Vertical Mass Transport Research Articles

Mean radiative energy balance and vertical mass fluxes in the equatorial upper troposphere and lower stratosphere

We use radiative transfer calculations to quantify vertical mass transport in the equatorial upper troposphere (UT) and lower stratosphere (LS), employing high resolution sonde measurements of temperature, ozone and water vapor at seven equatorial locations (10°S–10°N). The influence of clouds is examined using data from the International Satellite Cloud Climatology Project (ISCCP) and the Lidar‐In‐Space Technology Experiment (LITE). The resulting mean heating rate profiles show that the transition from radiative cooling to heating occurs significantly lower in the full sky case than in the clear sky case, demonstrating the importance of clouds for processes in the UT, such as troposphere‐to‐stratosphere transport (TST). The heating rate profiles are used to calculate mean vertical mass fluxes, which show a divergent mass flux from 15–19 km. This suggests that only a small part of the air ascending through the cold point tropopause can reach the middle stratosphere. Above 19 km the vertical motion is a non‐divergent upwelling mass flux consistent with the idea of a Brewer‐Dobson circulation driven by waves dissipating in the extratropical stratosphere. Lower down, other processes are also responsible for the upwelling.

Beryllium 7 radionucleide as a tracer of vertical air mass transport in the troposphere

7Be is a cosmogenic radionucleide (half life 53.3 days) produced by galactic cosmic rays and solar energetic particles in the upper atmosphere and is a potentially useful tracer of the short-term atmospheric air mass motion. We have measured the surface 7Be concentration in Tokyo (35N, 139E) since 2002 with a high-volume air sampler. The present data of surface Be-7 concentrations exhibit the enhancements in spring and autumn and the seasonal enhancements are not associated with scavenging by precipitation. In order to explain the measured enhancements, we propose the possibility of the downward and upward atmospheric flows in the troposphere caused by a pair of traveling anticyclone and extratropical cyclone that passes over Japan in spring and autumn with a period of a few days.

Dynamics and Energetics of Turbulent, Magnetized Disk Accretion around Black Holes: A First‐Principles Approach to Disk‐Corona‐Outflow Coupling

We present an analytic description of turbulent, magnetohydrodynamic (MHD) disk accretion around black holes that specifically addresses the relationship between radial and vertical mean field transport of mass, momentum, and energy, thereby complementing and extending numerical simulations. The azimuthal-vertical component of the magnetic stress is fundamental to an understanding of disk-corona-outflow coupling: when it is important for driving the angular momentum transport and mass accretion in the disk, it also has an important influence on the disk-corona-outflow energy budget. The Poynting flux derived from the product of this term with the Keplerian velocity also dominates the Poynting flux into the corona. The ratio of the coronal Alfven velocity to the Keplerian velocity is an important parameter in disk-corona-outflow physics. If this parameter is greater than unity, then energetically significant winds and Poynting flux into the corona occur. However, significant effects could also occur when this parameter is much less than unity. A limiting solution describing the case of angular momentum transport solely by the vertical-azimuthal stress has the property that all of the accretion power is channeled into a wind, some of which would be dissipated in the corona. More realistic solutions in which there is both radial and vertical transport of angular momentum would have different fractions of the accretion power emitted by the disk and corona, respectively. These results have important implications for existing accretion disk theory and for our interpretation of high-energy emission and nuclear outflows from the central engines of active galactic nuclei and galactic black hole candidates.

Tidal-induced Lagrangian and Eulerian mean circulation in the Bohai Sea

Long-term transport processes in coastal seas with time scales from weeks to seasons time scale are controlled by residual circulation. In the Bohai Sea, an ultrashallow shelf sea of China, tidal residual is almost the dominant factor to the circulation due to slight stratification and weak wind in summer. In order to establish an adequate hydrodynamic base to the ecosystem dynamics of the Bohai Sea, the differences of tide-induced Lagrangian and Eulerian mean circulation are discussed and calculated in this contribution. The Stokes drift is analyzed theoretically. According to Longuet-Higgins [Deep-Sea Res. 16 (1969) 431], the Lagrangian flow is the sum of the Eulerian flow and the Stokes drift that is induced by the mean kinetic energy and coastal nonlinear interaction. Stokes drift is large in the coastal sea and in areas where the vorticity and/or divergence are large. Vertical mass transports by Stokes drift are also the result of nonlinear interaction of current, water level and topography. Hamburg Shelf Ocean Model (HAMSOM) is applied in the Bohai Sea to simulate the tides and tidal currents. The tide-induced Lagrangian mean circulation and the Eulerian one are calculated at the same time. In the area where the Stokes drift is in the same direction as the Eulerian residual, the Lagrangian one is stronger than the Eulerian one. Where they are pointing in opposite directions, the Lagrangian one is small, like in the southwest of the Bohai Bay, Liaodong Bay and Bohai Strait. The Lagrangian residual current flows into the Bohai Bay along its southern bank causing deposition of Huanghe River sediments. This is in agreement with observations.

Radar observations of the kinematic, microphysical, and precipitation characteristics of two MCSs in TRMM LBA

Dual‐Doppler and polarimetric radar observations are used to analyze two mesoscale convective systems (MCSs) that occurred during the Tropical Rainfall Measuring Mission Large‐Scale Biosphere‐Atmosphere field campaign. The MCSs formed in different meteorological regimes, based on profiles of atmospheric wind and thermodynamic data. The first MCS event (26 January 1999) was a squall line that formed in low‐level easterly flow and had an intense leading line of convection. In contrast, the 25 February 1999 MCS formed in low‐level westerly flow and was best characterized by stratiform precipitation with embedded convective elements. The radar analyses suggest that the MCSs were distinct in terms of overall vertical structure characteristics. In particular, polarimetric radar cross sections indicated the presence of an active mixed phase zone in the easterly MCS that was largely absent in the westerly case. The easterly MCS had considerably more precipitation ice in the middle to upper troposphere compared to the westerly MCS. Composite analyses showed that the easterly MCS had higher peak reflectivities and a smaller reflectivity gradient above the 0°C level in convective regions of the storm compared to the westerly MCS event. Moreover, mean profiles of both vertical air motion and vertical mass transport in the convective portion of the easterly MCS were larger (over a factor of 2 at some heights below the 0°C level) than those in the westerly event. These observations suggest that the easterly and westerly wind regimes in the southwest Amazon region produce convection with different vertical structure characteristics, similar to regimes elsewhere in the global tropics (e.g., maritime continent).

Internal structure of uppermost oceanic crust along the Western Blanco Transform Scarp: Implications for subaxial accretion and deformation at the Juan de Fuca Ridge

[1] The uppermost 2 km of oceanic crust created near the southern end of the Juan de Fuca Ridge (∼60 mm/yr, full spreading rate) is exposed in a “tectonic window” created along the north wall of the Blanco Transform Fault. A total of 27 submersible dives transect this escarpment over a distance of >30 km, corresponding to ∼1 m.y. of spreading history. In this exposure, weakly deformed basaltic lavas grade downward into much more intensely fractured lavas cut by basaltic dikes. Lava flow surfaces dip persistently to the northwest (toward the spreading center) and the dikes dip southeast (away from the spreading center). The underlying sheeted dike complex is composed of subparallel dikes that dip moderately to the southeast. Discrete faults and more distributed cataclastic deformation zones separate the panels of sheeted dikes from one another. Disruption of the lava and dike units are interpreted as a result of dramatic, subaxial, vertical mass transport that created the “accommodation space” for the accumulation of a thickness of 1000–1500 m of basaltic lava. The observed patterns of tilting of lavas and dikes imply subsidence beneath the region of active volcanism (∼3 km wide) that is most rapid near the axis and diminishes quickly off-axis. Deformation that accommodates this subsidence has generated extensive fracture porosity in the subaxial region that could strongly influence upper crustal hydrothermal pathways, alteration history, seismic properties, and the distribution of subsurface biological communities.

Oxygen, carbon and strontium isotope systematics in two profiles across the Glarus thrust: implications for fluid flow

The Glarus thrust is a prominent tectonic feature in the eastern Helvetic Alps. It has been recognized as a potential major pathway for syntectonic crustal scale fluid flow. The oxygen, carbon and strontium isotope patterns obtained from two vertical profiles across the thrust indicate fundamentally different flow regimes in the southern section of the thrust, where the footwall is represented by Mesozoic limestones, and in the northern section, where the footwall is represented by Tertiary flysch. At the Grauberg locality in the south, the observed isotope patterns give evidence of a net mass transport component from the hanging wall Verrucano to the footwall limestone with a maximum time-integrated volumetric fluid flux of 6.1 m3/m2 In the south, the hydration of the lowermost 10 to 20 m of the hanging wall Verrucano requires introduction of an aqueous fluid by subhorizontal flow along the thrust with a minimum time integrated flux of 240 m3/m2. At the Lochseite locality in the north, the isotope patterns indicate a vertical mass transport component from the footwall flysch to the hanging wall Verrucano with a time-integrated fluid flux of 2.6 m3/m2. In the north, the fluids were probably derived from compaction and dehydration of the footwall flysch during thrusting. The ascending fluids were ponded below the Verrucano and 'lubricated' the thrust. Short-term pressure drops associated with seismic motion along the thrust led to the precipitation of calcite in veins at the thrust surface contributing material to the Lochseiten calc-mylonite, a thin calc-mylonite layer at the thrust contact. Although cross thrust fluid flow may have been two to three orders of magnitude smaller than flow along the thrust, it had a major impact on the isotopic composition of the Lochseiten calc-mylonite. In particular, it buffered the oxygen isotope composition of the calc-mylonite towards the relatively 18O-depleted composition of the hanging wall Verrucano in the south and towards the relatively 18O-enriched compositions of the footwall flysch in the north. By this mechanism a regional south to north 18O-enrichment trend was simulated within the Lochseiten calc-mylonite.

Dynamics of bottom boundary layers in the coastal ocean

The bottom boundary layer is the region adjacent to the sea floor, with a thickness typically on the order of meters to tens of meters, where turbulence generated by bottom drag produces vertical mixing of mass, heat, and momentum. Oceanic boundary layers are influenced not only by turbulent mixing, but also by planetary rotation, stratification, topography, surface waves, internal waves, and interaction with the erodible sea floor. Historically, understanding of the oceanic bottom boundary layer has been based on classical results in engineering and meteorology. However, recent theory and measurements have revealed unique features of oceanic boundary layers. Outstanding problems include measuring the interaction of the flow with the erodible sea floor; measuring the spatial scales of turbulent motions that accomplish vertical transport of mass, heat, and momentum; and understanding the processes that control the intensity and scale of boundary layer turbulence, particularly in stable stratification.

A simple model for the assessment of air quality in streets

An analytical model has been developed to calculate pollutant concentrations in a street. The concentration in the street is determined from a flux balance between the horizontal convective flux, the diffusive vertical flux and a continuous road transport emission source. The Prandtl-Taylor hypothesis is used to describe vertical turbulent mass transport. The model includes wind direction dependency, but does not necessarily assume re-circulation of the flow in the street canyon. The model was applied for ten streets in the City of Antwerp, Belgium and for the Podbielskistrasse in Hannover, Germany. Benzene concentrations obtained in the streets of Antwerp show a reasonable agreement with measured concentrations, provided that observed vehicle numbers are used and that the correct background concentrations and meteorological conditions are taken into account by the model.

Compositional gradients across mare‐highland contacts: Importance and geological implication of lateral transport

Observations of mixing across mare‐highland contacts using high‐resolution Clementine data allow a new assessment of the relative importance of vertical versus lateral mass transport on the Moon at least at mare‐highland contact. We analyze mare‐highland contacts in the Grimaldi, Orientale, and Fecunditatis basins and Tsiolkovsky crater through image‐based nonlinear spectral mixture modeling of Clementine ultraviolet‐visible (UV‐VIS) light spectrometer multi‐spectral data. The mare in these regions differ in ages, but they are characterized by having simple geological contacts. The symmetric distribution of mare and highland soil constituents across their geological contact indicates that lateral transport is more efficient than deep vertical transport during the formation of the observed mixing zones. Observations across the lunar limb with the Clementine UV‐VIS filters show that there is a stray light component of scattered light across high‐contrast albedo boundaries. However, the magnitude and spatial properties of scattered light do not significantly affect the nature of compositional boundaries determined here. Since repetitive meteorite bombardment governs lateral transport across the geological contacts and is a random process, a stochastic model is developed to describe this lateral transport. Analysis of the power decay law for crater ejecta thickness indicates that the high‐velocity ejecta travels long distances and follows a −3 power decay law. This results in an infinite variance, which requires an anomalous diffusion model since a classical diffusion model would be invalid. Mathematical modeling supports this result where it is shown that classical diffusion produces a relatively poor fit to profiles of material abundance, while the anomalous diffusion model fits the profiles adequately. These results indicate that high‐velocity ejecta dominates the formation of the observed compositional gradients, while the ejecta near the crater rim is relatively less important. On the basis of these ejecta distributions and the assumption of random impact cratering, we derive a relationship that can be used as an index for relative age dating of geological contacts as well as for investigating cratering rates.

Evolution and Dynamics of a Late-Stage Squall Line That Occurred on 20 February 1993 during TOGA COARE

Abstract Airborne Doppler and flight-level data are used to document the structure and evolution of portions of a late-stage horseshoe-shaped squall line system and its effect on vertical momentum and mass transports. This system, which occurred on 20 February 1993 during the Tropical Ocean Global Atmosphere Coupled Ocean–Atmosphere Response Experiment, was similar to many previously studied, but had some unique features. First, a slow-moving transverse band, which formed the southern leg of the horseshoe, drew most of its low-level updraft air from the squall-line stratiform region on its north side rather than the “environment” to the south. Second, a long-lived cell with many properties similar to a midlatitude supercell, formed 150 km to the rear of the squall line. This cell was tracked for 4 h, as it propagated into and then through the cold pool, and finally dissipated as it encountered the convection forming the northern edge of the horseshoe. Finally, as the squall line was dissipating, a new con...

Fingering Instability in Combustion

A thin solid (e.g., paper), burning against an oxidizing wind, develops a fingering instability with two decoupled length scales. The spacing between fingers is determined by the P\'eclet number (ratio between advection and diffusion). The finger width is determined by the degree two dimensionality. Dense fingers develop by recurrent tip splitting. The effect is observed when vertical mass transport (due to gravity) is suppressed. The experimental results quantitatively verify a model based on diffusion limited transport.

Nonlinear spectral mixture modeling of lunar multispectral data: Implications for lateral transport

Linear and nonlinear spectral mixture models applied to Clementine multispectral images of the Moon result in roughly similar spatial distributions of end‐member abundances. However, there are important differences in the absolute values of the predicted abundances. The magnitude of these differences and the implications for understanding geological processes are investigated across a geologic contact between mare and highland in the Grimaldi Basin on the western nearside of the Moon. Vertical and lateral mass transport due to impact cratering has redistributed mare and highland materials across the contract, creating a gradient in composition. Solutions to linear and nonlinear spectral mixture models for identical spectral end‐members of mature mare, mature highland, and fresh crater materials are compared across this simple geologic contact in the Grimaldi Basin. Formal estimates of uncertainty in the calculated fractions of the end‐members are ≈1%. Profiles of mare abundance across the contact are extracted and compared quantitatively. Profiles from the linear mixture models indicate that the geologic contact has an average mare abundance of 60% and the compositional boundary is asymmetric with more mare transported onto the highland side of the contact than highland onto the mare side of the contact. In contrast, the nonlinear abundance profiles indicate that the geologic contact has an average mare abundance of 50% and the compositional boundary is remarkably symmetric. Given the expectation that materials will be intimately mixed on the surface of the Moon and that the asymmetries implied by the linear model are not consistent with our understanding of lunar surface processes, the non‐linear spectral mixture model is preferred and should be applied whenever quantitative abundance information is required. The remarkable symmetry in the compositional gradients across this contact indicates that lateral mass transport dominates over vertical transport at this boundary.

A Zero Degree of Freedom Total Phosphorus Model: 1. Development for Onondaga Lake, New York

ABSTRACT A seasonal, two-layer, variable volume, mass balance model for total phosphorus in a stratifying eutrophic lake is developed and tested for a single spring to fall interval. The model recognizes settling, sediment release, and vertical mass transport as key in-lake processes mediating phosphorus dynamics. The application presented is termed a “zero degree of freedom” model, as all inputs are determined independently through field and laboratory studies conducted on a test system. The model is considered validated for the test system because simulation results closely match field observations with no calibration (adjustment of model coefficients). Loading reductions at an adjoining wastewater treatment plant, the lake's major phosphorus source, provided an opportunity for model verification. The model framework has utility for other eutrophic stratifying lakes and the “zero degree of freedom” approach will find application where opportunities for both calibration and verification do not exist.

Phase transitions in the Martian mantle: Implications for partially layered convection

Numerical simulations of mantle convection in Mars, using an axisymmetric spherical-shell model, show partial layering caused by the two exothermic olivine-spinel (α-β, β-γ) phase transitions. An extended Boussinesq approximation has been used in which viscous dissipation, adiabatic heating and cooling, and latent heat are included. The Rayleigh number ( Ra) has been varied between 5 × 10 5 and 10 8. The partial layering with the vertical velocity at the exothermic phase transitions varying strongly in space and time is the result of two opposing effects: the enhanced buoyancy of the phase boundaries by thermal anomalies and the impeding influences from the latent heat release (or consumption). The effect of the latent heat is stronger in Mars than the Earth because of the comparatively low pressure gradient in the Martian mantle and the smaller excess temperature of upwellings and downwellings. The time-series of the mean vertical mass transport across the phase transitions show oscillations between blocking and acceleration of the flow. The amplitude and the oscillations in the time-series increase with increasing Ra. Because of the partial layering, the planet will cool more slowly and less uniformly than suggested by thermal evolution models with parameterized convection. In addition, the number of strong mantle plumes is reduced to only a few upwellings. Such a pattern is suggested for Mars by the existence of two pronounced volcanic centers, Tharsis and Elysium. This could also cause a strong time dependence in the Martian volcanic activity. The latent heat release causes the mantle temperature to increase across each transition by about 50 K and produces a hot lower mantle and a liquid core. We have tested the case of a 85–350 km thick perovskite layer at the core-mantle boundary. A layer thicker than about 300 km would convect separately, and induce leaking to the mantle above at a significantly smaller rate compared to the layers induced by the olivine-spinel phase boundaries. For a perovskite layer smaller than about 300 km, the convective vigor near the core-mantle boundary decreases with the layer thickness.

Vertical transport of chlorinated hydrocarbons in unsaturated zone including effect of rainfall

Chlorinated hydrocarbons (CHCs) are highly volatile and little soluble in water, and can exist in unsaturated zone as vaporized, dissolved and undiluted non-aqueous phases. Therefore, it is of great importance to understand transport mechanism of CHCs with gas advection and diffusion in unsaturated zone, and then numerical analysis for vertical transport of CHCs in unsaturated zoneincluding effect of rainfall was conducted. Vertical one-dimensional fluid flow equations and mass transport equations for water and gas phases, and two layer model for mass transfer between the phases were employed in the model presented. The results showed that, though gas phase transport is usually dominant during dry period in unsaturated zone, transport in water phase overcomes that in gas phase during rainwater percolating period.

Modelling of melt segregation processes by high-temperature centrifuging of partially molten granites-II. Rayleigh-Taylor instability and sedimentation

SUMMARY The present experimental study deals with the laboratory modelling of two different mechanisms of gravitational percolation in partially melted rocks: ( 1) diapiric percolation of heavy material and (2) the sedimentation of heavy particles. These two mechanisms of mass transport in partially melted rocks result in different scales of the segregation process in the melt-crystal matrix. A centrifuge furnace was used to simulate the percolation of the heavy particle layer through the partially molten granite at temperatures of up to 1000 C. Samples of Beauvoir granite (Massif Central, France, grain size 0.16-0.5 mm with an initial degree of partial melting -45 per cent) were used as a matrix. A layer of Pt powder suspended in a melt of the same composition as the partially melted matrix was placed on the top of the granite sample. After centrifuging for various times (up to 2 x lo4 s), X-ray images of samples were obtained and the evolution of the percolation process of heavy suspension in the partially molten granite was monitored from the Pt particle distribution. The diapiric or finger regime of percolation starts when the growth rate of a Raleigh-Taylor instability of the heavy layer is faster than the Stokes sedimentation velocity of individual particles in the upper layer. This relationship is a complex function of the size and initial concentration of heavy particles, as well as the ratio of particle to crystal size, the permeability of the matrix, and the heterogeneity scale in the partially melted matrix. At small concentrations (several per cent) and at large concentrations (where close packing of heavy particles results in an anomalous viscosity increase in the upper heavy layer) Stokes sedimentation is dominant in the vertical percolation of the heavy material. The sinking velocity of the diapir decreases when the size of heavy particles in it becomes comparable with the size of crystals in the partially melted granite. In this situation the vertical sinking of the diapir is not stable and the horizontal instability of the vertical mass transport starts to become important. Mass transport via diapiric percolation results in more efficient crystal-melt segregation of partially melted rocks. The percolation of individual particles provides only local melt-crystal flow on a scale comparable with the heavy particle size. The diapiric percolation provides a much larger scale of partial melt segregation with a length-scale comparable with the diapir size.

Numerical study on the interannual oscillation of sea surface temperature in the South China Sea

A two and a half layer oceanic model of wind-driven, thermodynamical general circulation is applied to study the interannual oscillation of sea surface temperature (SST) in the South China Sea (SCS). The model consists of two active layers: the upper mixed layer (UML) and the seasonal thermocline, with the motionless abyss beneath them. The governing equations which include momentum, continuity and sea temperature for each active layer, can describe the physics of Boussinseq approximation, reduced gravity and equatorial β-plane. The formulas for the heat flux at the surface and at the interface between two active layers are designed on the Haney scheme. The entrainment and detrainment at the bottom of the UML induces vertical transport of mass, momentum and heat, and couples of dynamic and thermodynamic effects. Using leap-frog integrating scheme and the Arakawa—C grid the model is forced by a time-dependent wind anomaly stress pattern obtained from category analysis of COADS. The numerical results indicate that there is a kind of oscillation with about 30 months period. The paper supports the opinion that the SST interannual oscillation is the oceanic response to the forcing by monsoon wind anomalies in the SCS.

Development and Testing of a Total Phosphorus Model for Onondaga Lake

ABSTRACT Adynamic two-layer mass balance model for total phosphorus (TP) is developed for culturally eutrophic Onondaga Lake, NY, and tested for the May 1987 through 1990 period. The model accommodates key processes in the lake's phosphorus cycle, including settling of the particulate fraction of TP, sediment release, and vertical mass transport Model development and testing were supported by a comprehensive program of field and laboratory measurements and experiments, to determine model coefficients and external loads, and to establish temporal and vertical distributions of lake TP concentrations. The model performs well in tracking documented interannual, seasonal, and vertical distributions of TP in the lake, and thus is appropriate as a management tool to evaluate management scenarios aimed at abating the lake's cultural eutrophication problem.

Numerical studies of open ocean deep convection

Open ocean deep convection is examined with a nonhydrostatic model based on primitive equations. Strong cooling on the surface of the ocean enforces vertical motion which takes place in the narrow regions of convective cells. Different equations of state are considered, and it is shown that a linear equation of state with a constant thermal expansion coefficient cannot represent the buoyancy field and fluxes properly. The inclusion of thermobaric effects leads to additional vertical acceleration in the whole water column. The parametrization of the convective fluxes by a convective adjustment algorithm represents the horizontal mean temperature quite well but suppresses the entire vertical mass transport within the convective cells. This mass transport may be important for the transport of other tracers. Investigation of an energy cycle of the convective motion sorts out sources and sinks and reveals the conversion between different forms of energy during convective events. Both the vertical and the horizontal component of the Earth rotation vector contribute to the time mean energy balance with the same order of magnitude, but the instantaneous amplitudes of the distinct terms may differ substantially. A sensitivity study with respect to eddy and thermal diffusion coefficients distinguishes two regions; at high values of the diffusivities the velocities and tracer distributions show that a strong dependence on this values occurs, while for sufficiently small coefficients, only a weak dependence is observed.