scholarly journals A comparison of light backscattering and particle size distribution measurements in tropical cirrus clouds

2011 ◽  
Vol 4 (3) ◽  
pp. 557-570 ◽  
Author(s):  
F. Cairo ◽  
G. Di Donfrancesco ◽  
M. Snels ◽  
F. Fierli ◽  
M. Viterbini ◽  
...  
Keyword(s):  
Particle Size ◽  
Optical Properties ◽  
Volume Density ◽  
Size Distributions ◽  
Backscatter Coefficient ◽  
Particle Size Distributions ◽  
Particle Volume ◽  
Total Particle ◽  
Research Aircraft

Abstract. An FSSP-100 Optical Particle Counter designed to count and size particles in the micron range and a backscattersonde that measures in-situ particle optical properties such as backscatter and depolarization ratio, are part of the payload of the high altitude research aircraft M55 Geophysica. This aircraft was deployed in tropical field campaigns in Bauru, Brasil (TROCCINOX, 2004) Darwin, Australia (SCOUT-Darwin, 2005) and Ouagadougou, Burkina Faso (SCOUT-AMMA, 2006). In those occasions, measurements of particle size distributions and optical properties within cirrus cloud were performed. Scope of the present work is to assess and discuss the consistency between the particle volume backscatter coefficient observed by the backscattersonde and the same parameter retrieved by optical scattering theory applied to particle size distributions as measured by the FSSP-100. In addition, empirical relationships linking the optical properties measured in-situ by the backscattersonde, which generally can be obtained by remote sensing techniques (LIDAR), and microphysical bulk properties like total particle number, surface and volume density will be presented and discussed.

scholarly journals A comparison of light backscattering and particle size distribution measurements in tropical cirrus clouds

2010 ◽  
Vol 3 (5) ◽  
pp. 4059-4089 ◽  
Author(s):  
F. Cairo ◽  
G. Di Donfrancesco ◽  
M. Snels ◽  
F. Fierli ◽  
M. Viterbini ◽  
...  
Keyword(s):  
Particle Size ◽  
Optical Properties ◽  
Volume Density ◽  
Size Distributions ◽  
Backscatter Coefficient ◽  
Particle Size Distributions ◽  
Particle Volume ◽  
Total Particle ◽  
Research Aircraft

Abstract. An FSSP-100 Optical Particle Counter designed to count and size particles in the micron range and a backscattersonde that measures in-situ particle optical properties such as backscatter and depolarization ratio, are part of the payload of the high altitude research aircraft M55 Geophysica. This aircraft was deployed in tropical field campaigns in Bauru, Brasil (TROCCINOX, 2004) Darwin, Australia (SCOUT-Darwin, 2005) and Ouagadougou, Burkina Faso (SCOUT-AMMA, 2006). In those occasions, measurements of particle size distributions and optical properties within cirrus cloud were performed. Scope of the present work is to assess and discuss the consistency between the particle volume backscatter coefficient observed by the backscattersonde and the same parameter retrieved by optical scattering theory applied to particle size distributions as measured by the FSSP-100. In addition, empirical relationships linking the optical properties measured in-situ by the backscattersonde, which generally can be obtained by remote sensing techniques (LIDAR), and microphysical bulk properties like total particle number, surface and volume density will be presented and discussed.

scholarly journals Observations of Saharan dust microphysical and optical properties from the Eastern Atlantic during NAMMA airborne field campaign

2011 ◽  
Vol 11 (2) ◽  
pp. 723-740 ◽  
Author(s):  
G. Chen ◽  
L. D. Ziemba ◽  
D. A. Chu ◽  
K. L. Thornhill ◽  
G. L. Schuster ◽  
...  
Keyword(s):  
Particle Size ◽  
Optical Properties ◽  
Dust Particle ◽  
Saharan Dust ◽  
Dust Particles ◽  
Small Range ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Field Campaign ◽  
Sahara Dust

Abstract. As part of the international project entitled "African Monsoon Multidisciplinary Analysis (AMMA)", NAMMA (NASA AMMA) aimed to gain a better understanding of the relationship between the African Easterly Waves (AEWs), the Sahara Air Layer (SAL), and tropical cyclogenesis. The NAMMA airborne field campaign was based out of the Cape Verde Islands during the peak of the hurricane season, i.e., August and September 2006. Multiple Sahara dust layers were sampled during 62 encounters in the eastern portion of the hurricane main development region, covering both the eastern North Atlantic Ocean and the western Saharan desert (i.e., 5–22° N and 10–35° W). The centers of these layers were located at altitudes between 1.5 and 3.3 km and the layer thickness ranged from 0.5 to 3 km. Detailed dust microphysical and optical properties were characterized using a suite of in-situ instruments aboard the NASA DC-8 that included a particle counter, an Ultra-High Sensitivity Aerosol Spectrometer, an Aerodynamic Particle Sizer, a nephelometer, and a Particle Soot Absorption Photometer. The NAAMA sampling inlet has a size cut (i.e., 50% transmission efficiency size) of approximately 4 μm in diameter for dust particles, which limits the representativeness of the NAMMA observational findings. The NAMMA dust observations showed relatively low particle number densities, ranging from 268 to 461 cm−3, but highly elevated volume density with an average at 45 μm3 cm−3. NAMMA dust particle size distributions can be well represented by tri-modal lognormal regressions. The estimated volume median diameter (VMD) is averaged at 2.1 μm with a small range of variation regardless of the vertical and geographical sampling locations. The Ångström Exponent assessments exhibited strong wavelength dependence for absorption but a weak one for scattering. The single scattering albedo was estimated at 0.97 ± 0.02. The imaginary part of the refractive index for Sahara dust was estimated at 0.0022, with a range from 0.0015 to 0.0044. Closure analysis showed that observed scattering coefficients are highly correlated with those calculated from spherical Mie-Theory and observed dust particle size distributions. These values are generally consistent with literature values reported from studies with similar particle sampling size range.

scholarly journals Observations of Saharan dust microphysical and optical properties from the Eastern Atlantic during NAMMA airborne field campaign

2010 ◽  
Vol 10 (5) ◽  
pp. 13445-13493 ◽  
Author(s):  
G. Chen ◽  
L. D. Ziemba ◽  
D. A. Chu ◽  
K. L. Thornhill ◽  
G. L. Schuster ◽  
...  
Keyword(s):  
Particle Size ◽  
Optical Properties ◽  
Dust Particle ◽  
North Atlantic Ocean ◽  
Saharan Dust ◽  
Small Range ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Field Campaign ◽  
Sahara Dust

Abstract. As part of the international project entitled "African Monsoon Multidisciplinary Analysis (AMMA)", NAMMA (NASA AMMA) aimed to gain a better understanding of the relationship between the African Easterly Waves (AEWs), the Sahara Air Layer (SAL), and tropical cyclogenesis. The NAMMA airborne field campaign was based out of the Cape Verde Islands during the peak of the hurricane season, i.e., August and September 2006. Multiple Sahara dust layers were sampled during 62 encounters in the eastern portion of the hurricane main development region, covering both the eastern North Atlantic Ocean and the western Saharan desert (i.e., 5–22° N and 10–35° W). The centers of these layers were located at altitudes between 1.5 and 3.3 km and the layer thickness ranged from 0.5 to 3 km. Detailed dust microphysical and optical properties were characterized using a suite of in situ instruments aboard the NASA DC-8 that included a particle counter, an Ultra-High Sensitivity Aerosol Spectrometer, an Aerodynamic Particle Sizer, nephelometer, and Particle Soot Absorption Photometer. The NAMMA dust observations showed relatively low particle number densities, ranging from 268 to 461 cm−3, but highly elevated volume density with an average at 45 μm3 cm−3. NAMMA dust particle size distributions were well represented by tri-modal lognormal regressions. The estimated volume median diameter (VMD) is averaged at 2.1 μm with a small range of variation regardless of the vertical and geographical sampling locations. The absorption coefficient measurements exhibited a strong wavelength dependence for absorption but a weak one for scattering. The single scattering albedo was estimated at 0.97±0.02. Closure analyses showed that observed scattering and absorption coefficients are highly correlated with those calculated from spherical Mie-Theory and observed dust particle size distributions. The imaginary part of the refractive index for Sahara dust was estimated at 0.0022, with a range from 0.0015 to 0.0044. These values are generally consistent with literature values.

scholarly journals Measurement report: Vertical profiling of particle size distributions over Lhasa, Tibet: Tethered balloon-based in-situ measurements and source apportionment

2021 ◽  
Author(s):  
Liang Ran ◽  
Zhaoze Deng ◽  
Yunfei Wu ◽  
Jiwei Li ◽  
Zhixuan Bai ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Particle Size ◽  
Source Apportionment ◽  
Particle Mass ◽  
Size Distributions ◽  
Aerosol Formation ◽  
Tethered Balloon ◽  
Particle Size Distributions ◽  
Secondary Aerosol

Abstract. In-situ measurements of vertically resolved particle size distributions based on a tethered balloon system were carried out for the first time in the highland city of Lhasa over the Tibetan Plateau in summer 2020, using portable optical counters for the size range of 0.124~32 μm. The vertical structure of 112 aerosol profiles was found to be largely shaped by the evolution of the boundary layer (BL), with a nearly uniform distribution of aerosols within the daytime mixing layer and a sharp decline with the height in the shallow nocturnal boundary layer. During the campaign, the average mass concentration of particulate matters smaller than 2.5 μm in aerodynamic diameter (PM2.5) within the BL was around 3 μg m−3, almost four times of the amount in the free troposphere (FT), which was rarely affected by surface anthropogenic emissions. Though there was a lower level of particle mass in the residual layer (RL) than in the BL, a similarity in particle mass size distributions (PMSDs) suggested that particles in the RL might be of the same origin as particles in the BL. This was also in consistence with the source apportionment analysis based on the PMSDs. Three distinct modes were observed in the PMSDs for the BL and the RL. One mode was exclusively coarse particles up to roughly 15 μm and peaked around 5 μm. More than 50 % of total particle mass was often contributed by coarse mode particles in this area, which was thought to be associated with local dust resuspension. The mode peaking over 0.5~0.7 μm was representative of biomass burning on religious holidays and was found to be most pronounced on holiday mornings. The contribution from the religious burning factor rose from about 25 % on non-holidays to nearly 50 % on holiday mornings. The mode dominated by particles smaller than 0.3 μm was thought to be associated with combustion related emissions and/or secondary aerosol formation. In the FT coarse mode particles only accounted for less than 10 % of the total mass and particles larger than 5 μm were negligible. The predominant submicron particles in the FT might be related to secondary aerosol formation and the aging of existed particles. To give a full picture of aerosol physical and chemical properties and better understand the origin and impacts of aerosols in this area, intensive field campaigns involving measurements of vertically resolved aerosol chemical compositions in different seasons would be much encouraged in the future.

scholarly journals Dependence of solar radiative forcing of forest fire aerosol on ageing and state of mixture

2003 ◽  
Vol 3 (3) ◽  
pp. 881-891 ◽  
Author(s):  
M. Fiebig ◽  
A. Stohl ◽  
M. Wendisch ◽  
S. Eckhardt ◽  
A. Petzold
Keyword(s):  
Particle Size ◽  
Forest Fire ◽  
Radiative Forcing ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Fire Plume ◽  
Coagulation Rate ◽  
Mean Diameter ◽  
Convective Mixed Layer

Abstract. During airborne in situ measurements of particle size distributions in a forest fire plume originating in Northern Canada, an accumulation mode number mean diameter of 0.34 mm was observed over Lindenberg, Germany on 9 August 1998. Realizing that this is possibly the largest value observed for this property in a forest fire plume, scenarios of plume ageing by coagulation are considered to explain the observed size distribution, concluding that the plume dilution was inhibited in parts of the plume. The uncertainties in coagulation rate and transition from external to internal mixture of absorbing forest fire and non-absorbing background particles cause uncertainties in the plume's solar instantaneous radiative forcing of 20-40% and of a factor of 5-6, respectively. Including information compiled from other studies on this plume, it is concluded that the plume's characteristics are qualitatively consistent with a radiative-convective mixed layer.

The Impact of Facies Variability within the Harwich Formation on Ground Engineering in the London Area, UK.

2021 ◽  
pp. qjegh2020-136
Author(s):  
Justyna Edgar ◽  
Richard C. Ghail ◽  
James Lawrence ◽  
Jacqueline Skipper ◽  
Philippa J. Mason
Keyword(s):  
Particle Size ◽  
Fault Zones ◽  
Size Distributions ◽  
Infrastructure Projects ◽  
Particle Size Distributions ◽  
Facies Model ◽  
In Situ Observations ◽  
The Impact

The Eocene Harwich Formation, underlying the Greater London (UK) area, presents many construction problems for design and location of tunnels, pipelines, and other engineering infrastructure projects. Variable deposits make up the sequence of the Harwich Formation. These include cemented fault zones, hard grounds, loose gravel and sand that, when unexpectedly encountered, can cause construction delays and increase costs. Here, we interpret borehole cores and logs, in-situ observations coupled with borehole derived samples, and calculate particle-size distributions to develop a general facies model that accounts for the lithological distribution within the Harwich Formation. This provides an improved geological framework for proposed subsurface construction that can reduce inherent engineering uncertainties, not only in the London region, but potentially in other similar geological environments.

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