Average Vertical Velocity Research Articles

Effects of cumulus parameterization closures on simulations of summer precipitation over the United States coastal oceans

AbstractThis study evaluates the effects of major cumulus parameterization closures on summer precipitation simulations over the U.S. Atlantic Coasts and Gulf of Mexico. A series of mesoscale regional climate model simulations using an Ensemble Cumulus Parameterization (ECP) that incorporates multiple alternate closure schemes into a single cloud model formulation are conducted and compared to determine the systematic errors and relative performances of individual and combined closures in capturing precipitation spatiotemporal variations. The results show that closure algorithms largely affect precipitation's geographic distribution, frequency and intensity, and diurnal cycle. The quasi‐equilibrium and total instability adjustment closures simulate widespread wet biases, while the instability tendency closure produces systematic dry biases. Two closure algorithms based on the average vertical velocity at the cloud base and column moisture convergence complementarily reproduce the observed precipitation pattern and amount, and capture the frequency of heavy rainfall events better than other closures. In contrast, the instability tendency closures are better at capturing the diurnal phase but yield much larger deficits in amount. Therefore, cloud base vertical velocity and moisture convergence may be the primary factors controlling precipitation seasonal mean and daily variation, while the instability tendency may play a critical role in regulating the diurnal cycle phase.

Delineating seasonal porewater displacement on a tidal flat in the Bay of Bengal by thermal signature: Implications for submarine groundwater discharge

Summary Submarine groundwater discharge (SGD) to the Bay of Bengal is an important groundwater discharge process to southern Asia as well as to the global oceans. Water-fluxes in these regions are not very well understood. The present study demonstrates the use of sea-bed porewater temperature as a tracer for delineating seasonal SGD from a shallow coastal aquifer to the Bay of Bengal. Porewater temperature mapping along with chemical profile of porewater column were used to delineate groundwater discharge zones for different seasons in a hydrologic year. While, the temperature profiles were used to evaluate total groundwater discharge (both terrestrial and marine), the salinity and total dissolved solids profiles were used to evaluate the component due to terrestrial (freshwater) discharge. Several springs and seeps were mapped to finger-print the freshwater discharge zones and identify the terrestrial sourced-SGD temperature windows. These zones are also identified to be enriched with algal mats, and hence may indicate the pathways of nutrient–solute discharge that enhance the primary productivity in the marine ecosystem. Assuming vertical flow in the seabed, simulated rates of discharged groundwater provided a good match with measured discharge rates. The porewater fluxes were estimated by applying analytical solutions of the heat conduction–advection equations to the observed vertical temperature profiles. High resolution thermal profiles to identify T-SGD signatures and chemical profiles along mapped transects reveal the nuances of 3-D seasonal hydrodynamics of groundwater–seawater interactions. The calculated vertical porewater fluxes through the seabed ranged from negligible to 2.45 × 10 −2 m 3 /m 2 /d 1 within a zone extending from high tide line to 40 m offshore, and represent the vertical porewater velocity and the average vertical porewater velocity is found as 8.2 × 10 −3 m 3 /m 2 /d 1 . Approximations suggest that in present-day condition, total average annual SGD to Bay of Bengal is about 1.16 × 10 7 m 3 /y. Seasonal estimates suggest that the averages SGD during pre-monsoon and post-monsoon seasons are ranges 0.6–0.8 × 10 7 m 3 /y for pre-monsoon and 0.8–1.5 × 10 7 m 3 /y for post-monsoon, respectively. The findings suggest that monsoonal activity result in a significant porewater displacement from tidal flat sediments by increased groundwater discharge.

Using statistical learning to close two-fluid multiphase flow equations for a simple bubbly system

Direct numerical simulations of bubbly multiphase flows are used to find closure terms for a simple model of the average flow, using Neural Networks (NNs). The flow considered consists of several nearly spherical bubbles rising in a periodic domain where the initial vertical velocity and the average bubble density are homogeneous in two directions but non-uniform in one of the horizontal directions. After an initial transient motion the average void fraction and vertical velocity become approximately uniform. The NN is trained on a dataset from one simulation and then used to simulate the evolution of other initial conditions. Overall, the resulting model predicts the evolution of the various initial conditions reasonably well.

Direct numerical simulation of fully saturated flow in natural porous media at the pore scale: a comparison of three computational systems

Direct numerical simulations of flow through two millimeter-scale rock samples of limestone and sandstone are performed using three diverse fluid dynamic simulators. The resulting steady-state velocity fields are compared in terms of the associated empirical probability density functions (PDFs) and key statistics of the velocity fields. The pore space geometry of each sample is imaged at 5.06−μm voxel size resolution using X-ray microtomography. The samples offer contrasting characteristics in terms of total connected porosity (about 0.31 for the limestone and 0.07 for the sandstone) and are typical of several applications in hydrogeology and petroleum engineering. The three-dimensional fluid velocity fields within the explicit pore spaces are simulated using ANSYS® FLUENT® ANSYS Inc. (2009), EULAG Prusa et al. (Comput. Fluids 37, 1193–1207 2008), and SSTOKES Sarkar et al. (2002). These computational approaches are highly disperse in terms of algorithmic complexity, differ in terms of their governing equations, the adopted numerical methodologies, the enforcement of internal no-slip boundary conditions at the fluid-solid interface, and the computational mesh structure. As metrics of comparison to probe in a statistical sense the internal similarities/differences across sample populations of velocities obtained through the computational systems, we consider (i) integral quantities, such as the Darcy flux and (ii) main statistical moments of local velocity distributions including local correlations between velocity fields. Comparison of simulation results indicates that mutually consistent estimates of the state of flow are obtained in the analyzed samples of natural pore spaces despite the considerable differences associated with the three computational approaches. We note that in the higher porosity limestone sample, the structures of the velocity fields obtained using ANSYS FLUENT and EULAG are more alike than either compared against the results obtained using SSTOKES. In the low-porosity sample, the structures of the velocity fields obtained by EULAG and SSTOKES are more similar than either is to the fields obtained using ANSYS FLUENT. With respect to macroscopic quantities, ANSYS FLUENT and SSTOKES provide similar results in terms of the average vertical velocity for both of the complex microscale geometries considered, while EULAG tends to render the largest velocity values. The influence of the pore space structure on fluid velocity field characteristics is also discussed.

Asymmetry of internal waves and its effects on the ecological environment observed in the northern South China Sea

Ecological parameters, including current velocity, water temperature, and nutrient and chlorophyll a concentrations, accompanied by two internal solitary waves, were observed in the South China Sea deep basin from 2 October to 4 October, 2012. Both solitons belonged to the mode-1 category, which were characterized by a westward velocity exceeding 1ms−1 above 500m and an eastward velocity up to 0.1ms−1 below 500m. The observed structure of the vertical current was asymmetrical. For the first soliton, the downwelling region had a temporal scale of 32min and an average vertical velocity of 3cms−1, whereas the upwelling region had a temporal scale of 24min and an average vertical velocity of 2cms−1. For the second soliton, the temporal scale and average velocity were 36min and 2cms−1 in the downwelling, compared with 26min and 2cms−1 in the upwelling. On the basis of the convection equation, the downward net vertical displacements of water particles ranged from nearly zero to tens of meters with the maximum value in excess of 50m. Such asymmetry caused changes in temperature as high as 2.3°C, nutrient concentrations up to 12.04μmolL−1, and chlorophyll a concentration up to 0.12μgL−1 before and after the passage of the solitons.

Time‐wave velocity analysis for early earthquake damage detection in buildings: application to a damaged full‐scale RC building

SummaryAn algorithm for time velocity analysis of building response is presented, which identifies the wave velocity of vertically propagating waves through the building and detects their changes. The algorithm is intended for use in SHM systems for rapid assessment of the structural health and integrity following an earthquake. The velocities are identified by an interferometric algorithm, which involves least squares fit of pulses in impulse response functions. An important feature of this method is that it is not sensitive to the effects of soil–structure interaction. The algorithm is applied to a 12‐story RC building in Los Angeles, lightly damaged by the San Fernando 1971 earthquake. The results of the time velocity analysis are critically compared with results of analysis of input power, interstory drift, and instantaneous frequency. The identified average vertical wave velocity was initially ~140 m/s for the NS and ~110 m/s for the EW response and reduced by ~26% and 32%, respectively. The detected reduction of the fundamental frequency of vibration was larger (~44% for the NS and 48% for the EW response). The difference is interpreted to be due to softening of the soil–foundation system, to which the identified frequency of vibration is sensitive. The change was larger in the lower half of the building (~31% for the NS and ~37% for the EW response) as compared with the upper half (~24% for the NS and ~27% for the EW response), consistent with the observed damage. Copyright © 2015 John Wiley & Sons, Ltd.

Dynamics and mass transfer of rising bubbles in a homogenous swarm at large gas volume fraction

AbstractThe present work focuses on the collective effect on both bubble dynamics and mass transfer in a dense homogeneous bubble swarm for gas volume fractions${\it\alpha}$up to 30 %. The experimental investigation is carried out with air bubbles rising in a square column filled with water. Bubble size and shape are determined by means of a high-speed camera equipped with a telecentric lens. Gas volume fraction and bubble velocity are measured by using a dual-tip optical probe. The combination of these two techniques allows us to determine the interfacial area between the gas and the liquid. The transfer of oxygen from the bubbles to the water is measured from the time evolution of the concentration of oxygen dissolved in water, which is obtained by means of the gassing-out method. Concerning the bubble dynamics, the average vertical velocity is observed to decrease with${\it\alpha}$in agreement with previous experimental and numerical investigations, while the bubble agitation turns out to be weakly dependent on ${\it\alpha}$. Concerning mass transfer, the Sherwood number is found to be very close to that of a single bubble rising at the same Reynolds number, provided the latter is based on the average vertical bubble velocity, which accounts for the effect of the gas volume fraction on the bubble rise velocity. This conclusion is valid for situations where the diffusion coefficient of the gas in the liquid is very low (high Péclet number) and the dissolved gas is well mixed at the scale of the bubble. It is understood by considering that the transfer occurs at the front part of the bubbles through a diffusion layer which is very thin compared with all flow length scales and where the flow remains similar to that of a single rising bubble.

Permeability of the Lucky Strike deep-sea hydrothermal system: Constraints from the poroelastic response to ocean tidal loading

We use the time delay between tidal loading and the induced subsurface flow response to constrain the poroelastic behavior and permeability of the Lucky Strike hydrothermal field on the Mid-Atlantic Ridge. We demonstrate that high-temperature (T>200°C) exit-fluid discharge records from four hydrothermal sites across the field are highly coherent with contemporaneously acquired bottom pressure records at tidal periods, with the thermal response lagging pressure by ∼155° (5.3 h) on average across all sites for the semi-diurnal (M2) frequency over a three-year observation period. In a one-dimensional poroelastic model of ocean tidal loading this phase lag corresponds to a high-permeability system where pore pressure perturbations at the seafloor rapidly propagate downward from the seafloor interface until they encounter a permeability boundary. Our results suggest that at the Lucky Strike field this tidal pumping is largely restricted to the ∼600 m thick extrusive layer (i.e., seismic layer 2A). Under a plausible set of matrix elastic parameters, the ∼5.3 h lag between pressure and exit-fluid temperature is consistent with an effective matrix permeability of ∼10−10 m2 and an average vertical flow velocity of ∼0.02 m/s within the extrusive layer. Our results argue against tidal pumping of the entire crustal section between the seafloor and the axial magma chamber (at ∼3.4 kmbsf) because this scenario requires unrealistically high effective permeabilities (∼10−9 m2) and average vertical flow velocities (∼0.15 m/s) over this depth range. Our effective permeability estimate for the extrusive layer is broadly consistent with previous results, and indicates that flow must be channeled in discrete permeable pathways (e.g., faults, fissures) that cut through the extrusive volcanic layer.

SYNTHESIS OF CONTROL LAWS FOR AIRPLANE AUTOMATIC TOUCHDOWN ON THE CHASSIS

The resulting formation law of unperturbed unmanned aircraft alignment trajectory that guarantees equality of the contact point parameters to given values, and allows parametric changes, wind disturbance, difficulty trajectory is offered. As the criterion for the synthesis was elected the lowest average vertical velocity at the last 30% of the trajectory. This allowed small vertical velocity when touching, even in cases of early or delayed landing. Methods of stabilize laws analytical designing of the aircraft on landing trajectory is obtained. It provides effective control laws implemented by the limited use of controls. The technique is based on the proposed additional quality criterion and search algorithm of its extremum. This criterion is to minimize the error variance of the slope angle of the trajectory and maximum rudder deflection height. It is shown that this heuristic criterion increases the accuracy of the aircraft stabilizing on landing trajectory. It was established that the automated search algorithm of heuristic quality criterion global extremum on the set of Kalman-Letov functional parameters has improved reliability and increased performance. This algorithm can be used for other tasks extremum search. Its effectiveness is confirmed by testing for problems with known solutions. The results of simulation modeling for automatic landing of unmanned aircraft with inaccurately known parameters of the mathematical model with the action of wind shows enough quality of obtained control laws and usefulness of the proposed methods.

The vertical structure and kinematics of grand design spirals

Abstract We use an N-body simulation to study the 3D density distribution of spirals and the resulting stellar vertical velocities. Relative to the disc's rotation, the phase of the spiral's peak density away from the mid-plane trails that at the mid-plane. In addition, at fixed radius the density distribution is azimuthally skewed, having a shallower slope on the trailing side inside corotation and switching to shallower on the leading side beyond corotation. The spirals induce non-zero average vertical velocities, 〈Vz〉, as large as 〈Vz〉 ∼ 10–20 km s−1, consistent with recent observations in the Milky Way. The vertical motions are compressive (towards the mid-plane) as stars enter the spiral, and expanding (away from the mid-plane) as they leave it. Since stars enter the spiral on the leading side outside corotation and on the trailing side within corotation, the relative phase of the expanding and compressive motions switches sides at corotation. Moreover, because stars always enter the spiral on the shallow density gradient side and exit on the steeper side, the expanding motions are larger than the compressing motions.

Turbulence and Radiation in Stratocumulus-Topped Marine Boundary Layers: A Case Study from VOCALS-REx

AbstractObservations made during a 24-h period as part of the Variability of the American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study Regional Experiment (VOCALS-REx) are analyzed to study the radiation and turbulence associated with the stratocumulus-topped marine boundary layer (BL). The first 14 h exhibited a well-mixed (coupled) BL with an average cloud-top radiative flux divergence of ~130 W m−2; the BL was decoupled during the last 10 h with negligible radiative flux divergence. The averaged radiative cooling very close to the cloud top was −9.04 K h−1 in coupled conditions and −3.85 K h−1 in decoupled conditions. This is the first study that combined data from a vertically pointing Doppler cloud radar and a Doppler lidar to yield the vertical velocity structure of the entire BL. The averaged vertical velocity variance and updraft mass flux during coupled conditions were higher than those during decoupled conditions at all levels by a factor of 2 or more. The vertical velocity skewness was negative in the entire BL during coupled conditions, whereas it was weakly positive in the lower third of the BL and negative above during decoupled conditions. A formulation of velocity scale is proposed that includes the effect of cloud-top radiative cooling in addition to the surface buoyancy flux. When scaled by the velocity scale, the vertical velocity variance and coherent downdrafts had similar magnitude during the coupled and decoupled conditions. The coherent updrafts that exhibited a constant profile in the entire BL during both the coupled and decoupled conditions scaled well with the convective velocity scale to a value of ~0.5.

Measurements of the pore‐scale water flow through snow using Fluorescent Particle Tracking Velocimetry

Fluorescent Particle Tracking Velocimetry (FPTV) measurements of the pore‐scale water flow through the pore space of a wet‐snow sample are presented to demonstrate the applicability of this measurement technique for snow. For the experiments, ice‐cooled water seeded with micron sized fluorescent tracer particles is either sprinkled on top of a snow sample to investigate saturated and unsaturated gravity‐driven flow or supplied from a reservoir below the snow sample to generate upward flow driven by capillary forces. The snow sample is illuminated with a laser light sheet and the fluorescent light of the particles transported with the water in the pore space is recorded with a high‐speed camera equipped with an optical filter. Tracking algorithms are applied to the images to obtain flow paths and flow velocities. A flow loop found in a pore space for the case of saturated gravity flow together with the tortuosity of the particle trajectories indicate the three‐dimensionality of the water flow in wet snow. The average vertical flow velocities in the pore spaces were 11.2 mm s−1 for the downward saturated gravity flow and 9.6 mm s−1 for the upward flow that is driven by capillary forces for the limited cases presented as examples of the measurement technique. In the case of unsaturated gravity‐driven flow, the average and the maximum flow velocities were found to be 30 times smaller than for the saturated gravity flow. Velocity histograms show that the fraction of the total water flowing against the main flow direction was about 3–5%, and that the horizontal velocities average to zero for both the saturated gravity‐driven and the capillary flow.

Paleohydrogeology of the Cretaceous sediments of the Williston Basin using stable isotopes of water

Hydraulic and isotopic data collected from aquifers are routinely used to characterize hydrogeological conditions within sedimentary basins, but similar data from confining units are generally not collected despite their ability to provide insights on important water/solute transport controls. We characterized paleogroundwater flow and solute transport mechanisms across 384 m of Cretaceous shale (aquitard) in the Williston Basin, Canada, using high‐resolution depth profiles of water isotopes (δ18O, δ2H). Water samples were also collected from wells installed in the underlying regional sandy aquifer (Mannville Fm; 93 m thick) and from seepage inflows into potash mine shafts (to 825 m below ground). The 1‐D numerical transport modeling of δ18O profiles provided insight into large‐scale/long‐term solute transport in both Cretaceous sediments and the basin. Despite the potential for significant advective migration during glaciations, molecular diffusion appears to be the dominant solute transport mechanism through the aquitard. Simulations suggest average vertical groundwater velocities of <0.05 m/10 ka and an average excess hydraulic head of <10 m; these values are much less than anticipated by successive glaciations. The dominant paleoevent reflected in present‐day profiles is introduction during the Pleistocene of glaciogenic meteoric water to the aquifer underlying the shale, likely along an aquifer outcrop area east of the site or through local vertical conduits. Simulations suggest these recharge events occurred during one or more glacial periods. The isotopic profile over the upper 25 m of Pleistocene till and shale is consistent with glacial deposition and transport processes within these units over the Holocene (past 10 ka).

Lightning forecasting in southeastern Brazil using the WRF model

This paper introduces a lightning forecasting method called Potential Lightning Region (PLR), which is the probability of the occurrence of lightning over a region of interest. The PLR was calculated using a combination of meteorological variables obtained from high-resolution Weather Research and Forecasting (WRF) model simulations during the summer season in southeastern Brazil. The model parameters used in the PLR definition were: surface-based Convective Available Potential Energy (SBCAPE), Lifted Index (LI), K-Index (KI), average vertical velocity between 850 and 700hPa (w), and integrated ice-mixing ratio from 700 to 500hPa (QICE). Short-range runs of twelve non-severe thunderstorm cases were performed with the WRF model, using different convective and microphysical schemes. Through statistical evaluations, the WRF cloud parameterizations that best described the convective thunderstorms with lightning in southeastern Brazil were the combination of Grell–Devenyi and Thompson schemes. Two calculation methods were proposed: the Linear PLR and Normalized PLR. The difference between them is basically how they deal with the influence of lightning flashes over the WRF domain's grid points for the twelve thunderstorms analyzed. Three case studies were used to test both methods. A statistical evaluation lowering the spatial resolution of the WRF grid into larger areas was performed to study the behavior and accuracy of the PLR methods. The Normalized PLR presented the most suitable one, predicting flash occurrence appropriately.

Simple Models of Helical Baroclinic Vortices

Two distinct asymptotic solutions of the inviscid Boussinesq equations for a steady helical baroclinic Rankine-like vortex with pre- scribed buoyancy forcing are considered and critically compared. In both cases the relative distribution of the velocity components is the same across the vortex at all altitudes (the similarity assumption). The first vortex solution demonstrates monotonic growth with height of the vortex core radius, which becomes infinite at a certain critical altitude, and the corresponding attenuation of the vertical vorticity. The second vortex solution schematises the vortex core as an inverted cone of small angular aperture. These idealised vortices are then embedded in a convectively unstable boundary layer; the resulting approximate vortex solutions have been applied to determine the maximum rotational velocity in vortices. Both models predict essentially the same dependence of the model-inferred peak rotational velocity on the swirl number (the ratio of the maximum swirl velocity to the average vertical velocity in the main vortex updraft). The helicity budget of the vortex flow is analysed in detail, where applicable.

Terminal Falling Characteristics of a Sand Grain with Dufour and Soret Effects

The transient effect of double diffusive natural convection of flow in a differentially heated sand grain with Soret and Dufour coefficients is studied numerically. The right vertical wall has constant temperature Tc. The lower inlet opening is heated uniformly with fixed temperature Th and the velocity at the inlet of the fluid domain is set to the falling velocity Vi. The condition Th > Tc is maintained all over the domain. The concentration in right wall is maintained higher than inlet opening (Cc < Ch). The governing equations are solved numerically subject to appropriate boundary conditions by a penalty finite-element method. Solutions are obtained for fixed Prandtl number (Pr = 1.73), Rayleigh number (Ra = 104), Dufour coefficient (Df = 0.5) and Soret coefficient (Sr = 0.5). Transient analysis of the streamlines, isotherms, iso-concentration, falling velocity and forces on sand grain, the local and average Nusselt number and Sherwood number, temperature and concentration at subdomain centre as well as average form, subdomain horizontal and vertical velocities are presented graphically. It is found that the rate of heat transfer and mass transfer in the sand grain enhances and reduces respectively for shorter time periods and then they become almost steady.© 2013 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: http://dx.doi.org/10.3329/jsr.v5i1.10003 J. Sci. Res. 5 (1), 91-103 (2013)

Dynamical arching in a two dimensional granular flow

A study of grains flow in a two dimensional hopper using particle tracking and photoelastic methods is presented in this article. An intermittent network of contact forces consisting of force chains and arches is observed. This network is responsible for fluctuations in the average vertical velocity. The magnitude of these fluctuations depends on the hopper’s geometry, and it quickly reduces for large aperture size and small inclination angles. The average velocity field is described using a combination of harmonic angular functions and a power law of radial position. The mass flow rate is determined through the average velocity field and a Beverloo type scaling is obtained. We found that the effect of the inclination angle on the mass flow rate is given by $${\alpha/ \,(\sin\alpha)^{3/2}}$$ . It is also found that the critical aperture size, approaching jamming, depends linearly on $${\sin\alpha}$$ . At small D/d, the time average of the network of contact forces shows a boundary with characteristics resembling the free fall arch. We show that an arch can be built following the principal compression orientation of the stress tensor which captures the characteristics of the arches observed experimentally.

Discharge estimation of the Shin-Yuan Canal using indirect method

This study presents an indirect method for estimating the discharge of the Shin-Yuan Canal. It includes a new tool of velocity measurement, a method of discharge computation, and some technology. When the Shin-Yuan Canal was built, the issue of discharge measurement was not considered. The Shin-Yuan Canal was co-constructed with the Wan-Dan Canal. Therefore, direct discharge measurement was impossible. This study indirectly estimated the discharge of the Shin-Yuan Canal by controlling the pump discharge through a pumping station. And a stage-discharge rating curve was created for continuous and real-time monitoring of canal discharge. In order to improve measurement accuracy and reliability, this study adopted the acoustic digital current meter (ADC) for discharge measurement. The probabilistic velocity distribution equation was used to accurately calculate the average vertical velocity and the area-velocity principle was used to estimate the water discharge of the Wan-Dan Canal. According to the measurement results, the discharge rating curve of the Shin-Yuan Canal could be accurately established with the precise device, ADC, and the technologies which could effectively measure velocity. This method should be promoted and applied to other similar discharge measurement and monitoring issues of irrigation canals.

Vertical velocity structure of marine boundary layer trade wind cumulus clouds

[1] Oceanic trade wind cumulus clouds not only impact the Earth's radiation budget but also affect the boundary layer (BL) structure. Data from the deployment of Atmospheric Radiation Measurements (ARM)'s Mobile Facility at the island of Graciosa in the Azores is used to study the vertical velocity structure of these clouds. The surface fluxes as reported by the European Centre for Medium-Range Weather Forecasting (ECMWF) analysis model were used to characterize the dynamic structure of the BL. Cloud radar data from nine cases totaling to 114 hours and containing 557 cumulus cloud elements are analyzed to report hourly values of mean reflectivity, mean vertical velocity, cloud fraction, and cloud mass flux. The hourly averaged in-cloud vertical velocity was constant (∼0.35 m s−1) with height, while the average velocity of updrafts and vertically coherent updrafts increased from cloud base to cloud top. The reflectivity did not exhibit any significant changes between all, updraft and coherent updraft samples. The cloud fraction and mass flux showed similar vertical profiles with both having a peak near cloud base. The mass flux contribution of vertically coherent updrafts spanning through the entire cloud layer to the average updraft mass flux was ∼62%. The hourly values were classified based on the surface convective velocity scale (w*) as reported by the ECMWF model. The cloud fraction near cloud base during hours with w* less than 0.2 m s−1 was ∼6% while that during hours with w* greater than 0.6 m s−1 was ∼9%. The cloud base mass flux during hours with w* greater than 0.6 m s−1 was almost double that during hours with w* less than 0.2 m s−1.

Impact of the altitudinal Joule heating distribution on the thermosphere

[1] The thermospheric response at satellite altitudes along low Earth orbit is subject to the energy deposition locally, i.e., at high altitudes, and the vertical wave propagation from the energy injection at lower altitudes. In this study, a general circulation model has been run to investigate the source of nonhydrostatic effects and the sensitivity of the vertical wind and neutral density at satellite orbits to the energy deposited at low and high altitudes. Through comparing the simulations with and without the Joule heating enhancement above 150 km altitude, the impact of the heating at low and high altitudes on the high-altitude thermosphere has been separated. The numerical simulations show that most of the nonhydrostatic effects at high altitudes (300 km) arise from sources below 150 km and propagate vertically through the acoustic wave. The heating above 150 km is responsible for a large increase of the average vertical velocity (40 m/s) and neutral density (50%) at 300 km and higher altitudes.