scholarly journals Strong spectral dependence of light absorption by organic carbon particles formed by propane combustion

2006 ◽  
Vol 6 (10) ◽  
pp. 2981-2990 ◽  
Author(s):  
M. Schnaiter ◽  
M. Gimmler ◽  
I. Llamas ◽  
C. Linke ◽  
C. Jäger ◽  
...  
Keyword(s):  
Cross Sections ◽  
Vacuum Ultraviolet ◽  
Single Scattering ◽  
Absorption Cross ◽  
Propane Combustion ◽  
Tem Analysis ◽  
Carbon Particles ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Ångstrom Exponent

Abstract. We have measured the extinction and absorption cross sections of carbon particles emitted by a propane diffusion flame both in an aerosol chamber and on size-segregated samples deposited on optical windows. The absorption cross section, the single scattering albedo, and the Ångström exponent show drastic dependencies both on the C/O ratio and on the particle size. This is interpretated as being due to the appearance of nucleation modes of smaller organic particles at higher C/O ratios, which were detected by SMPS measurements and partially by TEM analysis. The spectral range of the validity of the absorption power-law (Ångström exponent) model is investigated by vacuum ultraviolet extinction measurements. These measurements give also indications for a preferentially aromatic nature of the OC component of the flame products.

scholarly journals Strong spectral dependence of light absorption by organic carbon particles formed by propane combustion

2006 ◽  
Vol 6 (2) ◽  
pp. 1841-1866 ◽  
Author(s):  
M. Schnaiter ◽  
M. Gimmler ◽  
I. Llamas ◽  
C. Linke ◽  
C. Jäger ◽  
...  
Keyword(s):  
Cross Sections ◽  
Vacuum Ultraviolet ◽  
Single Scattering ◽  
Absorption Cross ◽  
Propane Combustion ◽  
Tem Analysis ◽  
Carbon Particles ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Ångstrom Exponent

Abstract. We have measured the extinction and absorption cross sections of carbon particles emitted by a propane diffusion flame both in an aerosol chamber and on size-segregated samples deposited on optical windows. The absorption cross section, the single scattering albedo and the Ångström exponent show drastic dependencies both on the C/O ratio and on the particle size. This is interpretated as being due to the appearance of nucleation modes of smaller organic particles at higher C/O ratios, which were detected by SMPS measurements and partially by TEM analysis. The spectral range of the validity of the absorption power-law (Ångström exponent) model is investigated by vacuum ultraviolet extinction measurements. These measurements give also indications for a preferentially aromatic nature of the OC component of the flame products.

scholarly journals Retrieval of aerosol single-scattering albedo and polarized phase function from polarized sun-photometer measurements for Zanjan's atmosphere

2013 ◽  
Vol 6 (10) ◽  
pp. 2659-2669 ◽  
Author(s):  
A. Bayat ◽  
H. R. Khalesifard ◽  
A. Masoumi
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Atmospheric Aerosols ◽  
Phase Function ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Sun Photometer ◽  
Ångstrom Exponent

Abstract. The polarized phase function of atmospheric aerosols has been investigated for the atmosphere of Zanjan, a city in northwest Iran. To do this, aerosol optical depth, Ångström exponent, single-scattering albedo, and polarized phase function have been retrieved from the measurements of a Cimel CE 318-2 polarized sun-photometer from February 2010 to December 2012. The results show that the maximum value of aerosol polarized phase function as well as the polarized phase function retrieved for a specific scattering angle (i.e., 60°) are strongly correlated (R = 0.95 and 0.95, respectively) with the Ångström exponent. The latter has a meaningful variation with respect to the changes in the complex refractive index of the atmospheric aerosols. Furthermore the polarized phase function shows a moderate negative correlation with respect to the atmospheric aerosol optical depth and single-scattering albedo (R = −0.76 and −0.33, respectively). Therefore the polarized phase function can be regarded as a key parameter to characterize the atmospheric particles of the region – a populated city in the semi-arid area and surrounded by some dust sources of the Earth's dust belt.

scholarly journals Effects of different correction algorithms on absorption coefficient – a comparison of three optical absorption photometers at a boreal forest site

2021 ◽  
Vol 14 (10) ◽  
pp. 6419-6441
Author(s):  
Krista Luoma ◽  
Aki Virkkula ◽  
Pasi Aalto ◽  
Katrianne Lehtipalo ◽  
Tuukka Petäjä ◽  
...  
Keyword(s):  
Optical Properties ◽  
Absorption Coefficient ◽  
Boreal Forest ◽  
Single Scattering ◽  
Forest Site ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Boreal Environment ◽  
Absorption Photometer ◽  
Ångstrom Exponent

Abstract. We present a comparison between three absorption photometers that measured the absorption coefficient (σabs) of ambient aerosol particles in 2012–2017 at SMEAR II (Station for Measuring Ecosystem–Atmosphere Relations II), a measurement station located in a boreal forest in southern Finland. The comparison included an Aethalometer (AE31), a multi-angle absorption photometer (MAAP), and a particle soot absorption photometer (PSAP). These optical instruments measured particles collected on a filter, which is a source of systematic errors, since in addition to the particles, the filter fibers also interact with light. To overcome this problem, several algorithms have been suggested to correct the AE31 and PSAP measurements. The aim of this study was to research how the different correction algorithms affected the derived optical properties. We applied the different correction algorithms to the AE31 and PSAP data and compared the results against the reference measurements conducted by the MAAP. The comparison between the MAAP and AE31 resulted in a multiple-scattering correction factor (Cref) that is used in AE31 correction algorithms to compensate for the light scattering by filter fibers. Cref varies between different environments, and our results are applicable to a boreal environment. We observed a clear seasonal cycle in Cref, which was probably due to variations in aerosol optical properties, such as the backscatter fraction and single-scattering albedo, and also due to variations in the relative humidity (RH). The results showed that the filter-based absorption photometers seemed to be rather sensitive to the RH even if the RH was kept below the recommended value of 40 %. The instruments correlated well (R≈0.98), but the slopes of the regression lines varied between the instruments and correction algorithms: compared to the MAAP, the AE31 underestimated σabs only slightly (the slopes varied between 0.96–1.00) and the PSAP overestimated σabs only a little (the slopes varied between 1.01–1.04 for a recommended filter transmittance >0.7). The instruments and correction algorithms had a notable influence on the absorption Ångström exponent: the median absorption Ångström exponent varied between 0.93–1.54 for the different algorithms and instruments.

scholarly journals The Ångström Exponent and Single-Scattering Albedo of Black Carbon: Effects of Different Coating Materials

Atmosphere ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1103
Author(s):  
Jie Luo ◽  
Yongming Zhang ◽  
Qixing Zhang
Keyword(s):  
Black Carbon ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Optical Measurements ◽  
Coating Materials ◽  
Total Size ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Mixing States ◽  
Ångstrom Exponent

In this work, the absorption Ångström exponent (AAE), extinction Ångström exponent (EAE), and single-scattering albedo (SSA) of black carbon (BC) with different coating materials are numerically investigated. BC with different coating materials can provide explanations for the small AAE, small EAE, and large AAE observed in the atmosphere, which is difficult to be explained by bare BC aggregate models. The addition of organic carbon (OC) does not necessarily increase AAE due to the transformation of BC morphologies and the existence of non-absorbing OC. The addition of coating materials does also not necessarily decrease EAE. While the addition of coating materials can increase the total size of BC-containing particles, the effective refractive index can be modified by introducing the coating materials, so increases the EAE. We found that it is not possible to differentiate between thinly- and heavily-coated BC based on EAE or AAE alone. On the other hand, SSA is much less sensitive to the size and can provide much more information for distinguishing heavily-coated BC from thinly-coated BC. For BC with different coating materials and mixing states, AAE, EAE, and SSA show rather different sensitivities to particle size and composition ratios, and their spectral-dependences also exhibit distinct differences. Different AAE and EAE trends with BC/OC ratio were also found for BC with different coating materials and mixing states. Furthermore, we also found empirical fittings for AAE, EAE, SSA, and optical cross-sections, which may be useful for retrieving the size information based on the optical measurements.

scholarly journals Assessment and Improvement of MISR Angstrom Exponent and Single-Scattering Albedo Products Using AERONET Data in China

2017 ◽  
Vol 9 (7) ◽  
pp. 693 ◽  
Author(s):  
Yidan Si ◽  
Shenshen Li ◽  
Liangfu Chen ◽  
Huazhe Shang ◽  
Lei Wang ◽  
...  
Keyword(s):  
Single Scattering ◽  
Single Scattering Albedo ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Ångstrom Exponent

scholarly journals Constraining global aerosol emissions using POLDER/PARASOL satellite remote sensing observations

2019 ◽  
Author(s):  
Cheng Chen ◽  
Oleg Dubovik ◽  
Daven K. Henze ◽  
Mian Chin ◽  
Tatyana Lapyonok ◽  
...  
Keyword(s):  
Optical Depth ◽  
Model Simulation ◽  
A Priori ◽  
Single Scattering ◽  
A Posteriori ◽  
Modeling Framework ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Aerosol Emissions ◽  
Ångstrom Exponent

Abstract. We invert global black carbon (BC), organic carbon (OC) and desert dust (DD) aerosol emissions from POLDER/PARASOL spectral aerosol optical depth (AOD) and aerosol absorption optical depth (AAOD) using the GEOS-Chem inverse modelling framework. Our inverse modeling framework uses standard a priori emissions to provide a posteriori emissions that are constrained by POLDER/PARASOL AODs and AAODs. The following global emission values were retrieved for the three aerosol components: 18.4 Tg/yr for BC, 109.9 Tg/yr for OC, and 731.6 Tg/yr for DD for the year 2010. These values show a difference of +166.7 %, +184.0 %, and -42.4 % with respect to the a priori values of emission inventories used in standard GEOS-Chem runs. The model simulations using a posteriori emissions (i.e. retrieved emissions) provide values of 0.119 for global mean AOD and 0.0071 for AAOD at 550 nm, which are +13.3 % and +82.1 % higher than the AOD and AAOD obtained using the a priori values of emissions. Additionally, the a posteriori model simulation of AOD, AAOD, single scattering albedo, Ångström exponent, and absorption Ångström exponent show better agreement with independent AERONET, MODIS, and OMI measurements than the a priori simulation. Thus, this study suggests that using satellite-constrained global aerosol emissions in aerosol transport models can improve the accuracy of simulated global aerosol properties.

scholarly journals Emissions from the Open Laboratory Combustion of Cheatgrass (Bromus Tectorum)

Atmosphere ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 406
Author(s):  
Megan Rennie ◽  
Vera Samburova ◽  
Deep Sengupta ◽  
Chiranjivi Bhattarai ◽  
W. Patrick Arnott ◽  
...  
Keyword(s):  
Great Basin ◽  
Fire Ecology ◽  
Bromus Tectorum ◽  
Single Scattering ◽  
Combustion Efficiency ◽  
Angstrom Exponent ◽  
Combustion Properties ◽  
Combustion Emissions ◽  
Ångström Exponent ◽  
Ångstrom Exponent

Cheatgrass (Bromus Tectorum) is a highly invasive species in the Great Basin of the Western USA that is increasing the frequency and intensity of wildland fires. Though cheatgrass plays a significant role in the fire ecology of the Great Basin, very little is known about its combustion emissions. The fresh smoke from 16 open laboratory burns of cheatgrass was analyzed using real-time measurements and filter analysis. We presented measured intensive optical properties of the emitted smoke, including absorption Ångström exponent (AAE), scattering Ångström exponent (SAE), single scattering albedo (SSA), and other combustion properties, such as modified combustion efficiency (MCE) and fuel-based emission factors (EFs). In addition, we gave a detailed chemical analysis of polar organic species in cheatgrass combustion emissions. We presented EFs that showed a large variation between fuels and demonstrated that analysis of combustion emissions for specific fuels was important for studying and modeling the chemistry of biomass-burning emissions.

scholarly journals Classification of aerosols using multiple clustering techniques over Zanjan, Iran, during 2010-2014

2019 ◽  
Vol 99 ◽  
pp. 02007
Author(s):  
Maryam Gharibzadeh ◽  
Khan Alam ◽  
Yousefali Abedini ◽  
Abbasali Aliakbari Bidokhti
Keyword(s):  
Single Scattering ◽  
Dust Particles ◽  
Clustering Techniques ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Aerosol Types ◽  
Ångstrom Exponent ◽  
Volume Size ◽  
Aerosol Volume

A more detailed study and identification of aerosol types can help to better understand the sources and effects of aerosols. In the present study, a number of optical properties of aerosols have been investigated seasonal for discrimination of aerosol types during 2010-2014 over Zanjan, Iran. Also using AERosol RObotic NETwork (AERONET) data, aerosol was classified by multiple clustering techniques. Both fine and coarse modes particles were seen in seasonal averaged of Aerosol Volume Size Distribution (AVSD). Single Scattering Albedo (SSA) variations indicate the presence of scattering aerosol like dust in the spring, summer and fall, and dominance of absorbing type aerosols in the winter. The maximum value of the phase function was observed in the summer and in small scattering angle which can be due to presence of coarse mode dust particles. The scatter plot of Aerosol Optical Depth (AOD) versus Angstrom Exponent (AE) is one of the most effective methods to find aerosol types. Extinction Angstrom exponent (EAE) versus SSA and EAE versus absorption Angstrom exponent (AAE) are other ways to classification of aerosol types. Graphs show abundance of dust in the spring, summer and fall in Zanjan's atmosphere. Also presence of urban/industrial aerosols is in all seasons, especially in the fall and winter. In addition mixed aerosols exist in all seasons. On the other hand, no biomass burning aerosols found in Zanjan's atmosphere.

scholarly journals Retrieval of aerosol single scattering albedo and polarized phase function from polarized sun-photometer measurements for Zanjan atmosphere

2013 ◽  
Vol 6 (2) ◽  
pp. 3317-3338 ◽  
Author(s):  
A. Bayat ◽  
H. R. Khalesifard ◽  
A. Masoumi
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Phase Function ◽  
Complex Refractive Index ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Sun Photometer ◽  
Ångstrom Exponent

Abstract. Aerosol optical depth, Ångström exponent, single scattering albedo, and polarized phase function have been retrieved from polarized sun-photometer measurements for atmosphere of Zanjan (36.70° N, 48.51° E, and 1800 m a.m.s.l.) from January 2010 to December 2012. The results show that the maximum value of aerosol polarized phase function as well as the polarized phase function retrieved for a specific scattering angle (i.e. 60°), are strongly correlated with the Ångström exponent. The latter one has a meaningful variations respect to the changes in the complex refractive index of the atmospheric aerosols. Furthermore the polarized phase function shows a moderate negative correlation respect to atmospheric aerosol optical depth and single scattering albedo. Therefore the polarized phase function can be regarded as a key parameter to characterize the atmospheric particles.

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