Aerosol radiative forcing due to enhanced black carbon at an urban site in India

Abstract. Large uncertainties exist when estimating radiative effects of ambient black carbon (BC) aerosol. Previous studies about the BC aerosol radiative forcing mainly focus on the BC aerosols' mass concentrations and mixing states, while the effects of BC mass size distribution (BCMSD) were not well considered. In this paper, we developed a method of measuring the BCMSD by using a differential mobility analyzer in tandem with an Aethalometer. A comprehensive method of multiple charging corrections was proposed and implemented in measuring the BCMSD. Good agreement was obtained between the BC mass concentration integrated from this system and that measured in the bulk phase, demonstrating the reliability of our proposed method. Characteristics of the BCMSD and corresponding radiative effects were studied based on a field measurement campaign conducted in the North China Plain by using our own measurement system. Results showed that the BCMSD had two modes and the mean peak diameters of the modes were 150 and 503 nm. The BCMSD of the coarser mode varied significantly under different pollution conditions with peak diameter varying between 430 and 580 nm, which gave rise to significant variation in aerosol bulk optical properties. The direct aerosol radiative forcing was estimated to vary by 8.45 % for different measured BCMSDs of the coarser mode, which shared the same magnitude with the variation associated with assuming different aerosol mixing states (10.5 %). Our study reveals that the BCMSD as well as its mixing state in estimating the direct aerosol radiative forcing matters. Knowledge of the BCMSD should be fully considered in climate models.

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Wet removal of black carbon in Asian outflow: Aerosol Radiative Forcing in East Asia (A-FORCE) aircraft campaign

Journal of Geophysical Research Atmospheres ◽

10.1029/2011jd016552 ◽

2012 ◽

Vol 117 (D3) ◽

pp. n/a-n/a ◽

Cited By ~ 87

Author(s):

N. Oshima ◽

Y. Kondo ◽

N. Moteki ◽

N. Takegawa ◽

M. Koike ◽

...

Keyword(s):

East Asia ◽

Black Carbon ◽

Radiative Forcing ◽

Aerosol Radiative Forcing ◽

Aerosol Radiative ◽

Wet Removal

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Evidence for control of black carbon and sulfate relative mass concentrations on composite aerosol radiative forcing: Case of a coastal urban area

Journal of Geophysical Research Atmospheres ◽

10.1029/2011jd016752 ◽

2012 ◽

Vol 117 (D5) ◽

pp. n/a-n/a ◽

Cited By ~ 5

Author(s):

K. Niranjan ◽

T. Anjana Devi ◽

B. Spandana ◽

V. Sreekanth ◽

B. L. Madhavan

Keyword(s):

Black Carbon ◽

Urban Area ◽

Radiative Forcing ◽

Relative Mass ◽

Aerosol Radiative Forcing ◽

Aerosol Radiative ◽

Mass Concentrations

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Constraining direct aerosol radiative forcing using remote sensing and in-situ constraints

10.5194/egusphere-egu2020-17044 ◽

2020 ◽

Author(s):

Lucia Timea Deaconu ◽

Duncan Watson-Parris ◽

Philip Stier ◽

Lindsay Lee

Keyword(s):

Remote Sensing ◽

Black Carbon ◽

Optical Depth ◽

Radiative Forcing ◽

Removal Rates ◽

Aerosol Radiative Forcing ◽

Aerosol Absorption ◽

Direct Radiative Forcing ◽

Aerosol Radiative

Absorbing aerosols affect the climate system (radiative forcing, cloud formation, precipitation and more) by strongly absorbing solar radiation, particularly at ultraviolet and visible wavelengths. The environmental impacts of an absorbing aerosol layer are influenced by its single scattering albedo (SSA), the albedo of the underlying surface, and also by the atmospheric residence time and column concentration of the aerosols.Black-carbon (BC), the collective term used for strongly absorbing, carbonaceous aerosols, emitted by incomplete combustion of fossil fuel, biofuel and biomass, is a significant contributor to atmospheric absorption and probably a main-driver in inter-model differences and large uncertainties in estimating the aerosol radiative forcing due to aerosol-radiation interaction (RFari). Estimates of BC direct radiative forcing suggest a positive effect of +0.71 Wm-2 (Bond and Bergstrom (2006)) with large uncertainties [+0.08, +1.27] Wm-2. These uncertainties result from poor estimates of BC atmospheric burden (emissions and removal rates) and its radiative properties. The uncertainty in the burden is due to the uncertainty in emissions (7.5 [2, 29] Tg yr-1) and lifetime (removal rates). In comparison with the available observations, global climate models (GCMs) tend to under-predict absorption near source (e.g. at AERONET stations), and over-predict concentrations in remote regions (e.g. as measured by aircraft campaigns). This may be due to GCM&#8217;s weak emissions at the source, but longer lifetime of aerosols in the atmosphere.This study aims to address the parametric uncertainty of GCMs and constrain the direct radiative forcing using a perturbed parameter ensemble (PPE) and a collection of observations, from remote sensing to in-situ measurements. Total atmospheric aerosol extinction is quantified using satellite observations that provide aerosol optical depth (AOD), while the SSA is constrained by the use of high-temporal resolution aerosol absorption optical depth (AAOD) measured with AERONET sun-photometers (for near-source columnar information of aerosol absorption) and airborne black-carbon in-situ measurements collected and synthesised in the Global Aerosol Synthesis and Science Project (GASSP) (for properties of long-range transported aerosols). Measurements from the airborne campaigns ATOM and HIPPO are valuable for constraining aerosol absorption in remote areas, while CLARIFY and ORACLES, that were employed over Southeast Atlantic, are considered in our study for near source observations of biomass burning aerosols transported over the bright surface of stratocumulus clouds.Using the PPE to explore the uncertainties in the aerosol absorption as well as the dominant emission and removal processes, and by comparing with a variety of observations we have confidence to better constrain the aerosol direct radiative forcing.

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Quantifying uncertainty from aerosol and atmospheric parameters and their impact on climate sensitivity

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-17529-2018 ◽

2018 ◽

Vol 18 (23) ◽

pp. 17529-17543 ◽

Cited By ~ 4

Author(s):

Christopher G. Fletcher ◽

Ben Kravitz ◽

Bakr Badawy

Keyword(s):

Black Carbon ◽

Climate Sensitivity ◽

Radiative Forcing ◽

Deep Convection ◽

Cloud Amount ◽

Skill Score ◽

Model Parameters ◽

Atmospheric Parameters ◽

Aerosol Radiative Forcing ◽

Aerosol Radiative

Abstract. Climate sensitivity in Earth system models (ESMs) is an emergent property that is affected by structural (missing or inaccurate model physics) and parametric (variations in model parameters) uncertainty. This work provides the first quantitative assessment of the role of compensation between uncertainties in aerosol forcing and atmospheric parameters, and their impact on the climate sensitivity of the Community Atmosphere Model, Version 4 (CAM4). Running the model with prescribed ocean and ice conditions, we perturb four parameters related to sulfate and black carbon aerosol radiative forcing and distribution, as well as five atmospheric parameters related to clouds, convection, and radiative flux. In this experimental setup where aerosols do not affect the properties of clouds, the atmospheric parameters explain the majority of variance in climate sensitivity, with two parameters being the most important: one controlling low cloud amount, and one controlling the timescale for deep convection. Although the aerosol parameters strongly affect aerosol optical depth, their impacts on climate sensitivity are substantially weaker than the impacts of the atmospheric parameters, but this result may depend on whether aerosol–cloud interactions are simulated. Based on comparisons to inter-model spread of other ESMs, we conclude that structural uncertainties in this configuration of CAM4 likely contribute 3 times more to uncertainty in climate sensitivity than parametric uncertainties. We provide several parameter sets that could provide plausible (measured by a skill score) configurations of CAM4, but with different sulfate aerosol radiative forcing, black carbon radiative forcing, and climate sensitivity.

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Estimation of the aerosol radiative forcing at ground level, over land, and in cloudless atmosphere, from METEOSAT-7 observation: method and case study

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-625-2008 ◽

2008 ◽

Vol 8 (3) ◽

pp. 625-636 ◽

Cited By ~ 11

Author(s):

T. Elias ◽

J.-L. Roujean

Keyword(s):

Optical Thickness ◽

Temporal Variability ◽

Radiative Forcing ◽

Ground Level ◽

Aerosol Optical Thickness ◽

Reference Level ◽

Urban Site ◽

Spatial And Temporal Variability ◽

Aerosol Radiative Forcing ◽

Aerosol Radiative

Abstract. A new method is proposed to estimate the spatial and temporal variability of the solar radiative flux reaching the surface over land (DSSF), as well as the Aerosol Radiative Forcing (ARF), in cloud-free atmosphere. The objective of regional applications of the method is attainable by using the visible broadband of METEOSAT-7 satellite instrument which scans Europe and Africa on a half-hourly basis. The method relies on a selection of best correspondence between METEOSAT-7 radiance and radiative transfer computations. The validation of DSSF is performed comparing retrievals with ground-based measurements acquired in two contrasted environments: an urban site near Paris and a continental background site located South East of France. The study is concentrated on aerosol episodes occurring around the 2003 summer heat wave, providing 42 cases of comparison for variable solar zenith angle (from 59° to 69°), variable aerosol type (biomass burning emissions and urban pollution), and variable aerosol optical thickness (a factor 6 in magnitude). The method reproduces measurements of DSSF within an accuracy assessment of 20 W m−2 (5% in relative) in 70% of the situations, and within 40 W m−2 in 90% of the situations, for the two case studies considered here. Considering aerosol is the main contributor in changing the measured radiance at the top of the atmosphere, DSSF temporal variability is assumed to be caused only by aerosols, and consequently ARF at ground level and over land is also retrieved: ARF is computed as the difference between DSSF and a parameterised aerosol-free reference level. Retrievals are linearly correlated with the ground-based measurements of the aerosol optical thickness (AOT): sensitivity is included between 120 and 160 W m−2 per unity of AOT at 440 nm. AOT being an instantaneous measure indicative of the aerosol columnar amount, we prove the feasibility to infer instantaneous aerosol radiative impact at the ground level over land with METEOSAT-7 visible channel.

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Implications of multiple scattering on the assessment of black carbon aerosol radiative forcing

Journal of Quantitative Spectroscopy and Radiative Transfer ◽

10.1016/j.jqsrt.2014.06.018 ◽

2014 ◽

Vol 148 ◽

pp. 134-140 ◽

Cited By ~ 3

Author(s):

Vijayakumar S. Nair ◽

S. Suresh Babu ◽

K. Krishna Moorthy ◽

S.K. Satheesh

Keyword(s):

Black Carbon ◽

Multiple Scattering ◽

Radiative Forcing ◽

Aerosol Radiative Forcing ◽

Black Carbon Aerosol ◽

Aerosol Radiative

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Quantifying uncertainty from aerosol and atmospheric parameters and their impact on climate sensitivity

10.5194/acp-2018-650 ◽

2018 ◽

Author(s):

Christopher G. Fletcher ◽

Ben Kravitz ◽

Bakr Badawy

Keyword(s):

Black Carbon ◽

Climate Sensitivity ◽

Radiative Forcing ◽

Deep Convection ◽

Cloud Amount ◽

Model Parameters ◽

Atmospheric Parameters ◽

Aerosol Radiative Forcing ◽

Aerosol Parameters ◽

Aerosol Radiative

Abstract. Climate sensitivity in Earth System Models (ESMs) is an emergent property that is affected by structural (missing or inaccurate model physics) and parametric (variations in model parameters) uncertainty. This work provides the first quantitative assessment of the role of compensation between uncertainties in aerosol forcing and atmospheric parameters, and their impact on the climate sensitivity of the Community Atmosphere Model, Version 4 (CAM4). Running the model with prescribed ocean and ice conditions, we perturb four parameters related to sulfate and black carbon aerosol radiative forcing and distribution, as well as five atmospheric parameters related to clouds, convection, and radiative flux. The atmospheric parameters explain more than 85 \\% of the variance in climate sensitivity for the ranges of parameters explored here, with two parameters being the most important: one controlling low cloud amount, and one controlling the timescale for deep convection. Although the aerosol parameters strongly affect aerosol optical depth, the effects of these aerosol parameters on climate sensitivity are substantially weaker than the effects of the atmospheric parameters. Based on comparisons to inter-model spread of other ESMs, we conclude that structural uncertainties in this configuration of CAM4 likely contribute three times more to uncertainty in climate sensitivity than parametric uncertainty. We provide several parameter sets that could provide plausible (measured by a skill score) configurations of CAM4, but with different sulfate aerosol radiative forcing, black carbon radiative forcing, and climate sensitivity.

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