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.

scholarly journals Estimated impact of black carbon deposition during pre-monsoon season from Nepal Climate Observatory – Pyramid data and snow albedo changes over Himalayan glaciers

2010 ◽  
Vol 10 (14) ◽  
pp. 6603-6615 ◽  
Author(s):  
T. J. Yasunari ◽  
P. Bonasoni ◽  
P. Laj ◽  
K. Fujita ◽  
E. Vuillermoz ◽  
...  
Keyword(s):  
Lower Bound ◽  
Black Carbon ◽  
Dry Deposition ◽  
Monsoon Season ◽  
Deposition Velocity ◽  
Himalayan Region ◽  
Glacier Mass Balance ◽  
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. A total BC deposition rate was estimated as 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 analyses between equivalent BC concentration and particulate size distributions in the atmosphere. The BC deposition from the size distribution data was also estimated. It was 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. By assuming these albedo reductions continue throughout the year, and then applying simple numerical experiments with a glacier mass balance model, we estimated reductions would lead to runoff increases of 70–204 mm of water. This runoff is the 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 is comparable to those at similar altitudes in the Himalayan region, where glaciers and perpetual snow regions begin, in the vicinity of NCO-P. Our estimates from only BC are likely to represent a lower bound for snow albedo reductions, because we used a fixed slower deposition velocity. In addition, we excluded the effects of atmospheric wind and turbulence, snow aging, dust deposition, and snow albedo feedbacks. This preliminary study represents the first investigation of BC deposition and related albedo on snow, using atmospheric aerosol data observed at the southern slope in the Himalayas.

Linear regression analyses with censored data: estimation of PAH washout ratios and dry deposition velocities to a snow surface

1995 ◽  
Vol 22 (4) ◽  
pp. 819-833 ◽  
Author(s):  
Mukesh Sharma ◽  
Neil R. Thomson ◽  
Edward A. McBean
Keyword(s):  
Least Squares ◽  
Censored Data ◽  
Dry Deposition ◽  
Least Squares Method ◽  
Deposition Velocity ◽  
Snow Surface ◽  
Regression Analyses ◽  
Doubly Censored Data ◽  
Doubly Censored ◽  
Censored Observations

Detection limits of analyzing instruments are the main reason for censored observations of pollutant concentrations. An iterative least squares method for regression analyses is developed to suit the doubly censored data commonly observed in environmental engineering. The modified iterative least squares method utilizes the expected values of censored observations estimated from the probability density function of doubly censored data in a regression process. The modified method is examined for bias in the estimation of the parameters of a linear model, and in the estimation of the standard deviation of the regression. A mechanistic model for atmospheric transport and deposition of polycyclic aromatic hydrocarbons (PAHs) to a snow surface is formulated by utilizing the long-term PAH retention property of deep snowpacks. The modified iterative least squares method is applied to estimate the deposition parameters (dry deposition velocity and washout ratio) for various PAH species, since some of the PAH deposition levels were below the minimum detection limit of the analyzing instrument. The estimated parameters are examined statistically, and compare favourably with previously reported estimates of these parameters. Key words: censored data, regression, iterative least squares, PAHs, dry deposition velocity, washout ratio.

Estimated range of black carbon dry deposition and the related snow albedo reduction over Himalayan glaciers during dry pre-monsoon periods

2013 ◽  
Vol 78 ◽  
pp. 259-267 ◽  
Author(s):  
Teppei J. Yasunari ◽  
Qian Tan ◽  
K.-M. Lau ◽  
Paolo Bonasoni ◽  
Angela Marinoni ◽  
...  
Keyword(s):  
Black Carbon ◽  
Dry Deposition ◽  
Snow Albedo ◽  
Himalayan Glaciers

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 Snow Surface Albedo Sensitivity to Black Carbon: Radiative Transfer Modelling

Atmosphere ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1077
Author(s):  
Nicholas D. Beres ◽  
Magín Lapuerta ◽  
Francisco Cereceda-Balic ◽  
Hans Moosmüller
Keyword(s):  
Radiative Transfer ◽  
Black Carbon ◽  
Surface Albedo ◽  
Mass Density ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Snow Surface ◽  
Snow Albedo ◽  
Carbon Mass ◽  
The Relationship

The broadband surface albedo of snow can greatly be reduced by the deposition of light-absorbing impurities, such as black carbon on or near its surface. Such a reduction increases the absorption of solar radiation and may initiate or accelerate snowmelt and snow albedo feedback. Coincident measurements of both black carbon concentration and broadband snow albedo may be difficult to obtain in field studies; however, using the relationship developed in this simple model sensitivity study, black carbon mass densities deposited can be estimated from changes in measured broadband snow albedo, and vice versa. Here, the relationship between the areal mass density of black carbon found near the snow surface to the amount of albedo reduction was investigated using the popular snow radiative transfer model Snow, Ice, and Aerosol Radiation (SNICAR). We found this relationship to be linear for realistic amounts of black carbon mass concentrations, such as those found in snow at remote locations. We applied this relationship to measurements of broadband albedo in the Chilean Andes to estimate how vehicular emissions contributed to black carbon (BC) deposition that was previously unquantified.

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 Black carbon in snow in the upper Himalayan Khumbu Valley, Nepal: observations and modeling of the impact on snow albedo, melting, and radiative forcing

2014 ◽  
Vol 8 (5) ◽  
pp. 5035-5076 ◽  
Author(s):  
H.-W. Jacobi ◽  
S. Lim ◽  
M. Ménégoz ◽  
P. Ginot ◽  
P. Laj ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Monsoon Season ◽  
Regional Climate ◽  
Transfer Scheme ◽  
Monsoon Period ◽  
Annual Cycles ◽  
Snow Albedo ◽  
The Impact

Abstract. Black carbon (BC) in the snow in the Himalayas has recently attracted considerable interest due to its impact on snow albedo, snow and glacier melting, regional climate and water resources. A single particle soot photometer (SP2) instrument was used to measure refractory BC (rBC) in a series of surface snow samples collected in the upper Khumbu Valley in Nepal between November 2009 and February 2012. The obtained time series indicates annual cycles with maximum concentration before the onset of the monsoon season and fast decreases in rBC during the monsoon period. Measured concentrations ranged from a few ppb up to 70 ppb rBC. However, due to the handling of the samples the measured concentrations possess rather large uncertainties. Detailed modeling of the snowpack including the measured range and an estimated upper limit of rBC concentrations was performed to study the role of BC in the seasonal snowpack. Simulations were performed for three winter seasons with the snowpack model Crocus including a detailed description of the radiative transfer inside the snowpack. While the standard Crocus model strongly overestimates the height and the duration of the seasonal snowpack, a better calculation of the snow albedo with the new radiative transfer scheme enhanced the representation of the snow. However, the period with snow on the ground neglecting BC in the snow was still over-estimated between 37 and 66 days, which was further diminished by 8 to 15% and more than 40% in the presence of 100 or 300 ppb of BC. Compared to snow without BC the albedo is on average reduced by 0.027 and 0.060 in the presence of 100 and 300 ppb BC. While the impact of increasing BC in the snow on the albedo was largest for clean snow, the impact on the local radiative forcing is the opposite. Here, increasing BC caused an even larger impact at higher BC concentrations. This effect is related to an accelerated melting of the snowpack caused by a more efficient metamorphism of the snow due to an increasing size of the snow grains with increasing BC concentrations. The melting of the winter snowpack was shifted by 3 to 10 days and 17 to 27 days during the three winter seasons in the presence of 100 and 300 ppb BC compared to clean snow, while the simulated annual local radiative forcing corresponds to 3 to 4.5 and 10.5 to 13.0 W m−2. An increased sublimation or evaporation of the snow reduces the simulated radiative forcing leading to a net forcing that is lower by 0.5 to 1.5 W m−2, while the addition of 10 ppm dust causes an increase of the radiative forcing between 2.5 and 3 W m−2. According to the simulations 7.5 ppm of dust has an effect equivalent to 100 ppb of BC concerning the impact on the melting of the snowpack and the local radiative forcing.

scholarly journals Black carbon in snow in the upper Himalayan Khumbu Valley, Nepal: observations and modeling of the impact on snow albedo, melting, and radiative forcing

2015 ◽  
Vol 9 (4) ◽  
pp. 1685-1699 ◽  
Author(s):  
H.-W. Jacobi ◽  
S. Lim ◽  
M. Ménégoz ◽  
P. Ginot ◽  
P. Laj ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Monsoon Season ◽  
Regional Climate ◽  
Transfer Scheme ◽  
Monsoon Period ◽  
Annual Cycles ◽  
Snow Albedo ◽  
The Impact

Abstract. Black carbon (BC) in snow in the Himalayas has recently attracted considerable interest due to its impact on snow albedo, snow and glacier melting, regional climate and water resources. A single particle soot photometer (SP2) instrument was used to measure refractory BC (rBC) in a series of surface snow samples collected in the upper Khumbu Valley, Nepal between November 2009 and February 2012. The obtained time series indicates annual cycles with maximum rBC concentrations before the onset of the monsoon season and fast decreases during the monsoon period. Detected concentrations ranged from a few up to 70 ppb with rather large uncertainties due to the handling of the samples. Detailed modeling of the snowpack, including the detected range and an estimated upper limit of BC concentrations, was performed to study the role of BC in the seasonal snowpack. Simulations were performed for three winter seasons with the snowpack model Crocus, including a detailed description of the radiative transfer inside the snowpack. While the standard Crocus model strongly overestimates the height and the duration of the seasonal snowpack, a better calculation of the snow albedo with the new radiative transfer scheme enhanced the representation of the snow. However, the period with snow on the ground without BC in the snow was still overestimated between 37 and 66 days, which was further diminished by 8 to 15 % and more than 40 % in the presence of 100 or 300 ppb of BC. Compared to snow without BC, the albedo is reduced on average by 0.027 and 0.060 in the presence of 100 and 300 ppb BC. While the impact of increasing BC in the snow on the albedo was largest for clean snow, the impact on the local radiative forcing is the opposite. Here, increasing BC caused an even larger impact at higher BC concentrations. This effect is related to an accelerated melting of the snowpack caused by a more efficient metamorphism of the snow due to an increasing size of the snow grains with increasing BC concentrations. The melting of the winter snowpack was shifted by 3 to 10 and 17 to 27 days during the three winter seasons in the presence of 100 and 300 ppb BC compared to clean snow, while the simulated annual local radiative forcing corresponds to 3 to 4.5 and 10.5 to 13.0 W m−2. An increased sublimation or evaporation of the snow reduces the simulated radiative forcing, leading to a net forcing that is lower by 0.5 to 1.5 W m−2, while the addition of 10 ppm dust causes an increase of the radiative forcing between 2.5 and 3 W m−2. According to the simulations, 7.5 ppm of dust has an effect equivalent to 100 ppb of BC concerning the impact on the melting of the snowpack and the local radiative forcing.

scholarly journals Study of Black Carbon (BC) Mass Concentration Variation at a Coastal Region (Surat)

2020 ◽  
Vol 4 (1) ◽  
pp. 16
Author(s):  
Ranjitkumar Solanki ◽  
Kamlesh N. Pathak
Keyword(s):  
Black Carbon ◽  
Mass Concentration ◽  
Monsoon Season ◽  
Coastal Region ◽  
Concentration Data ◽  
Study Region ◽  
Local Boundary ◽  
Annual Variations ◽  
The Mean ◽  
Bc Aerosols

Black Carbon (BC) aerosols mass concentration was studied at Surat, Gujarat (India), a coastal region near the Tapi River at the Gulf of Khambhat. Using satellite data for solar extinction due to Black Carbon (BC) mass concentration, data were collected from the Giovanni platform developed by NASA. Results of the data for the 5-year period (January to December 2001–2005) are discussed here. Annual and Seasonal variations of Black Carbon (BC) in relation to changes in the regional meteorological conditions are discussed here. The data collected during January to December 2001–2005 indicated the annual average BC concentration. The mean annual variations of BC aerosols mass concentration saw its maximum in the month of December while minimum was seen in the month of July. The seasonal mean BC mass concentration observed to be at its lowest in monsoon season while its highest was in winter at the study region. Variation of the BC trend observed was higher in the month December and lower in the month of July which is mostly related to the changes in the local boundary layer.

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