Transport Mechanisms, Potential Sources, and Radiative Impacts of Black Carbon Aerosols on the Himalayas and Tibetan Plateau Glaciers

2021 ◽  
pp. 7-23
Author(s):  
Lekhendra Tripathee ◽  
Chaman Gul ◽  
Shichang Kang ◽  
Pengfei Chen ◽  
Jie Huang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
Transport Mechanisms ◽  
Radiative Impacts ◽  
Potential Sources ◽  
Carbon Aerosols ◽  
Black Carbon Aerosols

scholarly journals Black carbon fractal morphology and short-wave radiative impact: a modelling study

2011 ◽  
Vol 11 (8) ◽  
pp. 23103-23137
Author(s):  
M. Kahnert ◽  
A. Devasthale
Keyword(s):  
Optical Properties ◽  
Fractal Dimension ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Homogeneous Sphere ◽  
Radiative Impacts ◽  
Radiative Impact ◽  
Sphere Approximation ◽  
Carbon Aerosols ◽  
Black Carbon Aerosols

Abstract. We investigate the impact of the morphological properties of freshly emitted black carbon aerosols on optical properties and on radiative forcing. To this end, we model the optical properties of fractal black carbon aggregates by use of numerically exact solutions to Maxwell's equations within a spectral range from the UVC to the mid-IR. The results are coupled to radiative transfer computations, in which we consider six realistic case studies representing different atmospheric pollution conditions and surface albedos. The spectrally integrated radiative impacts of black carbon are compared for two different fractal morphologies, which brace the range of recently reported experimental observations of black carbon fractal structures. We also gauge our results by performing corresponding calculations based on the homogeneous sphere approximation, which is commonly employed in climate models. We find that at top of atmosphere the aggregate models yield radiative impacts that can be as much as 2 times higher than those based on the homogeneous sphere approximation. An aggregate model with a low fractal dimension can predict a radiative impact that is higher than that obtained with a high fractal dimension by a factor ranging between 1.1–1.6. Although the lower end of this scale seems like a rather small effect, a closer analysis reveals that the single scattering optical properties of more compact and more lacy aggregates differ considerably. In radiative flux computations there can be a partial cancellation due to the opposing effects of differences in the optical cross sections and asymmetry parameters. However, this cancellation effect can strongly depend on atmospheric conditions and is therefore quite unpredictable. We conclude that the fractal morphology of black carbon aerosols and their fractal parameters can have a profound impact on their radiative forcing effect, and that the use of the homogeneous sphere model introduces unacceptably high biases in radiative impact studies. We emphasise that there are other potentially important morphological features that have not been addressed in the present study, such as sintering and coating of freshly emitted black carbon by films of organic material.

scholarly journals Black Carbon Aerosols at Mt. Muztagh Ata, a High-Altitude Location in the Western Tibetan Plateau

2016 ◽  
Vol 16 (3) ◽  
pp. 752-763 ◽  
Author(s):  
Chong-Shu Zhu ◽  
Jun-Ji Cao ◽  
Bai-Qing Xu ◽  
Ru-Jin Huang ◽  
Ping Wang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
High Altitude ◽  
Black Carbon ◽  
Western Tibetan Plateau ◽  
Carbon Aerosols ◽  
Black Carbon Aerosols

scholarly journals Black carbon fractal morphology and short-wave radiative impact: a modelling study

2011 ◽  
Vol 11 (22) ◽  
pp. 11745-11759 ◽  
Author(s):  
M. Kahnert ◽  
A. Devasthale
Keyword(s):  
Optical Properties ◽  
Fractal Dimension ◽  
Black Carbon ◽  
Radiative Forcing ◽  
Homogeneous Sphere ◽  
Radiative Impacts ◽  
Radiative Impact ◽  
Sphere Approximation ◽  
Carbon Aerosols ◽  
Black Carbon Aerosols

Abstract. We investigate the impact of the morphological properties of freshly emitted black carbon aerosols on optical properties and on radiative forcing. To this end, we model the optical properties of fractal black carbon aggregates by use of numerically exact solutions to Maxwell's equations within a spectral range from the UVC to the mid-IR. The results are coupled to radiative transfer computations, in which we consider six realistic case studies representing different atmospheric pollution conditions and surface albedos. The spectrally integrated radiative impacts of black carbon are compared for two different fractal morphologies, which brace the range of recently reported experimental observations of black carbon fractal structures. We also gauge our results by performing corresponding calculations based on the homogeneous sphere approximation, which is commonly employed in climate models. We find that at top of atmosphere the aggregate models yield radiative impacts that can be as much as 2 times higher than those based on the homogeneous sphere approximation. An aggregate model with a low fractal dimension can predict a radiative impact that is higher than that obtained with a high fractal dimension by a factor ranging between 1.1–1.6. Although the lower end of this scale seems like a rather small effect, a closer analysis reveals that the single scattering optical properties of more compact and more lacy aggregates differ considerably. In radiative flux computations there can be a partial cancellation due to the opposing effects of different error sources. However, this cancellation effect can strongly depend on atmospheric conditions and is therefore quite unpredictable. We conclude that the fractal morphology of black carbon aerosols and their fractal parameters can have a profound impact on their radiative forcing effect, and that the use of the homogeneous sphere model introduces unacceptably high biases in radiative impact studies. We emphasise that there are other potentially important morphological features that have not been addressed in the present study, such as sintering and coating of freshly emitted black carbon by films of organic material. Finally, we found that the spectral variation of the absorption cross section of black carbon significantly deviates from a simple 1/λ scaling law. We therefore discourage the use of single-wavelength absorption measurements in conjunction with a 1/λ scaling relation in broadband radiative forcing simulations of black carbon.

scholarly journals Effects of Black Carbon Aerosols on the Indian Monsoon

2008 ◽  
Vol 21 (12) ◽  
pp. 2869-2882 ◽  
Author(s):  
Gerald A. Meehl ◽  
Julie M. Arblaster ◽  
William D. Collins
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
Bay Of Bengal ◽  
Indian Monsoon ◽  
The Tibetan Plateau ◽  
Bc Aerosols ◽  
Carbon Aerosols ◽  
Sst Gradient ◽  
Precipitation Trends ◽  
Black Carbon Aerosols

Abstract A six-member ensemble of twentieth-century simulations with changes to only time-evolving global distributions of black carbon aerosols in a global coupled climate model is analyzed to study the effects of black carbon (BC) aerosols on the Indian monsoon. The BC aerosols act to increase lower-tropospheric heating over South Asia and reduce the amount of solar radiation reaching the surface during the dry season, as noted in previous studies. The increased meridional tropospheric temperature gradient in the premonsoon months of March–April–May (MAM), particularly between the elevated heat source of the Tibetan Plateau and areas to the south, contributes to enhanced precipitation over India in those months. With the onset of the monsoon, the reduced surface temperatures in the Bay of Bengal, Arabian Sea, and over India that extend to the Himalayas act to reduce monsoon rainfall over India itself, with some small increases over the Tibetan Plateau. Precipitation over China generally decreases due to the BC aerosol effects. There is a weakened latitudinal SST gradient resulting from BC aerosols in the model simulations as seen in the observations, and this is present in the multiple-forcings experiments with the Community Climate System Model, version 3 (CCSM3), which includes natural and anthropogenic forcings (including BC aerosols). The BC aerosols and consequent weakened latitudinal SST gradient in those experiments are associated with increased precipitation during MAM in northern India and over the Tibetan Plateau, with some decreased precipitation over southwest India, the Bay of Bengal, Burma, Thailand, and Malaysia, as seen in observations. During the summer monsoon season, the model experiments show that BC aerosols have likely contributed to observed decreasing precipitation trends over parts of India, Bangladesh, Burma, and Thailand. Analysis of single ensemble members from the multiple-forcings experiment suggests that the observed increasing precipitation trends over southern China appear to be associated with natural variability connected to surface temperature changes in the northwest Pacific.

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