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De Rijcke, S., R. Verbeke, and T. Boelens. "The dynamics of general relativistic isotropic stellar cluster models: Do relativistic extensions of the Plummer model exist?" Monthly Notices of the Royal Astronomical Society 445, no. 3 (2014): 2404–13. http://dx.doi.org/10.1093/mnras/stu1912.
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Pridgen, Annette K., and W. Mark Wilder. "Relevance of GASB No. 34 to Financial Reporting by Municipal Governments." Accounting Horizons 27, no. 2 (2012): 175–204. http://dx.doi.org/10.2308/acch-50377.
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SYNOPSIS The Governmental Accounting Standards Board issued Statement No. 34, creating a new accrual-based financial reporting model. This study examines whether information from this model is associated with the default risk (a proxy for fiscal distress) of municipal governments and whether this information is incremental to that provided by the fund-based, modified-accrual reporting model. Ordered logistic regressions are used to analyze financial data from 2005 for a sample of 409 municipalities that participated in the Government Finance Officers Association award program. This study extends the work of Plummer et al. (2007) to municipal governments. In addition to the financial position indicator variable (total net assets/total revenues) examined by Plummer et al. (2007), this study provides evidence of the relevance of three other financial indicators (change in net assets/total net assets; total liabilities/total assets; and current assets/current liabilities). We also find that these accrual-based indicators provide information incremental to the fund-based model and that one fund-based measure (total fund balances/total fund revenues) also provides information incremental to the accrual indicator. These results are consistent with perceptions of regulators and others who expect accrual accounting to be a better measure of the economic costs of running a government than the traditional fund-based model. Data Availability: Contact the authors.
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Funato, Y., and J. Marino. "Evolution of Galaxies Through Their Interactions." Symposium - International Astronomical Union 171 (1996): 378. http://dx.doi.org/10.1017/s007418090023297x.
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We investigated how the encounters between galaxies change their mass M and velocity dispersion σ. We carried out a series of direct N-body simulation of encounters of two spherical galaxies. In Figure 1, the relative change of energy ΔE/E are plotted against that of mass ΔM/M for various initial conditions. The filled and open symbols correspond to the cases of Plummer model and relaxed Hernquist model, respectively. Here β ≡ (ΔE/E)/(ΔM/M).
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Matus Carrillo, D. R., M. Fellhauer, A. G. Alarcon Jara, C. A. Aravena, and F. Urrutia Zapata. "Modelling the Canes Venatici I dwarf spheroidal galaxy." Astronomy & Astrophysics 633 (January 2020): A91. http://dx.doi.org/10.1051/0004-6361/201935602.
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The aim of this work is to find a progenitor for Canes Venatici I (CVn I), under the assumption that it is a dark matter free object that is undergoing tidal disruption. With a simple point mass integrator, we searched for an orbit for this galaxy using its current position, position angle, and radial velocity in the sky as constraints. The orbit that gives the best results has the pair of proper motions μα = −0.099 mas yr−1 and μδ = −0.147 mas yr−1, that is, an apogalactic distance of 242.79 kpc and a perigalactic distance of 20.01 kpc. Using a dark matter free progenitor that undergoes tidal disruption, the best-fitting model matches the final mass, surface brightness, effective radius, and velocity dispersion of CVn I simultaneously. This model has an initial Plummer mass of 2.47 × 107 M⊙ and a Plummer radius of 653 pc, producing a remnant after 10 Gyr with a final mass of 2.45 × 105 M⊙, a central surface brightness of 26.9 mag arcsec−2, an effective radius of 545.7 pc, and a velocity dispersion with the value 7.58 km s−1. Furthermore, it is matching the position angle and ellipticity of the projected object in the sky.
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Ninkovic, S., and A. Valjarevic. "On the density and surface brightness profiles in globular star clusters." Serbian Astronomical Journal, no. 174 (2007): 43–46. http://dx.doi.org/10.2298/saj0774043n.
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A model of mass distribution, applicable to globular star clusters and proposed earlier, is reconsidered. It is shown that it can be related to the well-known Plummer-Schuster formula, and the equations yielding its dimensionless parameters are given. The corresponding surface density is calculated numerically. It is indicated that in a general case the surface density should not be proportional to the surface brightness and a more adequate formula relating these two quantities is proposed. .
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Frutos-Alfaro, F. "Reduction of the gravitational lens equation to a one-dimensional non-linear form for the tilted Plummer model family." Monthly Notices of the Royal Astronomical Society: Letters 376, no. 1 (2007): L72—L75. http://dx.doi.org/10.1111/j.1745-3933.2007.00289.x.
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Voth Schrag, Rachel J., and Kristen Ravi. "Measurement of Economic Abuse Among Women Not Seeking Social or Support Services and Dwelling in the Community." Violence and Victims 35, no. 1 (2020): 3–19. http://dx.doi.org/10.1891/0886-6708.vv-d-18-00154.
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Scholars have defined economic abuse (EA) as tactics used by abusive partners to undermine the self-sufficiency and economic self-efficacy of survivors of intimate partner violence (IPV). However, no measures of EA have been tested in non-IPV-service seeking samples. The current study assesses the psychometric properties of the Scale of Economic Abuse (SEA)-12 (Postmus, Plummer, & Stylianou, 2016) in a nonservice seeking sample of adult females attending community college. A quantitative web-based survey was administered to a simple random sample of female community college students (n = 435). Analyses included confirmatory factor analysis (CFA) and exploratory factor analysis (EFA). CFA indicated a poor fit for the three-factor model of the SEA-12 in this sample. The results of the EFA found a single factor model retaining four items (the Scale of Economic Abuse-Short, or SEAS). Women are experiencing EA outside of IPV service-seeking populations, and that tactics of economic control seem to be central to EA in this sample.
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Statler, Thomas S., Jeremiah P. Ostriker, and Haldan N. Cohn. "Evolution of Globular Clusters by Tidally-Captured Binaries through Core Collapse." Symposium - International Astronomical Union 126 (1988): 667–68. http://dx.doi.org/10.1017/s0074180900043527.
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We present calculations of globular cluster evolution performed by a modified Fokker-Planck approach, in which binaries formed by tidal capture are followed explicitly, along with subsequent heating mechanisms. The cluster is simulated by a two component model, using the cross sections of Press and Teukolsky (1977) for tidal capture, those of Hut (1984) for the single-binary encounters and for distant binary-binary encounters, and those of Mikkola (1983) for the strong binary-binary encounters. The initial state of the cluster is a Plummer model with N = 3 × 105 and scale radius ro = 1.13 pc. All stars are identical, with mass M∗ = 0.7M⊙ and R∗ = 0.57R⊙. This gives an initial core radius rc = 0.8 pc, and one-dimensional dispersion σ = 11.6 km s-1. All binaries are assumed to be identical, with separation a = 2.5R∗. There are no binaries in the cluster initially. Additional important effects, such as tidal truncation, tidal shocks, stellar evolution and mass loss, and stellar mergers, are not included.
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Baes, Maarten, Peter Camps, and Bert Vandenbroucke. "SpheCow: Flexible dynamical models for galaxies and dark matter haloes." Astronomy & Astrophysics 652 (August 2021): A36. http://dx.doi.org/10.1051/0004-6361/202141281.
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Simple but flexible dynamical models are useful for many purposes, including serving as the starting point for more complex models or numerical simulations of galaxies, clusters, or dark matter haloes. We present SpheCow, a new light-weight and flexible code that allows one to easily explore the structure and dynamics of any spherical model. Assuming an isotropic or Osipkov-Merritt anisotropic orbital structure, the code can automatically calculate the dynamical properties of any model with either an analytical density profile or an analytical surface density profile as starting point. We have extensively validated SpheCow using a combination of comparisons to analytical and high-precision numerical calculations, as well as the calculation of inverse formulae. SpheCow contains readily usable implementations for many standard models, including the Plummer, Hernquist, NFW, Einasto, Sérsic, and Nuker models. The code is publicly available as a set of C++ routines and as a Python module, and it is designed to be easily extendable, in the sense that new models can be added in a straightforward way. We demonstrate this by adding two new families of models in which either the density slope or the surface density slope is described by an algebraic sigmoid function. We advocate the use of the SpheCow code to investigate the full dynamical structure for models for which the distribution function cannot be expressed analytically and to explore a much wider range of models than is possible using analytical models alone.
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Carlotti, P., and G. R. Hunt. "An entrainment model for lazy turbulent plumes." Journal of Fluid Mechanics 811 (December 15, 2016): 682–700. http://dx.doi.org/10.1017/jfm.2016.714.
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An entrainment model for lazy turbulent plumes is proposed, the resulting solutions of the plume conservation equations are developed and the implications for plume behaviour are considered and compared with the available experimental data. Indeed, the applicability of the classic solutions of the conservation equations subject to source conditions that produce lazy plumes, i.e. those with suitably high source Richardson number, contains an essential weakness: the underlying assumption of a constant entrainment coefficient. While entrainment models prescribing the dependence of the entrainment coefficient on the local Richardson number have been proposed for forced plumes, corresponding formulations for lazy plumes have not until now been considered. In the context of saline plumes, the model is applied directly. For hot gaseous plumes, we use a modified definition of buoyancy flux to recover a constant buoyancy flux in a non-stratified environment, despite the specific heat varying with the temperature. After a brief review of existing forced-plume formulations of entrainment, a power-law variation is adopted for the lazy plume. The plume equations are solved for the parameter $0\leqslant \unicode[STIX]{x1D714}<1$, where $\unicode[STIX]{x1D714}$ denotes the exponent of the power law. The cases of pure plumes and lazy plumes are then analysed in more detail; to the best of our knowledge this represents the first modelling of variable entrainment for lazy plumes. Specifically, it is shown that classic plume theory is recovered for $\unicode[STIX]{x1D714}=0$, while for $\unicode[STIX]{x1D714}=1/5$ the plume equations may be solved using usual functions (notably polynomials) only. The results of the models for these cases are very similar, which advocates the idea of selecting systematically $\unicode[STIX]{x1D714}=1/5$, instead of $\unicode[STIX]{x1D714}=0$, for cases where the effect of variation of entrainment is weak, since the new model leads to simple calculations. In the case of very lazy plumes, it is shown that, provided that a relevant value of $\unicode[STIX]{x1D714}$ is chosen, the new model reproduces the available experimental results well.
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Hanawa, Tomoyuki, Takahiro Kudoh, and Kohji Tomisaka. "Fragmentation of a Filamentary Cloud Threaded by Perpendicular Magnetic Field." Proceedings of the International Astronomical Union 14, A30 (2018): 105. http://dx.doi.org/10.1017/s1743921319003600.
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AbstractFilamentary molecular clouds are thought to fragment to form clumps and cores. However, the fragmentation may be suppressed by magnetic force if the magnetic fields run perpendicularly to the cloud axis. We evaluate the effect using a simple model. Our model cloud is assumed to have a Plummer like radial density distribution, $\rho = {\rho _{\rm{c}}}{\left[ {1 + {r^2}/(2p{H^2})} \right]^{2p}}$ , where r and H denote the radial distance from the cloud axis and the scale length, respectively. The symbols, ρc and p denote the density on the axis and radial density index, respectively. The initial magnetic field is assumed to be uniform and perpendicular to the cloud axis. The model cloud is assumed to be supported against the self gravity by gas pressure and turbulence. We have obtained the growth rate of the fragmentation instability as a function of the wavelength, according to the method of Hanawa, Kudoh & Tomisaka (2017). The instability depends crucially on the outer boundary. If the displacement vanishes in regions very far from the cloud axis, cloud fragmentation is suppressed by a moderate magnetic field. If the displacement is constant along the magnetic field in regions very far from the cloud, the cloud is unstable even when the magnetic field is infinitely strong. The wavelength of the most unstable mode is longer for smaller index, p.
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Rooney, G. G. "Merging of two or more plumes arranged around a circle." Journal of Fluid Mechanics 796 (May 11, 2016): 712–31. http://dx.doi.org/10.1017/jfm.2016.272.
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A model is presented of merging turbulent plumes from sources evenly spaced around a horizontal circle in a quiescent, unstratified background. This follows the previously developed method of (i) identifying the boundaries of interacting plumes with velocity-potential contours of line sinks and (ii) closing the generalised plume equations with an entrainment assumption based on the integrated flux across the plume boundaries. It includes the simplest case of two merging plumes, as well as being applicable to plume flows in restricted corner configurations. The model is shown to display the expected limiting behaviour for the source plumes and the merged plume. Consideration of the plume fluxes in the merging region leads to a revision of the entrainment assumption. The resulting revised model compares satisfactorily with previous estimates of volume flux in two merging plumes.
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THEERTHAN, S. ANANDA, and JAYWANT H. ARAKERI. "A model for near-wall dynamics in turbulent Rayleigh–Bénard convection." Journal of Fluid Mechanics 373 (October 25, 1998): 221–54. http://dx.doi.org/10.1017/s0022112098002407.
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Experiments indicate that turbulent free convection over a horizontal surface (e.g. Rayleigh–Bénard convection) consists of essentially line plumes near the walls, at least for moderately high Rayleigh numbers. Based on this evidence, we propose here a two-dimensional model for near-wall dynamics in Rayleigh–Bénard convection and in general for convection over heated horizontal surfaces. The model proposes a periodic array of steady laminar two-dimensional plumes. A plume is fed on either side by boundary layers on the wall. The results from the model are obtained in two ways. One of the methods uses the similarity solution of Rotem & Classen (1969) for the boundary layer and the similarity solution of Fuji (1963) for the plume. We have derived expressions for mean temperature and temperature and velocity fluctuations near the wall. In the second approach, we compute the two-dimensional flow field in a two-dimensional rectangular open cavity. The number of plumes in the cavity depends on the length of the cavity. The plume spacing is determined from the critical length at which the number of plumes increases by one. The results for average plume spacing and the distribution of r.m.s. temperature and velocity fluctuations are shown to be in acceptable agreement with experimental results.
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Zhuang, Jiawei, Daniel J. Jacob, and Sebastian D. Eastham. "The importance of vertical resolution in the free troposphere for modeling intercontinental plumes." Atmospheric Chemistry and Physics 18, no. 8 (2018): 6039–55. http://dx.doi.org/10.5194/acp-18-6039-2018.
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Abstract. Chemical plumes in the free troposphere can preserve their identity for more than a week as they are transported on intercontinental scales. Current global models cannot reproduce this transport. The plumes dilute far too rapidly due to numerical diffusion in sheared flow. We show how model accuracy can be limited by either horizontal resolution (Δx) or vertical resolution (Δz). Balancing horizontal and vertical numerical diffusion, and weighing computational cost, implies an optimal grid resolution ratio (Δx ∕ Δz)opt ∼ 1000 for simulating the plumes. This is considerably higher than current global models (Δx ∕ Δz ∼ 20) and explains the rapid plume dilution in the models as caused by insufficient vertical resolution. Plume simulations with the Geophysical Fluid Dynamics Laboratory Finite-Volume Cubed-Sphere Dynamical Core (GFDL-FV3) over a range of horizontal and vertical grid resolutions confirm this limiting behavior. Our highest-resolution simulation (Δx ≈ 25 km, Δz ≈ 80 m) preserves the maximum mixing ratio in the plume to within 35 % after 8 days in strongly sheared flow, a drastic improvement over current models. Adding free tropospheric vertical levels in global models is computationally inexpensive and would also improve the simulation of water vapor.
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Plant, R. S., and G. C. Craig. "A Stochastic Parameterization for Deep Convection Based on Equilibrium Statistics." Journal of the Atmospheric Sciences 65, no. 1 (2008): 87–105. http://dx.doi.org/10.1175/2007jas2263.1.
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Abstract A stochastic parameterization scheme for deep convection is described, suitable for use in both climate and NWP models. Theoretical arguments and the results of cloud-resolving models are discussed in order to motivate the form of the scheme. In the deterministic limit, it tends to a spectrum of entraining/detraining plumes and is similar to other current parameterizations. The stochastic variability describes the local fluctuations about a large-scale equilibrium state. Plumes are drawn at random from a probability distribution function (PDF) that defines the chance of finding a plume of given cloud-base mass flux within each model grid box. The normalization of the PDF is given by the ensemble-mean mass flux, and this is computed with a CAPE closure method. The characteristics of each plume produced are determined using an adaptation of the plume model from the Kain–Fritsch parameterization. Initial tests in the single-column version of the Unified Model verify that the scheme is effective in producing the desired distributions of convective variability without adversely affecting the mean state.
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Apsley, D. D., and G. F. Lane-Serff. "Collapse of particle-laden buoyant plumes." Journal of Fluid Mechanics 865 (February 28, 2019): 904–27. http://dx.doi.org/10.1017/jfm.2019.74.
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Particle loading affects the dynamics of buoyant plumes, since the difference between particle and fluid densities is much greater than that in the fluid alone. In stratified environments, plume rise is density limited; after initial overshoot, the plume reaches a terminal level and spreads radially. Particles dropping from this horizontal intrusion may be re-entrained. This recycling of dense matter reduces plume buoyancy and intrusion height and, for sufficient load, can lead to plume collapse. Entrainment-based formulae yield a steady-state plume rise. We identify a new conserved quantity for such plumes. Integrating paths of particles dropping from the intrusion yields the fraction re-entrained. A simple mathematical model predicts from buoyancy ratio at source ($P=$ negative particle buoyancy divided by positive fluid buoyancy) whether a particle-laden plume will collapse. Under this model, for small settling velocity, a particle-laden plume will not collapse if $P<0.368$. Above this, collapse depends also on the amount of particle-free ambient fluid entrained in the overshoot region. For pure plumes, experimental evidence suggests that this is small. For forced plumes, more substantial overshoot and entrainment is shown to increase the critical ratio. An extension, based on successive recycling, estimates time to collapse. To investigate further we develop a simple computational model, coupling a ‘top-hat’ plume model, an analytical formula for radially decaying concentrations in the intrusion and an axisymmetric finite-volume solution for time-dependent settling and entrainment. The model can predict the impact of particle load on final rise, as well as the occurrence and time scales of plume collapse.
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Holland, Paul R., and Daniel L. Feltham. "The Effects of Rotation and Ice Shelf Topography on Frazil-Laden Ice Shelf Water Plumes." Journal of Physical Oceanography 36, no. 12 (2006): 2312–27. http://dx.doi.org/10.1175/jpo2970.1.
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Abstract A model of the dynamics and thermodynamics of a plume of meltwater at the base of an ice shelf is presented. Such ice shelf water plumes may become supercooled and deposit marine ice if they rise (because of the pressure decrease in the in situ freezing temperature), so the model incorporates both melting and freezing at the ice shelf base and a multiple-size-class model of frazil ice dynamics and deposition. The plume is considered in two horizontal dimensions, so the influence of Coriolis forces is incorporated for the first time. It is found that rotation is extremely influential, with simulated plumes flowing in near-geostrophy because of the low friction at a smooth ice shelf base. As a result, an ice shelf water plume will only rise and become supercooled (and thus deposit marine ice) if it is constrained to flow upslope by topography. This result agrees with the observed distribution of marine ice under Filchner–Ronne Ice Shelf, Antarctica. In addition, it is found that the model only produces reasonable marine ice formation rates when an accurate ice shelf draft is used, implying that the characteristics of real ice shelf water plumes can only be captured using models with both rotation and a realistic topography.
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Woodhouse, M. J., J. C. Phillips, and A. J. Hogg. "Unsteady turbulent buoyant plumes." Journal of Fluid Mechanics 794 (April 5, 2016): 595–638. http://dx.doi.org/10.1017/jfm.2016.101.
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We model the unsteady evolution of turbulent buoyant plumes following temporal changes to the source conditions. The integral model is derived from radial integration of the governing equations expressing the evolution of mass, axial momentum and buoyancy in the plume. The non-uniform radial profiles of the axial velocity and density deficit in the plume are explicitly captured by shape factors in the integral equations; the commonly assumed top-hat profiles lead to shape factors equal to unity. The resultant model for unsteady plumes is hyperbolic when the momentum shape factor, determined from the radial profile of the mean axial velocity in the plume, differs from unity. The solutions of the model when source conditions are maintained at constant values are shown to retain the form of the well-established steady plume solutions. We demonstrate through a linear stability analysis of these steady solutions that the inclusion of a momentum shape factor in the governing equations that differs from unity leads to a well-posed integral model. Therefore, our model does not exhibit the mathematical pathologies that appear in previously proposed unsteady integral models of turbulent plumes. A stability threshold for the value of the shape factor is also identified, resulting in a range of its values where the amplitudes of small perturbations to the steady solutions decay with distance from the source. The hyperbolic character of the system of equations allows the formation of discontinuities in the fields describing the plume properties during the unsteady evolution, and we compute numerical solutions to illustrate the transient development of a plume following an abrupt change in the source conditions. The adjustment of the plume to the new source conditions occurs through the propagation of a pulse of fluid through the plume. The dynamics of this pulse is described by a similarity solution and, through the construction of this new similarity solution, we identify three regimes in which the evolution of the transient pulse following adjustment of the source qualitatively differs.
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KAYE, N. B., and M. M. SCASE. "Straight-sided solutions to classical and modified plume flux equations." Journal of Fluid Mechanics 680 (June 20, 2011): 564–73. http://dx.doi.org/10.1017/jfm.2011.214.
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The classical plume model due to Morton, Taylor & Turner (Proc. R. Soc. Lond. A, vol. 234, 1956, pp. 1–23) is re-cast in terms of the non-dimensional plume radius, the plume ‘laziness’ defined as the squared ratio of the source radius and the jet length, and the buoyancy flux. It is shown that many of the key results of this classical model can then be read straight from the equations without recourse to solving them. Based on this observation, derivative models that consider plumes propagating through stratified environments or undergoing chemical reactions are similarly re-cast. We show again that key results can be read straight from the governing equations and results that have previously only been demonstrated numerically can be found analytically. In particular, we unify two previously distinct models that consider plumes propagating through stable and unstable stratified environments whose stratification has a power-law dependence on height. We present analytical solutions for the range of stratification power-law decay rates for which straight-sided plumes are possible. This result unifies the sets of solutions by Batchelor (Q. J. R. Meteorol. Soc., vol. 80, 1954, pp. 339–358) and Caulfield & Woods (J. Fluid Mech., vol. 360, 1998, pp. 229–248). We are able to explain the unstable behaviour previously found when the power lies in the range (−4, −8/3). Finally we show that this method also has limited advantages when applied to plumes with unsteady source conditions.
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Craske, John, and Maarten van Reeuwijk. "Generalised unsteady plume theory." Journal of Fluid Mechanics 792 (March 9, 2016): 1013–52. http://dx.doi.org/10.1017/jfm.2016.72.
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We develop a generalised unsteady plume theory and compare it with a new direct numerical simulation (DNS) dataset for an ensemble of statistically unsteady turbulent plumes. The theoretical framework described in this paper generalises previous models and exposes several fundamental aspects of the physics of unsteady plumes. The framework allows one to understand how the structure of the governing integral equations depends on the assumptions one makes about the radial dependence of the longitudinal velocity, turbulence and pressure. Consequently, the ill-posed models identified by Scase & Hewitt (J. Fluid Mech., vol. 697, 2012, pp. 455–480) are shown to be the result of a non-physical assumption regarding the velocity profile. The framework reveals that these ill-posed unsteady plume models are degenerate cases amongst a comparatively large set of well-posed models that can be derived from the generalised unsteady plume equations that we obtain. Drawing on the results of DNS of a plume subjected to an instantaneous step change in its source buoyancy flux, we use the framework in a diagnostic capacity to investigate the properties of the resulting travelling wave. In general, the governing integral equations are hyperbolic, becoming parabolic in the limiting case of a ‘top-hat’ model, and the travelling wave can be classified as lazy, pure or forced according to the particular assumptions that are invoked to close the integral equations. Guided by observations from the DNS data, we use the framework in a prognostic capacity to develop a relatively simple, accurate and well-posed model of unsteady plumes that is based on the assumption of a Gaussian velocity profile. An analytical solution is presented for a pure straight-sided plume that is consistent with the key features observed from the DNS.
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Griffin, Debora, Christopher Sioris, Jack Chen, et al. "The 2018 fire season in North America as seen by TROPOMI: aerosol layer height intercomparisons and evaluation of model-derived plume heights." Atmospheric Measurement Techniques 13, no. 3 (2020): 1427–45. http://dx.doi.org/10.5194/amt-13-1427-2020.
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Abstract. Before the launch of the TROPOspheric Monitoring Instrument (TROPOMI), only two other satellite instruments were able to observe aerosol plume heights globally, the Multi-angle Imaging SpectroRadiometer (MISR) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The TROPOMI aerosol layer height is a potential game changer, since it has daily global coverage, and the aerosol layer height retrieval is available in near real time. The aerosol layer height can be useful for aviation and air quality alerts, as well as for improving air quality forecasting related to wildfires. Here, TROPOMI's aerosol layer height product is evaluated with MISR and CALIOP observations for wildfire plumes in North America for the 2018 fire season (June to August). Further, observing system simulation experiments were performed to interpret the fundamental differences between the different products. The results show that MISR and TROPOMI are, in theory, very close for aerosol profiles with single plumes. For more complex profiles with multiple plumes, however, different plume heights are retrieved; the MISR plume height represents the top layer, and the plume height retrieved with TROPOMI tends to have an average altitude of several plume layers. The comparison between TROPOMI and MISR plume heights shows that, on average, the TROPOMI aerosol layer heights are lower, by approximately 600 m, compared to MISR, which is likely due to the different measurement techniques. From the comparison to CALIOP, our results show that the TROPOMI aerosol layer height is more accurate over dark surfaces, for thicker plumes, and plumes between approximately 1 and 4.5 km. MISR and TROPOMI are further used to evaluate the plume height of Environment and Climate Change Canada's operational forecasting system FireWork with fire plume injection height estimates from the Canadian Forest Fire Emissions Prediction System (CFFEPS). The modelled plume heights are similar compared to the satellite observations but tend to be slightly higher with average differences of 270–580 and 60–320 m compared to TROPOMI and MISR, respectively.
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LIMA NETO, IRAN E., and PRISCILA A. B. PARENTE. "Influence of mass transfer on bubble plume hydrodynamics." Anais da Academia Brasileira de Ciências 88, no. 1 (2016): 411–22. http://dx.doi.org/10.1590/0001-3765201520140453.
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ABSTRACT This paper presents an integral model to evaluate the impact of gas transfer on the hydrodynamics of bubble plumes. The model is based on the Gaussian type self-similarity and functional relationships for the entrainment coefficient and factor of momentum amplification due to turbulence. The impact of mass transfer on bubble plume hydrodynamics is investigated considering different bubble sizes, gas flow rates and water depths. The results revealed a relevant impact when fine bubbles are considered, even for moderate water depths. Additionally, model simulations indicate that for weak bubble plumes (i.e., with relatively low flow rates and large depths and slip velocities), both dissolution and turbulence can affect plume hydrodynamics, which demonstrates the importance of taking the momentum amplification factor relationship into account. For deeper water conditions, simulations of bubble dissolution/decompression using the present model and classical models available in the literature resulted in a very good agreement for both aeration and oxygenation processes. Sensitivity analysis showed that the water depth, followed by the bubble size and the flow rate are the most important parameters that affect plume hydrodynamics. Lastly, dimensionless correlations are proposed to assess the impact of mass transfer on plume hydrodynamics, including both the aeration and oxygenation modes.
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Stockmann, Fabienne, Laura Cobden, Frédéric Deschamps, Andreas Fichtner, and Christine Thomas. "Investigating the seismic structure and visibility of dynamic plume models with seismic array methods." Geophysical Journal International 219, Supplement_1 (2019): S167—S194. http://dx.doi.org/10.1093/gji/ggz334.
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SUMMARY Mantle plumes may play a major role in the transport of heat and mass through the Earth, but establishing their existence and structure using seismology has proven challenging and controversial. Previous studies have mainly focused on imaging plumes using waveform modelling and inversion (i.e. tomography). In this study we investigate the potential visibility of mantle plumes using array methods, and in particular whether we can detect seismic scattering from the plumes. By combining geodynamic modelling with mineral physics data we compute ‘seismic’ plumes whose shape and structure correspond to dynamically plausible thermochemical plumes. We use these seismic models to perform a full-waveform simulation, sending seismic waves through the plumes, in order to generate synthetic seismograms. Using velocity spectral analysis and slowness-backazimuth plots, we are unable to detect scattering. However at longer dominant periods (25 s) we see several arrivals from outside the plane of the great circle path, that are consistent with an apparent bending of the wave front around the plume conduit. At shorter periods (15 s), these arrivals are less obvious and less strong, consistent with the expected changes in the waves' behaviour at higher frequencies. We also detect reflections off the iron-rich chemical pile which serves as the plume source in the D″ region, indicating that D″ reflections may not always be due to a phase transformation. We suggest that slowness-backazimuth analysis may be a useful tool to locate mantle plumes in real array data sets. However, it is important to analyse the data at different dominant periods since, depending on the width of the plume, there is probably an optimum frequency band at which the plume is most visible. Our results also show the importance of studying the incoming energy in all directions, so that any apparently out-of-plane arrivals can be correctly interpreted.
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Carroll, Dustin, David A. Sutherland, Emily L. Shroyer, Jonathan D. Nash, Ginny A. Catania, and Leigh A. Stearns. "Modeling Turbulent Subglacial Meltwater Plumes: Implications for Fjord-Scale Buoyancy-Driven Circulation." Journal of Physical Oceanography 45, no. 8 (2015): 2169–85. http://dx.doi.org/10.1175/jpo-d-15-0033.1.
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AbstractFjord-scale circulation forced by rising turbulent plumes of subglacial meltwater has been identified as one possible mechanism of oceanic heat transfer to marine-terminating outlet glaciers. This study uses buoyant plume theory and a nonhydrostatic, three-dimensional ocean–ice model of a typical outlet glacier fjord in west Greenland to investigate the sensitivity of meltwater plume dynamics and fjord-scale circulation to subglacial discharge rates, ambient stratification, turbulent diffusivity, and subglacial conduit geometry. The terminal level of a rising plume depends on the cumulative turbulent entrainment and ambient stratification. Plumes with large vertical velocities penetrate to the free surface near the ice face; however, midcolumn stratification maxima create a barrier that can trap plumes at depth as they flow downstream. Subglacial discharge is varied from 1–750 m3 s−1; large discharges result in plumes with positive temperature and salinity anomalies in the upper water column. For these flows, turbulent entrainment along the ice face acts as a mechanism to vertically transport heat and salt. These results suggest that plumes intruding into stratified outlet glacier fjords do not always retain the cold, fresh signature of meltwater but may appear as warm, salty anomalies. Fjord-scale circulation is sensitive to subglacial conduit geometry; multiple point source and line plumes result in stronger return flows of warm water toward the glacier. Classic plume theory provides a useful estimate of the plume’s outflow depth; however, more complex models are needed to resolve the fjord-scale circulation and melt rates at the ice face.
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Burton, Ralph R., Mark J. Woodhouse, Alan M. Gadian, and Stephen D. Mobbs. "The Use of a Numerical Weather Prediction Model to Simulate Near-Field Volcanic Plumes." Atmosphere 11, no. 6 (2020): 594. http://dx.doi.org/10.3390/atmos11060594.
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In this paper, a state-of the art numerical weather prediction (NWP) model is used to simulate the near-field plume of a Plinian-type volcanic eruption. The NWP model is run at very high resolution (of the order of 100 m) and includes a representation of physical processes, including turbulence and buoyancy, that are essential components of eruption column dynamics. Results are shown that illustrate buoyant gas plume dynamics in an atmosphere at rest and in an atmosphere with background wind, and we show that these results agree well with those from theoretical models in the quiescent atmosphere. For wind-blown plumes, we show that features observed in experimental and natural settings are reproduced in our model. However, when comparing with predictions from an integral model using existing entrainment closures there are marked differences. We speculate that these are signatures of a difference in turbulent mixing for uniform and shear flow profiles in a stratified atmosphere. A more complex implementation is given to show that the model may also be used to examine the dispersion of heavy volcanic gases such as sulphur dioxide. Starting from the standard version of the weather research and forecasting (WRF) model, we show that minimal modifications are needed in order to model volcanic plumes. This suggests that the modified NWP model can be used in the forecasting of plume evolution during future volcanic events, in addition to providing a virtual laboratory for the testing of hypotheses regarding plume behaviour.
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Pimenta, Felipe M., A. D. Kirwan, and Pablo Huq. "On the Transport of Buoyant Coastal Plumes." Journal of Physical Oceanography 41, no. 3 (2011): 620–40. http://dx.doi.org/10.1175/2010jpo4473.1.
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Abstract The role of discharge conditions and shelf geometry on the transport of coastal plumes is studied with a fully nonlinear, primitive equation hydrodynamic model. The physical setting is an estuarine channel with a small discharge Rossby number. By simulating different discharge magnitudes, buoyant plumes are shown to be succinctly described by a simple coastal front model. Three results emerge from the model analysis. First, the plume transport is given by T = γ0(g′ph2/2f ), where γ0 is a parameter dependent on the ratio of the front and the plume widths, g′p is the plume reduced gravity, h is the plume maximum depth, and f is the Coriolis parameter. Second, this model links the plume transport directly to upstream river conditions with T = γQr, where Qr is the river outflow and γ is a parameter that relates to entrainment, the geometry of the plume front and shelf slope, and the fraction of freshwater carried downshelf. Third, these equations reduce to analytic results previously established for special cases, providing useful formulas to estimate the plume transport from hydrographic and river discharge observations.
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WOODS, ANDREW W. "A note on non-Boussinesq plumes in an incompressible stratified environment." Journal of Fluid Mechanics 345 (August 25, 1997): 347–56. http://dx.doi.org/10.1017/s0022112097006332.
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The recent work of Rooney & Linden (1996) is generalized to describe the motion of non-Boussinesq plumes in both uniform and stratified environments. Using an integral model in which the horizontal entrainment velocity is assumed to take the form uε=α(ρ¯/ρe) 1/2w where α is the entrainment coefficient, ρ¯ is the plume density, w the plume velocity and ρe the ambient density, it is shown that the vertical scale over which non-Boussinesq effects are significant is given by zB=5/3 (B2o/ (20α4g3))1/5 where Bo is the buoyancy flux at the source. In a uniform environment, the system admits similarity solutions such that the location of the source of a real plume lies a distance zB[mid ]ρo/Δρ[mid ] −5/3 beyond the point source of the similarity solution. The above entrainment law implies a fundamental difference between the motion of upward and downward propagating non-Boussinesq plumes, with the radius of upward propagating plumes being greater than that of the equivalent Boussinesq plume, while the radius of downward propagating plumes is smaller. In a stratified but incompressible environment the model predicts that non-Boussinesq effects are confined close to the source and that at each height, the plume velocity and the fluxes of mass, momentum and buoyancy coincide exactly with those of the equivalent Boussinesq plume. Furthermore, at the neutral buoyancy height, the plume radius equals that of the equivalent Boussinesq plume.
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Eastham, Sebastian D., and Daniel J. Jacob. "Limits on the ability of global Eulerian models to resolve intercontinental transport of chemical plumes." Atmospheric Chemistry and Physics 17, no. 4 (2017): 2543–53. http://dx.doi.org/10.5194/acp-17-2543-2017.
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Abstract. Quasi-horizontal chemical plumes in the free troposphere can preserve their concentrated structure for over a week, enabling transport on intercontinental scales with important environmental impacts. Global Eulerian chemical transport models (CTMs) fail to preserve these plumes due to fast numerical dissipation. We examine the causes of this dissipation and how it can be cured. Goddard Earth Observing System (GEOS-5) meteorological data at 0.25° × 0.3125° horizontal resolution and ∼ 0.5 km vertical resolution in the free troposphere are used to drive a worldwide ensemble of GEOS-Chem CTM plumes at resolutions from 0.25° × 0.3125° to 4° × 5°, in both 2-D (horizontal) and 3-D. Two-dimensional simulations enable examination of the sensitivity of numerical dissipation to grid resolution. We show that plume decay is driven by flow divergence and shear, filamenting the plumes until GEOS-Chem's high-order advection scheme cannot resolve gradients and fast numerical diffusion ensues. This divergence can be measured by the Lyapunov exponent (λ) of the flow. Dissipation of plumes is much faster at extratropical latitudes than in the tropics and this can be explained by stronger divergence. The plume decay constant (α) is linearly related to λ, and increasing grid resolution provides only modest benefits toward plume preservation. Three-dimensional simulations show near-complete dissipation of plumes within a few days, independent of horizontal grid resolution and even in the tropics. This is because vertical grid resolution is inadequate in all cases to properly resolve plume gradients. We suggest that finer vertical grid resolution in the free troposphere is essential for models to resolve intercontinental plumes, while current horizontal resolution in these models (∼ 1°) is sufficient.
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Koptev, Alexander, Sierd Cloetingh, and Todd A. Ehlers. "Longevity of small-scale (‘baby’) plumes and their role in lithospheric break-up." Geophysical Journal International 227, no. 1 (2021): 439–71. http://dx.doi.org/10.1093/gji/ggab223.
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SUMMARY Controversy between advocates of ‘active’ (plume-activated) versus ‘passive’ (driven by external tectonic stresses) modes of continental rifting and break-up has persisted for decades. To a large extent, inconsistencies between observations and models are rooted in the conceptual model of plumes as voluminous upwellings of hot material sourced from the deep mantle. Such large-scale plumes are expected to induce intensive magmatism and topographic uplift, thereby triggering rifting. In this case of an ‘active’ rifting-to-break-up system, emplacement of plume-related magmatism should precede the onset of rifting that is not observed in many rifted continental margins, thus providing a primary argument in favour of an antiplume origin for continental break-up and supercontinent fragmentation. However, mantle plumes are not restricted to whole-mantle (‘primary’) plumes emanating from the mantle-core boundary but also include ‘secondary’ plumes originating from the upper mantle transition zone or shallower. Over the last decades a number of such ‘secondary’ plumes with horizontal diameters of only ∼100–200 km (therefore, sometimes also called ‘baby’ plumes) have been imaged in the upper mantle below Europe and China. The longevity of such small-scale plumes and their impact on geodynamics of continental break-up have so far not been explored. We present results of a systematic parametrical analysis of relatively small thermal anomalies seeded at the base of the lithosphere. In particular, we explore the effects of variations in initial plume temperature (T = 1500–1700 °C) and size (diameter of 80–116 km), characteristics of the overlying lithosphere (e.g. ‘Cratonic’, ‘Variscan’, ‘Mesozoic’ and oceanic) and intraplate tectonic regimes (neutral or far-field extension of 2–10 mm yr–1). In tectonically neutral regimes, the expected decay time of a seismically detectable ‘baby’-plume varies from ∼20 to &gt;200 Myr and is mainly controlled by its initial size and temperature, whereas the effect of variations in the thermotectonic age of the overlying lithosphere is modest. These small but enduring plumes are able to trigger localized rifting and subsequent continental break-up occurring from ∼10 to &gt;300 Myr after the onset of far-field extension. Regardless of the thermomechanical structure of the lithosphere, relatively rapid (tens of Myr) break-up (observed in models with a hot plume and fast extension) favours partial melting of plume material. In contrast, in the case of a long-lasting (a few hundreds of Myr) pre-break-up phase (relatively cold plume, low extension rate), rifting is accompanied by modest decompressional melting of only ‘normal’ sublithospheric mantle. On the basis of the models presented, we distinguish two additional modes of continental rifting and break-up: (1) ‘semi-active’ when syn-break-up magmatism is carrying geochemical signatures of the deep mantle with deformation localized above the plume head not anymore connected by its tail to the original source of hot material and (2) ‘semi-passive’ when the site of final lithospheric rupture is controlled by a thermal anomaly of plume origin but without invoking its syn-break-up melting. These intermediate mechanisms are applicable to several segments of the passive continental margins formed during Pangea fragmentation.
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van den Bremer, T. S., and G. R. Hunt. "Two-dimensional planar plumes: non-Boussinesq effects." Journal of Fluid Mechanics 750 (June 4, 2014): 245–58. http://dx.doi.org/10.1017/jfm.2014.252.
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AbstractIn an accompanying paper (van den Bremer & Hunt, J. Fluid Mech., vol. 750, 2014, pp. 210–244) closed-form solutions, describing the behaviour of two-dimensional planar turbulent rising plumes from horizontal planar area and line sources in unconfined quiescent environments of uniform density, that are universally applicable to Boussinesq and non-Boussinesq plumes, are proposed. This universality relies on an entrainment velocity unmodified by non-Boussinesq effects, an assumption that is derived in the literature based on similarity arguments and is, in fact, in contradiction with the axisymmetric case, in which entrainment is modified by non-Boussinesq effects. Exploring these solutions, we show that a non-Boussinesq plume model predicts exactly the same behaviour with height for a pure plume as would a Boussinesq model, whereas the effects on forced and lazy plumes are opposing. Non-intuitively, the non-Boussinesq model predicts larger fluxes of volume and mass for lazy plumes, but smaller fluxes for forced plumes at any given height compared to the Boussinesq model. This raises significant questions regarding the validity of the unmodified entrainment model for planar non-Boussinesq plumes based on similarity arguments and calls for detailed experiments to resolve this debate.
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Kumar, R. K., H. W. Chiang, and F. Kalos. "Entrainment and Mixing in Vertical Buoyant Light-Gas Plumes." Journal of Energy Resources Technology 118, no. 1 (1996): 77–81. http://dx.doi.org/10.1115/1.2792697.
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A simple model is developed to determine the entrainment coefficient and the spread of a light-gas plume in a quiescent atmosphere. Experiments performed with low-velocity saltwater/freshwater and helium-in-air jets indicate that buoyant gas plumes spread significantly faster than thermal plumes. The calculated effluent concentrations are in excellent agreement with those measured when an entrainment coefficient of 0.15 is used in the plume equations. This is significantly higher than the entrainment coefficients of 0.075 to 0.093 reported for thermal plumes.
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Pols, S., A. Schwörer, P. Schilke, A. Schmiedeke, Á. Sánchez-Monge, and Th Möller. "The physical and chemical structure of Sagittarius B2." Astronomy & Astrophysics 614 (June 2018): A123. http://dx.doi.org/10.1051/0004-6361/201732498.
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Context. We model the emission of methyl cyanide (CH3CN) lines towards the massive hot molecular core Sgr B2(M). Aims. We aim to reconstruct the CH3CN abundance field, and investigate the gas temperature distribution as well as the velocity field. Methods. Sgr B2(M) was observed with the Atacama Large Millimeter/submillimeter Array (ALMA) in a spectral line survey from 211 to 275 GHz. This frequency range includes several transitions of CH3CN (including isotopologues and vibrationally excited states). We employed the three-dimensional radiative transfer toolbox Pandora in order to retrieve the velocity and abundance field by modeling different CH3CN lines. For this purpose, we based our model on the results of a previous study that determined the physical structure of Sgr B2(M), i.e., the distribution of dust dense cores, ionized regions, and heating sources. Results. The morphology of the CH3CN emission can be reproduced by a molecular density field that consists of a superposition of cores with modified Plummer-like density profiles. The averaged relative abundance of CH3CN with respect to H2 ranges from 4 × 10−11 to 2 × 10−8 in the northern part of Sgr B2(M) and from 2 × 10−10 to 5 × 10−7 in the southern part. In general, we find that the relative abundance of CH3CN is lower at the center of the very dense, hot cores, causing the general morphology of the CH3CN emission to be shifted with respect to the dust continuum emission. The dust temperature calculated by the radiative transfer simulation based on the available luminosity reaches values up to 900 K. However, in some regions vibrationally excited transitions of CH3CN are underestimated by the model, indicating that the predicted gas temperature, which is assumed to be equal to the dust temperature, is partly underestimated. The determination of the velocity component along the line of sight reveals that a velocity gradient from the north to the south exists in Sgr B2(M).
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Meir, Talmor, Julie Pullen, Alan F. Blumberg, Teddy R. Holt, Paul E. Bieringer, and George Bieberbach. "Simulation of Airborne Transport and Dispersion for Urban Waterside Releases." Journal of Applied Meteorology and Climatology 56, no. 1 (2017): 27–44. http://dx.doi.org/10.1175/jamc-d-16-0025.1.
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AbstractResults are presented from a tracer-release modeling study designed to examine atmospheric transport and dispersion (“T&D”) behavior surrounding the complex coastal–urban region of New York City, New York, where air–sea interaction and urban influences are prominent. The puff-based Hazard Prediction Assessment Capability (HPAC, version 5) model is run for idealized conditions, and it is also linked with the urbanized COAMPS (1 km) meteorological model and the NAM (12 km) meteorological model. Results are compared with “control” plumes utilizing surface meteorological input from 22 weather stations. In all configurations, nighttime conditions result in plume predictions that are more sensitive to small changes in wind direction. Plume overlap is reduced by up to 70% when plumes are transported during the night. An analysis of vertical plume cross sections and the nature of the underlying transport and the dispersion equations both suggest that heat flux gradients and boundary layer height gradients determine vertical transport of pollutants across land–sea boundaries in the T&D model. As a consequence, in both idealized and realistic meteorological configurations, waterfront releases generate greater plume discrepancies relative to plumes transported over land/urban surfaces. For transport over water (northwest winds), the higher-fidelity meteorological model (COAMPS) generated plumes with overlap reduced by about one-half when compared with that of the coarser-resolution NAM model (13% vs 24% during the daytime and 11% vs 18% during the nighttime). This study highlights the need for more sophisticated treatment of land–sea transition zones in T&D calculations covering waterside releases.
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Gabriel, A. H., F. Bely-Dubau, E. Tison, and L. Abbo. "Understanding structures at the base of the solar corona – polar plumes." Proceedings of the International Astronomical Union 4, S257 (2008): 145–49. http://dx.doi.org/10.1017/s1743921309029196.
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AbstractRecent work on coronal polar plumes (Gabriel et al. 2003, 2005) has aimed at determining the outflow velocity in plume and interplume regions, using the Doppler dimming technique on oxygen VI observations by SUMER and UVCS on SOHO. By comparing observations of SOHO/EIT with plume modelling, we show that the major part of plumes is the result of chance alignments along the line-of-sight of small enhancements in intensity. This confirms the so-called curtain model. These plumes can be attributed to reconnection activity along the boundaries of supergranule cells. A second population of plumes has a lower abundance and arises from surface bright points having a particular magnetic configuration. New observations using the Hinode/EIS spectrometer are in progress, with the aim of providing further insight for this model.
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Dupont, R., B. Pierce, J. Worden, et al. "Attribution and evolution of ozone from Asian wild fires using satellite and aircraft measurements during the ARCTAS campaign." Atmospheric Chemistry and Physics 12, no. 1 (2012): 169–88. http://dx.doi.org/10.5194/acp-12-169-2012.
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Abstract. We use ozone and carbon monoxide measurements from the Tropospheric Emission Spectrometer (TES), model estimates of Ozone, CO, and ozone pre-cursors from the Real-time Air Quality Modeling System (RAQMS), and data from the NASA DC8 aircraft to characterize the source and dynamical evolution of ozone and CO in Asian wildfire plumes during the spring ARCTAS campaign 2008. On the 19 April, NASA DC8 O3 and aerosol Differential Absorption Lidar (DIAL) observed two biomass burning plumes originating from North-Western Asia (Kazakhstan) and South-Eastern Asia (Thailand) that advected eastward over the Pacific reaching North America in 10 to 12 days. Using both TES observations and RAQMS chemical analyses, we track the wildfire plumes from their source to the ARCTAS DC8 platform. In addition to photochemical production due to ozone pre-cursors, we find that exchange between the stratosphere and the troposphere is a major factor influencing O3 concentrations for both plumes. For example, the Kazakhstan and Siberian plumes at 55 degrees North is a region of significant springtime stratospheric/tropospheric exchange. Stratospheric air influences the Thailand plume after it is lofted to high altitudes via the Himalayas. Using comparisons of the model to the aircraft and satellite measurements, we estimate that the Kazakhstan plume is responsible for increases of O3 and CO mixing ratios by approximately 6.4 ppbv and 38 ppbv in the lower troposphere (height of 2 to 6 km), and the Thailand plume is responsible for increases of O3 and CO mixing ratios of approximately 11 ppbv and 71 ppbv in the upper troposphere (height of 8 to 12 km) respectively. However, there are significant sources of uncertainty in these estimates that point to the need for future improvements in both model and satellite observations. For example, it is challenging to characterize the fraction of air parcels from the stratosphere versus those from the fire because of the low sensitivity of the TES CO estimates used to mark stratospheric air versus air parcels affected by the smoke plume. Model transport uncertainties, such as too much dispersion, results in a broad plume structure from the Kazakhstan fires that is approximately 2 km lower than the plume observed by aircraft. Consequently, the model and TES data do not capture the photochemical production of ozone in the Kazakhstan plume that is apparent in the aircraft in situ data. However, ozone and CO distributions from TES and RAQMS model estimates of the Thailand plume are within the uncertainties of the TES data. Therefore, the RAQMS model is better able to characterize the emissions from this fire, the mixing of ozone from the stratosphere to the plume, and the photochemical production and transport of ozone and ozone pre-cursors as the plume moves across the Pacific.
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Suselj, Kay, Marcin J. Kurowski, and João Teixeira. "On the Factors Controlling the Development of Shallow Convection in Eddy-Diffusivity/Mass-Flux Models." Journal of the Atmospheric Sciences 76, no. 2 (2019): 433–56. http://dx.doi.org/10.1175/jas-d-18-0121.1.
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Abstract This study addresses key aspects of shallow moist convection, as simulated by a multiplume eddy-diffusivity/mass-flux (EDMF) model. Two factors suggested in the literature to be essential for the development of convective plumes are investigated: surface conditions and lateral entrainment. The model consistently decomposes the subgrid vertical mixing into convective plumes and the nonconvective environment. The modeled convection shows low sensitivity to the surface plume area. The results indicate that plume development in the subcloud layer is controlled by both surface conditions and lateral entrainment. Their impact significantly changes in the cloud layer where the surface conditions are no longer important. The development of shallow convection is dominated by the interactions between the plumes and the large-scale field and is sensitive to the representation of the variability of thermodynamic properties between the plumes. A simple two-layer model of steady-state convection is proposed to help understand the role of these processes in shaping the properties of moist convection.
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Kimura, Satoshi, Paul R. Holland, Adrian Jenkins, and Matthew Piggott. "The Effect of Meltwater Plumes on the Melting of a Vertical Glacier Face." Journal of Physical Oceanography 44, no. 12 (2014): 3099–117. http://dx.doi.org/10.1175/jpo-d-13-0219.1.
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Abstract Freshwater produced by the surface melting of ice sheets is commonly discharged into ocean fjords from the bottom of deep fjord-terminating glaciers. The discharge of the freshwater forms upwelling plumes in front of the glacier calving face. This study simulates the meltwater plumes emanated into an unstratified environment using a nonhydrostatic ocean model with an unstructured mesh and subgrid-scale mixing calibrated by comparison to established plume theory. The presence of an ice face reduces the entrainment of seawater into the meltwater plumes, so the plumes remain attached to the ice front, in contrast to previous simple models. Ice melting increases with height above the discharge, also in contrast to some simple models, and the authors speculate that this “overcutting” may contribute to the tendency of icebergs to topple inwards toward the ice face upon calving. The overall melt rate is found to increase with discharge flux only up to a critical value, which depends on the channel size. The melt rate is not a simple function of the subglacial discharge flux, as assumed by many previous studies. For a given discharge flux, the geometry of the plume source also significantly affects the melting, with higher melt rates obtained for a thinner, wider source. In a wider channel, two plumes are emanated near the source and these plumes eventually coalesce. Such merged meltwater plumes ascend faster and increase the maximum melt rate near the center of the channel. The melt rate per unit discharge decreases as the subglacial system becomes more channelized.
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Preisler, Jan, and Edward S. Yeung. "Characterization of Matrix-Assisted Laser Desorption Based on Absorption and Acoustic Monitoring." Applied Spectroscopy 49, no. 12 (1995): 1826–33. http://dx.doi.org/10.1366/0003702953965920.
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Conventional methods for studying matrix-assisted desorption-ionization rely on mass spectroscopy. In this study, a 488-nm argon-ion laser beam is deflected by two acoustooptic deflectors to image plumes desorbed at atmospheric pressure via absorption. All species, including neutral molecules, are monitored. Interesting features, e.g., differences between the initial plume and subsequent plumes desorbed from the same spot, or the formation of two plumes from one laser shot, are observed. Total plume absorbance can be correlated with the acoustic signal generated by the desorption event. A model equation for the plume velocity as a function of time is proposed. Optical probing also enables accurate determination of plume velocities at reduced pressures. These results define the optimal conditions for desorbing analytes from matrices, as opposed to achieving a compromise between efficient desorption and efficient ionization as is practiced in mass spectrometry.
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Surl, Luke, Tjarda Roberts, and Slimane Bekki. "Observation and modelling of ozone-destructive halogen chemistry in a passively degassing volcanic plume." Atmospheric Chemistry and Physics 21, no. 16 (2021): 12413–41. http://dx.doi.org/10.5194/acp-21-12413-2021.
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Abstract. Volcanoes emit halogens into the atmosphere that undergo complex chemical cycling in plumes and cause destruction of ozone. We present a case study of the Mount Etna plume in the summer of 2012, when the volcano was passively degassing, using aircraft observations and numerical simulations with a new 3D model “WRF-Chem Volcano” (WCV), incorporating volcanic emissions and multi-phase halogen chemistry. Measurements of SO2 – an indicator of plume intensity – and ozone were made in the plume a few tens of kilometres from Etna, revealing a strong negative correlation between ozone and SO2 levels. From these observations, using SO2 as a tracer species, we estimate a mean in-plume ozone loss rate of 1.3×10−5 molecules of O3 per second per molecule of SO2. This value is similar to observation-based estimates reported very close to Etna's vents, indicating continual ozone loss in the plume up to at least tens of kilometres downwind. The WCV model is run with nested grids to simulate the plume close to the volcano at 1 km resolution. The focus is on the early evolution of passively degassing plumes aged less than 1 h and up to tens of kilometres downwind. The model is able to reproduce the so-called “bromine explosion”: the daytime conversion of HBr into bromine radicals that continuously cycle in the plume. These forms include the radical BrO, a species whose ratio with SO2 is commonly measured in volcanic plumes as an indicator of halogen ozone-destroying chemistry. The species BrO is produced in the ambient-temperature chemistry, with in-plume BrO / SO2 ratios on the order of 10−4 mol/mol, similar to those observed previously in Etna plumes. Wind speed and time of day are identified as non-linear controls on this ratio. Sensitivity simulations confirm the importance of near-vent radical products from high-temperature chemistry in initiating the ambient-temperature plume halogen cycling. Heterogeneous reactions that activate bromine also activate a small fraction of the emitted chlorine; the resulting production of chlorine radical Cl strongly enhances the methane oxidation and hence the formation of formaldehyde (HCHO) in the plume. Modelled rates of ozone depletion are found to be similar to those derived from aircraft observations. Ozone destruction in the model is controlled by the processes that recycle bromine, with about three-quarters of this recycling occurring via reactions between halogen oxide radicals. Through sensitivity simulations, a relationship between the magnitude of halogen emissions and ozone loss is established. Volcanic halogen cycling profoundly impacts the overall plume chemistry in the model, notably hydrogen oxide radicals (HOx), nitrogen oxides (NOx), sulfur, and mercury chemistry. In the model, it depletes HOx within the plume, increasing the lifetime of SO2 and hence slowing sulfate aerosol formation. Halogen chemistry also promotes the conversion of NOx into nitric acid (HNO3). This, along with the displacement of nitrate out of background aerosols in the plume, results in enhanced HNO3 levels and an almost total depletion of NOx in the plume. The halogen–mercury model scheme is simple but includes newly identified photo-reductions of mercury halides. With this set-up, the mercury oxidation is found to be slow and in near-balance with the photo-reduction of the plume. Overall, the model findings demonstrate that halogen chemistry has to be considered for a complete understanding of sulfur, HOx, reactive nitrogen, and mercury chemistry and of the formation of sulfate particles in volcanic plumes.
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Holland, Paul R. "Oscillating Dense Plumes." Journal of Physical Oceanography 41, no. 8 (2011): 1465–83. http://dx.doi.org/10.1175/2011jpo4532.1.
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Abstract The flow of dense polar shelf waters down continental slopes is a critical component of the global ocean circulation. Recent observations suggest that such plumes can be heavily impacted by tidal variability, and many of the world’s important dense-water sources are located in tidally active areas. Tides affect the source of dense water (by modulating the location of hydrographic gradients) and control the subsequent plume mixing and flow path. In an effort to separate these effects, dense plumes are modeled here by extending a classical one-dimensional plume model to two unsteady scenarios in which the plume path is fixed. The first case features a pulsed release of dense water into a stagnant ambient, and the model predicts that gravity waves propagate down the plume. Advective waves in plume density travel with the mean velocity of the current and thus have a wavelength of , the product of plume velocity and the oscillation period P. The second case is of a steady-sourced plume flowing through an ambient that has uniformly oscillating flow. This drives fluctuating shear at the plume–ambient interface (and/or seabed) that leads to variable entrainment of ambient fluid into the plume. Perturbed properties are subsequently advected by the plume, leading to standing “entrainment waves” that also have a wavelength of . Pulsed-source effects may be distinguished from variable-entrainment effects by the phase difference between waves in the different state variables of each plume. Both effects are maximized when the ratio , where L is the plume length. This condition is satisfied in the Ross Sea, Antarctica, where observations show dense plumes that are strongly affected by tides. Modeled pulsed-source effects qualitatively agree with the observations, implying that hydrographic variability in Ross Sea plumes is associated with variability in their dense-water source rather than unsteady plume mixing. These results might help inform the gathering and interpretation of oceanographic data in tidally active dense-water source regions.
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Brando, V. E., F. Braga, L. Zaggia, et al. "High-resolution satellite turbidity and sea surface temperature observations of river plume interactions during a significant flood event." Ocean Science 11, no. 6 (2015): 909–20. http://dx.doi.org/10.5194/os-11-909-2015.
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Abstract. Sea surface temperature (SST) and turbidity (T) derived from Landsat 8 (L8) imagery were used to characterize river plumes in the northern Adriatic Sea (NAS) during a significant flood event in November 2014. Circulation patterns and sea surface salinity (SSS) from an operational coupled ocean-wave model supported the interpretation of the plumes' interaction with the receiving waters and among them. There was a good agreement of the SSS, T, and SST fields at the sub-mesoscale and mesoscale delineation of the major river plumes. L8 30 m resolution also enabled the description of smaller plume structures. The different plumes' reflectance spectra were related to the lithological fingerprint of the sediments in the river catchments. Sharp fronts in T and SST delimited each single river plume. The isotherms and turbidity isolines' coupling varied among the plumes due to differences in particle loads and surface temperatures in the discharged waters. The surface expressions of all the river plumes occurring in NAS were classified based on the occurrence of the plume dynamical regions in the L8 30 m resolution imagery.
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Zender, C. S., A. G. Krolewski, M. G. Tosca, and J. T. Randerson. "Tropical biomass burning smoke plume size, shape, reflectance, and age based on 2001–2009 MISR imagery of Borneo." Atmospheric Chemistry and Physics Discussions 11, no. 11 (2011): 30989–1030. http://dx.doi.org/10.5194/acpd-11-30989-2011.
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Abstract. Land clearing for crops and plantations and grazing results in anthropogenic burning of tropical forests and peatlands in Indonesia, where images of fire-generated aerosol plumes have been captured by the Multi-angle Imaging SpectroRadiometer (MISR) since 2001. Our modeling studies show this smoke increases atmospheric heating, and reduces regional SST and dry-season precipitation, causing a potential feedback that increases drought-stress and air quality problems during El Niño years. Here we analyze the size, shape, optical properties, and age of fire-generated plumes in Borneo from 2001–2009. Most smoke flows with the prevailing southeasterly surface winds at 3–4 m s−1, and forms ovoid plumes whose mean length, height, and cross-plume width are 41 ± 1.4 (mean ± std. error) km, 708 ± 13 m, and 27 ± 0.75% of the plume length, respectively. Borneo smoke plume heights are similar to previously reported plume heights, yet Borneo plumes are nearly three times longer than previously studied plumes, possibly due to more persistent fires and greater fuel loads in peatlands than in other tropical forests. Plume area (median 169 ± 15 km2) varies exponentially with length, though for most plumes a linear relation provides a good approximation. The MISR-estimated plume optical properties involve greater uncertainties than the geometric properties, and show patterns consistent with smoke aging. Optical depth increases by 15–25% in the down-plume direction, consistent with hygroscopic growth and nucleation overwhelming the effects of particle dispersion. Both particle single-scattering albedo and top-of-atmosphere albedo peak about halfway down-plume, at values about 3% and 10% greater than at the origin, respectively. The initially oblong plumes become brighter and more circular with time, increasingly resembling smoke clouds. Wind speed does not explain a significant fraction of the variation in plume geometry. We provide a parameterization of plume shape that can help atmospheric models estimate the effects of plumes on weather, climate, and air quality. Plume age, the age of smoke furthest down-plume, is lognormally distributed with a median of 2.8 ± 0.3 h, significantly different than median ages reported in other studies. Intercomparison of our results with previous studies shows that the shape, height, optical depth, and lifetime characteristics reported for tropical biomass burning plumes on three continents are dissimilar and distinct from the same characteristics of wildfire plumes from the extratropics.
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Zender, C. S., A. G. Krolewski, M. G. Tosca, and J. T. Randerson. "Tropical biomass burning smoke plume size, shape, reflectance, and age based on 2001–2009 MISR imagery of Borneo." Atmospheric Chemistry and Physics 12, no. 7 (2012): 3437–54. http://dx.doi.org/10.5194/acp-12-3437-2012.
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Abstract. Land clearing for crops, plantations and grazing results in anthropogenic burning of tropical forests and peatlands in Indonesia, where images of fire-generated aerosol plumes have been captured by the Multi-angle Imaging SpectroRadiometer (MISR) since 2001. Here we analyze the size, shape, optical properties, and age of distinct fire-generated plumes in Borneo from 2001–2009. The local MISR overpass at 10:30 a.m. misses the afternoon peak of Borneo fire emissions, and may preferentially sample longer plumes from persistent fires burning overnight. Typically the smoke flows with the prevailing southeasterly surface winds at 3–4 m s−1, and forms ovoid plumes whose mean length, height, and cross-plume width are 41 km, 708 m, and 27% of the plume length, respectively. 50% of these plumes have length between 24 and 50 km, height between 523 and 993 m and width between 18% and 30% of plume length. Length and cross-plume width are lognormally distributed, while height follows a normal distribution. Borneo smoke plume heights are similar to previously reported plume heights, yet Borneo plumes are on average nearly three times longer than previously studied plumes. This could be due to sampling or to more persistent fires and greater fuel loads in peatlands than in other tropical forests. Plume area (median 169 km2, with 25th and 75th percentiles at 99 km2 and 304 km2, respectively) varies exponentially with length, though for most plumes a linear relation provides a good approximation. The MISR-estimated plume optical properties involve greater uncertainties than the geometric properties, and show patterns consistent with smoke aging. Optical depth increases by 15–25% in the down-plume direction, consistent with hygroscopic growth and nucleation overwhelming the effects of particle dispersion. Both particle single-scattering albedo and top-of-atmosphere reflectance peak about halfway down-plume, at values about 3% and 10% greater than at the origin, respectively. The initially oblong plumes become brighter and more circular with time, increasingly resembling smoke clouds. Wind speed does not explain a significant fraction of the variation in plume geometry. We provide a parameterization of plume shape that can help atmospheric models estimate the effects of plumes on weather, climate, and air quality. Plume age, the age of smoke furthest down-plume, is lognormally distributed with a median of 2.8 h (25th and 75th percentiles at 1.3 h and 4.0 h), different from the median ages reported in other studies. Intercomparison of our results with previous studies shows that the shape, height, optical depth, and lifetime characteristics reported for tropical biomass burning plumes on three continents are dissimilar and distinct from the same characteristics of non-tropical wildfire plumes.
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Cao, Zhixuan, Abani Patra, Marcus Bursik, E. Bruce Pitman, and Matthew Jones. "Plume-SPH 1.0: a three-dimensional, dusty-gas volcanic plume model based on smoothed particle hydrodynamics." Geoscientific Model Development 11, no. 7 (2018): 2691–715. http://dx.doi.org/10.5194/gmd-11-2691-2018.
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Abstract. Plume-SPH provides the first particle-based simulation of volcanic plumes. Smoothed particle hydrodynamics (SPH) has several advantages over currently used mesh-based methods in modeling of multiphase free boundary flows like volcanic plumes. This tool will provide more accurate eruption source terms to users of volcanic ash transport and dispersion models (VATDs), greatly improving volcanic ash forecasts. The accuracy of these terms is crucial for forecasts from VATDs, and the 3-D SPH model presented here will provide better numerical accuracy. As an initial effort to exploit the feasibility and advantages of SPH in volcanic plume modeling, we adopt a relatively simple physics model (3-D dusty-gas dynamic model assuming well-mixed eruption material, dynamic equilibrium and thermodynamic equilibrium between erupted material and air that entrained into the plume, and minimal effect of winds) targeted at capturing the salient features of a volcanic plume. The documented open-source code is easily obtained and extended to incorporate other models of physics of interest to the large community of researchers investigating multiphase free boundary flows of volcanic or other origins. The Plume-SPH code (https://doi.org/10.5281/zenodo. 572819) also incorporates several newly developed techniques in SPH needed to address numerical challenges in simulating multiphase compressible turbulent flow. The code should thus be also of general interest to the much larger community of researchers using and developing SPH-based tools. In particular, the SPH−ε turbulence model is used to capture mixing at unresolved scales. Heat exchange due to turbulence is calculated by a Reynolds analogy, and a corrected SPH is used to handle tensile instability and deficiency of particle distribution near the boundaries. We also developed methodology to impose velocity inlet and pressure outlet boundary conditions, both of which are scarce in traditional implementations of SPH. The core solver of our model is parallelized with the message passing interface (MPI) obtaining good weak and strong scalability using novel techniques for data management using space-filling curves (SFCs), object creation time-based indexing and hash-table-based storage schemes. These techniques are of interest to researchers engaged in developing particles in cell-type methods. The code is first verified by 1-D shock tube tests, then by comparing velocity and concentration distribution along the central axis and on the transverse cross with experimental results of JPUE (jet or plume that is ejected from a nozzle into a uniform environment). Profiles of several integrated variables are compared with those calculated by existing 3-D plume models for an eruption with the same mass eruption rate (MER) estimated for the Mt. Pinatubo eruption of 15 June 1991. Our results are consistent with existing 3-D plume models. Analysis of the plume evolution process demonstrates that this model is able to reproduce the physics of plume development.
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Holland, Paul R., Richard E. Hewitt, and Matthew M. Scase. "Wave Breaking in Dense Plumes." Journal of Physical Oceanography 44, no. 2 (2014): 790–800. http://dx.doi.org/10.1175/jpo-d-13-0110.1.
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Abstract Sinking dense plumes are important in many oceanographic settings, notably the polar formation of deep and bottom waters. The dense water sources feeding such plumes are commonly affected by tidal modulation, leading to plume variability on short time scales. In a simple unsteady theory of one-dimensional plumes (based on conservation equations for volume, momentum, and buoyancy), this plume variability is manifested as waves that travel down the resulting current. Using numerical techniques applied to the hyperbolic conservation equations, this study investigates the novel concept that these waves may break as they travel down the plumes, triggering intense local mixing between the dense fluid and surrounding ocean. The results demonstrate that the waves break at geophysically relevant distances from the plume source. The location of wave breaking is very sensitive to plume drag from the seabed, the properties of the dense source, and the amplitude and period of the source modulation. To the extent that the simple model represents the real world, these results suggest that wave breaking originating from the tidal modulation of dense plumes could lead to a strong and previously unexplored source of local deep-ocean mixing.
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Song, C. H., H. S. Kim, R. von Glasow, et al. "Source identification and budget analysis on elevated levels of formaldehyde within the ship plumes: a ship-plume photochemical/dynamic model analysis." Atmospheric Chemistry and Physics 10, no. 23 (2010): 11969–85. http://dx.doi.org/10.5194/acp-10-11969-2010.
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Abstract. Elevated levels of formaldehyde (HCHO) along the ship corridors have been observed by satellite sensors, such as ESA/ERS-2 GOME (Global Ozone Monitoring Experiment), and were also simulated by global 3-D chemistry-transport models. In this study, three likely sources of the elevated HCHO levels in the ship plumes as well as their contributions to the elevated HCHO levels (budget) were investigated using a newly-developed ship-plume photochemical/dynamic model: (1) primary HCHO emission from ships; (2) secondary HCHO production via the atmospheric oxidation of non-methane volatile organic compounds (NMVOCs) emitted from ships; and (3) atmospheric oxidation of CH4 within the ship plumes. For this ship-plume modelling study, the ITCT 2K2 (Intercontinental Transport and Chemical Transformation 2002) ship-plume experiment, which was carried out about 100 km off the coast of California on 8 May 2002 (11:00 local standard time), was chosen as a base study case because it is the best defined in terms of (1) meteorological data, (2) in-plume chemical composition, and (3) background chemical composition. From multiple ship-plume model simulations for the ITCT 2K2 ship-plume experiment case, CH4 oxidation by elevated levels of in-plume OH radicals was found to be the main factor responsible for the elevated levels of HCHO in the ITCT 2K2 ship-plume. More than ~88% of the HCHO for the ITCT 2K2 ship-plume is produced by this atmospheric chemical process, except in the areas close to the ship stacks where the main source of the elevated HCHO levels would be primary HCHO from the ships (due to the deactivation of CH4 oxidation from the depletion of in-plume OH radicals). Because of active CH4 oxidation by OH radicals, the instantaneous chemical lifetime of CH4 (τCH4) decreased to ~0.45 yr inside the ship plume, which is in contrast to τCH4 of ~1.1 yr in the background (up to ~41% decrease) for the ITCT 2K2 ship-plume case. A variety of likely ship-plume situations at three different latitudinal locations within the global ship corridors was also studied to determine the enhancements in the HCHO levels in the marine boundary layer (MBL) influenced by ship emissions. It was found that the ship-plume HCHO levels could be 19.9–424.9 pptv higher than the background HCHO levels depending on the latitudinal locations of the ship plumes (i.e., intensity of solar radiation and temperature), MBL stability and NOx emission rates. On the other hand, NMVOC emissions from ships were not found to be a primary source of photochemical HCHO production inside ship plumes due to their rapid and individual dilution. However, the diluted NMVOCs would contribute to the HCHO productions in the background air.
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Plant, Robert S. "A new modelling framework for statistical cumulus dynamics." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, no. 1962 (2012): 1041–60. http://dx.doi.org/10.1098/rsta.2011.0377.
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We propose a new modelling framework suitable for the description of atmospheric convective systems as a collection of distinct plumes. The literature contains many examples of models for collections of plumes in which strong simplifying assumptions are made, a diagnostic dependence of convection on the large-scale environment and the limit of many plumes often being imposed from the outset. Some recent studies have sought to remove one or the other of those assumptions. The proposed framework removes both, and is explicitly time dependent and stochastic in its basic character. The statistical dynamics of the plume collection are defined through simple probabilistic rules applied at the level of individual plumes, and van Kampen's system size expansion is then used to construct the macroscopic limit of the microscopic model. Through suitable choices of the microscopic rules, the model is shown to encompass previous studies in the appropriate limits, and to allow their natural extensions beyond those limits.
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Real, E., E. Orlandi, K. S. Law, et al. "Cross-hemispheric transport of central African biomass burning pollutants: implications for downwind ozone production." Atmospheric Chemistry and Physics 10, no. 6 (2010): 3027–46. http://dx.doi.org/10.5194/acp-10-3027-2010.
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Abstract. Pollutant plumes with enhanced concentrations of trace gases and aerosols were observed over the southern coast of West Africa during August 2006 as part of the AMMA wet season field campaign. Plumes were observed both in the mid and upper troposphere. In this study we examined the origin of these pollutant plumes, and their potential to photochemically produce ozone (O3) downwind over the Atlantic Ocean. Their possible contribution to the Atlantic O3 maximum is also discussed. Runs using the BOLAM mesoscale model including biomass burning carbon monoxide (CO) tracers were used to confirm an origin from central African biomass burning fires. The plumes measured in the mid troposphere (MT) had significantly higher pollutant concentrations over West Africa compared to the upper tropospheric (UT) plume. The mesoscale model reproduces these differences and the two different pathways for the plumes at different altitudes: transport to the north-east of the fire region, moist convective uplift and transport to West Africa for the upper tropospheric plume versus north-west transport over the Gulf of Guinea for the mid-tropospheric plume. Lower concentrations in the upper troposphere are mainly due to enhanced mixing during upward transport. Model simulations suggest that MT and UT plumes are 16 and 14 days old respectively when measured over West Africa. The ratio of tracer concentrations at 600 hPa and 250 hPa was estimated for 14–15 August in the region of the observed plumes and compares well with the same ratio derived from observed carbon dioxide (CO2) enhancements in both plumes. It is estimated that, for the period 1–15 August, the ratio of Biomass Burning (BB) tracer concentration transported in the UT to the ones transported in the MT is 0.6 over West Africa and the equatorial South Atlantic. Runs using a photochemical trajectory model, CiTTyCAT, initialized with the observations, were used to estimate in-situ net photochemical O3 production rates in these plumes during transport downwind of West Africa. The mid-troposphere plume spreads over altitude between 1.5 and 6 km over the Atlantic Ocean. Even though the plume was old, it was still very photochemically active (mean net O3 production rates over 10 days of 2.6 ppbv/day and up to 7 ppbv/day during the first days) above 3 km especially during the first few days of transport westward. It is also shown that the impact of high aerosol loads in the MT plume on photolysis rates serves to delay the peak in modelled O3 concentrations. These results suggest that a significant fraction of enhanced O3 in mid-troposphere over the Atlantic comes from BB sources during the summer monsoon period. According to simulated occurrence of such transport, BB may be the main source for O3 enhancement in the equatorial south Atlantic MT, at least in August 2006. The upper tropospheric plume was also still photochemically active, although mean net O3 production rates were slower (1.3 ppbv/day). The results suggest that, whilst the transport of BB pollutants to the UT is variable (as shown by the mesoscale model simulations), pollution from biomass burning can make an important contribution to additional photochemical production of O3 in addition to other important sources such as nitrogen oxides (NOx) from lightning.
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Soman, Vrishin R. "Hot Times in Tectonophysics: Mantle Plume Dynamics and Magmatic Perturbances." Journal of Environment and Ecology 11, no. 2 (2020): 19. http://dx.doi.org/10.5296/jee.v11i2.16475.
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Earth’s dynamic lithospheric (plate) motions often are not obvious when considered in relation to the temporal stability of the crust. Seismic radiology experiments confirm that the extreme pressures and temperatures in the mantle, and to a lesser extent the asthenosphere, result in a heterogeneously viscous rheology. Occasionally, magmatic fluid makes its way through the lithospheric plate to the surface, appearing typically as a volcano, fissure eruption, or lava flow. When occurring away from the edges of plate boundaries, these long-lasting suppliers of lava, present over millions of years, are called mantle plumes, or ‘hotspots.’ Conventional definitions of mantle plumes note that they are stationary with respect to each other and the motion of the plates, passively tracing historical plate motion in volcanic formations such as the Hawaiian-Emperor island arc – the Plate Model. In this model, mantle plumes primarily occur as a consequence of lithospheric extension.Recent empirical studies, however, have demonstrated that hotspots are not as geographically consistent as previously thought. They may move in relation to each other, as well as contribute actively toward lithospheric plate motions – the Plume Model. There is a lively, ongoing debate between the Plate and Plume hypotheses, essentially seeking to determine if mantle flow is merely a passive reaction to lithospheric plate motion (Plate Model), or whether plume activity in part drives this motion (Plume Model). More likely, it is a combination of passive and active mantle plume components that better describe the comprehensive behavior of these important and distinctive landscape forming features.
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Zhukov, A. N., I. S. Veselovsky, S. Koutchmy, and A. Llebaria. "Helical Magnetic Structure of White Light Polar Plumes." Symposium - International Astronomical Union 203 (2001): 434–36. http://dx.doi.org/10.1017/s0074180900219748.
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We describe the fine structure of white light polar plumes observed using SOHO/LASCO C2 coronagraph. The evolving helical structures of different scales are clearly seen on processed images (the processing is made to reveal the faint contrast objects). The observed structures trace the magnetic field lines, so the electric currents flow along the axes of plumes. An MHD model of a plume which takes into account field-aligned electric currents is developed. The model permits to understand the existence of high-density plasma inside the plume due to the balance between the magnetic forces and the transverse pressure gradient.