Vertical Profiles Of Pressure Research Articles

Analysis of Radon Near-Surface Measurements, Using Co-Located Ozone Data, Radio-Sounding Vertical Profiles, Sensible Heat Flux and Back-Trajectory Calculation

Simultaneous and co-located observations of near-surface Radon-222, ozone and meteorological parameters in a central Italy observation site operated by the University of L’Aquila (Italy), are used to study the physical drivers of the radon abundance during night-time hours. The knowledge of the potential temperature vertical gradient in the surface layer of nocturnal thermal inversion is made possible using co-located radio-sounding vertical profiles of pressure and temperature, thus making possible to indirectly infer the local surface flux of atmospheric radon (16 ± 6 mBq m−2 s−1). The dynamical removal due to turbulent convective motions is found to be the dominant controlling process, determining large differences in the near-surface radon abundance between stable and unstable conditions of the nocturnal Planetary Boundary Layer (PBL). Usual unstable PBL conditions during daytime hours induce an effective dynamical vertical dilution of surface radon, which rapidly reaches a quasi-steady-state abundance during mid-day and afternoon hours, with very low concentration values (5.1 ± 2.0 Bq m−3). Using back-trajectory reanalyses, estimates of local radon fluxes and vertical mixing efficiencies inside the PBL along the air mass latitudinal-longitudinal path and finally the irreversible radon loss due to radioactive decay, we have explored the fraction of daytime radon attributable to long-range advection in the continental near-mountain measurement site of L’Aquila (44 ± 18%).

Characteristics of atmospheric variables over the southern coast of West Java in the presence of Australian Monsoon and MRG waves

The characteristics of atmospheric variables over the southern coast of West Java in the presence of Australian Monsoon (AUM) and Mixed Rossby-Gravity (MRG) waves were investigated by conducting a dedicated radiosonde observation campaign from 26 to 29 September 2022 at Pameungpeuk Station (107.7°E, 7.6°S). The vertical profiles of pressure, temperature, relative humidity, and wind in the presence of the AUM and MRG waves were obtained and analyzed. The Global Navigation Satellite System - Radio Occultation (GNSS-RO) and the latest ECMWF climate reanalysis (ERA5) data were used to identify the MRG waves features using Hovmöller, space-time spectral, and wavelet analyses. Furthermore, spatial and time-series analyses were performed to study the wave propagation. The results showed the characteristics of atmospheric variables over Pameungpeuk Station in the presence of the AUM and MRG waves. We found that the presence of AUM significantly reduced the relative humidity, particularly in the region from 2 to 10 km altitude, and enhanced the average wind speed during the campaign compared to the wet season. Moreover, we found the reduction of low-level pressure, the enhancement of temperature and relative humidity in the mid-troposphere, and the weakening of the easterly and southerly winds during the dry phase approaching the wet phase of the MRG waves over the southern coast of West Java following the wave structure and propagation.

Drone-Based Vertical Atmospheric Temperature Profiling in Urban Environments

The accurate and detailed measurement of the vertical temperature, humidity, pressure, and wind profiles of the atmosphere is pivotal for high-resolution numerical weather prediction, the determination of atmospheric stability, as well as investigation of small-scale phenomena such as urban heat islands. Traditional approaches, such as weather balloons, have been indispensable but are constrained by cost, environmental impact, and data sparsity. In this article, we investigate uncrewed aerial systems (UASs) as an innovative platform for in situ atmospheric probing. By comparing data from a drone-mounted semiconductor temperature sensor (TMP117) with traditional radiosonde measurements, we spotlight the UAS-collected atmospheric data’s accuracy and such system suitability for atmospheric surface layer measurement. Our research encountered challenges linked with the inherent delays in achieving ambient temperature readings. However, by applying specific data processing techniques, including smoothing methodologies like the Savitzky–Golay filter, iterative smoothing, time shift, and Newton’s law of cooling, we have improved the data accuracy and consistency. In this article, 28 flights were examined and certain patterns between different methodologies and sensors were observed. Temperature differentials were assessed over a range of 100 m. The article highlights a notable accuracy achievement of 0.16 ± 0.014 °C with 95% confidence when applying Newton’s law of cooling in comparison to a radiosonde RS41’s data. Our findings demonstrate the potential of UASs in capturing accurate high-resolution vertical temperature profiles. This work posits that UASs, with further refinements, could revolutionize atmospheric data collection.

Low-pressure and low-temperature phase equilibria applied to Pluto’s lower atmosphere

ABSTRACT While phase equilibria at conditions on Pluto’s surface have been studied, the fate of the equilibria in the lower atmosphere as the altitude increases has not. In this study, the gravitational effect is included in the thermodynamic modelling so that not only the deposition point can be located, but also the vertical pressure and density profiles below the deposition point can be determined, along with the corresponding compositional profiles in the equilibrium phases. The non-ideality of vapour-solid phase equilibria at low pressures and temperatures is also discussed for Pluto’s applications to allow for more accurate calculations if a conventional method, such as modified Raoult’s law, is used.

In-situ measurements of energetic depth-limited wave loading

An extensive database of in situ measurements of wave impact pressure on the wall of a composite breakwater and associated explanatory variables (i.e., waves, wind, and water level) was collected in a particularly high-energy wave environment. Due to the bottom profile, which includes a wide mound of concrete blocks with a seaward edge that rises to the Lowest Astronomical Tide level over a large distance, most waves break before reaching the monitored barrier, making the data set representative of depth-limited wave loading. Maximum pressure is consistently found at the sensor position closest to the mean free surface, and statistically, a decrease of maximum pressure with the altitude is observed. Nevertheless, the database also shows a wide variety of vertical profiles of maximum pressure. A detailed analysis of the pressure signal shows that there are two impact classes associated with large pressure values. The first is mostly observed during stormy conditions with relatively slow pressure variations over time and a fairly uniform spatial distribution. The second class exhibits very limited pressure peaks in time and space and is most often observed during moderate sea states and high water levels. The pressure signals for each class agree well with the prediction of the PROVERB impact classification based on breakwater dimensions, water level, and wave parameters. Our dataset also shows the existence of impacts with simultaneous large pressure and rise time, which extends the range of the observed values of the pressure impulse already reported in-situ from 31000 Pa.s to 100000 Pa.s. For strong impacts that show regular upward propagation, the peak pressure propagation velocity was estimated and most values remain below 20 m/s. Finally, we performed a statistical analysis to relate the maximum pressure to a number of variables, including offshore wave parameters, water level, and wind parameters. The multiple linear regression model created confirms the dominant influence of wave height and the negligible influence of the wind on pressure maxima. The other wave parameters are still significant but of secondary importance. Finally, the upper bound of the 99% prediction interval predicts the maximum pressure given a set of wave and water level conditions with a good confidence level which is an encouraging result.

Numerical Weather Predictions and Re-Analysis as Input for Lidar Inversions: Assessment of the Impact on Optical Products

The atmospheric molecular number density can be obtained from atmospheric temperature and pressure profiles and is a significant input parameter for the inversion of lidar measurements. When measurements of vertical profiles of temperature and pressure are not available, atmospheric models are typically considered a valid alternative option. This paper investigates the influence of different atmospheric models (forecast and reanalysis) on the retrieval of aerosol optical properties (extinction and backscatter coefficients) by applying Raman and elastic-only methods to lidar measurements, to assess their use in lidar data processing. In general, reanalyzes are more accurate than forecasts, but, typically, they are not delivered in time for allowing near-real-time lidar data analysis. However, near-real-time observation is crucial for real-time monitoring of the environment and meteorological studies. The forecast models used in the paper are provided by the Integrated Forecasting System operated by the European Centre for Medium-Range Weather Forecasts (IFS_ECMWF) and the Global Data Assimilation System (GDAS), whereas the reanalysis model is obtained from the fifth-generation European Centre for Medium-Range Weather Forecasts ReAnalysis v5 (ERA5). The lidar dataset consists of measurements collected from four European Aerosol Research Lidar Network (EARLINET) stations during two intensive measurement campaigns and includes more than 200 cases at wavelengths of 355 nm, 532 nm, and 1064 nm. We present and discuss the results and influence of the forecast and reanalysis models in terms of deviations of the derived aerosol optical properties. The results show that the mean relative deviation in molecular number density is always below ±3%, while larger deviations are shown in the derived aerosol optical properties, and the size of the deviation depends on the retrieval method together with the different wavelengths. In general, the aerosol extinction coefficient retrieval is more dependent on the model used than the aerosol backscatter retrievals are. The larger influence on the extinction retrieval is mainly related to the deviation in the gradient of the temperature profile provided by forecast and reanalysis models rather than the absolute deviation of the molecular number density. We found that deviations in extinction were within ±5%, with a probability of 83% at 355 nm and 60% at 532 nm. Moreover, for aerosol backscatter coefficient retrievals, different models can have a larger impact when the backscatter coefficient is retrieved with the elastic method than when the backscatter coefficient is calculated using the Raman method at both 355 nm and 532 nm. In addition, the atmospheric aerosol load can also influence the deviations in the aerosol extinction and backscatter coefficients, showing a larger impact under low aerosol loading scenarios.

Characteristic Decrease in the Value of Rapeseed Evapotranspiration after Its Ripening

This paper presents the methodology of taking measurements of active surface energy balance components using the Bowen method. It discusses the applied measurement system, an important part of which are HMD 50U/50Y measurement sensors from Vaisala, adapted to work in the field. Their operation is a source of data for determining vertical profiles of temperature and water vapour pressure. These data are used to determine the turbulence components of the energy balance, i.e., sensible and latent heat. Measurements taken during the vegetative season on rape field showed that intensive evaporation occurred in the period until the end of June and that its decrease coincided with the decrease in the value of the degree of plant development determined on the basis of LAI records. In spring, during the period of intensive plant development, the decade sums of evaporation reached 30 mm, after which their quantities fell to the range of 10–15 mm. They became higher only in the periods of precipitation, when the water from the interception was available.

Pressure profile definition over the metal orthotropic deck surface of the decking superstructure ballast pocket from the local load action

The article discusses the interaction issue between the track and the rolling stock to determine the forces working on the track during the passage of a rolling load, and their further distribution through the ballast bed. The study aims to determine the vertical pressure profile working on the orthotropic metal ballast bed slab of the railway superstructure. To determine the load share from the rolling stock transferred from the rails to the cross-sleepers, the rail is represented as a beam of infinite length with one or several concentrated forces. To determine the cross-sleeper stress-strain state, it is considered as a short beam on a cushion course. The article presents the substantiation of the flow mechanics formulas application possibility to the ballast bed. Based on the Boussinesq problem solution, calculation formulas are obtained for determining the pressure along with the ballast bed plate. The results obtained by the proposed method were compared with other authors’ experimental data and the finite element modeling results in the Midas FEA software package. The analysis took into account the design features of the ballast bed plates and the track superstructure on the existing superstructures. A theoretical study of the influence of the sheet of the covering bending stiffness on the pressure profile northing is carried out. The proposed method is applicable for various superstructure and the ballast bed slab, and also takes into account the uneven pressure distribution on the inner and outer rails from the trainload, changes in eccentricity along the length of the structure, different thickness of the ballast bed under the cross-sleepers ends, as well as the effect of centrifugal force.

Simulating summer mixing heights in California's San Joaquin Valley using the WRF meteorological model with three land surface modules

During the 1990 SARMAP/AUSPEX study a network of rawinsondes was flown at 3- and 6-h intervals to evaluate the meteorological conditions conducive high ozone concentrations in the Central Valley of California. Vertical profiles of air temperature, humidity, and pressure from 9 of the sites were used to determine maximum daily mixing heights in California’s San Joaquin Valley (SJV) during the period August 3–6, 1990 and to evaluate their spatial distribution. The analysis showed a general pattern of increasing mixing heights from north to south within the SJV. But, it also showed that mixing heights were lower in areas in proximity to irrigated agriculture. The WRF prognostic meteorological model was used to simulate mixing heights during this period using three land surface modules (LSM): thermal diffusion (TD), Noah, and Pleim-Xiu (PXU). The maximum daily mixing heights simulated using the TD LSM were generally negatively biased; while those simulated using the Noah and PXU LSMs were positively biased. The differences in simulated mixing heights were attributed to differences in how crop land irrigation water is represented within each LSM. The TD LSM effectively assumes a fixed soil water content, but of sufficient magnitude to reflect latent heat fluxes associated with crop land irrigation. The PXU and Noah LSMs include comprehensive descriptions of the soil water budget. However, soil water may be depleted in the arid summer climate and these LSMs provide no direct means of accounting for water added through irrigation. The LSMs were also sensitive to estimates of ground cover in irrigated areas. For all 9 sites, the root mean square error (RMSE) for maximum daily mixing heights for the TD LSM, the Noah LSM, and the PXU LSM was 269, 350, and 366 m, respectively; and the biases for the 9 sites were − 161, 355, and 437 m, respectively. Using the assumption of well-managed irrigation and leaf area index (LAI) estimates from AVHRR remote sensing data sets, adjustments to the WRF input files were made to update soil water contents and ground cover for irrigated crop land use. Using the Noah LSM with the adjusted files, site-specific mixing height biases were reduced up to a factor of 4 and, for all sites, the RMSE for maximum daily mixing heights were reduced from 350 to 260 m; for the PXU LSM RMSEs were reduced from 366 to 238 m; and for the TD LSM from 269 to 231 m. This analysis illustrates the importance of accounting for the effects of applied irrigation water and ground cover in the simulation of mixing heights during the arid summer within the SJV. Irrigation can influence actual mixing heights and their distribution within a domain. It also illustrates that the choice of LSM is of less importance than setting LSM parametrizations to values appropriate for the modeling domain.

Improving the Estimation of Weighted Mean Temperature in China Using Machine Learning Methods

As a crucial parameter in estimating precipitable water vapor from tropospheric delay, the weighted mean temperature (Tm) plays an important role in Global Navigation Satellite System (GNSS)-based water vapor monitoring techniques. However, the rigorous calculation of Tm requires vertical profiles of temperature and water vapor pressure that are difficult to acquire in practice. As a result, empirical models are widely used but have limited accuracy. In this study, we use three machine learning methods, i.e., random forest (RF), backpropagation neural network (BPNN), and generalized regression neural network (GRNN), to improve the estimation of empirical Tm in China. The basic idea is to use the high-quality radiosonde observations estimated Tm to calibrate and optimize the empirical Tm through machine learning methods. Validating results show that the three machine learning methods improve the Tm accuracy by 37.2%, 32.6%, and 34.9% compared with the global pressure and temperature model 3 (GPT3). In addition to the overall accuracy improvement, the proposed methods also mitigate the accuracy variations in space and time, guaranteeing evenly high accuracy. This study provides a new idea to estimate Tm, which could potentially contribute to the GNSS meteorology.

Pressure balance in the multiphase ISM of cosmologically simulated disc galaxies

ABSTRACT Pressure balance plays a central role in models of the interstellar medium (ISM), but whether and how pressure balance is realized in a realistic multiphase ISM is not yet well understood. We address this question by using a set of FIRE-2 cosmological zoom-in simulations of Milky Way-mass disc galaxies, in which a multiphase ISM is self-consistently shaped by gravity, cooling, and stellar feedback. We analyse how gravity determines the vertical pressure profile as well as how the total ISM pressure is partitioned between different phases and components (thermal, dispersion/turbulence, and bulk flows). We show that, on average and consistent with previous more idealized simulations, the total ISM pressure balances the weight of the overlying gas. Deviations from vertical pressure balance increase with increasing galactocentric radius and with decreasing averaging scale. The different phases are in rough total pressure equilibrium with one another, but with large deviations from thermal pressure equilibrium owing to kinetic support in the cold and warm phases, which dominate the total pressure near the mid-plane. Bulk flows (e.g. inflows and fountains) are important at a few disc scale heights, while thermal pressure from hot gas dominates at larger heights. Overall, the total mid-plane pressure is well-predicted by the weight of the disc gas and we show that it also scales linearly with the star formation rate surface density (ΣSFR). These results support the notion that the Kennicutt–Schmidt relation arises because ΣSFR and the gas surface density (Σg) are connected via the ISM mid-plane pressure.

Experimental realization of incipient active failure in sand heap by seismic loading

Sand heaps avalanche when a static angle of repose is exceeded, and freeze at a dynamic angle of repose. The stress distribution in a planar sand heap stabilized at the angle of repose with an incipient active failure condition, by which the material is on the verge of failure everywhere, was examined. At the time of construction, the vertical pressure was initially not in the incipient failure. A slight amount of seismic loading using the sinusoidal motions of a shaking table was set up with just enough energy to rearrange the sand particles, to erase the formation history, and to fluctuate local density inside a sand heap without an excessive loss of mass. During the experiments, laser displacement sensors and pressure gauges were employed to monitor the vertical displacements above and the vertical pressures below the sand heap respectively. The non-linear differential equations, characterizing the stress distribution in an active sand heap, were formulated under the Mohr–Coulomb failure criterion and numerically solved by the Newton method. Bulk solids started flowing after the state of incipient failure; therefore, the experimental vertical pressure profiles were found to gradually conform to the theoretical vertical pressure profiles if the sand heap was subjected to sufficient excitation.

An improved depth‐averaged nonhydrostatic shallow water model with quadratic pressure approximation

SummaryPhase‐resolved information is necessary for many coastal wave problems, for example, for the wave conditions in the vicinity of harbor structures. Two‐dimensional (2D) depth‐averaging shallow water models are commonly used to obtain a phase‐resolved solution near the coast. These models are in general more computationally effective compared with computational fluid dynamics software and will be even more capable if equipped with a parallelized code. In the current article, a 2D wave model solving the depth‐averaged continuity equation and the Euler equations is implemented in the open‐source hydrodynamic code REEF3D. The model is based on a nonhydrostatic extension and a quadratic vertical pressure profile assumption, which provides a better approximation of the frequency dispersion. It is the first model of its kind to employ high‐order discretization schemes and to be fully parallelized following the domain decomposition strategy. Wave generation and absorption are achieved with a relaxation method. The simulations of nonlinear long wave propagations and transformations over nonconstant bathymetries are presented. The results are compared with benchmark wave propagation cases. A large‐scale wave propagation simulation over realistic irregular topography is shown to demonstrate the model's capability of solving operational large‐scale problems.

A Sensitivity Study of the 4.8 µm Carbon Dioxide Absorption Band in the MWIR Spectral Range

The measurements of gas concentrations in the atmosphere are recently developed thanks to the availability of gases absorbing spectral channels in space sensors and strictly depending on the instrument performances. In particular, measuring the sources of carbon dioxide is of high interest to know the distribution, both spatial and vertical, of this greenhouse gas and quantify the natural/anthropogenic sources. The present study aims to understand the sensitivity of the CO2 absorption band at 4.8 µm to possibly detect and measure the spatial distribution of emissions from point sources (i.e., degassing volcanic plumes, fires, and industrial emissions). With the aim to define the characteristics of future multispectral imaging space radiometers, the performance of the CO2 4.8 µm absorption band was investigated. Simulations of the “Top of Atmosphere” (TOA) radiance have been performed by using real input data to reproduce realistic scenarios on a volcanic high elevation point source (>2 km): actual atmospheric background of CO2 (~400 ppm) and vertical atmospheric profiles of pressure, temperature, and humidity obtained from probe balloons. The sensitivity of the channel to the CO2 concentration has been analyzed also varying surface temperatures as environmental conditions from standard to high temperature. Furthermore, response functions of operational imaging sensors in the middle wave infrared spectral region were used. The channel width values of 0.15 µm and 0.30 µm were tested in order to find changes in the gas concentration. Simulations provide results about the sensitivity necessary to appreciate carbon dioxide concentration changes considering a target variation of 10 ppm in gas column concentration. Moreover, the results show the strong dependence of at-sensor radiance on the surface temperature: radiances sharply increase, from 1 Wm−2sr−1µm−1 (in the “standard condition”) to >1200 Wm−2sr−1µm−1 (in the warmest case) when temperatures increase from 300 to 1000 K. The highest sensitivity has been obtained considering the channel width equal to 0.15 µm with noise equivalent delta temperature (NEDT) values in the range from 0.045 to 0.56 K at surface temperatures ranging from 300 to 1000 K.

Features of atmospheric disturbances in temperate latitudes before strong earthquakes (M> 7) according to satellite measurements

An ATOVS and MERRA data archive containing temperature values at isobaric levels from 1000 to 50 hPa was formed to study the atmospheric effects observed over the foci of two strong earthquakes with magnitudes M = 7,3. The first seismic event was recorded on August 19, 1992 in the northern Tien Shan and the second on November 12, 2017 in the border areas of the Zagros folded mountain belt. According to USGS intense aftershock activity in these regions began with these seismic events. Using correlation and spectral analysis we studied the vertical profiles of temperature and pressure in a disturbed atmosphere over seismically active regions. The modified anomaly index was calculated at isobaric levels from 500 to 50 hPa and on its basis the registered temperature anomalies were investigated.

Atmospheric data set from the Geodetic Observatory Wettzell during the CONT-17 VLBI campaign

Abstract. Continuous very long baseline interferometry (VLBI) observations are designed to obtain highly accurate data for detailed studies of high-frequency Earth rotation variations, reference frame stability, and daily to sub-daily site motions. During the CONT-17 campaign that covered a time span of 15 days between 28 November and 12 December 2017, a comprehensive data set of atmospheric observations was acquired at the Geodetic Observatory Wettzell, where three radio telescopes contributed to three different networks which have been established for this campaign. These data were supplemented by weather model data. The data set is made available to all interested users in order to provide an optimal database for the analysis and interpretation of the CONT-17 VLBI data. In addition, it is an outstanding data set for the validation and comparison of tropospheric parameters resulting from different space techniques with regard to the establishment of a common atmosphere at co-location sites. The regularly recorded atmospheric parameters comprise many meteorological quantities (pressure, temperature, humidity, wind, radiation, and precipitation) taken from the local weather station close to the surface, solar radiation intensity, temperatures up to 1000 m above the surface from a temperature profiler, total vapor and liquid water content from a water vapor radiometer, and cloud coverage and cloud temperatures from a nubiscope. Additionally, vertical profiles of pressure, temperature, and humidity from radiosonde balloons and from numerical weather models were used for comparison and validation. The graphical representation and comparison show a good correlation in general but also some disagreements in certain weather situations. While the accuracy and the temporal and spatial resolution of the individual data sets are very different, the data as a whole characterize the atmospheric conditions around Wettzell during the CONT-17 campaign comprehensively and represent a sound basis for further investigations (https://doi.org/10.1594/PANGAEA.895518; Klügel et al., 2018).

NUMERICAL AND HYDRAULIC EXPERIMENTS ON BORE PRESSURE DUE TO TSUNAMI

The 2011 Tohoku earthquake tsunami struck a wide area of the northeastern coast of Japan, and many coastal structures and buildings were damaged by the tsunami. Most of the buildings were damaged by the tsunami wave pressure. After the tsunami, characteristics of tsunami waive pressures have been investigated by many researcher, and are being clarified. As shown in previous studies, there are three regimes charactering the vertical pressure profiles. The first one is the impulsive pressure, which is observed just after the tsunami-bore impacted structures. In this regime, strong hydrodynamic pressures are generated by the fluid-solid impact process. After that, the bore pressure is observed, and both the hydrodynamic and hydrostatic pressures contribute the pressure profile. After that, the flow near the structures reaches a quasi-steady state, and the pressure profile becomes hydrostatic. Most of the evaluation equations of tsunami wave pressure proposed by the previous studies can be used against the impulsive pressures and the pressures in the quasi-steady-state regime. On the other hand, the characteristics and quantitative evaluations of the bore pressure remain immature. In this study, in order to clarify the characteristics of the bore pressure, experiments on the bore pressure are carried out, and furthermore, three-dimensional numerical simulations are also carried out.

Toward modeling the spatial pressure field of tropical cyclones: Insights from Typhoon Hato (1713)

Information about the pressure field of tropical cyclones (TCs) is of crucial importance for determining a TC's wind structure. However, despite the fact that TC pressure deficit (ΔP) decreases with increasing height below a TC's outflow layer, most existing models focus only on the radial distribution of TC pressure. Quantitative studies on the spatial pressure field of TCs are considerably limited. This study presents a field study on the vertical pressure profiles of Typhoon Hato which is one of the few strongest sampled TCs in Hong Kong. Meteorological observations from eight radiosonde balloons released at different storm-relative positions during Hato's passage are investigated. Results show that the vertical profiles of ΔP below the outflow layer are distributed linearly with respect to altitude, with the slope increasing almost linearly with the increase of surface pressure deficit. Based on the above observation, an empirical model of the typhoon's spatial pressure field is established. Budget analysis of ΔP is then conducted. Both the dry-air component and water-vapor component are found to be evident. This study further presents an analytical model of TC pressure deficit. Comparison of results with various values of key input model parameters show that the model prediction is highly sensitive to the lapse rate of atmospheric temperature and surface air temperature. It is believed that both the empirical model and the analytical model have the potential to facilitate the development of TC spatial wind-field models.

Comparison of solid phase closure models in Eulerian-Eulerian simulations of a circulating fluidized bed riser

In this work, computational fluid dynamics with Eulerian-Eulerian modeling approach is used in the investigation of the effect of the solid phase closure models on the hydrodynamics of a circulating fluidized bed riser. The studied models are the kinetic theory of granular flow and the powder modulus model. Computational performance and model prediction accuracy are investigated by performing transient simulations for three different cases and for different mesh sizes. The modeling results are compared with measured vertical pressure profile, external circulation mass flow rates, and particle velocity and concentration profiles obtained from a laboratory scale circulating fluidized bed unit. Additionally the computational times are compared to estimate the computational performance and to investigate if a simpler set of closures is computationally more affordable. The results indicate that both closure models can give good predictions for some quantities, while lacking in other quantities. The results indicate that the closure models for the solid phase have a noticeable effect on the model predictions, such as the vertical pressure profile and external circulation rate of the particles.

The Study of Zonal Circulation of Venus’s Atmosphere by Data Analysis of Radio Occultation Measurements Made by Venera-15 and -16 Satellites

The vertical profiles of temperature and pressure obtained from radio occultation measurements made by satellites Venera-15 and -16 from October 1983 to September 1984 are used for the analysis of wind speed in Venus’s atmosphere. The altitude and latitude dependences of zonal wind speed in the middle atmosphere of the planet’s northern and southern hemispheres are identified at altitudes from 50 to 80 km over the latitude interval of 60°–85°. Zonal speeds were determined assuming cyclostrophic atmosphere balance. The existence of jet flows, whose maximal speed is ~100 m/s and axis is placed at an altitude near 60 km within the latitude zone of 73°–75° N, is confirmed in the northern polar atmosphere of the planet. The results of wind speed measurements in the southern hemisphere clearly show that the jet flows exist at an altitude around 62 km at latitudes from 70° to 72° S, and their zonal speed reaches a maximum of ~115 m/s. It is found that these jets at high latitudes are stipulated by negative latitudinal temperature gradients at altitudes below the jet flow axes in Venus’s polar atmosphere.