scholarly journals Metrics to quantify the importance of mixing state for CCN activity

2017 ◽  
Vol 17 (12) ◽  
pp. 7445-7458 ◽  
Author(s):  
Joseph Ching ◽  
Jerome Fast ◽  
Matthew West ◽  
Nicole Riemer
Keyword(s):  
Cloud Condensation Nuclei ◽  
Mixing State ◽  
State Information ◽  
Model Simulations ◽  
Internal Mixing ◽  
State Index ◽  
Mixed Populations ◽  
Aerosol Aging ◽  
Relationship Of ◽  
The Relationship

Abstract. It is commonly assumed that models are more prone to errors in predicted cloud condensation nuclei (CCN) concentrations when the aerosol populations are externally mixed. In this work we investigate this assumption by using the mixing state index (χ) proposed by Riemer and West (2013) to quantify the degree of external and internal mixing of aerosol populations. We combine this metric with particle-resolved model simulations to quantify error in CCN predictions when mixing state information is neglected, exploring a range of scenarios that cover different conditions of aerosol aging. We show that mixing state information does indeed become unimportant for more internally mixed populations, more precisely for populations with χ larger than 75 %. For more externally mixed populations (χ below 20 %) the relationship of χ and the error in CCN predictions is not unique and ranges from lower than −40 % to about 150 %, depending on the underlying aerosol population and the environmental supersaturation. We explain the reasons for this behavior with detailed process analyses.

scholarly journals Metrics to quantify the importance of mixing state for CCN activity

2016 ◽  
Author(s):  
Joseph Ching ◽  
Jerome Fast ◽  
Matthew West ◽  
Nicole Riemer
Keyword(s):  
Chem Phys ◽  
Mixing State ◽  
State Information ◽  
Model Simulations ◽  
Internal Mixing ◽  
State Index ◽  
Mixed Populations ◽  
Aerosol Aging ◽  
Relationship Of ◽  
The Relationship

Abstract. It is commonly assumed that models are more prone to errors in predicted CCN concentrations when the aerosol populations are externally mixed. However, it has been difficult to rigorously investigate this assumption because appropriate metrics for mixing state were lacking and metrics needed to quantify the error in CCN concentrations due to mixing state effects were unavailable. In this work we use the mixing state index (χ) proposed by Riemer and West (Atmos. Chem. Phys., 13, 11423–11439, 2013) to quantify the degree of external and internal mixing of aerosol populations. We combine this metric with particle-resolved model simulations to quantify error in CCN predictions when mixing state information is neglected, exploring a range of scenarios that cover different conditions of aerosol aging. We show that mixing state information does indeed become unimportant for more internally-mixed populations, more precisely for populations with χ larger than 60 %. For more externally-mixed populations (χ below 20 %) the relationship of χ and the error in CCN predictions is not unique, and ranges from lower than −40 % to about 150 %, depending on the underlying aerosol population and the environmental supersaturation. We explain the reasons for this behavior with detailed process analyses.

scholarly journals The impact of aerosol size-dependent hygroscopicity and mixing state on the cloud condensation nuclei potential over the north-east Atlantic

2021 ◽  
Vol 21 (11) ◽  
pp. 8655-8675
Author(s):  
Wei Xu ◽  
Kirsten N. Fossum ◽  
Jurgita Ovadnevaite ◽  
Chunshui Lin ◽  
Ru-Jin Huang ◽  
...  
Keyword(s):  
Biological Activity ◽  
Chemical Composition ◽  
Cloud Condensation Nuclei ◽  
Mixing State ◽  
East Atlantic ◽  
Size Dependent ◽  
North East ◽  
The North ◽  
Internal Mixing ◽  
The Impact

Abstract. We present an aerosol cloud condensation nuclei (CCN) closure study over the north-east Atlantic Ocean using six approximating methods. The CCN number concentrations (NCCN) were measured at four discrete supersaturations (SSs; 0.25 %, 0.5 %, 0.75 % and 1.0 %). Concurrently, aerosol number size distribution, sub-saturation hygroscopic growth factor and bulk PM1 chemical composition were obtained at matching time resolution and after a careful data validation exercise. Method A used a constant bulk hygroscopicity parameter κ of 0.3; method B used bulk PM1 chemical composition measured by an aerosol mass spectrometer (AMS); method C utilised a single growth factor (GF) size (165 nm) measured by a humidified tandem differential mobility analyser (HTDMA); method D utilised size-dependent GFs measured at 35, 50, 75, 110 and 165 nm; method E divided the aerosol population into three hygroscopicity modes (near-hydrophobic, more-hygroscopic and sea-salt modes), and the total CCN number in each mode was cumulatively added up; method F used the full-size-scale GF probability density function (GF–PDF) in the most complex approach. The studied periods included high-biological-activity and low-biological-activity seasons in clean marine and polluted continental air masses to represent and discuss the most contrasting aerosol populations. Overall, a good agreement was found between estimated and measured NCCN with linear regression slopes ranging from 0.64 to 1.6. The temporal variability was captured very well, with Pearson's R value ranging from 0.76 to 0.98 depending on the method and air mass type. We further compared the results of using different methods to quantify the impact of size-dependent hygroscopicity and mixing state and found that ignoring size-dependent hygroscopicity induced overestimation of NCCN by up to 12 %, and ignoring a mixing state induced overestimation of NCCN by up to 15 %. The error induced by assuming an internal mixing in highly polluted cases was largely eliminated by dividing the full GF–PDF into three conventional hygroscopic modes, while assuming an internal mixing in clean marine aerosol did not induce significant error.

scholarly journals Quantifying aerosol mixing state with entropy and diversity measures

2013 ◽  
Vol 13 (6) ◽  
pp. 15615-15662
Author(s):  
N. Riemer ◽  
M. West
Keyword(s):  
Species Diversity ◽  
Cloud Condensation Nuclei ◽  
Chemical Species ◽  
Climate Impacts ◽  
Mixing State ◽  
Population Mixing ◽  
Information Theoretic ◽  
Low Mass ◽  
State Index ◽  
Definition Of

Abstract. This paper presents the first quantitative metric for aerosol population mixing state, defined as the distribution of per-particle chemical species composition. This new metric, the mixing state index χ, is an affine ratio of the average per-particle species diversity Dα and the bulk population species diversity Dγ, both of which are based on information-theoretic entropy measures. The mixing state index χ enables the first rigorous definition of the spectrum of mixing states from so-called external mixture to internal mixture, which is significant for aerosol climate impacts, including aerosol optical properties and cloud condensation nuclei activity. We illustrate the usefulness of this new mixing state framework with model results from the stochastic particle-resolved model PartMC-MOSAIC. These results demonstrate how the mixing state metrics evolve with time for several archetypal cases, each of which isolates a specific process such as coagulation, emission, or condensation. Further, we present an analysis of the mixing state evolution for a complex urban plume case, for which these processes occur simultaneously. We additionally derive theoretical properties of the mixing state index and present a family of generalized mixing state indexes that vary in the importance assigned to low-mass-fraction species.

Simulation of particle diversity and mixing state over Greater Paris: a model–measurement inter-comparison

2016 ◽  
Vol 189 ◽  
pp. 547-566 ◽  
Author(s):  
Shupeng Zhu ◽  
Karine N. Sartelet ◽  
Robert M. Healy ◽  
John C. Wenger
Keyword(s):  
Chemical Composition ◽  
Single Particle ◽  
Rural Areas ◽  
Urban Areas ◽  
Chem Phys ◽  
Mixing State ◽  
Average Value ◽  
Internal Mixing ◽  
State Index ◽  
Different Sources

Air quality models are used to simulate and forecast pollutant concentrations, from continental scales to regional and urban scales. These models usually assume that particles are internally mixed, i.e. particles of the same size have the same chemical composition, which may vary in space and time. Although this assumption may be realistic for continental-scale simulations, where particles originating from different sources have undergone sufficient mixing to achieve a common chemical composition for a given model grid cell and time, it may not be valid for urban-scale simulations, where particles from different sources interact on shorter time scales. To investigate the role of the mixing state assumption on the formation of particles, a size-composition resolved aerosol model (SCRAM) was developed and coupled to the Polyphemus air quality platform. Two simulations, one with the internal mixing hypothesis and another with the external mixing hypothesis, have been carried out for the period 15 January to 11 February 2010, when the MEGAPOLI winter field measurement campaign took place in Paris. The simulated bulk concentrations of chemical species and the concentrations of individual particle classes are compared with the observations of Healy et al. (Atmos. Chem. Phys., 2013, 13, 9479–9496) for the same period. The single particle diversity and the mixing-state index are computed based on the approach developed by Riemer et al. (Atmos. Chem. Phys., 2013, 13, 11423–11439), and they are compared to the measurement-based analyses of Healy et al. (Atmos. Chem. Phys., 2014, 14, 6289–6299). The average value of the single particle diversity, which represents the average number of species within each particle, is consistent between simulation and measurement (2.91 and 2.79 respectively). Furthermore, the average value of the mixing-state index is also well represented in the simulation (69% against 59% from the measurements). The spatial distribution of the mixing-state index shows that the particles are not mixed in urban areas, while they are well mixed in rural areas. This indicates that the assumption of internal mixing traditionally used in transport chemistry models is well suited to rural areas, but this assumption is less realistic for urban areas close to emission sources.

scholarly journals The impact of aerosol size-dependent hygroscopicity and mixing state on the cloud condensation nuclei potential over the Northeast Atlantic

2021 ◽  
Author(s):  
Wei Xu ◽  
Kirsten N. Fossum ◽  
Jurgita Ovadnevaite ◽  
Chunshui Lin ◽  
Ru-Jin Huang ◽  
...  
Keyword(s):  
Biological Activity ◽  
Chemical Composition ◽  
Growth Factor ◽  
Cloud Condensation Nuclei ◽  
Condensation Nuclei ◽  
Mixing State ◽  
Northeast Atlantic ◽  
Size Dependent ◽  
Internal Mixing ◽  
The Impact

Abstract. We present an aerosol cloud condensation nuclei (CCN) closure study over the Northeast Atlantic Ocean using six approximating methods. The CCN number concentrations (NCCN) were measured at four discrete super-saturations (SS, 0.25, 0.5, 0.75 and 1.0 %). Concurrently, aerosol number size distribution, sub-saturation hygroscopic growth factor and bulk PM1 chemical composition were obtained at matching time resolution and after a careful data validation exercise. Method A used a constant bulk hygroscopicity parameter κ of 0.3; method B used bulk PM1 chemical composition measured by an aerosol mass spectrometer (AMS); method C and D utilized a single size (165 nm) growth factor (GF) measured by humidified tandem differential mobility analyzer (HTDMA); method C utilized size-dependent GFs measured at 35, 50, 75, 110 and 165 nm; method E divided the aerosol population into three hygroscopicity modes (near-hydrophobic, more-hygroscopic and sea-salt modes) and the total CCN number in each mode was cumulatively added up; method F used the full size scale GF probability density function (GF-PDF) in the most complex approach. The studied periods included high biological activity and low biological activity seasons in clean marine and polluted continental air masses to represent and discuss the most contrasting aerosol populations. Overall, a good agreement was found between estimated and measured NCCN with a linear regression slopes ranging from 0.64 and 1.6. The temporal variability was captured very well with Pearson's R value ranging from 0.76 to 0.98 depending on the method and air mass type. We further compared the results of using different methods to quantify the impact of size-dependent hygroscopicity and mixing state and found that ignoring size-dependent hygroscopicity induced overestimation of NCCN by up to 12 %, and ignoring a mixing state induced overestimation of NCCN by up to 15 %. The error induced by assuming an internal mixing in highly polluted cases was largely eliminated by dividing the full GF-PDf into three conventional hygroscopic modes while assuming an internal mixing in clean marine aerosol did not induced significant error.

scholarly journals Quantifying aerosol mixing state with entropy and diversity measures

2013 ◽  
Vol 13 (22) ◽  
pp. 11423-11439 ◽  
Author(s):  
N. Riemer ◽  
M. West
Keyword(s):  
Species Diversity ◽  
Cloud Condensation Nuclei ◽  
Chemical Species ◽  
Climate Impacts ◽  
Mixing State ◽  
Population Mixing ◽  
Information Theoretic ◽  
Low Mass ◽  
State Index ◽  
Definition Of

Abstract. This paper presents the first quantitative metric for aerosol population mixing state, defined as the distribution of per-particle chemical species composition. This new metric, the mixing state index χ, is an affine ratio of the average per-particle species diversity Dα and the bulk population species diversity Dγ, both of which are based on information-theoretic entropy measures. The mixing state index χ enables the first rigorous definition of the spectrum of mixing states from so-called external mixture to internal mixture, which is significant for aerosol climate impacts, including aerosol optical properties and cloud condensation nuclei activity. We illustrate the usefulness of this new mixing state framework with model results from the stochastic particle-resolved model PartMC-MOSAIC. These results demonstrate how the mixing state metrics evolve with time for several archetypal cases, each of which isolates a specific process such as coagulation, emission, or condensation. Further, we present an analysis of the mixing state evolution for a complex urban plume case, for which these processes occur simultaneously. We additionally derive theoretical properties of the mixing state index and present a family of generalized mixing state indexes that vary in the importance assigned to low-mass-fraction species.

Seasonal Feeding by Phyllophaga crinita and Anomala spp. (Coleoptera: Scarabaeidae) Larvae in Northeastern Mexico

1996 ◽  
Vol 31 (3) ◽  
pp. 301-305 ◽  
Author(s):  
L. A. Rodriguez-del-Bosque
Keyword(s):  
Life Cycle ◽  
Seedling Emergence ◽  
Field Conditions ◽  
Larval Feeding ◽  
Northeastern Mexico ◽  
Mixed Populations ◽  
Simulated Field ◽  
Relationship Of ◽  
The Relationship

Larval feeding by Phyllophaga crinita (Burmeister) and Anomala spp. (mixed populations of A. flavipennis Burmeister and A. foraminosa Bates) was studied under simulated field conditions in northern Tamaulipas, Mexico. Each month from July 1994 to February 1995, 50 field-collected larvae of P. crinita and Anomala spp. were placed individually in plastic pots with soil and corn seeds, and damage was evaluated 10 d after seedling emergence. Secondinstar P. crinita caused 41% root loss in July, whereas third instars caused most damage (66–88% root loss) during July–September. Feeding by P. crinita decreased gradually from October to December, and ceased in January–February. In contrast, feeding by Anomala spp. peaked in July and again in November (73 and 53% root loss, respectively), a result of the bivoltine life cycle of these species in this region. The relationship of these findings to similar studies is discussed.

The relationship of the scleractinian corals to the rugose corals

Paleobiology ◽  
1980 ◽  
Vol 6 (02) ◽  
pp. 146-160 ◽  
Author(s):  
William A. Oliver
Keyword(s):  
Critical Points ◽  
Scleractinian Corals ◽  
Convincing Evidence ◽  
Early Triassic ◽  
Rugose Corals ◽  
History Of ◽  
The Subject ◽  
Relationship Of ◽  
The Relationship ◽  
Biologic Factors

The Mesozoic-Cenozoic coral Order Scleractinia has been suggested to have originated or evolved (1) by direct descent from the Paleozoic Order Rugosa or (2) by the development of a skeleton in members of one of the anemone groups that probably have existed throughout Phanerozoic time. In spite of much work on the subject, advocates of the direct descent hypothesis have failed to find convincing evidence of this relationship. Critical points are:(1) Rugosan septal insertion is serial; Scleractinian insertion is cyclic; no intermediate stages have been demonstrated. Apparent intermediates are Scleractinia having bilateral cyclic insertion or teratological Rugosa.(2) There is convincing evidence that the skeletons of many Rugosa were calcitic and none are known to be or to have been aragonitic. In contrast, the skeletons of all living Scleractinia are aragonitic and there is evidence that fossil Scleractinia were aragonitic also. The mineralogic difference is almost certainly due to intrinsic biologic factors.(3) No early Triassic corals of either group are known. This fact is not compelling (by itself) but is important in connection with points 1 and 2, because, given direct descent, both changes took place during this only stage in the history of the two groups in which there are no known corals.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

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