scholarly journals Physical and optical properties of aged biomass burning aerosol from wildfires in Siberia and the Western USA at the Mt. Bachelor Observatory

2016 ◽  
Vol 16 (23) ◽  
pp. 15185-15197 ◽  
Author(s):  
James R. Laing ◽  
Daniel A. Jaffe ◽  
Jonathan R. Hee
Keyword(s):  
Optical Properties ◽  
Pacific Northwest ◽  
Biomass Burning ◽  
Geometric Mean ◽  
Fine Particulate Matter ◽  
Single Scattering ◽  
Absorption Efficiency ◽  
Size Distributions ◽  
Scanning Mobility Particle Sizer ◽  
Scattering Coefficients

Abstract. The summer of 2015 was an extreme forest fire year in the Pacific Northwest. Our sample site at the Mt. Bachelor Observatory (MBO, 2.7 km a.s.l.) in central Oregon observed biomass burning (BB) events more than 50 % of the time during August. In this paper we characterize the aerosol physical and optical properties of 19 aged BB events during August 2015. Six of the 19 events were influenced by Siberian fires originating near Lake Baikal that were transported to MBO over 4–10 days. The remainder of the events resulted from wildfires in Northern California and Southwestern Oregon with transport times to MBO ranging from 3 to 35 h. Fine particulate matter (PM1), carbon monoxide (CO), aerosol light scattering coefficients (σscat), aerosol light absorption coefficients (σabs), and aerosol number size distributions were measured throughout the campaign. We found that the Siberian events had a significantly higher Δσabs∕ΔCO enhancement ratio, higher mass absorption efficiency (MAE; Δσabs∕ΔPM1), lower single scattering albedo (ω), and lower absorption Ångström exponent (AAE) when compared with the regional events. We suggest that the observed Siberian events represent that portion of the plume that has hotter flaming fire conditions and thus enabled strong pyroconvective lofting and long-range transport to MBO. The Siberian events observed at MBO therefore represent a selected portion of the original plume that would then have preferentially higher black carbon emissions and thus an enhancement in absorption. The lower AAE values in the Siberian events compared to regional events indicate a lack of brown carbon (BrC) production by the Siberian fires or a loss of BrC during transport. We found that mass scattering efficiencies (MSE) for the BB events ranged from 2.50 to 4.76 m2 g−1. We measured aerosol size distributions with a scanning mobility particle sizer (SMPS). Number size distributions ranged from unimodal to bimodal and had geometric mean diameters (Dpm) ranging from 138 to 229 nm and geometric standard deviations (σg) ranging from 1.53 to 1.89. We found MSEs for BB events to be positively correlated with the geometric mean of the aerosol size distributions (R2 = 0.73), which agrees with Mie theory. We did not find any dependence on event size distribution to transport time or fire source location.

scholarly journals Physical and Optical Properties of Aged Biomass Burning Aerosol from Wildfires in Siberia and the Western US at the Mt. Bachelor Observatory

2016 ◽  
Author(s):  
James R. Laing ◽  
Dan A. Jaffe ◽  
Jonathan R. Hee
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Geometric Mean ◽  
Fine Particulate Matter ◽  
Absorption Efficiency ◽  
Absorption Enhancement ◽  
Size Distributions ◽  
Fire Plume ◽  
Scanning Mobility Particle Sizer ◽  
North West

Abstract. The summer of 2015 was an extreme forest fire year in the Pacific North West. Our sample site at Mt. Bachelor Observatory (MBO, 2.7 km a.s.l.) in central Oregon observed biomass burning events more than 50 % of the time during August. In this paper we characterize the aerosol physical and optical properties of 19 aged biomass burning (BB) events during August 2015. Six of the nineteen events were influenced by Siberian fires originating near Lake Baikal. The remainder of the events resulted from wildfires in Northern California and Southwestern Oregon with transport times to MBO ranging from 4.5–35 hours. Fine particulate matter (PM1), carbon monoxide (CO), aerosol light scattering (σscat) and absorption (σabs), and aerosol number size distributions were measured throughout the campaign. We found that the Siberian events had significantly higher Δσabs/ΔCO enhancement ratio, higher mass absorption efficiency (MAE; Δσabs/ΔPM1), lower single scattering albedo (ω), and lower Absorption Ångström exponent (AAE) when compared with the regional events. We suspect the Siberian events observed represent a portion of the fire plume that has hotter flaming fire conditions that enabled strong pyro-convective lofting and long transport to MBO. These plumes would then have preferentially higher black carbon emissions and thus absorption enhancement. The lower AAE values in the Siberian events compared to regional events indicates a lack of brown carbon (BrC) production by the Siberian fires or a loss of BrC during transport. We found that mass scattering efficiencies (MSE) for the BB events to range from 2.50–4.76 m2 g−1. We measured aerosol size distributions with a scanning mobility particle sizer (SMPS). Number size distributions ranged from unimodal to bimodal and had geometric mean diameters ranging from 138–229 nm and geometric standard deviations ranging from 1.53–1.89. We found MSE’s for BB events to be positively correlated with the geometric mean of the aerosol size distributions (R2 = 0.73), which agrees with Mie Theory. We did not find any dependence on event size distribution to transport time or fire source location.

scholarly journals Optical closure experiments for biomass smoke aerosols

2010 ◽  
Vol 10 (3) ◽  
pp. 7469-7494 ◽  
Author(s):  
L. E. Mack ◽  
E. J. T. Levin ◽  
S. M. Kreidenweis ◽  
D. Obrist ◽  
H. Moosmüller ◽  
...  
Keyword(s):  
Optical Properties ◽  
Complex Refractive Index ◽  
Single Scattering ◽  
Size Distributions ◽  
Laboratory Studies ◽  
Biomass Smoke ◽  
Scattering Coefficients ◽  
Aerosol Absorption ◽  
Southeastern Us ◽  
Highly Sensitive

Abstract. The FLAME experiments were a series of laboratory studies of the chemical, physical, and optical properties of fresh smokes from the combustion of wildland fuels that are burned annually in the western and southeastern US. The burns were conducted in the combustion chamber of the USFS Fire Sciences Laboratory in Missoula, Montana. Here we discuss the retrieval of optical properties for a variety of fuels burned in FLAME 2, using nephelometer-measured scattering coefficients, photoacoustically-measured aerosol absorption coefficients, and size distribution measurements. Uncertainties are estimated from the various instrument characteristics and from instrument calibration studies. Our estimates of single scattering albedo for different dry smokes varied from 0.43–0.99, indicative of the wide variations in smoke aerosol chemical composition that were observed. In selected case studies, we retrieved the complex refractive index from the measurements, but show that these are highly sensitive to the uncertainties in measured size distributions.

scholarly journals Tropical biomass burning smoke plume size, shape, reflectance, and age based on 2001–2009 MISR imagery of Borneo

2012 ◽  
Vol 12 (7) ◽  
pp. 3437-3454 ◽  
Author(s):  
C. S. Zender ◽  
A. G. Krolewski ◽  
M. G. Tosca ◽  
J. T. Randerson
Keyword(s):  
Optical Properties ◽  
Tropical Forests ◽  
Optical Depth ◽  
Biomass Burning ◽  
Single Scattering ◽  
Particle Dispersion ◽  
Hygroscopic Growth ◽  
Smoke Plume ◽  
Fire Emissions ◽  
Plume Geometry

Abstract. Land clearing for crops, plantations and grazing results in anthropogenic burning of tropical forests and peatlands in Indonesia, where images of fire-generated aerosol plumes have been captured by the Multi-angle Imaging SpectroRadiometer (MISR) since 2001. Here we analyze the size, shape, optical properties, and age of distinct fire-generated plumes in Borneo from 2001–2009. The local MISR overpass at 10:30 a.m. misses the afternoon peak of Borneo fire emissions, and may preferentially sample longer plumes from persistent fires burning overnight. Typically the smoke flows with the prevailing southeasterly surface winds at 3–4 m s−1, and forms ovoid plumes whose mean length, height, and cross-plume width are 41 km, 708 m, and 27% of the plume length, respectively. 50% of these plumes have length between 24 and 50 km, height between 523 and 993 m and width between 18% and 30% of plume length. Length and cross-plume width are lognormally distributed, while height follows a normal distribution. Borneo smoke plume heights are similar to previously reported plume heights, yet Borneo plumes are on average nearly three times longer than previously studied plumes. This could be due to sampling or to more persistent fires and greater fuel loads in peatlands than in other tropical forests. Plume area (median 169 km2, with 25th and 75th percentiles at 99 km2 and 304 km2, respectively) varies exponentially with length, though for most plumes a linear relation provides a good approximation. The MISR-estimated plume optical properties involve greater uncertainties than the geometric properties, and show patterns consistent with smoke aging. Optical depth increases by 15–25% in the down-plume direction, consistent with hygroscopic growth and nucleation overwhelming the effects of particle dispersion. Both particle single-scattering albedo and top-of-atmosphere reflectance peak about halfway down-plume, at values about 3% and 10% greater than at the origin, respectively. The initially oblong plumes become brighter and more circular with time, increasingly resembling smoke clouds. Wind speed does not explain a significant fraction of the variation in plume geometry. We provide a parameterization of plume shape that can help atmospheric models estimate the effects of plumes on weather, climate, and air quality. Plume age, the age of smoke furthest down-plume, is lognormally distributed with a median of 2.8 h (25th and 75th percentiles at 1.3 h and 4.0 h), different from the median ages reported in other studies. Intercomparison of our results with previous studies shows that the shape, height, optical depth, and lifetime characteristics reported for tropical biomass burning plumes on three continents are dissimilar and distinct from the same characteristics of non-tropical wildfire plumes.

scholarly journals Modelling the optical properties of fresh biomass burning aerosol produced in a smoke chamber: results from the EFEU campaign

2007 ◽  
Vol 7 (4) ◽  
pp. 12657-12686 ◽  
Author(s):  
K. Hungershöfer ◽  
K. Zeromskiene ◽  
Y. Iinuma ◽  
G. Helas ◽  
J. Trentmann ◽  
...  
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Atmospheric Chemistry ◽  
Absorption Efficiency ◽  
Max Planck ◽  
Fresh Biomass ◽  
Biomass Burning Aerosol ◽  
Smoke Chamber ◽  
The Impact ◽  
Mass Absorption Efficiency

Abstract. A better characterisation of the optical properties of biomass burning aerosol as a function of the burning conditions is required in order to quantify their effects on climate and atmospheric chemistry. Controlled laboratory combustion experiments with different fuel types were carried out at the combustion facility of the Max Planck Institute for Chemistry (Mainz, Germany) as part of the 'Impact of Vegetation Fires on the Composition and Circulation of the Atmosphere' (EFEU) project. Using the measured size distributions as well as mass scattering and absorption efficiencies, Mie calculations provided mean effective refractive indices of 1.60−0.010i and 1.56−0.010i (λ=0.55 μm) for smoke particles emitted from the combustion of savanna grass and an African hardwood (musasa), respectively. The relatively low imaginary parts suggest that the light-absorbing carbon of the investigated fresh biomass burning aerosol is only partly graphitized, resulting in strongly scattering and less absorbing particles. While the observed variability in mass scattering efficiencies was consistent with changes in particle size, the changes in the mass absorption efficiency can only be explained, if the chemical composition of the particles varies with combustion conditions.

scholarly journals Intercomparison of biomass burning aerosol optical properties from in situ and remote-sensing instruments in ORACLES-2016

2019 ◽  
Vol 19 (14) ◽  
pp. 9181-9208 ◽  
Author(s):  
Kristina Pistone ◽  
Jens Redemann ◽  
Sarah Doherty ◽  
Paquita Zuidema ◽  
Sharon Burton ◽  
...  
Keyword(s):  
Optical Properties ◽  
Case Studies ◽  
Biomass Burning ◽  
Radiative Forcing ◽  
Measurement Techniques ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Aerosol Optical Properties ◽  
Biomass Burning Aerosol

Abstract. The total effect of aerosols, both directly and on cloud properties, remains the biggest source of uncertainty in anthropogenic radiative forcing on the climate. Correct characterization of intensive aerosol optical properties, particularly in conditions where absorbing aerosol is present, is a crucial factor in quantifying these effects. The southeast Atlantic Ocean (SEA), with seasonal biomass burning smoke plumes overlying and mixing with a persistent stratocumulus cloud deck, offers an excellent natural laboratory to make the observations necessary to understand the complexities of aerosol–cloud–radiation interactions. The first field deployment of the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) campaign was conducted in September of 2016 out of Walvis Bay, Namibia. Data collected during ORACLES-2016 are used to derive aerosol properties from an unprecedented number of simultaneous measurement techniques over this region. Here, we present results from six of the eight independent instruments or instrument combinations, all applied to measure or retrieve aerosol absorption and single-scattering albedo. Most but not all of the biomass burning aerosol was located in the free troposphere, in relative humidities typically ranging up to 60 %. We present the single-scattering albedo (SSA), absorbing and total aerosol optical depth (AAOD and AOD), and absorption, scattering, and extinction Ångström exponents (AAE, SAE, and EAE, respectively) for specific case studies looking at near-coincident and near-colocated measurements from multiple instruments, and SSAs for the broader campaign average over the month-long deployment. For the case studies, we find that SSA agrees within the measurement uncertainties between multiple instruments, though, over all cases, there is no strong correlation between values reported by one instrument and another. We also find that agreement between the instruments is more robust at higher aerosol loading (AOD400>0.4). The campaign-wide average and range shows differences in the values measured by each instrument. We find the ORACLES-2016 campaign-average SSA at 500 nm (SSA500) to be between 0.85 and 0.88, depending on the instrument considered (4STAR, AirMSPI, or in situ measurements), with the interquartile ranges for all instruments between 0.83 and 0.89. This is consistent with previous September values reported over the region (between 0.84 and 0.90 for SSA at 550nm). The results suggest that the differences observed in the campaign-average values may be dominated by instrument-specific spatial sampling differences and the natural physical variability in aerosol conditions over the SEA, rather than fundamental methodological differences.

scholarly journals STUDY OF AEROSOL OPTICAL PROPERTIES OVER TWO SITES IN THE FOOTHILLS OF THE CENTRAL HIMALAYAS

2018 ◽  
Vol XLII-3 ◽  
pp. 1493-1497 ◽  
Author(s):  
D. Rupakheti ◽  
S. Kang ◽  
Z. Cong ◽  
M. Rupakheti ◽  
L. Tripathee ◽  
...  
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Asymmetry Parameter ◽  
Monsoon Season ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Aerosol Optical Properties ◽  
Central Himalayas ◽  
Aerosol Types ◽  
Volume Size

Atmospheric aerosol possesses impacts on climate system and ecological environments, human health and agricultural productivity. The environment over Himalayas and Tibetan Plateau region are continuously degraded due to the transport of pollution from the foothills of the Himalayas; mostly the Indo-Gangetic Plain (IGP). Thus, analysis of aerosol optical properties over two sites; Lumbini and Kathmandu (the southern slope of central Himalayas) using AERONET’s CIMEL sun photometer were conducted in this study. Aerosol optical depth (AOD at 500 nm), angstrom exponent (α or AE), volume size distribution (VSD), single scattering albedo (SSA) and asymmetry parameter (AP) were studied for 2013–2014 and the average AOD was found to be: 0.64 ± 0.41 (Lumbini) and 0.45 ± 0.30 (Kathmandu). The average AE was found to be: 1.25 ± 0.24 and 1.26 ± 0.18 respectively for two sites. The relation between AOD and AE was used to discriminate the aerosol types over these sites which indicated anthropogenic, mixed and biomass burning origin aerosol constituted the major aerosol types in Lumbini and Kathmandu. A clear bi-modal distribution of aerosol volume size was observed with highest volume concentration during the post-monsoon season in fine mode and pre-monsoon season in coarse mode (Lumbini) and highest value over both modes during pre-monsoon season in Kathmandu. The single scattering albedo (SSA) and asymmetry parameter (AP) analyses suggested aerosols over the Himalayan foothills sites are dominated by absorbing and anthropogenic aerosols from urban and industrial activities and biomass burning. Long-term studies are essential to understand and characterize the nature of aerosol over this research gap zone.

scholarly journals In situ measurements of aerosols optical properties and number size distributions in a subarctic coastal region of Norway

2011 ◽  
Vol 11 (12) ◽  
pp. 32921-32964
Author(s):  
S. Mogo ◽  
V. E. Cachorro ◽  
J. F. Lopez ◽  
E. Montilla ◽  
B. Torres ◽  
...  
Keyword(s):  
Optical Properties ◽  
Single Scattering ◽  
Mean Value ◽  
The Arctic ◽  
Optical Parameters ◽  
Size Distributions ◽  
Air Mass ◽  
Air Masses ◽  
Particle Sizer

Abstract. In situ measurements of aerosol optical properties were made in the summer of 2008 at the ALOMAR station facility (69°16 N, 16°00 E), located at a rural site in the north of the island of Andøya (Vesterålen archipelago), approximately 300 km north of the Arctic Circle. The extended three-month campaign was part of the POLARCAT Project (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport) of the International Polar Year (IPY-2007-2008). Its goal was to characterize the aerosols of this sub-Arctic area, which are frequently transported to the Arctic region. The ambient light-scattering coefficient, σs (550 nm), at ALOMAR had a measured hourly mean value of 5.41 Mm−1 (StD = 3.55 Mm−1), and the light-absorption coefficient, σa (550 nm), had a measured hourly mean value of 0.40 Mm−1 (StD = 0.27 Mm−1). The scattering/absorption Ångström exponents, αs,a, are used for a detailed analysis of the variations of the spectral shape of σs,a. Whereas αs demonstrates the presence of two particle sizes corresponding to two types of aerosols, the αa demonstrates only one type of absorbing aerosol particles. Values of αa above 1 were not observed. The single-scattering albedo, ω0, ranged from 0.62 to 0.99 (mean = 0.91, StD = 0.05), and the relationships of this property to the absorption/scattering coefficients and the Ångström exponents are presented. The concentration of the particles was monitored using a scanning mobility particle sizer (SMPS), an aerodynamic particle sizer (APS) and an ultrafine condensation particle counter (UCPC). The shape of the median size distribution of the particles in the submicrometer fraction was bimodal, and the submicrometer, micrometer and total concentrations presented hourly mean values of 1277 cm3 (StD = 1563 cm3), 1 cm3 (StD = 1 cm3) and 2463 cm3 (StD = 4251 cm3), respectively. The modal correlations were investigated, and the concentration of particles sized between 30 and 100 nm (Aitken mode) are presented as a function of the concentration of the particles sized between 100 and 390 nm (accumulation mode). The optical and the microphysical parameters are related to each other, and the results are presented. The origins and pathways of air masses were examined by computing the back-trajectories in a trajectory model (HYSPLIT). Six geographical sectors were defined to classify the air masses, and, based on the sector classification, the linkage between the air mass origin and the optical parameters was established. Aerosol size distributions were also evaluated in relation to the air masses. The relationships between the air mass origins and other parameters, especially those related to the single scattering albedo, allow us to describe two characteristic situations: northern and western air masses, which had predominantly marine aerosols, presented lower optical parameter values, indicating predominantly coarser and non-absorbent particles; and eastern and southern air masses, in which continental aerosols were predominant, presented higher values for all optical parameters, indicating the presence of smaller absorbent particles.

scholarly journals Intercomparison of biomass burning aerosol optical properties from in-situ and remote-sensing instruments in ORACLES-2016

2019 ◽  
Author(s):  
Kristina Pistone ◽  
Jens Redemann ◽  
Sarah Doherty ◽  
Paquita Zuidema ◽  
Sharon Burton ◽  
...  
Keyword(s):  
Optical Properties ◽  
Case Studies ◽  
Biomass Burning ◽  
Radiative Forcing ◽  
Measurement Techniques ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Aerosol Optical Properties ◽  
Biomass Burning Aerosol

Abstract. The total effect of aerosols, both directly and on cloud properties, remains the biggest source of uncertainty in anthropogenic radiative forcing on the climate. Correct characterization of intensive aerosol optical properties, particularly in conditions where absorbing aerosol is present, is a crucial factor in quantifying these effects. The Southeast Atlantic Ocean (SEA), with seasonal biomass burning smoke plumes overlying and mixing with a persistent stratocumulus cloud deck, offers an excellent natural laboratory to make the observations necessary to understand the complexities of aerosol-cloud-radiation interactions. The first field deployment of the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) campaign was conducted in September of 2016 out of Walvis Bay, Namibia. Data collected during ORACLES-2016 are used to derive aerosol properties from an unprecedented number of simultaneous measurement techniques over this region. Here we present results from six of the eight independent instruments or instrument combinations, all applied to measure or retrieve aerosol absorption and single scattering albedo. Most but not all of the biomass-burning aerosol was located in the free troposphere, in relative humidities typically ranging up to 60 %. We present the single scattering albedo (SSA), absorbing and total aerosol optical depth (AOD and AAOD), and absorption, scattering, and extinction Ångström exponents (AAE, SAE, EAE) for specific case studies looking at near-coincident and -colocated measurements from multiple instruments, and SSAs for the broader campaign average over the monthlong deployment. For the case studies, we find that SSA agrees within the measurement uncertainties between multiple instruments, though, over all cases, there is no strong correlation between values reported by one instrument and another. We also find that agreement between the instruments is more robust at higher aerosol loading (AOD400 > 0.4). The campaign-wide average and range shows differences in the values measured by each instrument. We find the ORACLES-2016 campaign-average SSA at 500 nm (SSA500) to be between 0.85 and 0.88, depending on the instrument considered (4STAR, AirMSPI, or in situ measurements), with the inter-quartile ranges for all instruments between 0.83 and 0.89. This is consistent with previous September values reported over the region (between 0.84 and 0.90 for SSA at 550 nm). The results suggest that the differences observed in the campaign-average values may be dominated by instrument-specific spatial sampling differences and the natural physical variability in aerosol conditions over the SEA, rather than fundamental methodological differences.

scholarly journals Updated African biomass burning emission inventories in the framework of the AMMA-IDAF program, with an evaluation of combustion aerosols

2010 ◽  
Vol 10 (19) ◽  
pp. 9631-9646 ◽  
Author(s):  
C. Liousse ◽  
B. Guillaume ◽  
J. M. Grégoire ◽  
M. Mallet ◽  
C. Galy ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Transport Model ◽  
Regional Scale ◽  
Single Scattering ◽  
Emission Inventories ◽  
Chemistry Transport Model ◽  
Scattering Coefficients ◽  
Vertical Distributions ◽  
Combustion Aerosols ◽  
Aerosol Module

Abstract. African biomass burning emission inventories for gaseous and particulate species have been constructed at a resolution of 1 km by 1km with daily coverage for the 2000–2007 period. These inventories are higher than the GFED2 inventories, which are currently widely in use. Evaluation specifically focusing on combustion aerosol has been carried out with the ORISAM-TM4 global chemistry transport model which includes a detailed aerosol module. This paper compares modeled results with measurements of surface BC concentrations and scattering coefficients from the AMMA Enhanced Observations period, aerosol optical depths and single scattering albedo from AERONET sunphotometers, LIDAR vertical distributions of extinction coefficients as well as satellite data. Aerosol seasonal and interannual evolutions over the 2004–2007 period observed at regional scale and more specifically at the Djougou (Benin) and Banizoumbou (Niger) AMMA/IDAF sites are well reproduced by our global model, indicating that our biomass burning emission inventory appears reasonable.

scholarly journals A shape model of internally mixed soot particles derived from artificial surface tension

2018 ◽  
Author(s):  
Hiroshi Ishimoto ◽  
Rei Kudo ◽  
Kouji Adachi
Keyword(s):  
Surface Tension ◽  
Optical Properties ◽  
Biomass Burning ◽  
Single Scattering ◽  
Dipole Approximation ◽  
Water Soluble ◽  
Shape Model ◽  
Soot Particles ◽  
Artificial Surface ◽  
Aggregate Shape

Abstract. To retrieve the physical properties of aerosols from multi-channel ground-based/satellite measurements, we developed a shape model of coated soot particles and created a dataset of their optical properties. Bare soot particles were assumed to have an aggregate shape, and two types of aggregates with different size–shape dependences were modeled using a polyhedral Voronoi structure. To simulate the detailed shape properties of mixtures of soot aggregates and adhered water-soluble substances, we propose a simple model of surface tension derived from the artificial surface potential. The light-scattering properties of the modeled particles with different volume fractions of water-soluble material were calculated using the finite-difference time-domain method and discrete-dipole approximation. The results of the single-scattering albedo and asymmetry factors were compared to those of conventional internally mixed spheres (i.e., effective medium spheres based on the Maxwell–Garnett approximation and simple core–shell spheres). In addition, the lidar backscattering properties (i.e., lidar ratios and linear depolarization ratios) of the modeled soot particles were investigated. For internally mixed soot particles, the lidar backscattering properties were sensitive to the shape of the soot particles and the volume mixing ratio of the assumed water-soluble components. However, the average optical properties of biomass burning smoke, which have been reported from in situ field and laboratory measurements, were difficult to explain based on the individually modeled particle. Nonetheless, our shape model and its calculated optical properties are expected to be useful as an alternative model for biomass burning smoke particles in advanced remote sensing via multi-channel radiometer and lidar measurements.

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