scholarly journals Development of a new semi-empirical parameterization for below-cloud scavenging of size-resolved aerosol particles by both rain and snow

2013 ◽  
Vol 6 (4) ◽  
pp. 5901-5945 ◽  
Author(s):  
X. Wang ◽  
L. Zhang ◽  
M. D. Moran
Keyword(s):  
Linear Relationship ◽  
Aerosol Particle ◽  
Field Experiments ◽  
Aerosol Particles ◽  
Particle Sizes ◽  
Data Set ◽  
Wide Range ◽  
Cloud Scavenging ◽  
Two Parameters ◽  
Semi Empirical

Abstract. A parameter called the scavenging coefficient Λ is widely used in aerosol chemical transport models (CTMs) to describe below-cloud scavenging of aerosol particles by rain and snow. However, uncertainties associated with available size-resolved theoretical formulations for Λ span one to two orders of magnitude for rain scavenging and nearly three orders of magnitude for snow scavenging. Two recent reviews of below-cloud scavenging of size-resolved particles recommended that the upper range of the available theoretical formulations for Λ should be used in CTMs based on uncertainty analyses and comparison with limited field experiments. Following this recommended approach, a new semi-empirical parameterization for size-resolved Λ has been developed for below-cloud scavenging of atmospheric aerosol particles by both rain (Λrain) and snow (Λsnow). The new parameterization is based on the 90th percentile of Λ values from an ensemble data set containing calculated using all possible "realizations" of available theoretical Λ formulas and covering a large range of aerosol particle sizes and precipitation intensities (R). For any aerosol particle size of diameter d, a strong linear relationship between the 90th-percentile log10(Λ) and log10(R), which is equivalent to a power-law relationship between Λ and R, is identified. The log-linear relationship, which is characterized by two parameters (slope and y-intercept), is then further parameterized by fitting these two parameters as polynomial functions of aerosol size d. A comparison of the new parameterization with limited measurements in the literature in terms of the magnitude of Λ and the relative magnitudes of Λrain and Λsnow suggests that it is a reasonable approximation. Advantages of this new semi-empirical parameterization compared to traditional theoretical formulations for Λ include its applicability to below-cloud scavenging by both rain and snow over a wide range of particle sizes and precipitation intensities, ease of implementation in any CTM with a representation of size-distributed particulate matter, and a known representativeness based on the consideration in its development of all available theoretical formulations and field-derived estimates for Λ(d) and their associated uncertainties.

scholarly journals Development of a new semi-empirical parameterization for below-cloud scavenging of size-resolved aerosol particles by both rain and snow

2014 ◽  
Vol 7 (3) ◽  
pp. 799-819 ◽  
Author(s):  
X. Wang ◽  
L. Zhang ◽  
M. D. Moran
Keyword(s):  
Linear Relationship ◽  
Aerosol Particle ◽  
Field Experiments ◽  
Aerosol Particles ◽  
Particle Sizes ◽  
Data Set ◽  
Wide Range ◽  
Cloud Scavenging ◽  
Two Parameters ◽  
Semi Empirical

Abstract. A parameter called the scavenging coefficient Λ is widely used in aerosol chemical transport models (CTMs) to describe below-cloud scavenging of aerosol particles by rain and snow. However, uncertainties associated with available size-resolved theoretical formulations for Λ span one to two orders of magnitude for rain scavenging and nearly three orders of magnitude for snow scavenging. Two recent reviews of below-cloud scavenging of size-resolved particles recommended that the upper range of the available theoretical formulations for Λ should be used in CTMs based on uncertainty analyses and comparison with limited field experiments. Following this recommended approach, a new semi-empirical parameterization for size-resolved Λ has been developed for below-cloud scavenging of atmospheric aerosol particles by both rain (Λrain) and snow (Λsnow). The new parameterization is based on the 90th percentile of Λ values from an ensemble data set calculated using all possible "realizations" of available theoretical Λ formulas and covering a large range of aerosol particle sizes and precipitation intensities (R). For any aerosol particle size of diameter d, a strong linear relationship between the 90th-percentile log10 (Λ) and log10 (R), which is equivalent to a power-law relationship between Λ and R, is identified. The log-linear relationship, which is characterized by two parameters (slope and y intercept), is then further parameterized by fitting these two parameters as polynomial functions of aerosol size d. A comparison of the new parameterization with limited measurements in the literature in terms of the magnitude of Λ and the relative magnitudes of Λrain and Λsnow suggests that it is a reasonable approximation. Advantages of this new semi-empirical parameterization compared to traditional theoretical formulations for Λ include its applicability to below-cloud scavenging by both rain and snow over a wide range of particle sizes and precipitation intensities, ease of implementation in any CTM with a representation of size-distributed particulate matter, and a known representativeness, based on the consideration in its development, of all available theoretical formulations and field-derived estimates for Λ (d) and their associated uncertainties.

scholarly journals Laser ablation aerosol particle time-of-flight mass spectrometer (LAAPTOF): performance, reference spectra and classification of atmospheric samples

2018 ◽  
Vol 11 (4) ◽  
pp. 2325-2343 ◽  
Author(s):  
Xiaoli Shen ◽  
Ramakrishna Ramisetty ◽  
Claudia Mohr ◽  
Wei Huang ◽  
Thomas Leisner ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Aerosol Particle ◽  
Mass Spectrometer ◽  
Size Range ◽  
Aerosol Particles ◽  
Time Of Flight ◽  
Polystyrene Latex ◽  
Dust Particles ◽  
Data Set ◽  
Flight Mass Spectrometer

Abstract. The laser ablation aerosol particle time-of-flight mass spectrometer (LAAPTOF, AeroMegt GmbH) is able to identify the chemical composition and mixing state of individual aerosol particles, and thus is a tool for elucidating their impacts on human health, visibility, ecosystem, and climate. The overall detection efficiency (ODE) of the instrument we use was determined to range from  ∼  (0.01 ± 0.01) to  ∼  (4.23 ± 2.36) % for polystyrene latex (PSL) in the size range of 200 to 2000 nm,  ∼  (0.44 ± 0.19) to  ∼  (6.57 ± 2.38) % for ammonium nitrate (NH4NO3), and  ∼  (0.14 ± 0.02) to  ∼  (1.46 ± 0.08) % for sodium chloride (NaCl) particles in the size range of 300 to 1000 nm. Reference mass spectra of 32 different particle types relevant for atmospheric aerosol (e.g. pure compounds NH4NO3, K2SO4, NaCl, oxalic acid, pinic acid, and pinonic acid; internal mixtures of e.g. salts, secondary organic aerosol, and metallic core–organic shell particles; more complex particles such as soot and dust particles) were determined. Our results show that internally mixed aerosol particles can result in spectra with new clusters of ions, rather than simply a combination of the spectra from the single components. An exemplary 1-day ambient data set was analysed by both classical fuzzy clustering and a reference-spectra-based classification method. Resulting identified particle types were generally well correlated. We show how a combination of both methods can greatly improve the interpretation of single-particle data in field measurements.

KERNEL-BASED EXPONENTIAL GREY WOLF OPTIMIZER FOR RAPID CENTROID ESTIMATION IN DATA CLUSTERING

2016 ◽  
Vol 78 (11) ◽  
Author(s):  
Amolkumar Narayan Jadhav ◽  
Gomathi N.
Keyword(s):  
Data Clustering ◽  
Objective Evaluation ◽  
Multidimensional Data ◽  
Grey Wolf Optimizer ◽  
Similar Data ◽  
Grey Wolf ◽  
Data Set ◽  
Wide Range ◽  
Centroid Estimation ◽  
Two Parameters

Clustering finds variety of application in a wide range of disciplines because it is mostly helpful for grouping of similar data objects together. Due to the wide applicability, different algorithms have been presented in the literature for segmenting large multidimensional data into discernible representative clusters. Accordingly, in this paper, Kernel-based exponential grey wolf optimizer (KEGWO) is developed for rapid centroid estimation in data clustering. Here, KEGWO is newly proposed to search the cluster centroids with a new objective evaluation which considered two parameters called logarithmic kernel function and distance difference between two top clusters. Based on the new objective function and the modified KEGWO algorithm, centroids are encoded as position vectors and the optimal location is found for the final clustering. The proposed KEGWO algorithm is evaluated with banknote authentication Data Set, iris dataset and wine dataset using four metrics such as, Mean Square Error, F-measure, Rand co-efficient and jaccord coefficient. From the outcome, we proved that the proposed KEGWO algorithm outperformed the existing algorithms.   

scholarly journals MOPSMAP v1.0: a versatile tool for the modeling of aerosol optical properties

2018 ◽  
Vol 11 (7) ◽  
pp. 2739-2762 ◽  
Author(s):  
Josef Gasteiger ◽  
Matthias Wiegner
Keyword(s):  
Optical Properties ◽  
Aerosol Particles ◽  
Fortran Program ◽  
Refractive Indices ◽  
Nonspherical Particles ◽  
Hygroscopic Growth ◽  
Web Interface ◽  
Data Set ◽  
Optical Modeling ◽  
Wide Range

Abstract. The spatiotemporal distribution and characterization of aerosol particles are usually determined by remote-sensing and optical in situ measurements. These measurements are indirect with respect to microphysical properties, and thus inversion techniques are required to determine the aerosol microphysics. Scattering theory provides the link between microphysical and optical properties; it is not only needed for such inversions but also for radiative budget calculations and climate modeling. However, optical modeling can be very time-consuming, in particular if nonspherical particles or complex ensembles are involved. In this paper we present the MOPSMAP package (Modeled optical properties of ensembles of aerosol particles), which is computationally fast for optical modeling even in the case of complex aerosols. The package consists of a data set of pre-calculated optical properties of single aerosol particles, a Fortran program to calculate the properties of user-defined aerosol ensembles, and a user-friendly web interface for online calculations. Spheres, spheroids, and a small set of irregular particle shapes are considered over a wide range of sizes and refractive indices. MOPSMAP provides the fundamental optical properties assuming random particle orientation, including the scattering matrix for the selected wavelengths. Moreover, the output includes tables of frequently used properties such as the single-scattering albedo, the asymmetry parameter, or the lidar ratio. To demonstrate the wide range of possible MOPSMAP applications, a selection of examples is presented, e.g., dealing with hygroscopic growth, mixtures of absorbing and non-absorbing particles, the relevance of the size equivalence in the case of nonspherical particles, and the variability in volcanic ash microphysics. The web interface is designed to be intuitive for expert and nonexpert users. To support users a large set of default settings is available, e.g., several wavelength-dependent refractive indices, climatologically representative size distributions, and a parameterization of hygroscopic growth. Calculations are possible for single wavelengths or user-defined sets (e.g., of specific remote-sensing application). For expert users more options for the microphysics are available. Plots for immediate visualization of the results are shown. The complete output can be downloaded for further applications. All input parameters and results are stored in the user's personal folder so that calculations can easily be reproduced. The web interface is provided at https://mopsmap.net (last access: 9 July 2018) and the Fortran program including the data set is freely available for offline calculations, e.g., when large numbers of different runs for sensitivity studies are to be made.

A comprehensive database of the optical properties of irregular aerosol particles for radiative transfer simulations

2021 ◽  
Author(s):  
Masanori Saito ◽  
Ping Yang ◽  
Jiachen Ding ◽  
Xu Liu
Keyword(s):  
Optical Properties ◽  
Radiative Transfer ◽  
Aerosol Particle ◽  
Volcanic Ash ◽  
Aerosol Particles ◽  
Single Scattering ◽  
Dust Aerosol ◽  
Index Of Refraction ◽  
Particle Sizes

AbstractA database (TAMUdust2020) of the optical properties of irregular aerosol particles is developed for applications to radiative transfer simulations involving aerosols, particularly dust and volcanic ash particles. The particle shape model assumes an ensemble of irregular hexahedral geometries to mimic complex aerosol particle shapes in nature. State-of-the-art light scattering computational capabilities are employed to compute the single-scattering properties of these particles for wide ranges of values of the size parameter, the index of refraction, and the degree of sphericity. The database therefore is useful for various radiative transfer applications over a broad spectral region from ultraviolet to infrared. Overall, agreement between simulations and laboratory/in-situ measurements is achieved for the scattering phase matrix and backscattering of various dust aerosol and volcanic ash particles. Radiative transfer simulations of active and passive spaceborne sensor signals for dust plumes with various aerosol optical depths and the effective particle sizes clearly demonstrate the applicability of the database for aerosol studies. In particular, the present database includes, for the first time, robust backscattering of nonspherical particles spanning the entire range of aerosol particle sizes, which shall be useful to appropriately interpret lidar signals related to the physical properties of aerosol plumes. Furthermore, thermal infrared simulations based on in-situ measured refractive indices of dust aerosol particles manifest the effects of the regional variations of aerosol optical properties. This database includes a user-friendly interface to obtain user-customized aerosol single-scattering properties with respect to spectrally dependent complex refractive index, size, and the degree of sphericity.

scholarly journals The Asian tropopause aerosol layer within the 2017 monsoon anticyclone: microphysical properties derived from aircraft-borne in situ measurements

2021 ◽  
Vol 21 (19) ◽  
pp. 15259-15282
Author(s):  
Christoph Mahnke ◽  
Ralf Weigel ◽  
Francesco Cairo ◽  
Jean-Paul Vernier ◽  
Armin Afchine ◽  
...  
Keyword(s):  
Particle Size ◽  
Aerosol Particle ◽  
Aerosol Particles ◽  
Aerosol Layer ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Data Set ◽  
Microphysical Properties ◽  
Aerosol Particle Size

Abstract. The Asian summer monsoon is an effective pathway for aerosol particles and precursors from the planetary boundary layer over Central, South, and East Asia into the upper troposphere and lower stratosphere. An enhancement of aerosol particles within the Asian monsoon anticyclone (AMA), called the Asian tropopause aerosol layer (ATAL), has been observed by satellites. We discuss airborne in situ and remote sensing observations of aerosol microphysical properties conducted during the 2017 StratoClim field campaign within the AMA region. The aerosol particle measurements aboard the high-altitude research aircraft M55 Geophysica (maximum altitude reached of ∼20.5 km) were conducted with a modified ultra-high-sensitivity aerosol spectrometer – airborne (UHSAS-A; particle diameter detection range of 65 nm to 1 µm), the COndensation PArticle counting System (COPAS, detecting total concentrations of submicrometer-sized particles), and the New Ice eXpEriment – Cloud and Aerosol Spectrometer with Detection of POLarization (NIXE-CAS-DPOL). In the COPAS and UHSAS-A vertical particle mixing ratio (PMR) profiles and the size distribution profiles (for number, surface area, and volume concentration), the ATAL is evident as a distinct layer between ∼370 and 420 K potential temperature (Θ). Within the ATAL, the maximum detected PMRs (from the median profiles) were ∼700 mg−1 for particle diameters between 65 nm and 1 µm (UHSAS-A) and higher than 2500 mg−1 for diameters larger than 10 nm (COPAS). These values are up to 2 times higher than those previously found at similar altitudes in other tropical locations. The difference between the PMR profiles measured by the UHSAS-A and the COPAS indicate that the region below the ATAL at Θ levels from 350 to 370 K is influenced by the nucleation of aerosol particles (diameter <65 nm). We provide detailed analyses of the vertical distribution of the aerosol particle size distributions and the PMR and compare these with previous tropical and extratropical measurements. The backscatter ratio (BR) was calculated based on the aerosol particle size distributions measured in situ. The resulting data set was compared with the vertical profiles of the BR detected by the multiwavelength aerosol scatterometer (MAS) and an airborne miniature aerosol lidar (MAL) aboard the M55 Geophysica and by the satellite-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The data of all four methods largely agree with one another, showing enhanced BR values in the altitude range of the ATAL (between ∼15 and 18.5 km) with a maximum at 17.5 km altitude. By means of the AMA-centered equivalent latitude calculated from meteorological reanalysis data, it is shown that such enhanced values of the BR larger than 1.1 could only be observed within the confinement of the AMA.

scholarly journals Estimated variability of below-cloud aerosol removal by rainfall for observed aerosol size distributions

2002 ◽  
Vol 2 (6) ◽  
pp. 2095-2131 ◽  
Author(s):  
C. Andronache
Keyword(s):  
Size Distribution ◽  
Field Experiments ◽  
Aerosol Particles ◽  
Rainfall Rate ◽  
Aerosol Size Distribution ◽  
Size Distributions ◽  
Coarse Particles ◽  
Distribution Parameters ◽  
Cloud Scavenging ◽  
Scavenging Rates

Abstract. Below-cloud scavenging (BCS) coefficients of aerosols by rainfall are estimated for reported aerosol size distributions measured during field experiments in various environments. The method employed is based on explicit calculations of the efficiency of collision between a raindrop and aerosol particles. Results show that BCS coefficient increases with rainfall rate and has a significant dependence on aerosol size distribution parameters. Thus, BCS is important for very small particles (with diameters less than 0.01 µm) and for coarse particles (with diameters larger than 2 µm). For rainfall rate R ~ 1 mm hr -1, the 0.5-folding time of these particles is of the order of one hour. It is shown that BCS is negligible for aerosol particles in the range [0.1-1] µm if compared with in-cloud scavenging rates for low and moderate rainfall rates (R ~ 0.1-10 mm hr -1). The results indicate that a boundary layer aerosol size distribution with coarse mode is drastically affected very shortly after rain starts (in a fraction of one hour) and consequently, the below-cloud aerosol size distribution becomes dominated by particles in the accumulation mode.

scholarly journals Estimated variability of below-cloud aerosol removal by rainfall for observed aerosol size distributions

2003 ◽  
Vol 3 (1) ◽  
pp. 131-143 ◽  
Author(s):  
C. Andronache
Keyword(s):  
Size Distribution ◽  
Field Experiments ◽  
Numerical Models ◽  
Aerosol Particles ◽  
Rainfall Rate ◽  
Aerosol Size Distribution ◽  
Size Distributions ◽  
Aerosol Mass Concentration ◽  
Raindrop Size Distribution ◽  
Cloud Scavenging

Abstract. Below-cloud scavenging (BCS) coefficients of aerosols by rainfall are estimated for reported aerosol size distributions measured during field experiments in various environments. The method employed is based on explicit calculations of the efficiency of collision between a raindrop and aerosol particles. Such BCS coefficients can be used in numerical models that describe: 1) the detailed evolution of aerosol size distribution and, 2) the evolution of total aerosol mass concentration. The effects of raindrop size distribution and aerosol size distribution variability on BCS coefficients are illustrated using observed data. Results show that BCS coefficient increases with rainfall rate and has a significant dependence on aerosol size distribution parameters. Thus, BCS is important for very small particles (with diameters less than 0.01 μm) and for coarse particles (with diameters larger than 2 µm). For rainfall rate R ~ 1 mm hr-1, the 0.5-folding time of these particles is of the order of one hour. It is shown that BCS is negligible for aerosol particles in the range [0.1-1] µm if compared with in-cloud scavenging rates for low and moderate rainfall rates ( R ~ 0.1-10 mm hr-1). The results indicate that a boundary layer aerosol size distribution with coarse mode is drastically affected very shortly after rain starts (in a fraction of one hour) and consequently, the below-cloud aerosol size distribution becomes dominated by particles in the accumulation mode.

Decomposition rates of coarse woody debris—A review with particular emphasis on Australian tree species

2003 ◽  
Vol 51 (1) ◽  
pp. 27 ◽  
Author(s):  
J. Mackensen ◽  
J. Bauhus ◽  
E. Webber
Keyword(s):  
Tree Species ◽  
Coarse Woody Debris ◽  
Field Experiments ◽  
Woody Debris ◽  
Initial Density ◽  
Decay Resistance ◽  
Decay Rates ◽  
Mean Annual Temperature ◽  
Data Set ◽  
Wide Range

We reviewed the decay patterns and lifetimes (time to reach 95% mass loss) of coarse woody debris (CWD) on the forest floor. The objectives were to identify the factors influencing the decomposition process of CWD and to provide estimates of lifetimes for CWD from Australian tree species. This information is required for greenhouse accounting of forestry activities and land use change as well as the sustainable management of CWD in forest ecosystems. The analysis of a global data set on decay rates of CWD showed that, in particular, the mean annual temperature was a main driver of decomposition, accounting for 34% of the variation in decay rates. The Q10, the factor by which biological processes accelerate when temperature increases by 10�C, was 2.53. Additional determinants of CWD decay rates were the initial density of wood and the diameter of logs. Median and average lifetimes derived from 184 decay rates were 49 and 92 years, respectively, which is considerably higher than the 10-year default for all litter proposed by the Intergovernmental Panel on Climate Change. The pattern of decay in most cases followed a negative exponential curve. To overcome the paucity of information on decomposition of CWD in Australian forests and woodlands, decay rates for a large number of species were derived from wood durability and decay resistance studies. For native Australian species, lifetimes ranged from 7 years in Eucalyptus regnans to 375 years in E. camaldulensis. The lifetimes for timber durability Classes 1–4 were 54, 39, 26 and 11 years, respectively, below 30� latitude and without the influence of termites. However, the experimental conditions under which durability and decay resistance are commonly determined are substantially different from the situation under which CWD decomposes in the field. These estimates must therefore be regarded as minimum lifetimes for CWD of most species. To determine decay rates of CWD with greater certainty, long-term field experiments in a wide range of ecosystems are required.

Structure Guided Molecular Docking Assisted Alignment Dependent 3DQSAR Study on Steroidal Aromatase Inhibitors (SAIs) as Anti-breast Cancer Agents

2019 ◽  
Vol 16 (7) ◽  
pp. 808-817 ◽  
Author(s):  
Laxmi Banjare ◽  
Sant Kumar Verma ◽  
Akhlesh Kumar Jain ◽  
Suresh Thareja
Keyword(s):  
Breast Cancer ◽  
Molecular Docking ◽  
Aromatase Inhibitors ◽  
Direct Synthesis ◽  
3D Qsar ◽  
Chemotherapeutic Agents ◽  
Modeling Tools ◽  
Data Set ◽  
Wide Range ◽  
Steroidal Aromatase Inhibitors

Background: In spite of the availability of various treatment approaches including surgery, radiotherapy, and hormonal therapy, the steroidal aromatase inhibitors (SAIs) play a significant role as chemotherapeutic agents for the treatment of estrogen-dependent breast cancer with the benefit of reduced risk of recurrence. However, due to greater toxicity and side effects associated with currently available anti-breast cancer agents, there is emergent requirement to develop target-specific AIs with safer anti-breast cancer profile. Methods: It is challenging task to design target-specific and less toxic SAIs, though the molecular modeling tools viz. molecular docking simulations and QSAR have been continuing for more than two decades for the fast and efficient designing of novel, selective, potent and safe molecules against various biological targets to fight the number of dreaded diseases/disorders. In order to design novel and selective SAIs, structure guided molecular docking assisted alignment dependent 3D-QSAR studies was performed on a data set comprises of 22 molecules bearing steroidal scaffold with wide range of aromatase inhibitory activity. Results: 3D-QSAR model developed using molecular weighted (MW) extent alignment approach showed good statistical quality and predictive ability when compared to model developed using moments of inertia (MI) alignment approach. Conclusion: The explored binding interactions and generated pharmacophoric features (steric and electrostatic) of steroidal molecules could be exploited for further design, direct synthesis and development of new potential safer SAIs, that can be effective to reduce the mortality and morbidity associated with breast cancer.

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