scholarly journals A Microphysical Bulk Formulation Based on Scaling Normalization of the Particle Size Distribution. Part I: Description

2005 ◽  
Vol 62 (12) ◽  
pp. 4206-4221 ◽  
Author(s):  
Wanda Szyrmer ◽  
Stéphane Laroche ◽  
Isztar Zawadzki
Keyword(s):  
Particle Size ◽  
High Resolution ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Numerical Models ◽  
Radar Data ◽  
Retrieval Algorithm ◽  
Microphysical Processes ◽  
The Moment ◽  
Microphysical Parameterization

Abstract The authors address the problem of optimization of the microphysical information extracted from a simulation system composed of high-resolution numerical models and multiparameter radar data or other available measurements. As a tool in the exploration of this question, a bulk microphysical scheme based on the general approach of scaling normalization of particle size distribution (PSD) is proposed. This approach does not rely on a particular functional form imposed on the PSD and naturally leads to power-law relationships between the PSD moments providing an accurate and compact PSD representation. To take into account the possible evolution of the shape/curvature of the distribution, ignored within standard one- and two-moment microphysical schemes, a new three-moment scheme based on the two-moment scaling normalization is proposed. The methodology of the moment retrieval included in the three-moment scheme can also be useful as a retrieval algorithm combining different remote sensing observations. The developed bulk microphysical scheme presents a unified formulation for microphysical parameterization using one, two, or three independent moments, suitable in the context of data assimilation. The effectiveness of the scheme with different combinations of independent moments is evaluated by comparison with a very high resolution spectral model within a 1D framework on representative microphysical processes: rain sedimentation and evaporation.

scholarly journals Stratospheric aerosol particle size information in Odin-OSIRIS limb scatter spectra

2013 ◽  
Vol 6 (3) ◽  
pp. 5065-5099
Author(s):  
L. A. Rieger ◽  
A. E. Bourassa ◽  
D. A. Degenstein
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Imaging System ◽  
Stratospheric Aerosol ◽  
Retrieval Algorithm ◽  
Aerosol Layer ◽  
Aerosol Extinction ◽  
Model Calculations ◽  
Size Information

Abstract. The Optical Spectrograph and InfraRed Imaging System (OSIRIS) on-board the Odin satellite has now taken over a decade of limb scatter measurements that have been used to retrieve the Version 5 stratospheric aerosol extinction product. This product is retrieved using a representative particle size distribution to calculate scattering cross sections and scattering phase functions for the forward model calculations. In this work the information content of OSIRIS measurements with respect to stratospheric aerosol is systematically examined for the purpose of retrieving particle size information along with the extinction coefficient. The benefit of using measurements at different wavelengths and scattering angles in the retrieval is studied and it is found that incorporation of the 1530 nm radiance measurement is key for a robust retrieval of particle size information. It is also found that using OSIRIS measurements at different solar geometries simultaneously provides little additional benefit. Based on these results, an improved aerosol retrieval algorithm is developed that couples the retrieval of aerosol extinction and mode radius of a log-normal particle size distribution. Comparison of these results with coincident measurements from SAGE III show agreement in retrieved extinction to within approximately 10% over the bulk of the aerosol layer, which is comparable to Version 5. The retrieved particle size, when converted to Ångström coefficient, shows good qualitative agreement with SAGE II measurements made at somewhat shorter wavelengths.

scholarly journals Characterization of Particle Size Distribution of Plasma Lipoproteins in Dairy Cattle Using High-Resolution Polyacrylamide Electrophoresis

2021 ◽  
Vol 2 ◽  
Author(s):  
Marcos Jofree Duran ◽  
Jasmine Kannampuzha-Francis ◽  
Daryl Nydam ◽  
Erica Behling-Kelly
Keyword(s):  
Particle Size ◽  
High Resolution ◽  
Particle Size Distribution ◽  
Dairy Cattle ◽  
Size Distribution ◽  
Low Density Lipoproteins ◽  
Plasma Lipoproteins ◽  
Low Density ◽  
Lipoprotein Particle ◽  
Lipoprotein Particle Size

Plasma lipoproteins play critical roles in energy metabolism and inflammation. Concentrations of high-density lipoproteins (HDL) are linked to reproductive outcomes and milk yields in dairy cattle. Low-density lipoproteins (LDL), which are enzymatically formed in the blood from very low-density lipoproteins (VLDL) following secretion by the liver, have been used as a surrogate marker of liver function due to the rapid influx of circulating VLDL into the lactating mammary gland. In humans, the composition of plasma lipoproteins is reflected in lipoprotein particle size distribution, and both of these parameters are highly predictive of disease development and related health outcomes. Bovine HDL are overall larger, less dense particles compared to human HDL. Lipoprotein particle size distribution in both health and disease is understudied in the bovine. We hypothesize that a more detailed analysis of lipoproteins could hold diagnostic and/or prognostic value in the study of dairy cattle health and production. In this study, we took the first steps in this characterization and used a high-resolution polyacrylamide gel electrophoretic assay to better define LDL and HDL at the subfraction level in Holstein cows at different stages of lactation. We extensively characterized the lipoprotein particle size distribution in healthy lactating dairy cattle. We identified subfractions of LDL that were prominent only in the dry period and subfractions of HDL that were highest in cows during mid-lactation. Use of this method could be informative in the study of multiple herds and management strategies, including longitudinal evaluation of animals and production parameters.

scholarly journals Mineral snowflakes on exoplanets and brown dwarfs

2020 ◽  
Vol 639 ◽  
pp. A107 ◽  
Author(s):  
D. Samra ◽  
Ch. Helling ◽  
M. Min
Keyword(s):  
Particle Size ◽  
High Resolution ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Brown Dwarfs ◽  
Spherical Particles ◽  
Cloud Formation ◽  
Spectral Features ◽  
Spherical Cloud ◽  
Cloud Particles

Context. Exoplanet atmosphere characterisation has become an important tool in understanding exoplanet formation, evolution, and it also is a window into potential habitability. However, clouds remain a key challenge for characterisation: upcoming space telescopes (e.g. the James Webb Space Telescope, JWST, and the Atmospheric Remote-sensing Infrared Exoplanet Large-survey) and ground-based high-resolution spectrographs (e.g. the next-generation CRyogenic high-resolution InfraRed Echelle Spectrograph) will produce data requiring detailed understanding of cloud formation and cloud effects for a variety of exoplanets and brown dwarfs. Aims. We aim to understand how the micro-porosity of cloud particles affects the cloud structure, particle size, and material composition on exoplanets and brown dwarfs. We further examine the spectroscopic effects of micro-porous particles, the particle size distribution, and non-spherical cloud particles. Methods. We expanded our kinetic non-equilibrium cloud formation model to study the effect of micro-porosity on the cloud structure using prescribed 1D (Tgas–pgas) profiles from the DRIFT-PHOENIX model atmosphere grid. We applied the effective medium theory and the Mie theory to model the spectroscopic properties of cloud particles with micro-porosity and a derived particle size distribution. In addition, we used a statistical distribution of hollow spheres to represent the effects of non-spherical cloud particles. Results. Highly micro-porous cloud particles (90% vacuum) have a larger surface area, enabling efficient bulk growth higher in the atmosphere than for compact particles. Increases in single scattering albedo and cross-sectional area for these mineral snowflakes cause the cloud deck to become optically thin only at a wavelength of ~100 μm instead of at the ~20 μm for compact cloud particles. A significant enhancement in albedo is also seen when cloud particles occur with a locally changing Gaussian size distribution. Non-spherical particles increase the opacity of silicate spectral features, which further increases the wavelength at which the clouds become optically thin. Conclusions. Retrievals of cloud properties, particularly particle size and mass of clouds, are biased by the assumption of compact spherical particles. The JWST mid-infrared instrument will be sensitive to signatures of micro-porous and non-spherical cloud particles based on the wavelength at which clouds are optically thin. Details of spectral features are also dependent on particle shape, and greater care must be taken in modelling clouds as observational data improves.

Cloud Microphysical Implications for Marine Cloud Brightening: The Importance of the Seeded Particle Size Distribution

2021 ◽  
Author(s):  
Fabian Hoffmann ◽  
Graham Feingold
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Cloud Model ◽  
Cloud Microphysics ◽  
Cloud Water ◽  
Aerosol Size Distribution ◽  
Size Spectrum ◽  
Optimal Size ◽  
Microphysical Processes

AbstractMarine cloud brightening (MCB) has been proposed as a viable way to counteract global warming by artificially increasing the albedo and lifetime of clouds via deliberate seeding of aerosol particles. Stratocumulus decks, which cover wide swaths of the Earth’s surface, are considered the primary target for this geoengineering approach. The macroscale properties of this cloud type exhibit a high sensitivity to cloud microphysics, exposing the potential for undesired changes in cloud optical properties in response to MCB. In this study, we apply a highly detailed Lagrangian cloud model, coupled to an idealized parcel model as well as a full three-dimensional large-eddy simulation model, to show that the choice of seeded particle size distribution is crucial to the success of MCB, and that its efficacy can be significantly reduced by undesirable microphysical processes. The presence of even a small number of large particles in the seeded size spectrum may trigger significant precipitation, which will reduce cloud water and may even break up the cloud deck, reducing the scene albedo and hence counteracting MCB. On the other hand, a seeded spectrum comprising a large number of small particles reduces the fraction of activated cloud droplets, increases entrainment and evaporation of cloud water, also reducing the efficiency of MCB. In between, there may exist an aerosol size distribution that minimizes undesirable microphysical processes and enables optimal MCB. This optimal size distribution is expected to be case-dependent.

scholarly journals Aircraft observations and model simulations of concentration and particle size distribution in the Eyjafjallajökull volcanic ash cloud

2013 ◽  
Vol 13 (3) ◽  
pp. 1277-1291 ◽  
Author(s):  
H. F. Dacre ◽  
A. L. M. Grant ◽  
B. T. Johnson
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Volcanic Ash ◽  
Fine Particles ◽  
Large Fraction ◽  
Vertical Wind Shear ◽  
Microphysical Processes ◽  
The Uk ◽  
Ash Cloud

Abstract. The Eyjafjallajökull volcano in Iceland emitted a cloud of ash into the atmosphere during April and May 2010. Over the UK the ash cloud was observed by the FAAM BAe-146 Atmospheric Research Aircraft which was equipped with in-situ probes measuring the concentration of volcanic ash carried by particles of varying sizes. The UK Met Office Numerical Atmospheric-dispersion Modelling Environment (NAME) has been used to simulate the evolution of the ash cloud emitted by the Eyjafjallajökull volcano during the period 4–18 May 2010. In the NAME simulations the processes controlling the evolution of the concentration and particle size distribution include sedimentation and deposition of particles, horizontal dispersion and vertical wind shear. For travel times between 24 and 72 h, a 1/t relationship describes the evolution of the concentration at the centre of the ash cloud and the particle size distribution remains fairly constant. Although NAME does not represent the effects of microphysical processes, it can capture the observed decrease in concentration with travel time in this period. This suggests that, for this eruption, microphysical processes play a small role in determining the evolution of the distal ash cloud. Quantitative comparison with observations shows that NAME can simulate the observed column-integrated mass if around 4% of the total emitted mass is assumed to be transported as far as the UK by small particles (< 30 μm diameter). NAME can also simulate the observed particle size distribution if a distal particle size distribution that contains a large fraction of < 10 μm diameter particles is used, consistent with the idea that phraetomagmatic volcanoes, such as Eyjafjallajökull, emit very fine particles.

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