Maximum Vertical Velocity Research Articles

Urban growth and land subsidence: Multi-decadal investigation using human settlement data and satellite InSAR in Morelia, Mexico

Limited attention is typically paid to the cause-effect relationship between land subsidence due to aquifers overexploitation in expanding metropolises and urban growth models and patterns. This paper implements an integrated urban and satellite Interferometric Synthetic Aperture Radar (InSAR) approach to investigate subsidence, multi-decadal urban growth and peopling trends in the Metropolitan Area of Morelia (ZMM) in the Mexican state of Michoacán. Stacking of JRC's Global Human Settlement Layer, DLR's World Settlement Footprint and INEGI's National Geostatistical Framework datasets reveals a predominant edge-expansion growth model, with urban densification in 1975–2020 and some sprawling in 1990–2000. Population of the ZMM doubled in the last 30 years, reaching over 1 million inhabitants. The ENVISAT and Sentinel-1 InSAR analysis confirms that subsidence is structurally-controlled by the main normal faults within the Cuitzeo half-graben. Differential sinking and ground discontinuities are aligned with buried tectonic faults and contrasting compressible sediment thickness. Non-linearly deforming subsidence bowls develop at extraction wells in both old and newly urbanized sectors of the ZMM. Maximum vertical displacement velocities increased from −2.5 cm/year in 2003−2010 to −9.0 cm/year in 2014–2021, with subsidence migrating towards recently urbanized zones. More than 250 new groundwater wells were added to the public registry since 2000, many of which within new urban sectors. Time-lapse InSAR reveals a 4 km2 rapidly subsiding bowl that formed at the largest social housing neighbourhood of Villas del Pedregal, as building lots were progressively completed and sold, and new wells registered. With angular distortions due to the differential subsidence reaching 0.12% in 2014–2021, new buildings and roads are exposed to fracturing and surface faulting risk of comparable level as the city historic building blocks located along the main faults. By providing useful insights into the relationship between urban growth and land subsidence in the ZMM, the approach proves valuable for application to other metropolises worldwide.

Buoyancy Driven Flow, Heat Transfer, and Entropy Generation Characteristics for Different Heater Geometries Placed in Cryogenic Liquid: A Computational Fluid Dynamics Study

Abstract The present work reports a 3D computational study of buoyancy-driven flow and heat transfer characteristics for a localized heater (analogous to superconductor) submerged in cryogenic liquid nitrogen in an enclosure. Seven different heater geometries are considered and the effect of heater geometry on flow and heat transfer characteristics is illustrated. The heater is generating heat at a constant rate (W/m3). Continuity, momentum, and energy equations are solved using the finite volume method. Liquid flow and heat transfer features are demonstrated with the help of velocity vector and temperature contours. Rayleigh number, average Nusselt number, the maximum vertical velocity of fluid flow, and the average velocity of fluid flow are the parameters that are considered for comparing seven different geometries of the heater. Additionally, an analysis of the entropy generation owing to the transfer of heat and friction due to fluid flow is reported. Furthermore, the dependency of average Nusselt number, maximum velocity of the fluid, entropy generation owing to transfer of heat, and fluid friction as a function of heat generation rate is illustrated graphically. The results of this study indicate that heater geometry can considerably affect the transfer of heat, fluid flow features, and entropy generation under the same heat generation rate in the heater. The highest average Nusselt number on the heater surface is obtained when heater geometry is circular, whereas the lowest value of total entropy generation in the domain is obtained when heater geometry is an equilateral triangle.

Effects of Number Concentration of Cloud Condensation Nuclei on Moist Convection Formation

AbstractWe examined the sensitivity of the formation of moist convection to the number of aerosols that serve as cloud condensation nuclei (CCN) based on a set of numerical experiments using a nonhydrostatic model with a bin cloud microphysics model. Additionally, a linear stability analysis for an air parcel incorporating effects of the CCN number concentration (NCCN) has been conducted to further demonstrate the findings in numerical experiments. The results of the numerical experiments show that moist convection does not form when NCCN ≤ 10 cm−3. The sensitivity to NCCN can be divided into three regimes: when NCCN ≤ 10 cm−3, convection does not form or not fully develop; when 1 ≤ NCCN ≤ 102 cm−3, maximum vertical velocity increases with NCCN; and when NCCN ≥ 102 cm−3, the intensity of convection does not largely depend on NCCN. We demonstrate that the main reason convection does not form under environments with a small NCCN is that the time scale for condensation is longer than that to change environmental conditions. Given a supersaturated environment, fewer droplets form when NCCN is small and the size of droplets is potentially large. Consequently, the amount of latent heating is limited and the air parcel cannot obtain buoyancy within a reasonable time scale. Linear stability analysis using a parcel model considering the effect of NCCN without ice-phase processes shows unstable and stable regimes as a function of the number of droplets. The analytically obtained critical droplet number for the convection formation well corresponds to the minimum NCCN beyond which convection forms in the present numerical experiments.

Coherent Velocity Structures in the Mixed Layer: Characteristics, Energetics, and Turbulent Kinetic Energy Budget

AbstractVelocity, hydrographic, and microstructure observations collected under moderate to high winds, large surface waves, and significant ocean-surface heat losses were utilized to examine coherent velocity structures (CVS) and turbulent kinetic energy (TKE) budget in the mixed layer on the outer shelf in the northern Gulf of Mexico in February 2017. The CVS exhibited larger downward velocities in downwelling regions and weaker upward velocities in broader upwelling regions, elevated vertical velocity variance, vertical velocity maxima in the upper part of the mixed layer, and phasing of crosswind velocities relative to vertical velocities near the base of the mixed layer. Temporal scales ranged from 10 to 40 min, and estimated lateral scales ranged from 90 to 430 m, which were 1.5–6 times as large as the mixed layer depth. Nondimensional parameters, Langmuir and Hoenikker numbers, indicated that plausible forcing mechanisms were surface-wave-driven Langmuir vortex and destabilizing surface buoyancy flux. The rate of change of TKE, shear production, Stokes production, buoyancy production, vertical transport of TKE, and dissipation in the TKE budget were evaluated. The shear and Stokes productions, dissipation, and vertical transport of TKE were the dominant terms. The buoyancy production term was important at the sea surface, but it decreased rapidly in the interior. A large imbalance term was found under the unstable, high-wind, and high–sea state conditions. The cause of this imbalance cannot be determined with certainty through analyses of the available observations; however, our speculation is that the pressure transport is significant under these conditions.

Scalings for unsteady natural convection boundary layer under time-varying heating flux in a small Prandtl number fluid

The unsteady natural convection boundary layer (NCBL) on a vertical wall heated by time-varying flux in initially quiescent homogeneous fluid with a small Prandtl number (Pr) was studied. Scalings for the parameters typifying NCBL behavior, including plate temperature, maximum vertical velocity, thermal boundary-layer thickness, and velocity boundary-layer thickness, at different development stages, and the time for the transition from the start-up stage to the quasi-steady state, were developed by scaling analysis. The obtained scalings were compared to and validated by the numerical results with different values of Pr, the Rayleigh number Ra and the dimensionless time-varying heat flux frequency fn, over 106 ≤ Ra ≤ 109, 0.01 ≤ Pr ≤ 0.5, and 0.001 ≤ fn ≤ 0.025. It is also found that the development of the boundary layer at the start-up stage is one-dimensional and but becomes two-dimensional at the quasi-steady state.

Orbital eccentricities as indicators of stellar populations

Context.In previous work, we showed how the planar and vertical eccentricities of disc stars,eande′, could be used as indicators of the stars’ kinematic populations. For a local stellar sample drawn from theGaiaDR2 catalogue, these populations were represented geometrically in the eccentricity diagram,e′2vs.e2, approximately separated by straight lines.Aims.In the current work, we propose a new relationship between the star’s perpendicular velocity and its vertical eccentricity, allowing for a reevaluation of the critical vertical eccentricity and maximum height,zmax, specific to each population component.Methods.We approximated the local potential function to be consistent with the actual shape of the curve that relates the maximum vertical speed of a star and its maximum height. The curve corresponds to a non-linear restoring vertical force, where the stiffness decreases with an increase in the maximum height. The constants involved in this fitting, together with the population velocity dispersions, determine the specific region for each population in the eccentricity diagram.Results.The new classification determines 88% of the sample is made up of thin disc stars and 9% of thick disc stars, whereby 3% of the stars have been relabelled, by providing thinner thin and thick discs. Nested thin disc subsamples allow us to estimate Strömberg’s asymmetric drift equation, leading to a heliocentric velocity of the circular orbit ofVc ≈ −12.9 km s−1, an absolute rotation velocity of Θc ≈ 227 km s−1, and a rotation component of the Galactocentric velocity of the Sun at Θ⊙ ≈ 240 km s−1.Conclusions.The thin disc stars of our local sample are characterised based on values 0 ≤ e ≤ 0.32, 0 ≤ e′ ≤ 0.09, andzmax = 0.7 kpc. Disc stars satisfy 0 ≤ e ≤ 0.44, 0 ≤ e′ ≤ 0.18,zmax = 1.5 kpc. The maximum vertical peculiar velocity for disc stars is found to bew0 = 115 km s−1. The assumed potential provides a stellar density of the disc vanishing atz0 = 1.8 kpc. The approximate behaviour in the local disc is that a small decrease in the stiffness is associated with a relative decrease in the limiting velocity, which produces a thinner disc and a loss of stars in the local cylinder, both in a similar proportion to the limiting velocity.

Quantitative Assessment of Vertical and Horizontal Deformations Derived by 3D and 2D Decompositions of InSAR Line-of-Sight Measurements to Supplement Industry Surveillance Programs in the Tengiz Oilfield (Kazakhstan)

This research focused on the quantitative assessment of the surface deformation velocities and rates and their natural and man-made controlling factors at Tengiz Oilfield in Kazakhstan using the Small Baseline Subset remote sensing technique followed by 3D and 2D decompositions and cosine corrections to derive vertical and horizontal movements from line-of-sight (LOS) measurements. In the present research we applied time-series of Sentinel-1 satellite images acquired during 2018–2020. All ground deformation derivatives showed the continuous subsidence at the Tengiz oilfield with increasing velocity. 3D and 2D decompositions of LOS measurements to vertical movement showed that the Tengiz Oil Field 2018–2020 continuously subsided with the maximum annual vertical deformation velocity around 70 mm. Based on the LOS measurements, the maximum annual subsiding velocity was observed to be 60 mm. Cosine corrections of LOS measurements to vertical movement, however, revealed a maximum annual vertical deformation velocity of 77 mm. The vertical deformation confirmed typical patterns of subsidence caused by oil extraction. Detected east-west and north-south horizontal movements at the Tengiz field clearly indicated that the study area crossed by seismic faults is affected by natural tectonic processes. The overall RMSE of 3D decomposed vertical deformation in relationship to LOS measurements and cosine corrections were in the range of 10–13 mm and 6–8 mm, correspondingly. The results of the present research will support operators of oil and gas fields and also other types of infrastructure to evaluate the actual differences of InSAR ground deformation measurements against the required standards and the precision of measurements depending on the operational needs, timeframes and availability of radar imagery.

Composited structure of non‐precipitating shallow cumulus clouds

AbstractThe normalized distributions of thermodynamic and dynamical variables both within and outside shallow clouds are investigated through a composite algorithm using large‐eddy simulations of oceanic and continental cases. The normalized magnitude is maximum near the cloud centre and decreases outwards. While relative humidity (RH) and cloud liquid water () decrease smoothly to match the environment, the vertical velocity, virtual potential temperature (), and potential temperature () perturbations have more complicated behaviour towards the cloud boundary. Below the inversion layer, becomes negative before the vertical velocity has turned from an updraft to a subsiding shell outside the cloud, indicating the presence of a transition zone where the updraft is negatively buoyant. Due to the downdraft outside the cloud and enhanced horizontal turbulent mixing across the edge, the normalized turbulent kinetic energy (TKE) and horizontal turbulent kinetic energy (HTKE) decrease more slowly from the cloud centre outwards than the thermodynamic variables. The distributions all present asymmetric structures in response to the vertical wind shear, with more negatively buoyant air, stronger downdrafts, and larger TKE on the downshear side. We discuss several implications of the distributions for theoretical models and parameterizations. Positive buoyancy near the cloud base is mostly due to the virtual effect of water vapour, emphasizing the role of moisture in triggering. The mean vertical velocity is found to be approximately half the maximum vertical velocity within each cloud, providing a constraint to achieve possible power‐law distributions for some models. Finally, the normalized distributions for different variables are used to estimate the vertical heat and moisture fluxes within clouds. The results suggest that distributions near the cloud edge and variability of maximum perturbations need careful treatment. The fluxes are underestimated in the inversion layer because cloud‐top downdrafts cannot be captured well.

Climatological sensitivities of shallow-cumulus bulk entrainment in continental and oceanic locations

AbstractCumulus entrainment is a complex process that has long challenged conceptual understanding and atmospheric prediction. To investigate this process observationally, two retrievals are used to generate multi-year climatologies of shallow-cumulus bulk entrainment (ϵ) at two Atmospheric Radiation Measurement cloud observatories, one in the US southern Great Plains (SGP) and the other in the Azores archipelago in the eastern North Atlantic (ENA). The statistical distributions of ϵ thus obtained, as well as certain environmental and cloud-related sensitivities of ϵ, are consistent with previous findings from large-eddy simulations. The retrieved ϵ robustly increases with cloudlayer relative humidity and decreases in wider clouds and cloud ensembles with larger cloud-base mass fluxes. While ϵ also correlates negatively with measures of cloud-layer vigor (e.g., maximum in-cloud vertical velocity and cloud depth), the extent to which these metrics actually regulate ϵ (or vice-versa) is unclear. Novel sensitivities of ϵ include a robust decrease of ϵ with increasing subcloud wind speed in oceanic flows, as well as a decrease of ϵ with increasing cloud-base mass flux in individual cumuli. A strong land–ocean contrast in ϵ is also found, with median values of 0.5-0.6 km−1 at the continental SGP site and and 1.0-1.1 km−1 at the oceanic ENA site. This trend is associated with drier and deeper cloud layers, along with larger cloud-base mass fluxes, at SGP, all of which favor reduced ϵ. The flow-dependence of retrieved ϵ implies that its various sensitivities should be accounted for in cumulus parameterization schemes.

Assimilation of the Maximum Vertical Velocity Converted From Total Lightning Data Through the EnSRF Method

AbstractA total lightning data assimilation (LDA) scheme is developed at the cloud‐resolving scale in this study. The LDA scheme assimilates total lightning data through the ensemble square root filter (EnSRF) method based on the relationship between the maximum vertical velocity and the instantaneous flash rate. To verify the effect of LDA, three assimilation experiments based on a convective activity on July 6, 2019 are performed. The results show that all LDA experiments can improve the forecast. LDA improves the water vapor field and provides a warm and moist environment in which convection can develop. LDA can also increase the convergence at low levels and the divergence at upper levels, which leads to intense convection development. However, the LDA experiment that does not consider vertical localization (LDA_no) shows excessive adjustments of the model variables, which leads to overestimation of precipitation. The LDA experiment which adjusts the state variables in the charge zone (LDA_CZ) underestimates the forecast. The LDA experiment using a global group filter (GGF) localization function (LDA_GGF) is optimal in theory and produces a better forecast. The results of LDA_GGF show that the interaction between the cold pool and the strong low‐level vertical wind shear in front of the cold pool is beneficial for triggering new convection in front of the convection, which leads to a rapid shifting in convective activity. In addition, the LDA_GGF scheme is evaluated further for a rainfall process on August 1, 2020 and obtains similar forecast improvements for composite reflectivity and accumulated precipitation.

A comparative study of effect of heater orientation on flow and heat transfer characteristics in buoyancy driven flow in cryogenic liquid

The present study aims to analyse the buoyancy driven fluid flow and heat transfer characteristics using different heater orientation in liquid nitrogen for cooling superconductor. For this purpose, a localized circular heater (analogous to superconductor) generating heat at constant rate submerged in liquid nitrogen enclosure is analysed. The study is performed with two orientations of heater; one is vertical and another is horizontal. The entropy generation associated with heat transfer and fluid flow is also discussed in the present study. The Rayleigh number, average Nusselt number, maximum vertical velocity, entropy generation and Bejan number are used as comparing parameters for two orientations of heater. Under same heat generation rate, Rayleigh number is comparatively higher for vertically oriented heater whereas average Nusselt number is comparatively higher for horizontally oriented heater. The maximum vertical velocity of fluid is higher when heater is vertically oriented. The horizontally oriented heater has comparatively less value of thermal entropy generation than vertically oriented heater but horizontally oriented heater has higher value of fluid friction irreversibility. In summary, horizontally oriented heater has comparatively higher value of total entropy generation than vertically oriented heater. Bejan number is higher for horizontally oriented heater. In overall study, the value of Bejan number is less than 0.5; therefore, it can be said that fluid friction irreversibility is more dominated than heat transfer irreversibility.

Turbulence Characteristics in Submerged Hydraulic Jump Below Silled Sluice Gates besides Studying alos The Scale Effects in Free Efflux Below Gate of Variable Openings.(Dept.C)

In the present research, an experimental set up was arranged to investigate the scale effects in the free efflux below the sluice gate of variable openings and also to study the turbulence structure in the generated submerged hydraulic jump below the silled gate. The objective of the present study research was is to analyze the collected experimental data on the effect of constructing a sill under a sluice gate on the free and submerged flow bellow it. Also, this paper presents the results of a laser Doppler Anemometry (LDA) study of submerged hydraulic jumps in a horizontal rectangular channel with the different submergence factor S and different inlet Froude number Fr1. Measurements include surface profiles , mean velocity components of ū andV– ;turbulence intensities u and v' and turbulence shear stress, u vꞌ Major flow characteristics of submerged hydraulic jumps were discussed and analyzed , The flow in the fully developed region is found to have some degree of similarity . It was also found that a submerged jump was three dimensional in nature. The maximum vertical velocity in the recirculating zone for all submerged jumps is about 7% of U1. Also, the results show that the maximum streamwise velocity near the center plane was smaller than that near the side wall . The turbulence shear stress near the center is about 46% higher than that near the side wall. After the jump the flow will recover into a two dimensional flow. The coefficient of discharge becames smaller at constant opening ratio Y1/h1. The results showed that there was a close relationship between the scale effects in the contraction coefficients and in the discharge coefficients. The energy dissipation in effluxes was also related to the scale effect in the discharge coefficients closely. The scale effects in the contraction coefficient and in the coefficients of energy loss which are the main factors composing the discharge coefficients showed the same trend as in the discharge coefficient.

Lightning Data Assimilation Scheme in a 4DVAR System and Its Impact on Very Short-Term Convective Forecasting

AbstractA proof-of-concept method for the assimilation of total lightning observations in the 4DVAR framework is proposed and implemented into the Variational Doppler Radar Analysis System (VDRAS). Its performance is evaluated for the very short-term precipitation forecasts of a localized convective event over northeastern China. The lightning DA scheme assimilated pseudo-observations for vertical velocity fields derived from observed total lightning rates and statistically computed vertical velocity profile from VDRAS analysis data. To reduce representative errors of the derived vertical velocity, a distance-weighted horizontal interpolation is applied to the input data prior to the DA. The case study reveals that although 0–2-h precipitation nowcasts are improved by assimilating lightning data alone compared to CTRL (no radar or lightning) and RAD (radar only), better results are obtained when the lightning data are assimilated with radar data simultaneously. The assimilation of both data sources results in improved dynamical consistency with enhanced updraft and latent heat as well as improved moisture distributions. Additional experiments are conducted to evaluate the sensitivity of the combined DA scheme to varied vertical velocity profiles, radii of horizontal interpolation, binning time intervals, and relationships used to estimate the maximum vertical velocity from lightning flash rates. It is shown that the scheme is robust to these variations with both radar and lightning assimilated data.

Understanding mechanisms for trends in Sahelian squall lines: Roles of thermodynamics and shear

AbstractSquall lines dominate rainfall in the West African Sahel, and evidence suggests they have increased in intensity over recent decades. Stronger wind shear may be a key driver of this trend and could continue to strengthen with climate change. However, global numerical models struggle to capture the role of shear for organised convection, making predictions of changing rainfall intensities in the Sahel uncertain. To investigate the impact of recent and possible future environmental changes, and to isolate thermodynamic effects from shear effects, idealised squall line simulations were initialised with a profile representative of the present day: this profile was then modified using trends from reanalyses and climate projections. Increased shear led to increased storm intensity and rainfall, but the effects of the thermodynamic changes dominated the effects from shear. Simulations initiated with future profiles produced shorter‐lived storms, likely due to increased convective inhibition and the absence of large‐scale convergence or synoptic variability in the idealised model. A theoretical model based on the relative inflow of convectively unstable air and moisture was found to predict bulk characteristics of the storms accurately, including mean rain rates and area‐averaged maximum vertical velocities, explaining the role of shear. However, the model is not a prognostic tool as rainfall is dependent on the storm speed, which remains a free parameter. The study shows the importance of shear to long‐term rainfall trends and highlights the need for climate models to include effects of shear to capture changes in extreme rainfall.

Technology of Coal Seam Long Borehole Blasting and Comprehensive Evaluation Method of Pressure Relief Effect in High Rockburst Proneness Longwall Panel

On August 2, 2019, a catastrophic rockburst disaster occurred in Tangshan mine, causing death of 7 miners. After the investigation, the coal mine is facing reproduction. Taking the 0291 panel as the engineering background, this paper studies the coal seam blasting pressure relief and ground stress monitoring technology in working face retreat. During the roadway development and working face excavation, coal seam blasting was adopted to transfer the high ground stress of coal seam to the deep ground of the coal body. The blasting operation is presented in detail in this paper. In the working face retreat stage, drilling powder method, hydraulic shield resistance monitoring, roof displacement, and vibration monitoring methods are implemented. The results show that the pressure relief range of coal seam is 4–12 m in the coal mass after blasting. The shield working resistance is stable at 20–30 MPa. The range of relative displacement of the roof is about −1.0 to 2.5 mm, and the maximum vertical vibration velocity is in the range of 7–11 cm/s, up to 12 cm/s. The measured parameters are acceptable, so it is concluded that 0291 panel can be safely mined. This study provides a reference for the coal seam blasting design for rockburst coal mine and provides a technical means for the analysis of pressure release effect and dynamic pressure monitoring during working face retreating.

Experimental study on the vertical motion of colliding gravity currents

Predicting the consequences of colliding gravity currents remains one of the most significant challenges in geophysical fluid dynamics. While the collision phenomenon has long been established through field observations, irregular natural occurrence and measurement limitations denied a comprehensive quantitative analysis of its dynamics. Herein, we experimentally studied colliding gravity currents to describe the collision dynamics and quantify essential parameters that are difficult to measure in nature. Visualization techniques and particle image velocimetry were deployed to monitor the flow evolution and obtain the flow field of the colliding gravity currents. Results revealed that as gravity currents propagated into proximity, vertical motions developed along the respective fronts’ leading edge and became enhanced as the currents merged at collision. Although both symmetric and asymmetric collisions initiated a significant vertical displacement of the mixed fluid, the lifting pattern was dependent on the ratio of reduced gravities of the colliding currents. The displaced fluids reached maximum vertical velocity at low height; however, the velocity reduced as the displaced fluids approached maximum heights. The maximum height attained by the displaced fluid was a significant fraction of the initial fluid depth in the lock, regardless of the reduced gravity ratio. This paper quantifies the vertical motion of the displaced fluid during the collision process, describes the relationship between relevant current parameters and the vertical motions, and provides valuable preliminary contributions toward improving the overall understanding of collision dynamics at the frontal boundary.

Urbanization-induced land and aerosol impacts on sea-breeze circulation and convective precipitation

Abstract. Changes in land cover and aerosols resulting from urbanization may impact convective clouds and precipitation. Here we investigate how Houston urbanization can modify sea-breeze-induced convective cloud and precipitation through the urban land effect and anthropogenic aerosol effect. The simulations are carried out with the Chemistry version of the Weather Research and Forecasting model (WRF-Chem), which is coupled with spectral-bin microphysics (SBM) and the multilayer urban model with a building energy model (BEM-BEP). We find that Houston urbanization (the joint effect of both urban land and anthropogenic aerosols) notably enhances storm intensity (by ∼ 75 % in maximum vertical velocity) and precipitation intensity (up to 45 %), with the anthropogenic aerosol effect more significant than the urban land effect. Urban land effect modifies convective evolution: speed up the transition from the warm cloud to mixed-phase cloud, thus initiating surface rain earlier but slowing down the convective cell dissipation, all of which result from urban heating-induced stronger sea-breeze circulation. The anthropogenic aerosol effect becomes evident after the cloud evolves into the mixed-phase cloud, accelerating the development of storm from the mixed-phase cloud to deep cloud by ∼ 40 min. Through aerosol–cloud interaction (ACI), aerosols boost convective intensity and precipitation mainly by activating numerous ultrafine particles at the mixed-phase and deep cloud stages. This work shows the importance of considering both the urban land and anthropogenic aerosol effects for understanding urbanization effects on convective clouds and precipitation.

Quantitative assessment of ground deformations for the risk management of petroleum and gas pipelines using radar interferometry

The primary objective of these studies was to quantitatively assess the ground deformation velocities and rates and their natural and man-made controlling factors as the potential risks along the seismically active 70 km section of buried Baku-Tbilisi-Ceyhan Oil, South Caucasus Gas, Western Route Oil and South Caucasus Pipeline Expansion Gas pipelines in Azerbaijan using Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique. PS-InSAR analysis showed that the continuous subsidence was prevailing in the kilometer range of 13-70 of pipelines crossing two active seismic faults. The ground uplift deformations were observed in the pipeline kilometer range of 0-13. The minimum and maximum vertical ground movement velocities were observed to be −21.3 mm/y and 14.1 mm/y along 70 km section of pipelines with 250 m buffer zone. Both of these sites were observed at the range of seismic faults. The spatial distribution of sites with ground deformation velocity less than −15 mm/y and more than 15 mm/y was diverse and random all along 70 km of pipelines without any cumulative spatial patterns. Based on the lower mean, variation and standard deviation of pixel values, the seismic fault in the kilometer range of 21-31 revealed its higher vulnerability to subsidence processes rather than the Seismic Fault in the kilometer range of 46-54. The ground deformation velocities within the range of Seismic Fault KP21-31 revealed the minimum and maximum values of −19.74 mm/y and 14.1 mm/y, respectively whereas at the Seismic Fault KP46-54, the minimum and maximum values were −17.07 mm/y and 9.29 mm/y, respectively. Encouraging level of agreement with the regression coefficients of 0.92 and 0.96 for known subsiding sites at KP28 + 500 and KP52 + 750 and 0.97 and 0.96 for known uplifting sites at KP04 + 900 and KP35 + 050 respectively was observed between the high-precision GPS and PS-InSAR measurements. The diverse spatial distribution and variation of ground movement processes along pipelines demonstrated that general geological and geotechnical understanding of the study area is not sufficient to find and mitigate all the critical sites of subsidence and uplifts for the pipeline operators. The prediction of the potential subsidence or uplift locations based on the field visual verifications holds a lot of uncertainties without broad and detailed scale airborne and satellite space observation technologies. The justification of the budget for the geotechnical maintenance activities along long-range oil and gas pipelines requires sophisticated prioritization and planning of the remediation sites and clear quantitative and qualitative risk assessment proving the activeness of these sites and effectiveness of the remediation measures. This means that the PS-InSAR – based approach outlined in this paper is a significant improvement over current ground-based monitoring practices or can significantly contribute them in the initial phase of risk assessment and prioritization.

A Formula for the Maximum Vertical Velocity in Supercell Updrafts

AbstractIn supercell environments, previous authors have shown strong connections between the vertical wind shear magnitude, updraft width, and entrainment. Based on these results, it is hypothesized that the influences of entrainment-driven dilution on buoyancy and maximum updraft vertical velocity w in supercell environments are a predictable function of the vertical wind shear profile. It is also hypothesized that the influences of pressure perturbation forces on maximum updraft w are small because of a nearly complete offset between upward dynamic pressure forces and downward buoyant pressure forces. To address these hypotheses, we derive a formula for the maximum updraft w that incorporates the effects of entrainment-driven dilution on buoyancy but neglects pressure gradient forces. Solutions to this formula are compared with output from previous numerical simulations. This formula substantially improves predictions of maximum updraft w over past CAPE-derived formulas for maximum updraft w, which supports the first hypothesis. Furthermore, integrated vertical accelerations along trajectories show substantial offsets between dynamic and buoyant pressure forces, supporting the second hypothesis. It is argued that the new formula should be used in addition to CAPE-derived measures for w in forecast and research applications when accurate diagnosis of updraft speed is required.

Influence of tilting effect on charge structure and lightning flash density in two different convective environments

AbstractThe influence of the tilting effect on charge density and lightning flash density was investigated using idealized Weather Research and Forecasting explicit charging/discharge module (WRF‐ELEC) simulations for two thunderclouds. No shear (NS) and with shear (WS) simulations were conducted based on different values of wind velocity components in input sounding. Results from the NS and WS simulations show that the tilting effect extended the lifetime of the simulated convective clouds in both case studies, while leading to higher maximum vertical velocity only for the environment with intense convection. The ice and graupel in the cloud cell appear almost simultaneously in both the NS and WS simulations for the two case studies, but larger values are obtained for the WS simulations. It is noted that the increase of convection intensity postpones the larger values to the mature stage. The tilting effect results in an increase of total non‐inductive charging, especially in a severe thundercloud. Moreover, the tilting effect does not lead to the same results for the polarity and intensity of charge density in the two studied cases. In the real case study, a dipolar charge structure was seen for both NS and WS simulations, but the intensity of charge density decreased with regard to the tilting effect. In contrast, the intensity of the charge increased with the tilting effect and resulted in tripolarity in the idealized case with a high value of convective available potential energy. Finally, considering the tilting effect leads to an increase of the number of lightning occurrences in the two case studies.