Applicability of the Langmuir equation to simulate the vertical mass flux profile

2021 ◽  
Vol 14 (16) ◽  
Author(s):  
Huanyu Shi ◽  
Zhibao Dong ◽  
Nan Xiao ◽  
Qinni Huang
Keyword(s):  
Mass Flux ◽  
Langmuir Equation ◽  
Flux Profile

2D Mass Flux Profile of an Oblique Shock Train in a Scramjet Isolator via Dual-Frequency Comb Spectroscopy

2022 ◽  
Author(s):  
David Yun ◽  
Ryan K. Cole ◽  
Sean C. Coburn ◽  
Kristin M. Rice ◽  
Jeffrey M. Donbar ◽  
...  
Keyword(s):  
Mass Flux ◽  
Frequency Comb ◽  
Oblique Shock ◽  
Dual Frequency ◽  
Shock Train ◽  
Flux Profile

Measuring shallow convective mass flux profiles in the trade wind region

2021 ◽  
Author(s):  
Marcus Klingebiel ◽  
Heike Konow ◽  
Bjorn Stevens
Keyword(s):  
Mass Flux ◽  
Large Scale ◽  
Doppler Radar ◽  
Cloud Base ◽  
Trade Wind ◽  
Doppler Lidar ◽  
Shallow Convection ◽  
Lidar Measurements ◽  
Flux Profile ◽  
Convective Mass Flux

AbstractMass flux is a key quantity in parameterizations of shallow convection. To estimate the shallow convective mass flux as accurately as possible, and to test these parameterizations, observations of this parameter are necessary. In this study, we show how much the mass flux varies and how this can be used to test factors that may be responsible for its variation. Therefore, we analyze long term Doppler radar and Doppler lidar measurements at the Barbados Cloud Observatory over a time period of 30 months, which results in a mean mass flux profile with a peak value of 0.03 kg m−2 s−1 at an altitude of ~730 m, similar to observations from Ghate et al. (2011) at the Azores Islands. By combining Doppler radar and Doppler lidar measurements, we find that the cloud base mass flux depends mainly on the cloud fraction and refutes an idea based on large eddy simulations, that the velocity scale is in major control of the shallow cumulus mass flux. This indicates that the large scale conditions might play a more important role than what one would deduce from simulations using prescribed large-scale forcings.

scholarly journals Reverse Engineering the Tropical Precipitation–Buoyancy Relationship

2018 ◽  
Vol 75 (5) ◽  
pp. 1587-1608 ◽  
Author(s):  
Fiaz Ahmed ◽  
J. David Neelin
Keyword(s):  
Mass Flux ◽  
Environmental Influence ◽  
Deep Convection ◽  
Lower Troposphere ◽  
Rapid Onset ◽  
Thermodynamic Structure ◽  
Tropical Precipitation ◽  
Flux Profile ◽  
Vertical Variations ◽  
The Tropics

The tropical precipitation–moisture relationship, characterized by rapid increases in precipitation for modest increases in moisture, is conceptually recast in a framework relevant to plume buoyancy and conditional instability in the tropics. The working hypothesis in this framework links the rapid onset of precipitation to integrated buoyancy in the lower troposphere. An analytical expression that relates the buoyancy of an entraining plume to the vertical thermodynamic structure is derived. The natural variables in this framework are saturation and subsaturation equivalent potential temperatures, which capture the leading-order temperature and moisture variations, respectively. The use of layer averages simplifies the analytical and subsequent numerical treatment. Three distinct layers, the boundary layer, the lower free troposphere, and the midtroposphere, adequately capture the vertical variations in the thermodynamic structure. The influence of each environmental layer on the plume is assumed to occur via lateral entrainment, corresponding to an assumed mass-flux profile. The fractional contribution of each layer to the midlevel plume buoyancy (i.e., the layer weight) is estimated from TRMM 3B42 precipitation and ERA-Interim thermodynamic profiles. The layer weights are used to “reverse engineer” a deep-inflow mass-flux profile that is nominally descriptive of the tropical atmosphere through the onset of deep convection. The layer weights—which are nearly the same for each of the layers—constitute an environmental influence function and are also used to compute a free-tropospheric integrated buoyancy measure. This measure is shown to be an effective predictor of onset in conditionally averaged precipitation across the global tropics—over both land and ocean.

A Simple Parameterization for Detrainment in Shallow Cumulus

2008 ◽  
Vol 136 (2) ◽  
pp. 560-576 ◽  
Author(s):  
Wim C. de Rooy ◽  
A. Pier Siebesma
Keyword(s):  
Mass Flux ◽  
Eddy Simulation ◽  
Shallow Cumulus ◽  
Wide Range ◽  
Flux Profile ◽  
Current Mass ◽  
Lateral Mixing ◽  
Environmental Air ◽  
Bulk Parameter ◽  
Les Model

Abstract For a wide range of shallow cumulus convection cases, large-eddy simulation (LES) model results have been used to investigate lateral mixing as expressed by the fractional entrainment and fractional detrainment rates. It appears that the fractional entrainment rates show much less variation from hour to hour and case to case than the fractional detrainment rates. Therefore, in the parameterization proposed here, the fractional entrainment rates are assumed to be described as a fixed function of height, roughly following the LES results. Based on the LES results a new, more flexible parameterization for the detrainment process is developed that contains two important dependencies. First, based on cloud ensemble principles it can be understood that deeper cloud layers call for smaller detrainment rates. All current mass flux schemes ignore this cloud-height dependence, which evidently leads to large discrepancies with observed mass flux profiles. The new detrainment formulation deals with this dependence by considering the mass flux profile in a nondimensionalized way. Second, both relative humidity of the environmental air and the buoyancy excess of the updraft influence the detrainment rates and, therefore, the mass flux profiles. This influence can be taken into account by borrowing a parameter from the buoyancy-sorting concept and using it in a bulk sense. LES results show that with this bulk parameter, the effect of environmental conditions on the fractional detrainment rate can be accurately described. A simple, practical but flexible parameterization for the fractional detrainment rate is derived and evaluated in a single-column model (SCM) for three different shallow cumulus cases, which shows the clear potential of this parameterization. The proposed parameterization is an attractive and more robust alternative for existing, more complex, buoyancy-sorting-based mixing schemes, and can be easily incorporated in current mass flux schemes.

scholarly journals Airborne Doppler Observations of the Inner-Core Structural Differences between Intensifying and Steady-State Tropical Cyclones

2013 ◽  
Vol 141 (9) ◽  
pp. 2970-2991 ◽  
Author(s):  
Robert Rogers ◽  
Paul Reasor ◽  
Sylvie Lorsolo
Keyword(s):  
Steady State ◽  
Tropical Cyclones ◽  
Vertical Velocity ◽  
Mass Flux ◽  
Inner Core ◽  
Outer Core ◽  
Intensity Increase ◽  
Velocity Spectrum ◽  
Convective Bursts ◽  
Flux Profile

Abstract Differences in the inner-core structure of intensifying [IN; intensity increase of at least 20 kt (24 h)−1, where 1 kt = 0.51 m s−1] and steady-state [SS; intensity remaining between ±10 kt (24 h)−1] tropical cyclones (TCs) are examined using composites of airborne Doppler observations collected from NOAA P-3 aircraft missions. The IN dataset contains 40 eyewall passes from 14 separate missions, while the SS dataset contains 53 eyewall passes from 14 separate missions. Intensifying TCs have a ringlike vorticity structure inside the radius of maximum wind (RMW); lower vorticity in the outer core; a deeper, stronger inflow layer; and stronger axisymmetric eyewall upward motion compared with steady-state TCs. There is little difference in the vortex tilt between 2 and 7 km, and both IN and SS TCs show an eyewall precipitation and updraft asymmetry whose maxima are located in the downshear and downshear-left region. The azimuthal coverage of eyewall and outer-core precipitation is greater for IN TCs. There is little difference in the distribution of downdrafts and weak to moderate updrafts in the eyewall. The primary difference is seen at the high end of the vertical velocity spectrum, where IN TCs have a larger number of convective bursts. These bursts accomplish more vertical mass flux, but they compose such a small portion of the total vertical velocity distribution that there is little difference in the shape of the net mass flux profile. The radial location of convective bursts for IN TCs is preferentially located inside the RMW, where the axisymmetric vorticity is generally higher, whereas for SS TCs the bursts are located outside the RMW.

scholarly journals Numerical study of the time development of drifting snow and its relation to the spatial development

2004 ◽  
Vol 38 ◽  
pp. 343-350 ◽  
Author(s):  
Masaki Nemoto ◽  
Kouichi Nishimura ◽  
Syunichi Kobayashi ◽  
Kaoru Izumi
Keyword(s):  
Steady State ◽  
Mass Flux ◽  
Numerical Study ◽  
Stochastic Theory ◽  
Similar Tendency ◽  
Drifting Snow ◽  
Suspension Process ◽  
Taylor’S Hypothesis ◽  
Flux Profile ◽  
Total Mass Flux

AbstractThe time evolution of drifting snow under a steady wind is estimated using a new numerical model of drifting snow. In the model, Lagrangian stochastic theory is used to incorporate the effect of turbulence on the motion of drifting-snow particles. This method enables us to discuss both the saltation and the suspension process. Aerodynamic entrainment, grain/bed collision (splash process), wind modification and particle size distribution are also taken into account. The calculations show that the time needed by the total mass flux to reach a steady state appears to be 3–5 s. Vertical profiles of horizontal mass flux near the surface show a similar tendency. In contrast, it takes >50 s for the wind speed and the whole mass-flux profile to reach a steady state. This longer time depends on the time-scale of the turbulent diffusion, which is responsible for the mass flux extending to an order of a few meters in height. Applying Taylor’s hypothesis, the estimated length scale at which drifting snow reaches equilibrium is around 400 m. This result is comparable with previously reported field observations.

Numerical Study of Horizontal Pneumatic Conveying of Powder in Different Gravitational Environments

2011 ◽  
Author(s):  
Santiago Lai´n ◽  
Martin Sommerfeld ◽  
Leonardo Botina
Keyword(s):  
Mass Flux ◽  
Small Particle ◽  
Numerical Study ◽  
Particle Mass ◽  
Wall Roughness ◽  
Mass Loading ◽  
Pneumatic Conveying ◽  
Gravitational Settling ◽  
Flux Profile ◽  
Micro Gravity

This paper evaluates the performance of horizontal pneumatic conveying under different gravity environments. An Euler-Lagrange approach validated versus ground experiments is employed to predict the relevant particle variables such as particle mass flux and mean conveying velocity in Lunar and micro-gravity conditions. Gravity reduced computations predict an increase of particle-wall collisions with the upper wall of the channel affecting greatly the particle mass flux profile in the case of low wall roughness and small particle mass loading. If gravitational settling is reduced, e.g. by means of higher wall roughness and/or higher particle mass loadings, particle mean conveying velocity is very similar in Earth and micro-gravity conditions.

scholarly journals A Discussion of Mathematical Models Used to Simulate the Vertical Mass Flux Profile of the Mega-Dune

2020 ◽  
Vol 1670 ◽  
pp. 012011
Author(s):  
Huanyu Shi ◽  
Zhibao Dong ◽  
Nan Xiao ◽  
Qinni Huang
Keyword(s):  
Mathematical Models ◽  
Mass Flux ◽  
Flux Profile

scholarly journals Comparison of Simulations of Updraft Mass Fluxes and Their Response to Increasing Aerosol Concentration between a Bin Scheme and a Bulk Scheme in a Deep-Convective Cloud System

2019 ◽  
Vol 2019 ◽  
pp. 1-29
Author(s):  
Seoung Soo Lee ◽  
Chang-Hoon Jung ◽  
Sen Chiao ◽  
Junshik Um ◽  
Yong-Sang Choi ◽  
...  
Keyword(s):  
Mass Flux ◽  
Cloud Droplet ◽  
Convective Cloud ◽  
Mass Fluxes ◽  
Flux Profile ◽  
Gust Fronts ◽  
Cloud Droplet Number Concentration ◽  
Microphysical Processes ◽  
Snow Loading ◽  
Peak Value

Key microphysical processes whose parameterizations have substantial impacts on the simulation of updraft mass fluxes and their response to aerosol are investigated in this study. For this investigation, comparisons of these parameterizations are made between a bin scheme and a bulk scheme. These comparisons show that the differences in the prediction of cloud droplet number concentration (CDNC) between the two schemes determine whether aerosol-induced invigoration of updrafts or convection occurs. While the CDNC prediction leads to aerosol-induced invigoration of updrafts and an associated 20% increase in the peak value of the updraft-mass-flux vertical profile in the bin scheme, it leads to aerosol-induced suppression of updrafts and an associated 7% decrease in the peak value in the bulk scheme. The comparison also shows that the differences in ice processes, in particular, in the snow loading lead to the different vertical patterns of the updraft-mass-flux profile, which is represented by the peak value and its altitude, between the schemes. Higher loading of snow leads to around 20–30% higher mean peak value and its around 40% higher altitude in the bin scheme than in the bulk scheme. When differences in the CDNC prediction and ice processes are removed, differences in the invigoration and the vertical pattern disappear between the schemes. However, despite this removal, differences in the magnitude of updraft mass fluxes still remain between the schemes. Associated with this, the peak value is around 10% different between the schemes. Also, after the removal, there are differences in the magnitude between cases with different aerosol concentrations for each scheme. Associated with this, the peak value is also around 10% different between those cases for each scheme. The differences between the cases with different aerosol concentrations for each scheme are generated by different evaporative cooling and different intensity of gust fronts between those cases. The remaining differences between the schemes are generated by different treatments of collection and sedimentation processes.

Precipitation Processes and Vortex Alignment during the Intensification of a Weak Tropical Cyclone in Moderate Vertical Shear

2020 ◽  
Vol 148 (5) ◽  
pp. 1899-1929 ◽  
Author(s):  
Robert F. Rogers ◽  
Paul D. Reasor ◽  
Jonathan A. Zawislak ◽  
Leon T. Nguyen
Keyword(s):  
Mass Flux ◽  
Structural Changes ◽  
Doppler Radar ◽  
Deep Convection ◽  
Vertical Wind Shear ◽  
Lower Troposphere ◽  
Cooperative Interaction ◽  
Vertical Shear ◽  
Low Level ◽  
Flux Profile

Abstract The mechanisms underlying the development of a deep, aligned vortex, and the role of convection and vertical shear in this process, are explored by examining airborne Doppler radar and deep-layer dropsonde observations of the intensification of Hurricane Hermine (2016), a long-lived tropical depression that intensified to hurricane strength in the presence of moderate vertical wind shear. During Hermine’s intensification the low-level circulation appeared to shift toward locations of deep convection that occurred primarily downshear. Hermine began to steadily intensify once a compact low-level vortex developed within a region of deep convection in close proximity to a midlevel circulation, causing vorticity to amplify in the lower troposphere primarily through stretching and tilting from the deep convection. A notable transition of the vertical mass flux profile downshear of the low-level vortex to a bottom-heavy profile also occurred at this time. The transition in the mass flux profile was associated with more widespread moderate convection and a change in the structure of the deep convection to a bottom-heavy mass flux profile, resulting in greater stretching of vorticity in the lower troposphere of the downshear environment. These structural changes in the convection were related to a moistening in the midtroposphere downshear, a stabilization in the lower troposphere, and the development of a mid- to upper-level warm anomaly associated with the developing midlevel circulation. The evolution of precipitation structure shown here suggests a multiscale cooperative interaction across the convective and mesoscale that facilitates an aligned vortex that persists beyond convective time scales, allowing Hermine to steadily intensify to hurricane strength.

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