local meteorological and surface conditions. The resulting velocity is significantly larger and varies by a factor of eight in the Arctic (0.03–0.24 cm s−1), increases the fraction of dry to total BC deposition (16 % to 25 %), yet leaves the total BC deposition and BCsnow in the Arctic unchanged. This is largely explained by the offsetting higher dry and lower wet deposition fluxes. Additionally, we account for the effect of the Wegener-Bergeron-Findeisen (WBF) process in mixed-phase clouds, which releases BC particles from condensed phases (water drops and ice crystals) back to the interstitial air and thereby substantially reduces the scavenging efficiency of BC (by 43–76 % in the Arctic). The resulting BCsnow is up to 80 % higher, BC loading is considerably larger (from 0.25 to 0.43 mg  m−2), and BC lifetime is markedly prolonged (from 9 to 16 days) in the Arctic. Over all, flaring emissions increase BCair in the Arctic (by ~ 20 ng m−3), the updated dry deposition velocity more than halves BCair (by ~ 20 ng  m−3), and the WBF effect increases BCair by 25–70 % during winter and early spring. The resulting model simulation of BCsnow is substantially improved (within 10 % of the observations) and the discrepancies of BCair are much smaller during snow season at Barrow, Alert and Summit (from −67 %–−47 % to −46 %–3 %). Our results point toward an urgent need for better characterization of flaring emissions of BC (e.g. the emission factors, temporal and spatial distribution), extensive measurements of both the dry deposition of BC over snow and ice, and the scavenging efficiency of BC in mixed-phase clouds.

scholarly journals Factors controlling black carbon distribution in the Arctic

2017 ◽  
Vol 17 (2) ◽  
pp. 1037-1059 ◽  
Author(s):  
Ling Qi ◽  
Qinbin Li ◽  
Yinrui Li ◽  
Cenlin He
Keyword(s):  
Black Carbon ◽  
Dry Deposition ◽  
Model Comparison ◽  
Model Simulation ◽  
Deposition Velocity ◽  
Mixed Phase ◽  
The Arctic ◽  
Mixed Phase Clouds ◽  
Scavenging Efficiency ◽  
Snow And Ice

Abstract. We investigate the sensitivity of black carbon (BC) in the Arctic, including BC concentration in snow (BCsnow, ng g−1) and surface air (BCair, ng m−3), as well as emissions, dry deposition, and wet scavenging using the global three-dimensional (3-D) chemical transport model (CTM) GEOS-Chem. We find that the model underestimates BCsnow in the Arctic by 40 % on average (median  =  11.8 ng g−1). Natural gas flaring substantially increases total BC emissions in the Arctic (by ∼ 70 %). The flaring emissions lead to up to 49 % increases (0.1–8.5 ng g−1) in Arctic BCsnow, dramatically improving model comparison with observations (50 % reduction in discrepancy) near flaring source regions (the western side of the extreme north of Russia). Ample observations suggest that BC dry deposition velocities over snow and ice in current CTMs (0.03 cm s−1 in the GEOS-Chem) are too small. We apply the resistance-in-series method to compute a dry deposition velocity (vd) that varies with local meteorological and surface conditions. The resulting velocity is significantly larger and varies by a factor of 8 in the Arctic (0.03–0.24 cm s−1), which increases the fraction of dry to total BC deposition (16 to 25 %) yet leaves the total BC deposition and BCsnow in the Arctic unchanged. This is largely explained by the offsetting higher dry and lower wet deposition fluxes. Additionally, we account for the effect of the Wegener–Bergeron–Findeisen (WBF) process in mixed-phase clouds, which releases BC particles from condensed phases (water drops and ice crystals) back to the interstitial air and thereby substantially reduces the scavenging efficiency of clouds for BC (by 43–76 % in the Arctic). The resulting BCsnow is up to 80 % higher, BC loading is considerably larger (from 0.25 to 0.43 mg m−2), and BC lifetime is markedly prolonged (from 9 to 16 days) in the Arctic. Overall, flaring emissions increase BCair in the Arctic (by ∼ 20 ng m−3), the updated vd more than halves BCair (by ∼ 20 ng m−3), and the WBF effect increases BCair by 25–70 % during winter and early spring. The resulting model simulation of BCsnow is substantially improved (within 10 % of the observations) and the discrepancies of BCair are much smaller during the snow season at Barrow, Alert, and Summit (from −67–−47 % to −46–3 %). Our results point toward an urgent need for better characterization of flaring emissions of BC (e.g., the emission factors, temporal, and spatial distribution), extensive measurements of both the dry deposition of BC over snow and ice, and the scavenging efficiency of BC in mixed-phase clouds. In addition, we find that the poorly constrained precipitation in the Arctic may introduce large uncertainties in estimating BCsnow. Doubling precipitation introduces a positive bias approximately as large as the overall effects of flaring emissions and the WBF effect; halving precipitation produces a similarly large negative bias.

scholarly journals Effects of the Wegener–Bergeron–Findeisen process on global black carbon distribution

2017 ◽  
Vol 17 (12) ◽  
pp. 7459-7479 ◽  
Author(s):  
Ling Qi ◽  
Qinbin Li ◽  
Cenlin He ◽  
Xin Wang ◽  
Jianping Huang
Keyword(s):  
Black Carbon ◽  
Transport Model ◽  
Mixed Phase ◽  
The Arctic ◽  
Deposition Flux ◽  
Chemical Transport Model ◽  
Washout Ratio ◽  
Cloud Scavenging ◽  
Mixed Phase Clouds ◽  
Scavenging Efficiency

Abstract. We systematically investigate the effects of Wegener–Bergeron–Findeisen process (hereafter WBF) on black carbon (BC) scavenging efficiency, surface BCair, deposition flux, concentration in snow (BCsnow, ng g−1), and washout ratio using a global 3-D chemical transport model (GEOS-Chem). We differentiate riming- versus WBF-dominated in-cloud scavenging based on liquid water content (LWC) and temperature. Specifically, we implement an implied WBF parameterization using either temperature or ice mass fraction (IMF) in mixed-phase clouds based on field measurements. We find that at Jungfraujoch, Switzerland, and Abisko, Sweden, where WBF dominates in-cloud scavenging, including the WBF effect strongly reduces the discrepancies of simulated BC scavenging efficiency and washout ratio against observations (from a factor of 3 to 10 % and from a factor of 4–5 to a factor of 2). However, at Zeppelin, Norway, where riming dominates, simulation of BC scavenging efficiency, BCair, and washout ratio become worse (relative to observations) when WBF is included. There is thus an urgent need for extensive observations to distinguish and characterize riming- versus WBF-dominated aerosol scavenging in mixed-phase clouds and the associated BC scavenging efficiency. Our model results show that including the WBF effect lowers global BC scavenging efficiency, with a higher reduction at higher latitudes (8 % in the tropics and up to 76 % in the Arctic). The resulting annual mean BCair increases by up to 156 % at high altitudes and at northern high latitudes because of lower temperature and higher IMF. Overall, WBF halves the model–observation discrepancy (from −65 to −30 %) of BCair across North America, Europe, China and the Arctic. Globally WBF increases BC burden from 0.22 to 0.29–0.35 mg m−2 yr−1, which partially explains the gap between observed and previous model-simulated BC burdens over land. In addition, WBF significantly increases BC lifetime from 5.7 to  ∼  8 days. Additionally, WBF results in a significant redistribution of BC deposition in source and remote regions. Specifically, it lowers BC wet deposition (by 37–63 % at northern mid-latitudes and by 21–29 % in the Arctic), while it increases dry deposition (by 3–16 % at mid-latitudes and by 81–159 % in the Arctic). The resulting total BC deposition is lower at mid-latitudes (by 12–34 %) but higher in the Arctic (by 2–29 %). We find that WBF decreases BCsnow at mid-latitudes (by  ∼  15 %) but increases it in the Arctic (by 26 %) while improving model comparisons with observations. In addition, WBF dramatically reduces the model–observation discrepancy of washout ratios in winter (from a factor of 16 to 4). The remaining discrepancies in BCair, BCsnow and BC washout ratios suggest that in-cloud removal in mixed-phased clouds is likely still excessive over land.

scholarly journals Effects of Wegener-Bergeron-Findeisen Process on Global Black Carbon Distribution

2016 ◽  
Author(s):  
Ling Qi ◽  
Qinbin Li ◽  
Cenlin He ◽  
Xin Wang ◽  
Jianping Huang
Keyword(s):  
Transport Model ◽  
Liquid Water Content ◽  
Mixed Phase ◽  
The Arctic ◽  
Deposition Flux ◽  
Chemical Transport Model ◽  
Washout Ratio ◽  
Lower Temperature ◽  
Mixed Phase Clouds ◽  
Scavenging Efficiency

Abstract. We systematically investigate the effects of Wegener-Bergeron-Findeisen (WBF) on BC scavenging efficiency, surface BCair, deposition flux, concentration in snow (BCsnow, ng g−1), and washout ratio using a global 3D chemical transport model (GEOS-Chem). We differentiate riming- versus WBF-dominated in-cloud scavenging based on liquid water content (LWC) and temperature. Specifically, we relate WBF to either temperature or ice mass fraction (IMF) in mixed-phase clouds. We find that at Jungfraujoch, Switzerland and Abisko, Sweden, where WBF dominates, the discrepancies of simulated BC scavenging efficiency and washout ratio are significantly reduced (from a factor of 3 to 10 % and from a factor of 4–5 to a factor of two). However, at Zeppelin, Norway, where riming dominates, simulation of BC scavenging efficiency, BCair, and washout ratio become worse (relative to observations) when WBF is included. There is thus an urgent need for extensive observations to distinguish and characterize riming- versus WBF-dominated aerosol scavenging in mixed-phase clouds and the associated BC scavenging efficiency. We find the reduction resulting from WBF to global BC scavenging efficiency varies substantially, from 8 % in the tropics to 76 % in the Arctic. The resulting annual mean BCair increases by up to 156 % at high altitudes and at northern high latitudes because of lower temperature and higher IMF. Overall, WBF halves the model-observation discrepancy (from −65 % to −30 %) of BCair across North America, Europe, China and the Arctic. Globally WBF increases BC burden from 0.22 to 0.29–0.35 mg m−2 yr−1, which partially explains the gap between observed and previous model simulated BC burdens over land. In addition, WBF significantly increases BC lifetime from 5.7 days to ~8 days. Additionally, WBF results in a significant redistribution of BC deposition in source and remote regions. Specifically, it lowers BC wet deposition (by 37–63 % at northern mid-latitudes and by 21–29 % in the Arctic) while increases dry deposition (by 3–16 % at mid-latitudes and by 81–159 % in the Arctic). The resulting total BC deposition is lower at mid-latitudes (by 12–34 %) but higher in the Arctic (by 2–29 %). We find that WBF decreases BCsnow at mid-latitudes (by ~15 %) but increases it in the Arctic (by 26 %) while improving model comparisons with observations. In addition, WBF dramatically reduces the model-observation discrepancy of washout ratios in winter (from a factor of 16 to 4). The remaining discrepancies in BCair, BCsnow and BC washout ratios suggest that in-cloud removal in mixed-phased clouds is likely still excessive over land.

scholarly journals Characteristic nature of vertical motions observed in Arctic mixed-phase stratocumulus

2013 ◽  
Vol 13 (11) ◽  
pp. 31079-31125 ◽  
Author(s):  
J. Sedlar ◽  
M. D. Shupe
Keyword(s):  
Vertical Velocity ◽  
Vertical Mixing ◽  
Vertical Motion ◽  
Temperature Inversion ◽  
Arctic Sea Ice ◽  
Cloud Layer ◽  
Mixed Phase ◽  
The Arctic ◽  
Cloud Base ◽  
Mixed Phase Clouds

Abstract. Over the Arctic Ocean, little is known, observationally, on cloud-generated buoyant overturning vertical motions within mixed-phase stratocumulus clouds. Characteristics of such motions are important for understanding the diabatic processes associated with the vertical motions, the lifetime of the cloud layer and its micro- and macrophysical characteristics. In this study, we exploit a suite of surface-based remote sensors over the high Arctic sea ice during a week-long period of persistent stratocumulus in August 2008 to derive the in-cloud vertical motion characteristics. In-cloud vertical velocity skewness and variance profiles are found to be strikingly different from observations within lower-latiatude stratocumulus, suggesting these Arctic mixed-phase clouds interact differently with the atmospheric thermodynamics (cloud tops extending above a stable temperature inversion base) and with a different coupling state between surface and cloud. We find evidence of cloud-generated vertical mixing below cloud base, regardless of surface-cloud coupling state, although a decoupled surface-cloud state occurred most frequently. Detailed case studies are examined focusing on 3 levels within the cloud layer, where wavelet and power spectral analyses are applied to characterize the dominant temporal and horizontal scales associated with cloud-generated vertical motions. In general, we find a positively-correlated vertical motion signal across the full cloud layer depth. The coherency is dependent upon other non-cloud controlled factors, such as larger, mesoscale weather passages and radiative shielding of low-level stratocumulus by multiple cloud layers above. Despite the coherency in vertical velocity across the cloud, the velocity variances were always weaker near cloud top, relative to cloud mid and base. Taken in combination with the skewness, variance and thermodynamic profile characteristics, we observe vertical motions near cloud-top that behave differently than those from lower within the cloud layer. Spectral analysis indicates peak cloud-generated w variance timescales slowed only modestly during decoupled cases relative to coupled; horizontal wavelengths only slightly increased when transitioning from coupling to decoupling. The similarities in scales suggests that perhaps the dominant forcing for all cases is generated from the cloud layer, and it is not the surface forcing that characterizes the time and space scales of in-cloud vertical velocity variance. This points toward the resilient nature of Arctic mixed-phase clouds to persist when characterized by thermodynamic regimes unique to the Arctic.

scholarly journals Preliminary estimation of black carbon deposition from Nepal Climate Observatory-Pyramid data and its possible impact on snow albedo changes over Himalayan glaciers during the pre-monsoon season

2010 ◽  
Vol 10 (4) ◽  
pp. 9291-9328 ◽  
Author(s):  
T. J. Yasunari ◽  
P. Bonasoni ◽  
P. Laj ◽  
K. Fujita ◽  
E. Vuillermoz ◽  
...  
Keyword(s):  
Lower Bound ◽  
Size Distribution ◽  
Black Carbon ◽  
Dry Deposition ◽  
Monsoon Season ◽  
Deposition Velocity ◽  
Himalayan Region ◽  
Snow Surface ◽  
Concentration Data ◽  
Snow Albedo

Abstract. The possible minimal range of reduction in snow surface albedo due to dry deposition of black carbon (BC) in the pre-monsoon period (March–May) was estimated as a lower bound together with the estimation of its accuracy, based on atmospheric observations at the Nepal Climate Observatory-Pyramid (NCO-P) sited at 5079 m a.s.l. in the Himalayan region. We estimated a total BC deposition rate of 2.89 μg m−2 day−1 providing a total deposition of 266 μg m−2 for March–May at the site, based on a calculation with a minimal deposition velocity of 1.0×10−4 m s−1 with atmospheric data of equivalent BC concentration. Main BC size at NCO-P site was determined as 103.1–669.8 nm by correlation analysis between equivalent BC concentration and particulate size distribution in the atmosphere. We also estimated BC deposition from the size distribution data and found that 8.7% of the estimated dry deposition corresponds to the estimated BC deposition from equivalent BC concentration data. If all the BC is deposited uniformly on the top 2-cm pure snow, the corresponding BC concentration is 26.0–68.2 μg kg−1 assuming snow density variations of 195–512 kg m−3 of Yala Glacier close to NCO-P site. Such a concentration of BC in snow could result in 2.0–5.2% albedo reductions. From a simple numerical calculations and if assuming these albedo reductions continue throughout the year, this would lead to a runoff increases of 70–204 mm of water drainage equivalent of 11.6–33.9% of the annual discharge of a typical Tibetan glacier. Our estimates of BC concentration in snow surface for pre-monsoon season can be considered comparable to those at similar altitude in the Himalayan region, where glaciers and perpetual snow region starts in the vicinity of NCO-P. Our estimates from only BC are likely to represent a lower bound for snow albedo reductions, since a fixed slower deposition velocity was used and atmospheric wind and turbulence effects, snow aging, dust deposition, and snow albedo feedbacks were not considered. This study represents the first investigation about BC deposition on snow from atmospheric aerosol data in Himalayas and related albedo effect is especially the first track at the southern slope of Himalayas.

Determining PM2.5 dry deposition velocity on plant leaves: An indirect experimental method

2019 ◽  
Vol 46 ◽  
pp. 126467 ◽  
Author(s):  
Shan Yin ◽  
Xuyi Zhang ◽  
Annie Yu ◽  
Ningxiao Sun ◽  
Junyao Lyu ◽  
...  
Keyword(s):  
Experimental Method ◽  
Dry Deposition ◽  
Deposition Velocity ◽  
Plant Leaves ◽  
Dry Deposition Velocity

scholarly journals Aerosol dry deposition measured with eddy-covariance technique at Wasa and Aboa, DronningMaud Land, Antarctica

2002 ◽  
Vol 35 ◽  
pp. 355-361 ◽  
Author(s):  
Anna Grönlund ◽  
Douglas Nilsson ◽  
Ismo K. Koponen ◽  
Aki Virkkula ◽  
Margareta E. Hansson
Keyword(s):  
Eddy Covariance ◽  
Dry Deposition ◽  
Transfer Functions ◽  
Deposition Velocity ◽  
Ice Core ◽  
Brownian Diffusion ◽  
Wind Component ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Dry Deposition Velocity

AbstractInterpretation of ice-core records in terms of changes in atmospheric concentrations requires understanding of the various parameters within air–snow transfer functions. the dry-deposition velocity is one of these parameters, dependent on local meteorological conditions and thereby also affected by climate changes. We have determined aerosol dry-deposition velocities by measurements of aerosol particle-number concentration and the vertical wind component with an eddy-covariance system close to the Swedish and Finnish research stations Wasa and Aboa in Dronning Maud Land, Antarctica. Measurements were performed over a smooth, snow-covered area and over moderately rough, rocky ground during 4 and 19 days, respectively, in January 2000. the median dry-deposition velocity determined 5.25 mabove the surface was 0.33 and 0.80 cm s–1, respectively. the large difference between the two sites was mainly due to the stratification of the surface boundary layer, the surface albedo and the surface roughness height. the dry-deposition number fluxes were dominated by the particle-size modes defined as ultrafine and Aitken, withmean diameters around 14 and 42 nm, respectively. A larger dry-deposition velocity, owing to stronger Brownian diffusion, for the smaller ultrafine mode was verified by the measurements.

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