<p>Dust storm genesis is one of several high-impact weather phenomena that ... more <p>Dust storm genesis is one of several high-impact weather phenomena that may result from Rossby wave breaking (RWB). The wave propagation into low latitudes over North Africa facilitates instability through upper-level divergence and the reduction of the static stability ahead of the cyclonic side of the wave train, and therefore modulates the low-level tropospheric conditions in dust source areas.</p><p>The analysis of three dust storm case studies that strongly impacted the Iberian Peninsula and another one impacting the Cape Verde Islands indicates that a <em>double</em> RWB process within the Polar Jet (PJ) stream over the eastern North Atlantic and western Europe is a common large-scale upper-level precursor to the formation of the large North African dust storms and subsequent transport of dust (Orza et al, 2020; Dhital et al, 2020).</p><p>The synoptic and larger subsynoptic scale features were analyzed using ERA-Interim reanalysis while mesoscale features were studied by high-resolution WRF-CHEM simulations. There are substantial differences between the case studies in the location and geometry of upper- and low-level features following the first break (Dhital et al, 2020; 2021). However, in all case studies (1) RWB within the PJ stream is observed; (2) there is a substantial poleward expansion of the upper-level subtropical ridge; and (3) the secondary RWB is amplified by nonlinear wave reflection from the first break.</p><p>Preliminary results from a larger number of cases study indicate the relevance of secondary RWB in the PJ stream. The dynamics may also result in cutoff lows and amplified low-PV ridging accompanying cyclogenesis and heatwaves, respectively, which emphasizes the need to improve our understanding of the involved processes.</p><p>- Dhital S, ML Kaplan, JAG Orza, S Fiedler (2020). Atmospheric dynamics of a Saharan dust outbreak over Mindelo, Cape Verde Islands, preceded by Rossby wave breaking: Multiscale observational analyses and simulations. J. Geophys. Res. Atmos. 125, e2020JD032975.</p><p>- Dhital S, ML Kaplan, JAG Orza, S Fiedler (2021). Poleward Transport of African Dust to the Iberian Peninsula Organized by a Barrier Jet and Hydraulic Jumps: Observations and High-Resolution Simulation Analyses. Atmos. Environ. 261, 118574.</p><p>- Orza JAG, S Dhital, S Fiedler, ML Kaplan (2020). Large Scale Upper-level Precursors for Dust Storm Formation over North Africa and Poleward Transport to the Iberian Peninsula. Part I: An Observational Analysis. Atmos. Environ. 237, 117688.</p><p> </p>
Physical Characterization of Pharmaceutical Solids, 1995
The main aim of this research was to prepare nanoparticles of nickel oxide through a new mixed re... more The main aim of this research was to prepare nanoparticles of nickel oxide through a new mixed reverse microemulsion route. Quaternary microemulsion (water/surfactant/cosurfactant/oil-phase) was used to synthesize nickel oxide nanoparticles. The microemulsion was prepared by Tween-80, Aerosol-OT, n-Propanol, Cyclohexane, and Nickel Chloride. Previously nickel oxide nanoparticles were synthesized by reverse microemulsion method but the novelty of the process lies in the fact that conventionally either cationic or anionic or non ionic surfactants are used for the synthesis of nickel oxide nanoparticles.Whereas in the present developed novel process preparation of nickel oxide nanoparticles has been carried out using a unique blend system consisting of Tween-80 and AOT. The average particle size of as synthesized nickel oxide powder, calculated by Scherrer equation, is observed to be 14 nm. The X-ray diffraction pattern confirms the presence of pure bunsenite phase with FCC Scanning Electron Microscopy (SEM) shows that particles have spherical morphology.
The time dependence of deviations from the Gaussian state in a freely cooling homogeneous system ... more The time dependence of deviations from the Gaussian state in a freely cooling homogeneous system of smooth inelastically colliding spheres is investigated by kinetic theory. We determine the full time dependence of the coefficients of an expansion around the Gaussian state in Generalized Laguerre polynomials. Approximating this system of equations to sixth order, we find that the asymptotic state, where the mean energy T follows Haff's law with time independent cooling rate, is reached within a few collisions per particle. Two-dimensional molecular dynamics simulations confirm our results and show exponential behavior in the high-energy tails.
Studies of radionuclide activities in aerosol particles provide a means for evaluating the integr... more Studies of radionuclide activities in aerosol particles provide a means for evaluating the integrated effects of transport and meteorology on the atmospheric loadings of substances with different sources. Measurements of aerosol mass concentration and specific activities of 7 Be and 210 Pb in aerosols at Málaga (36°43′ 40″ N; 4°28′ 8″ W) for the period 2000-2006 were used to obtain the relationships between radionuclide activities and airflow patterns by comparing the data grouped by air mass trajectory clusters. The average concentration values of 7 Be and 210 Pb over the 7 year period have been found to be 4.6 and 0.58 mBq m −3 , respectively, with mean aerosol mass concentration of 53.6 μg m −3. The identified air flow types arriving at Málaga reflect the transitional location of the Iberian Peninsula and show significant differences in radionuclide activities. Air concentrations of both nuclides and the aerosol mass concentration are controlled predominantly by the synoptic scenarios leading to the entrance of dust-laden continental flows from northern Africa and the arrival of polar maritime air masses, as implied by the strong correlations found between the monthly frequencies of the different air masses and the specific activities of both radionuclides. Correlations between activity concentrations and precipitation are significant though lower than with air masses.
Particulate matter emissions from paved roads are currently one of the main challenges for a sust... more Particulate matter emissions from paved roads are currently one of the main challenges for a sustainable transport in Europe. Emissions are scarcely estimated due to the lack of knowledge about the resuspension process severely hampering a reliable simulation of PM and heavy metals concentrations in large cities and evaluation of population exposure. In this study the Emission Factors from road dust resuspension on a Mediterranean freeway were estimated per single vehicle category and PM component (OC, EC, mineral dust and metals) by means of the deployment of vertical profiles of passive samplers and terminal concentration estimate. The estimated PMio emission factors varied from 12 to 47 mg VKT-1 (VICT: Vehicle Kilometer Traveled) with an average value of 22.7 ± 14.2 mg VKT-1. Emission Factors for heavy and light duty vehicles, passenger cars and motorbikes were estimated, based on average fleet composition and EPA ratios, in 187-733 mg VKT-1 , 33-131 VKT-1 , 9.4-36.9 VKT" 1 and 0.8-3.3 VKT-1 , respectively. These range of values are lower than previous estimates in Mediterranean urban roads, probably due to the lower dust reservoir on freeways. PM emitted material was dominated by mineral dust (9-10 mg VKT-1), but also OC and EC were found to be major components and approximately 14-25% and 2-9% of average PM exhaust emissions from diesel passenger cars on highways respectively.
ABSTRACT Water soluble ions, methanesulfonate, organic and elemental carbon, and metals in PM2.5 ... more ABSTRACT Water soluble ions, methanesulfonate, organic and elemental carbon, and metals in PM2.5 and PM1 samples were analysed by Positive Matrix Factorization to identify and quantify major sources of fine particles at a Central Mediterranean site. The cluster analysis of four-day back trajectories was used to determine the dependence of PM2.5 and PM1 levels and composition on air-flows. The cluster analysis has identified six, six, and seven distinct air-flow types arriving at 500, 1500, and 3000 m above sea level (asl), respectively. Slow-west (Wslow) and north-eastern (NE) flows at 500 and 1500 m asl were the most frequent and were associated with the highest PM2.5 and PM1 concentrations. The PM concentrations from combustion sources including biomass burning were at their maximum under north-western (NW) flows. Similarly, the ammonium sulphate source was enhanced under Wslow and NE flows. South-eastern Mediterranean Sea air-flows were associated with the highest PM2.5 concentrations due to the heavy-oil-combustion source and the highest PM2.5 and PM1 concentrations due to the secondary marine source. PM2.5 concentrations due to the reacted dust and traffic source and PM1 concentrations due to the nitrate with reacted dust and mixed anthropogenic source showed no clear dependence on air-flows. This work highlights the different impact of aerosol sources on PM2.5 and PM1 fractions, being PM1 more adequate to control anthropogenic emissions from combustion sources.
An initially homogeneous freely evolving fluid of inelastic hard spheres develops inhomogeneities... more An initially homogeneous freely evolving fluid of inelastic hard spheres develops inhomogeneities in the flow field u(r, t) (vortices) and in the density field n (r, t)(clusters), driven by unstable fluctuations, δa = {δn, δu}. Their spatial correlations, , as measured in molecular dynamics simulations, exhibit long range correlations; the mean vortex diameter grows as [Formula: see text]; there occur transitions to macroscopic shearing states, etc. The Cahn–Hilliard theory of spinodal decomposition offers a qualitative understanding and quantitative estimates of the observed phenomena. When intrinsic length scales are of the order of the system size, effects of physical boundaries and periodic boundaries (finite size effects in simulations) are important.
This study presents the meso-β/γ scale dynamical features involved in an extreme African dust out... more This study presents the meso-β/γ scale dynamical features involved in an extreme African dust outbreak, which occurred during 20-21 February 2016 over the Iberian Peninsula (IP), the southwest corn...
The variations in tropospheric transport pathways over a 20 year period, 1990-2009, are studied a... more The variations in tropospheric transport pathways over a 20 year period, 1990-2009, are studied at six locations in Europe. Three Atlantic (Lisbon, Mace Head, and Cabauw) and three Mediterranean sites (Malaga and Elche in the western part and Lecce in the central Mediterranean) are considered. The work is based on the identification of flow types at each location by robust cluster analysis of the trajectories, the assessment of temporal trends for each advection pattern, and subsequent quantification of the association, at the monthly scale, between the North Atlantic Oscillation (NAO) index (NAOi) and the frequency of occurrence of the identified flows. This exploratory study demonstrates the usefulness of the approach for specific locations in a context where synoptic circulation/weather-type classifications are usually used. A different number of advection pathways were identified at each location. Common features to all the sites were prevalence of westerly flows, strong seasona...
Replacement of cond-mat/0002383. Re-analysis of computer simulations, new figures and modificatio... more Replacement of cond-mat/0002383. Re-analysis of computer simulations, new figures and modification of conclusions.
Backtrajectory differences and clustering sensitivity to the meteorological input data are studie... more Backtrajectory differences and clustering sensitivity to the meteorological input data are studied. Trajectories arriving in Southeast Spain (Elche), at 3000, 1500 and 500 m for the 7-year period 2000-2006 have been computed employing two widely used meteorological data sets: the NCEP/NCAR Reanalysis and the FNL data sets. Differences between trajectories grow linearly at least up to 48 h, showing faster
<p>Dust storm genesis is one of several high-impact weather phenomena that ... more <p>Dust storm genesis is one of several high-impact weather phenomena that may result from Rossby wave breaking (RWB). The wave propagation into low latitudes over North Africa facilitates instability through upper-level divergence and the reduction of the static stability ahead of the cyclonic side of the wave train, and therefore modulates the low-level tropospheric conditions in dust source areas.</p><p>The analysis of three dust storm case studies that strongly impacted the Iberian Peninsula and another one impacting the Cape Verde Islands indicates that a <em>double</em> RWB process within the Polar Jet (PJ) stream over the eastern North Atlantic and western Europe is a common large-scale upper-level precursor to the formation of the large North African dust storms and subsequent transport of dust (Orza et al, 2020; Dhital et al, 2020).</p><p>The synoptic and larger subsynoptic scale features were analyzed using ERA-Interim reanalysis while mesoscale features were studied by high-resolution WRF-CHEM simulations. There are substantial differences between the case studies in the location and geometry of upper- and low-level features following the first break (Dhital et al, 2020; 2021). However, in all case studies (1) RWB within the PJ stream is observed; (2) there is a substantial poleward expansion of the upper-level subtropical ridge; and (3) the secondary RWB is amplified by nonlinear wave reflection from the first break.</p><p>Preliminary results from a larger number of cases study indicate the relevance of secondary RWB in the PJ stream. The dynamics may also result in cutoff lows and amplified low-PV ridging accompanying cyclogenesis and heatwaves, respectively, which emphasizes the need to improve our understanding of the involved processes.</p><p>- Dhital S, ML Kaplan, JAG Orza, S Fiedler (2020). Atmospheric dynamics of a Saharan dust outbreak over Mindelo, Cape Verde Islands, preceded by Rossby wave breaking: Multiscale observational analyses and simulations. J. Geophys. Res. Atmos. 125, e2020JD032975.</p><p>- Dhital S, ML Kaplan, JAG Orza, S Fiedler (2021). Poleward Transport of African Dust to the Iberian Peninsula Organized by a Barrier Jet and Hydraulic Jumps: Observations and High-Resolution Simulation Analyses. Atmos. Environ. 261, 118574.</p><p>- Orza JAG, S Dhital, S Fiedler, ML Kaplan (2020). Large Scale Upper-level Precursors for Dust Storm Formation over North Africa and Poleward Transport to the Iberian Peninsula. Part I: An Observational Analysis. Atmos. Environ. 237, 117688.</p><p> </p>
Physical Characterization of Pharmaceutical Solids, 1995
The main aim of this research was to prepare nanoparticles of nickel oxide through a new mixed re... more The main aim of this research was to prepare nanoparticles of nickel oxide through a new mixed reverse microemulsion route. Quaternary microemulsion (water/surfactant/cosurfactant/oil-phase) was used to synthesize nickel oxide nanoparticles. The microemulsion was prepared by Tween-80, Aerosol-OT, n-Propanol, Cyclohexane, and Nickel Chloride. Previously nickel oxide nanoparticles were synthesized by reverse microemulsion method but the novelty of the process lies in the fact that conventionally either cationic or anionic or non ionic surfactants are used for the synthesis of nickel oxide nanoparticles.Whereas in the present developed novel process preparation of nickel oxide nanoparticles has been carried out using a unique blend system consisting of Tween-80 and AOT. The average particle size of as synthesized nickel oxide powder, calculated by Scherrer equation, is observed to be 14 nm. The X-ray diffraction pattern confirms the presence of pure bunsenite phase with FCC Scanning Electron Microscopy (SEM) shows that particles have spherical morphology.
The time dependence of deviations from the Gaussian state in a freely cooling homogeneous system ... more The time dependence of deviations from the Gaussian state in a freely cooling homogeneous system of smooth inelastically colliding spheres is investigated by kinetic theory. We determine the full time dependence of the coefficients of an expansion around the Gaussian state in Generalized Laguerre polynomials. Approximating this system of equations to sixth order, we find that the asymptotic state, where the mean energy T follows Haff's law with time independent cooling rate, is reached within a few collisions per particle. Two-dimensional molecular dynamics simulations confirm our results and show exponential behavior in the high-energy tails.
Studies of radionuclide activities in aerosol particles provide a means for evaluating the integr... more Studies of radionuclide activities in aerosol particles provide a means for evaluating the integrated effects of transport and meteorology on the atmospheric loadings of substances with different sources. Measurements of aerosol mass concentration and specific activities of 7 Be and 210 Pb in aerosols at Málaga (36°43′ 40″ N; 4°28′ 8″ W) for the period 2000-2006 were used to obtain the relationships between radionuclide activities and airflow patterns by comparing the data grouped by air mass trajectory clusters. The average concentration values of 7 Be and 210 Pb over the 7 year period have been found to be 4.6 and 0.58 mBq m −3 , respectively, with mean aerosol mass concentration of 53.6 μg m −3. The identified air flow types arriving at Málaga reflect the transitional location of the Iberian Peninsula and show significant differences in radionuclide activities. Air concentrations of both nuclides and the aerosol mass concentration are controlled predominantly by the synoptic scenarios leading to the entrance of dust-laden continental flows from northern Africa and the arrival of polar maritime air masses, as implied by the strong correlations found between the monthly frequencies of the different air masses and the specific activities of both radionuclides. Correlations between activity concentrations and precipitation are significant though lower than with air masses.
Particulate matter emissions from paved roads are currently one of the main challenges for a sust... more Particulate matter emissions from paved roads are currently one of the main challenges for a sustainable transport in Europe. Emissions are scarcely estimated due to the lack of knowledge about the resuspension process severely hampering a reliable simulation of PM and heavy metals concentrations in large cities and evaluation of population exposure. In this study the Emission Factors from road dust resuspension on a Mediterranean freeway were estimated per single vehicle category and PM component (OC, EC, mineral dust and metals) by means of the deployment of vertical profiles of passive samplers and terminal concentration estimate. The estimated PMio emission factors varied from 12 to 47 mg VKT-1 (VICT: Vehicle Kilometer Traveled) with an average value of 22.7 ± 14.2 mg VKT-1. Emission Factors for heavy and light duty vehicles, passenger cars and motorbikes were estimated, based on average fleet composition and EPA ratios, in 187-733 mg VKT-1 , 33-131 VKT-1 , 9.4-36.9 VKT" 1 and 0.8-3.3 VKT-1 , respectively. These range of values are lower than previous estimates in Mediterranean urban roads, probably due to the lower dust reservoir on freeways. PM emitted material was dominated by mineral dust (9-10 mg VKT-1), but also OC and EC were found to be major components and approximately 14-25% and 2-9% of average PM exhaust emissions from diesel passenger cars on highways respectively.
ABSTRACT Water soluble ions, methanesulfonate, organic and elemental carbon, and metals in PM2.5 ... more ABSTRACT Water soluble ions, methanesulfonate, organic and elemental carbon, and metals in PM2.5 and PM1 samples were analysed by Positive Matrix Factorization to identify and quantify major sources of fine particles at a Central Mediterranean site. The cluster analysis of four-day back trajectories was used to determine the dependence of PM2.5 and PM1 levels and composition on air-flows. The cluster analysis has identified six, six, and seven distinct air-flow types arriving at 500, 1500, and 3000 m above sea level (asl), respectively. Slow-west (Wslow) and north-eastern (NE) flows at 500 and 1500 m asl were the most frequent and were associated with the highest PM2.5 and PM1 concentrations. The PM concentrations from combustion sources including biomass burning were at their maximum under north-western (NW) flows. Similarly, the ammonium sulphate source was enhanced under Wslow and NE flows. South-eastern Mediterranean Sea air-flows were associated with the highest PM2.5 concentrations due to the heavy-oil-combustion source and the highest PM2.5 and PM1 concentrations due to the secondary marine source. PM2.5 concentrations due to the reacted dust and traffic source and PM1 concentrations due to the nitrate with reacted dust and mixed anthropogenic source showed no clear dependence on air-flows. This work highlights the different impact of aerosol sources on PM2.5 and PM1 fractions, being PM1 more adequate to control anthropogenic emissions from combustion sources.
An initially homogeneous freely evolving fluid of inelastic hard spheres develops inhomogeneities... more An initially homogeneous freely evolving fluid of inelastic hard spheres develops inhomogeneities in the flow field u(r, t) (vortices) and in the density field n (r, t)(clusters), driven by unstable fluctuations, δa = {δn, δu}. Their spatial correlations, , as measured in molecular dynamics simulations, exhibit long range correlations; the mean vortex diameter grows as [Formula: see text]; there occur transitions to macroscopic shearing states, etc. The Cahn–Hilliard theory of spinodal decomposition offers a qualitative understanding and quantitative estimates of the observed phenomena. When intrinsic length scales are of the order of the system size, effects of physical boundaries and periodic boundaries (finite size effects in simulations) are important.
This study presents the meso-β/γ scale dynamical features involved in an extreme African dust out... more This study presents the meso-β/γ scale dynamical features involved in an extreme African dust outbreak, which occurred during 20-21 February 2016 over the Iberian Peninsula (IP), the southwest corn...
The variations in tropospheric transport pathways over a 20 year period, 1990-2009, are studied a... more The variations in tropospheric transport pathways over a 20 year period, 1990-2009, are studied at six locations in Europe. Three Atlantic (Lisbon, Mace Head, and Cabauw) and three Mediterranean sites (Malaga and Elche in the western part and Lecce in the central Mediterranean) are considered. The work is based on the identification of flow types at each location by robust cluster analysis of the trajectories, the assessment of temporal trends for each advection pattern, and subsequent quantification of the association, at the monthly scale, between the North Atlantic Oscillation (NAO) index (NAOi) and the frequency of occurrence of the identified flows. This exploratory study demonstrates the usefulness of the approach for specific locations in a context where synoptic circulation/weather-type classifications are usually used. A different number of advection pathways were identified at each location. Common features to all the sites were prevalence of westerly flows, strong seasona...
Replacement of cond-mat/0002383. Re-analysis of computer simulations, new figures and modificatio... more Replacement of cond-mat/0002383. Re-analysis of computer simulations, new figures and modification of conclusions.
Backtrajectory differences and clustering sensitivity to the meteorological input data are studie... more Backtrajectory differences and clustering sensitivity to the meteorological input data are studied. Trajectories arriving in Southeast Spain (Elche), at 3000, 1500 and 500 m for the 7-year period 2000-2006 have been computed employing two widely used meteorological data sets: the NCEP/NCAR Reanalysis and the FNL data sets. Differences between trajectories grow linearly at least up to 48 h, showing faster
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Papers by Jose Orza