Showing papers on "Microphysics published in 2001"
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TL;DR: In this article, a short theoretical overview of the effects of particle microphysics on particle single-scattering characteristics is presented. But, the assumption of sphericity is rarely made after first having studied the effect of nonsphericity and having concluded that they are negligible.
Abstract: The convenient availability and simplicity of the Lorenz-Mie theory has resulted in a widespread practice of treating nonspherical particles (especially those in random orientation) as if they were spheres to which Lorenz-Mie results are applicable. However, the assumption of sphericity is rarely made after first having studied the effects of nonsphericity and having concluded that they are negligible. On the contrary, overwhelming evidence suggests that scattering properties of nonspherical particles, including those in random orientation, can significantly differ from those of volume- or surface-equivalent spheres. Hence, the last few decades have demonstrated major research efforts aimed at a significantly better understanding of the effects of particle shape and morphology on electromagnetic scattering. The goal of this presentation is to provide a concise summary of these efforts. The recent availability of theoretical techniques for computing single and multiple scattering of light by realistic polydispersions of spherical and nonspherical particles and the strong dependence of the Stokes scattering matrix on particle size, shape, and refractive index make polarization and depolarization measurements a powerful particle characterization tool. This presentation will focus on recent applications of photopolarimetric and lidar depolarization measurements to remote sensing characterization of tropospheric aerosols, polar stratospheric clouds (PSCs) and contrails. The talk will include (1) a short theoretical overview of the effects of particle microphysics on particle single-scattering characteristics; (2) the use of multi-angle multi-spectral photopolarimetry to retrieve the optical thickness, size distribution, refractive index, and number concentration of tropospheric aerosols over the ocean surface; and (3) the application of the T-matrix method to constraining the PSC and contrail particle microphysics using multi-spectral measurements of lidar backscatter and depolarization
205 citations
TL;DR: A cumulus parameterization based on mass fluxes, convective-scale vertical velocities, and mesoscale effects has been incorporated in an atmospheric general circulation model (GCM) as discussed by the authors.
Abstract: A cumulus parameterization based on mass fluxes, convective-scale vertical velocities, and mesoscale effects has been incorporated in an atmospheric general circulation model (GCM). Most contemporary cumulus parameterizations are based on convective mass fluxes. This parameterization augments mass fluxes with convective-scale vertical velocities as a means of providing a method for incorporating cumulus microphysics using vertical velocities at physically appropriate (subgrid) scales. Convective-scale microphysics provides a key source of material for mesoscale circulations associated with deep convection, along with mesoscale in situ microphysical processes. The latter depend on simple, parameterized mesoscale dynamics. Consistent treatment of convection, microphysics, and radiation is crucial for modeling global-scale interactions involving clouds and radiation. Thermodynamic and hydrological aspects of this parameterization in integrations of the Geophysical Fluid Dynamics Laboratory SKYHI GCM...
151 citations
TL;DR: In this paper, a numerical cloud model with explicit microphysical processes and turbulent effects was used to reproduce highly supercooled water in convective clouds (1.8 gm−3 at −37.5°C).
Abstract: Aircraft observations of highly supercooled water in convective clouds (1.8 gm−3 at −37.5°C) were reproduced by a numerical cloud model with explicit microphysical processes and turbulent effects. The model showed that large concentrations of small cloud droplets induced by high concentrations of CCN and a strong updraft were essential in reproducing the observations. The same model reproduced microphysically maritime clouds with fast depletion of cloud water by just changing the CCN spectrum. The constrains imposed by these extreme conditions revealed the weakness of existing cloud parameterizations, and the necessity of inclusion of very detailed explicit microphysical and turbulent cloud processes in cloud models.
129 citations
03 Jan 2001
TL;DR: In this article, six different convective-stratiform separation techniques, including a new technique that utilizes the ratio of vertical and terminal velocities, are compared and evaluated using two-dimensional numerical simulations of a tropical [Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE)] and midlatitude continental [Preliminary Regional Experiment for STORM-Central (PRESTORM)] squall line.
Abstract: Six different convective-stratiform separation techniques, including a new technique that utilizes the ratio of vertical and terminal velocities, are compared and evaluated using two-dimensional numerical simulations of a tropical [Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE)] and midlatitude continental [Preliminary Regional Experiment for STORM-Central (PRESTORM)] squall line. The simulations are made using two different numerical advection schemes: 4th order and positive definite advection. Comparisons are made in terms of rainfall, cloud coverage, mass fluxes, apparent heating and moistening, mean hydrometeor profiles, CFADs (Contoured Frequency with Altitude Diagrams), microphysics, and latent heating retrieval. Overall, it was found that the different separation techniques produced results that qualitatively agreed. However, the quantitative differences were significant. Observational comparisons were unable to conclusively evaluate the performance of the techniques. Latent heating retrieval was shown to be sensitive to the use of separation technique mainly due to the stratiform region for methods that found very little stratiform rain. The midlatitude PRESTORM simulation was found to be nearly invariant with respect to advection type for most quantities while for TOGA COARE fourth order advection produced numerous shallow convective cores and positive definite advection fewer cells that were both broader and deeper penetrating above the freezing level.
114 citations
TL;DR: In this paper, the authors examined how emissions from the Indian subcontinent modify the microphysical properties of trade wind cumulus clouds over the Indian Ocean and found that droplet concentrations were a factor of 3 higher, droplet effective diameters were 35% smaller, and drizzle was observed 25% as often than in the pristine regions, as delineated from the concentrations of condensation nuclei.
Abstract: In this study, we examine how emissions from the Indian subcontinent modify the microphysical properties of trade wind cumulus clouds over the Indian Ocean. In situ microphysical data from 18 National Center for Atmospheric Research C130 research flights during the Indian Ocean Experiment (INDOEX) in February-March 1999, in polluted to pristine regions, as delineated from the concentrations of condensation nuclei (CN), were analyzed. Cloud properties were found to vary in a systematic way during the five gradient flights: i.e., those flights in which the C130 flew from about 4.5° N latitude in the high-CN regions, south across the intertropical convergence zone (ITCZ) into the clean regime, then farther south to about 8° S latitude. The high-CN regime contained relatively large concentrations of small droplets as compared to the low-CN regime, where low concentrations of large droplets, and more frequent drizzle, were measured. An analysis of the data from penetrations into thousands of clouds during all 18 flights supports these qualitative observations: In the polluted regions, the droplet concentrations were a factor of 3 higher, the droplet effective diameters were 35% smaller, and drizzle was observed 25% as often than in the pristine regions; in both polluted and pristine regions, the bulk cloud properties (liquid water content (LWC), vertical velocity, cloud horizontal dimensions) were approximately the same. Even larger differences in the microphysical properties between the high-CN, intermediate-CN, and low-CN regimes were noted when the data set was partitioned by the LWC. A high ratio offorward scattering spectrometer probe (FSSP) to CN concentrations was noted in the low-CN regime, whereas in the high-CN regime this ratio was small. Droplet growth calculations in an adiabatic, ID parcel model over a 300 m cloud depth support the droplet observations and indicate that the cloud optical depths in the high CN regime could have been as large as twice those in the low CN regime as a result of differences in the cloud condensation nucleus (CCN) population. The corresponding albedos of about 0.54 in the high CN regime and 0.47 in the low CN regime signify potentially large differences in albedo for the typical vertical velocities observed in INDOEX clouds, but it is unclear how entrainment would affect this difference. The calculations indicate that stronger updrafts associated with deep convection could lead to a larger difference between the microphysics of high-CN and low-CN regions.
114 citations
TL;DR: In this article, a direct and consistent application of dynamic and thermodynamic principles, in conjunction with parameterized microphysics, is proposed to facilitate numerical modeling of weather systems in a moist atmosphere.
Abstract: Moist convection is an exquisite yet powerful participant in the creation of weather on our planet. To facilitate numerical modeling of weather systems in a moist atmosphere, a direct and consistent application of dynamic and thermodynamic principles, in conjunction with parameterized microphysics, is proposed. An earlier formulation of reversible thermodynamics, in terms of the mass of air and water substance and the total entropy, is now extended to include the irreversible process of precipitation through parameterized microphysics. The dynamic equations are also formulated to account consistently for the mass and momentum of precipitation. The theoretical proposal is tested with a two-dimensional model that utilizes a versatile and accurate spectral method based on a cubic-spline representation of the spatial fields. In order to allow a wide range of scale interactions, the model is configured on multiply nested domains of outwardly decreasing resolution, with noise-free, two-way interfaces. ...
94 citations
TL;DR: In this paper, a broad range of sensitivity experiments are carried out so that the significance of each change to the model can be put into context, along with changes to the parametrization of microphysics and radiation in the CRM along with the influence of dimensionality, horizontal resolution and domain size.
Abstract: It is important to understand the variability of results which can be produced in a cloud-resolving model (CRM) before using its output to develop parametrizations. In the work presented here a broad range of sensitivity experiments are carried out so that the significance of each change to the model can be put into context. Changes to the parametrization of microphysics and radiation in the CRM are considered along with the influence of dimensionality, horizontal resolution and domain size. Further detailed sensitivity studies are then carried out to investigate the impact of the spatial and temporal distribution of the radiative heating.
The results presented show that, out of all the sensitivity studies considered, no particular feature or physical parametrization in a CRM dominates. The domain size, horizontal grid length, use of a third dimension and parametrization of microphysics all significantly impact the simulation in some way. Radiative heating has a large impact on the simulation because it dominates over the large-scale forcing above 8 km. However, the magnitude of this impact is strongly dependent on other aspects of the model, such as the choice of microphysical scheme. A diurnal cycle, which is inherent in the large-scale forcing, is not significantly enhanced by radiation in the CRM. However, accounting for the temporal and spatial variability in the radiative heating is important because neglecting this is shown to overestimate the strength of convection.
93 citations
TL;DR: In this paper, the circulation of H2SO4 in the Tropics was studied by simultaneously solving advection and cloud microphysics equations using a one-dimensional model that includes a weak upwelling representing the rising branch of Hadley circulation near the equator.
Abstract: As the global distribution of Venusian H2SO4–H2O clouds is strongly related to the global circulation of H2SO4 governed by wind transport and sedimentation of droplets, the circulation of H2SO4 in the Tropics was studied by simultaneously solving advection and cloud microphysics equations using a one-dimensional model that includes a weak upwelling representing the rising branch of Hadley circulation near the equator. H2SO4 vapor in the upper cloud region is supplied by photochemical production and condenses into cloud droplets that are removed from the tropical atmosphere by Hadley circulation, whereas in middle and lower cloud regions, dynamical processes supply H2SO4 vapor from below such that resultant droplets are large and fall against the upwelling. The combination of the mean upward advection of vapor and the sedimentation of droplets leads to accumulation of H2SO4 and H2O vapor near the cloud base: an observed phenomenon. A separate model run was performed to investigate the effect of tr...
69 citations
TL;DR: In this article, a three-dimensional cloud model for the study of formation and evolution of moist convective storms on the giant planets has been presented, which is a finite-difference model that solves the dynamic and thermodynamic equations forward in time under the anelastic approximation including microphysics in a parameterized form.
64 citations
TL;DR: A nested grid primitive equation model (RAMS version 3b) was used to simulate a high-precipitation (HP) supercell, which produced two weak tornadoes.
Abstract: A nested grid primitive equation model (RAMS version 3b) was used to simulate a high-precipitation (HP) supercell, which produced two weak tornadoes. Six telescoping nested grids allowed atmospheric flows ranging from the synoptic scale down to the tornadic scale to be represented in the simulation. All convection in the simulation was initiated with resolved vertical motion and subsequent condensation–latent heating from the model microphysics; no warm bubbles or cumulus parameterizations were used. Part I of this study focuses on the simulated storm evolution and its transition into a bow echo. The simulation initially produced a classic supercell that developed at the intersection between a stationary front and an outflow boundary. As the simulation progressed, additional storms developed and interacted with the main storm to produce a single supercell. This storm had many characteristics of an HP supercell and eventually evolved into a bow echo with a rotating comma-head structure. An analysi...
60 citations
TL;DR: Aircraft measurements of liquid water content (LWC) made at sampling frequencies of 1 and 2 kHz with a particle volume monitor (PVM) probe from horizontal traverses in stratocumulus clouds during the Southern Ocean Cloud Experiment (SOCE) and cumulus clouds in this article were described.
Abstract: Aircraft measurements of liquid water content (LWC) made at sampling frequencies of 1 and 2 kHz with a particle volume monitor (PVM) probe from horizontal traverses in stratocumulus clouds during the Southern Ocean Cloud Experiment and cumulus clouds during the Small Cumulus Microphysics Study are described. The spectral density of the LWC measurements is calculated and compared to the −5/3 scaling law. The effect of PVM sampling noise is found to be small in most cases. Most measurements follow approximately the −5/3 law until cloud scales decrease below about 5 m in length. Below this length LWC variance can exceed that predicted by the −5/3 law. It is suggested that the enhanced LWC variance at small scales is related to entrainment of environmental air into the clouds, which changes primarily the droplet concentration.
TL;DR: In this paper, a simple method for the inclusion of melting layer microwave radiative properties into cloud model simulations is presented for sensitivity studies of passive and active microwave signatures of rainclouds as well as for the generation of retrieval databases for aircraft and satellite radar/radiometer applications.
TL;DR: In this article, a one-dimensional version of a cloud model with an explicit microphysics scheme was used to simulate a case study of middle and upper level cloud formation and evolution that was observed during the FIRE Arctic Clouds Experiment.
Abstract: A one-dimensional version of a cloud model with an explicit microphysics scheme is used to simulate a case study of middle and upper level cloud formation and evolution that was observed during the FIRE Arctic Clouds Experiment. In the simulations, the midlevel altostratus cloud is initially liquid phase, then partially freezes, and exists in mixed phase for several hours with a relative equilibrium between the rate of drop production by condensation and their depletion by freezing. The dominant mode of cirrus formation was periodic homogeneous freezing of deliquescent submicron haze particles. These crystal layers form near the tropopause and, subsequently, precipitate into the middle troposphere, causing seeding of the underlying altostratus cloud. Sensitivity tests are conducted varying the initial humidity and nucleation schemes.
TL;DR: In this article, the authors used a size and composition-resolved externally mixed aerosol microphysical model and a delta-Eddington exponential-sum-fit radiation algorithm to examine the interactions between aerosol particles and cloud drops, and their influence on solar radiation.
Abstract: We use a size- and composition-resolved externally mixed aerosol microphysical model and a delta-Eddington exponential-sum-fit radiation algorithm to examine the interactions between aerosol particles and cloud drops, and their influence on solar radiation. Both the aerosol model and the radiation code are designed to explicitly handle external and internal aerosol particle and cloud drop mixtures. Using observations from the Monterey Area Ship Track (MAST) Experiment, we model changes in aerosol and cloud drop size distributions for a clean marine cloud and ship track and a continentally influenced marine cloud and ship track. Linking these results to the radiation algorithm with a Mie-scattering subroutine, we investigate the corresponding changes in cloud albedo, cloud absorption, and transmission. The differences in 0.3–3.0 μm albedo and transmission between the clouds and ship tracks as a result of the changes in drop size distribution and composition are found to be substantial, and the composition of the cloud drops is found to be important particularly in the continentally influenced case. Both the clouds and ship tracks enhance atmospheric absorption with respect to a clear sky, with a cloud forcing ratio ranging from 1.15 to 1.37, where the clear sky is defined to be cloud- and aerosol-free. Sensitivity studies are performed with respect to the updraft velocity, the updraft area fraction, dilution of the ship emissions, and the composition of supermicron continental particles. The radiation results are also compared with Meteorological Research Flight (MRF) C-130 in situ aircraft measurements and with parameterizations of the “Twomey effect.”
01 May 2001
TL;DR: In this paper, an explicit multiphase chemistry model coupled with quasi-spectral microphysics, based upon Berry and Reinhardt's parameterizations, has been initialized with polluted conditions as observed at the Puy de Dome mountain in the center of France and for a maritime cloud.
Abstract: Abstract An explicit multiphase chemistry model (Atm. Environ. 34 (29/30) (2000) 5015) has been coupled with quasi-spectral microphysics, based upon Berry and Reinhardt's parameterizations (1974a, b). This coupled model has been initialized with polluted conditions as observed at the Puy de Dome mountain in the center of France and for a maritime cloud. The presence of clouds results in two effects on multiphase chemistry: a direct effect through mass transfer, solubility and reactivity, and an indirect effect through microphysical transfer from cloud water into rainwater and redistribution of reactive soluble species among interstitial air, cloud droplets and raindrops. Results demonstrate that microphysical processes are necessary to sketch out the complex, nonlinear multiphase chemistry in a real cloud. In addition to the direct exchange through mass transfer, incorporation of reactive oxidants such as HO x in droplets can arise and consequently make those species no longer available for reacting in the gas-phase. Moreover, microphysical coalescence conversions favor NO x destruction and enhance the chemical nitric acid production. Coalescence of cloud drops to form rain transfers dissolved species into drops that are undersaturated compared to Henry's law equilibrium. The rain becomes a reservoir for these species, allowing aqueous chemistry to produce more nitric acid than would be possible without the presence of rain. Finally, for the different cloud types, the fate of those intermediate and reactive species is investigated, looking at their budget in clear sky situation versus cloudy and/or rainy situations.
TL;DR: In this article, a new bulk cloud microphysics scheme that accounts for aerosol microphysical properties and size distribution is implemented into the single-column version of the ARCSyM.
Abstract: A new bulk cloud microphysics scheme that accounts for aerosol microphysical properties and size distribution is implemented into the single-column version of the ARCSyM. This scheme is distinguished from other bulk microphysics schemes by its prognostic determination of cloud particle number concentration and saturation ratio. The new scheme is compared to a simpler bulk microphysics scheme and observations taken during the FIRE Arctic Clouds Experiment in May 1998. Qualitatively, the two microphysics schemes are generally in agreement with the observed cloud formation and evolution. Comparison with aircraft measurements at 3 times shows that the new scheme better discriminates cloud phase and reproduces reasonably well the observed liquid and ice water content for two cases. The better performance of the new scheme is attributed to its more elaborated treatment of the freezing process which is made possible by the prognostic determination of cloud particle number concentration and the assumption of a bimodal lognormal cloud size distribution. Sensitivity studies are performed to assess four aerosol microphysical properties on the evolution of cloud microphysical processes. Results show that the IFN concentration, the aerosol number concentration, the slope of the aerosol size distribution, and the aerosol solubility may impact substantially on cloud phase and total water content. The liquid water path and ice water path can vary by as much as 100 g m−2 locally as a result of the variation of these parameters related to aerosols.
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TL;DR: In this paper, it is shown that the mysterious quantum prescription of microphysics has analogues at the scale of stars, galaxies and superclusters, the common feature in all these cases being Brownian type fractality.
Abstract: It is shown that the mysterious quantum prescription of microphysics has analogues at the scale of stars, galaxies and superclusters, the common feature in all these cases being Brownian type fractality. These considerations are shown to lead to pleasingly meaningful results in agreement with observed data.
TL;DR: In this article, an explicit multiphase chemistry model was coupled with quasi-spectral microphysics, based upon Berry and Reinhardt's parameterizations, to sketch out the complex, nonlinear multi-phase chemistry in a real cloud.
TL;DR: An aerosol microphysics dataset was used to model backscatter in the 0.35-11-mum wavelength range, with the results validated by comparison with measured cw and pulsed lidarBackscatter obtained during two NASA-sponsored airborne field experiments.
Abstract: An aerosol microphysics dataset was used to model backscatter in the 0.35-11-mum wavelength range, with the results validated by comparison with measured cw and pulsed lidar backscatter obtained during two NASA-sponsored airborne field experiments. Different atmospheric features were encountered, with aerosol backscatter ranging over 4 orders of magnitude. Modeled conversion functions were used to convert existing lidar backscatter datasets to 2.1 mum. Resulting statistical distribution shows the midtropospheric aerosol backscatter background mode of beta(2.1) to be between ~3.0 x 10(-10) and ~1.3 x 10(-9) m(-1) sr(-1), ~10-20 times higher than that for beta(9.1); and a beta(2.1) boundary layer mode of ~1.0 x 10(-7) to ~1.3 x 10(-6) m(-1) sr(-1), ~3-5 times higher than beta(9.1).
TL;DR: A mesoscale simulation of the 19-21 July 1996 Saguenay flood cyclone was performed using the Canadian Mesoscale Compressible Community (MC2) model to study the processes leading to the explosive development and the large amount of precipitation.
Abstract: A mesoscale simulation of the 19–21 July 1996 Saguenay flood cyclone was performed using the Canadian Mesoscale Compressible Community (MC2) model to study the processes leading to the explosive development and the large amount of precipitation. The performance of the simulation is verified by careful comparison with available observations with particular emphasis on the quantitative forecast of precipitation. It was shown that the model accurately simulates the wind, temperature, and humidity fields. Using the Kong and Yau microphysics scheme, the model performs quite well in the threat scores over a broad range of precipitation thresholds. Comparison of model precipitation against an objective analysis from rain gauge measurements and against the time evolution of accumulated precipitation at specific sites indicates generally good agreement except that the magnitude of the maxima is about 10% lower in the simulation. Potential vorticity (PV) inversion and sensitivity experiments show that the ...
TL;DR: In this paper, four different Atmospheric Radiation Measurement Program Cloud and Radiation Test Bed (ARM-CART) datasets were used to force an SCM in a number of simulations performed to study the influence of land surface fluxes on precipitation, which broadly confirmed the previous findings that an increase in the solar absorption and surface evaporation helps to increase the local rainfall, but they also reveal that the magnitude of the rainfall increase is strongly affected by the ability of the background circulation to promote moist convection.
Abstract: Four different Atmospheric Radiation Measurement Program Cloud and Radiation Test Bed (ARM–CART) Single-Column Model (SCM) datasets were used to force an SCM in a number of simulations performed to study the influence of land surface fluxes on precipitation. The SCM employed Goddard Earth Observing System (GEOS-2) GCM physics, which includes a recent version of prognostic cloud scheme (Microphysics of Clouds with Relaxed Arakawa–Schubert), and a land model (Simplified Simple Biosphere Model) coupled to a highly resolved soil hydrological description in the vertical. The four ARM–CART datasets employed in these studies are referred as case 1, case 3, case 4, and case 8. The SCM simulation results broadly confirm the previous findings that an increase in the solar absorption and surface evaporation helps to increase the local rainfall, but they also reveal that the magnitude of the rainfall increase is strongly affected by the ability of the background circulation to promote moist convection. The s...
TL;DR: In this paper, the authors investigated the possible effects of hygroscopic flare seeding on the changes in the spectra of hydrometeors and the resulting radar-derived properties, such as storm rain mass, rain flux, and rainfall amount.
Abstract: Numerical calculations using a cloud model with detailed microphysics are conducted to investigate the possible effects of hygroscopic flare seeding on the changes in the spectra of hydrometeors and the resulting radar-derived properties, such as storm rain mass, rain flux, and rainfall amount. The results indicate that, in continental clouds, seeding can significantly change the distribution functions of the precipitation particles, the radar reflectivity–rainfall (Z–R) relationship, and the radar-derived properties. Therefore, different Z–R relationships derived respectively from unseeded and seeded clouds should be used to estimate properly the effects of seeding with hygroscopic flares. The results also show that the effects of hygroscopic seeding on maritime clouds are small and there is little difference in the Z–R relationship and the precipitation properties between the seeded and the unseeded cases.
TL;DR: In this article, it was observed that some sections of the aerosol size distribution trade water thus limiting the time that a section may experience the aqueous chemistry and three characteristic times explain the trading of water between different sections during the cloud's lifetime, and why transport to particles is fast or slow in different distributions.
TL;DR: In this paper, an optimal estimation approach is applied to the physical retrieval of single-layer cloud optical properties (optical depth and effective radius) using multispectral imager channels on the western Geostationary Operational Environmental Satellite (GOES 10).
Abstract: An optimal estimation approach is applied to the physical retrieval of single-layer cloud optical properties (optical depth and effective radius) using multispectral imager channels on the western Geostationary Operational Environmental Satellite (GOES 10). The retrieval includes diagnostic information pertaining to uncertainty and dependence on a priori assumptions required by the forward model. Satellite retrievals of 0.65-μm cloud optical depth and effective radius (micrometers) for marine stratocumulus (in both drizzle and drizzle-free conditions) during the CloudSat Antecedent Validation Experiment and tropical cirrus during the Atmospheric Radiation Measurement (ARM)-Unmanned Aerospace Vehicle spring flight series are examined together with data from the NASA/Jet Propulsion Laboratory Airborne Cloud Radar (ACR), the ARM Cloud Detection Lidar, and the Colorado State University Scanning Spectral Polarimeter (SSP) instruments. Optical depths are found to be consistent between GOES and SSP after taking into account the degradation of responsivity in GOES channel 1. Colocated ACR/GOES observations support past evidence that passive satellite detection of drizzle size droplets (in terms of a significant positive bias in the retrieved effective radius) may be possible under certain conditions. The ability of a dual lidar/radar active observing system to provide independent information over different cloud particle size regimes is illustrated and speaks to the vertical variability of cloud microphysics. The GOES estimate of effective radius was found to be more representative of the upper 0.5 km of the cirrus clouds examined.
TL;DR: In this article, a new flux method is presented for the numerical solution of the stochastic collection equation (SCE) in cloud models dealing with two-component cloud microphysics.
TL;DR: It is argued that the appearance ofviolation is illusory, and the worry about coincidence misleading, and the authors cannot expect the special sciences at the level of the microparticles.
Abstract: More laws obtain in the world,it appears, than just those of microphysics –e.g. laws of genetics, perceptual psychology,economics. This paper assumes there indeedare laws in the special sciences, and notjust scrambled versions of microphysical laws. Yet the objects which obey them are composedwholly of microparticles. How can themicroparticles in such an object lawfully domore than what is required of them by the lawsof microphysics? Are there additional laws formicroparticles – which seems to violate closureof microphysics – or is the ``more'' acoincidental outcome of microphysics itself? This paper argues that the appearance ofviolation is illusory, and the worry aboutcoincidence misleading. We cannot expect tounderstand the special sciences at the level ofthe microparticles.
01 Jan 2001
TL;DR: In this article, a transition from the classical mechanics of Newton and his successors to the electrodynamics of Maxwell, Boltzmann, Gibbs, and others indicated a transition to microphysics; when applied to explain the behaviour of atomic and molecular ensembles, it exhibited serious limitations of the classical approach.
Abstract: The invention of quantum and wave mechanics and the great, if not complete, progress achieved by these theories in describing atomic, molecular, solid-state and—to some extent—nuclear phenomena, established a domain of microphysics in addition to the previously existing macrophysics. To the latter domain of classical theories created since the 17th century applied—principally, the mechanics of Newton and his successors, and the electrodynamics of Maxwell, Hertz, Lorentz, and Einstein. The statistical mechanics of Maxwell, Boltzmann, Gibbs, Einstein, and others indicated a transition to microphysics; when applied to explain the behaviour of atomic and molecular ensembles, it exhibited serious limitations of the classical approach. Classical theories were closely connected with a continuous description of matter and the local causality of physical processes. The microscopic phenomena exhibited discontinuities, ‘quantum’ features, which demanded changes from the classical description.
01 Jan 2001
TL;DR: A modular and flexible particle-based Lattice Solid Model (LSM) was developed to provide a basis to study the physics of rocks and the non-linear dynamics of earthquakes as mentioned in this paper.
Abstract: The particle-based Lattice Solid Model (LSM) was developed to provide a basis to study the physics of rocks and the non-linear dynamics of earthquakes. In previous work, intact material was modelled as particles bonded together by elastic-brittle links in a regular 2D triangular lattice and the model was applied to the study of fault zone evolution. A new modular and flexible LSM approach has been developed that allows different microphysics to be easily added and removed at the grain scale to enable the effect of different microphysics on macroscopic behaviour to be studied. The model is extended to allow three-dimensional simulations to be performed and particles of different sizes to be specified. The new model provides a basis to investigate nucleation, rupture and slip pulse propagation in complex fault zones without the previous model limitation of a regular low-level surface geometry.
TL;DR: A brief comparison of some of the methods that have been introduced can be found in this article, where the authors compare the most common accelerator models are stochastic in nature and involve nonequilibrium plasma properties that are also often poorly understood.
Abstract: Cosmic-ray acceleration, although physically important in many astrophysical contexts, is difficult to incorporate into numerical models,. because it involves microphysics that is generally far from thermodynamic equilibrium, and also because the length and time scales for that physics typically range over many orders of magnitude, reflecting the huge range of particle rigidities that must be represented. The most common accelerator models are stochastic in nature and involve nonequilibrium plasma properties that are also often poorly understood. Still, nature clearly finds a way to produce simple, robust and almost scale-free energy distributions for the cosmic-rays. Their importance has inspired a number of approaches to examining the production and transport of cosmic-ray particles in numerical simulations. I offer here a brief comparison of some of the methods that have been introduced.