Level Of Buoyancy Research Articles

Field Observations Reveal How Plunging Mixing and Sediment Resuspension Affect the Pathway of a Dense River Inflow Into a Deep Stratified Lake

AbstractThe pathway of dense river inflows into lakes, which affects the lake water quality, is not accurately predicted by existing models. The pathway of a dense riverine inflow in a lake with a submerged canyon is analyzed based on measurements during a 4‐month period of weakening lake stratification and weakening density excess between river and epilimnion. In line with models, the dense riverine inflow plunges upon entering the lake, continues as an underflow on the sloping lake bottom, and finally intrudes at its level of neutral buoyancy. Underflow and interflow velocities are O(0.1 m s−1). The river inflow is finally trapped in the pycnocline most of the time, even when the river's density excess and the lake's stratification are marginal. This trapping in the pycnocline is explained by the reduction of the inflow density excess due to the intense plunging mixing, which is an order of magnitude larger than that obtained in confined laboratory flumes. The pathway of the dense riverine inflow is affected by interactions of the underflow with the lake bottom and sedimentary processes. A canyon carved by the underflows confines and accelerates the underflow, which enhances its capacity to entrain and carry sediment. The entrainment of sediment that was previously deposited on the canyon bottom accelerates the underflow. Due to both effects, the underflow can temporarily break through the pycnocline and reach the hypolimnion. Existing models explain these observations qualitatively, but a quantitative prediction would require better parameterizations of the plunging mixing and the sedimentary processes.

Academic and Workplace Buoyancy and its Association with Demographic Variables among Health Sciences’ Undergraduates

Academic buoyancy is important for influencing students’ ability to face academic challenges. It describes learners’ ability to defeat academic difficulties. It is an important factor on the psycho-educational landscape assisting students experiencing setbacks. Clinical/workplace buoyancy can help health sciences’ students to face the challenges in error-prone learning atmosphere. Objective: To assess the level of academic and workplace buoyancy and its association with demographic variables among health sciences’ undergraduates. Methods: Analytical cross-sectional research with convenient sampling was carried out on 222 undergraduates of Sohail University, Karachi. Ethical approval was taken from the ERC, Sohail University. Data were collected through Academic Buoyancy Scale. By using SPSS Version 25.0, the data were analyzed. Descriptive statistics were calculated and Chi-square was applied to observe the association of buoyancy with demographic variables. Results: In this study, mostly participants (98.6%) belong to the age 22-24 years. Over 50% of the partakers (55.9%) were females. All items of workplace and academic buoyancy had a significant association with study program (p-value 0.000, 0.010,0.002,0.021 respectively) while only 2 items showed significant association with study year (p-value 0.012 and 0.028). There was no significant association of buoyancy with variables like age, gender, religion and marital status. Conclusions: This study’s findings highlighted the buoyancy levels among health sector undergraduates. The association of buoyancy was found significant with study program and some items with CGPA and study year. These findings indicated the need to enhance positive traits like buoyancy among health sector undergraduates.

Investigating Convective Processes Underlying ENSO: New Insights Into the Fixed Anvil Temperature Hypothesis

AbstractInterannual variations provide insight into the sensitivity of convective processes. Thus, CloudSat and ERA5 are used to explore the relationship among convective cores, outflows and environmental conditions during El Niño‐Southern Oscillation (ENSO) cycles. Results reveal greater upper‐tropospheric stability during El Niño, resulting in a lower level of neutral buoyancy compared to La Niña. However, outflow levels remain relatively consistent across ENSO cycles. This suggests that, despite less favorable conditions for deep convection during El Niño, stronger convective intensity is required to achieve outflow levels comparable to those in La Niña. Indeed, our results suggest that convection observed during El Niño tends to have broader cores and lower entrainment rates, translating to greater intensity compared to La Niña. These findings emphasize the importance of considering both large‐scale and convective‐scale processes, providing an update to the fixed anvil temperature (FAT) and the proportionately higher anvil temperature (PHAT) hypotheses as originally proposed.

Economic System of Islām as a Panacea to Economic Recession in Nigeria ‎

The National Bureau of statistics in July 2016 officially announced that Nigeria has entered into a recession, its first in 29 years. According to the data provided by the World Bank, the most recent time that the nation saw such a significant instance of economic downturn was while Ibrahim Babangida was in power. During that time period, the economy of Nigeria had a decline of 0.51% in the first quarter of 1987 and 0.82% in the second quarter of the same year. The disaggregation of the results for 2016 into its individual quarters revealed the sharpest decline, which was 2.4 percent, and a turning point after that. This is going by the manifestation of economic hardships experienced by the populace, even up to this moment. In point of fact, Nigeria's economy went from a level of economic buoyancy to a level of economic recession in the second quarter of 2016, and it has maintained negative growths in all quarters of that year up to 2017. This downward trend is expected to continue throughout 2017. In a bid to cushion the effect of this situation, the government in the short and medium terms took some measures (policies and reforms) to reverse the recession and put it on the path of growth reliance. In spite of these encouraging developments and despite the fact that it has been two years since the National Bureau of Statistics (NBS) officially declared that Nigeria had emerged from recession in its quarterly report on the country's Gross Domestic Product (GDP), the country's economic situation is still difficult, particularly with regard to the continued high cost of food. For a long-term solution, this paper, therefore, examines some measures of Islamic economic system, which is recession proof, due to the fact that it is basically premised on the fundamental sources of Islam, Sharī῾ah. The paper concludes that if these measures are taken into consideration by the government, it will not only lift the economy out of its current phase but will also guarantee a secure economy. The paper adopts analytical research methods, using majorly secondary data collection.

Taxpayers’ Perception of Public Sector Fiscal Responsibility and Voluntary Tax Compliance Behaviour in Rivers State, Nigeria

This study which is on the influence of taxpayers' perception of public sector fiscal responsibility on voluntary tax compliance is motivated by the quality of government fiscal responsibility, the level of tax compliance by the public and the reported low level of tax buoyancy and elasticity in Nigeria. The study adopts cross sectional survey research design. Four hundred and three (403) copies of valid questionnaire were used for the study; this represents 85% of the respondents. The collected data were analyzed using both descriptive and inferential statistics. The proposed hypotheses for the study were tested using regression analysis. The study provides evidence to show that voluntary tax compliance is low in Rivers State, Nigeria as on the average, voluntary tax compliance produced a mean score of 2.0928 and standard deviation of 0.469592.The study also provides evidence indicating that public accountability, government fiscal transparency, balanced and surplus budget, public information dissemination and government public engagements are key drivers of voluntary tax compliance and their relationships with voluntary compliance are positive and significant. Hence, it could be reasonably concluded that voluntary tax compliance is lacking in Rivers State leading to the recommendations that revenue authorities in Rivers State, Nigeria should intensify efforts to identify, register and bring to the tax net all eligible taxpayers operating in the formal and informal sectors by synergizing with financial firms and various professional bodies and trade unions. Public institutions should make public accountability and fiscal transparency their core mandate so as to earn public confidence geared towards improved tax compliance behaviour.

Self-Instruction Training Untuk Meningkatkan Derajat Academic Buoyancy Mahasiswa

This study aims to determine the effect of self-instruction training interventions in increasing the level of student academic buoyancy. Students need to have a high level of academic buoyancy in order to be able to overcome daily academic challenges and overcome the decline in academic self-regulation (Martin & Marsh, 2009). Students who have a low or moderate degree of academic buoyancy will have obstacles in overcoming daily academic challenges and academic setbacks. This condition causes low academic achievement that students have. In order to overcome this problem, this research examines whether self-instruction training interventions with CBT can help students increase their degree of academic buoyancy. This self-instruction technique is a behavior modification technique that has two uses, namely improving maladaptive mindsets, becoming positive mindsets, which are then used to direct individuals by giving positive instructions to themselves to make behavior changes to become more adaptive (Meichenbaum, in Martin & Pear 2015). This study uses a single subject design with AB research pattern. The participant of this study was a male student at the Faculty of Medicine, with a moderate degree of academic buoyancy. The results of the study show that the self-instruction training technique can increase the degree of academic buoyancy.

Academic buoyancy of university students and its relationship to academic average in light of some demographic variables

Academic buoyancy reflects the student's ability to encounter the ordinary challenges he faces in the academic context, and it positively contributes to the student's behaviors. This study aims to measure the level of academic buoyancy among university students, identify its relationship to their academic average, and determine the differences in their academic buoyancy level in terms of gender and academic discipline variables. The descriptive-analytical research design was utilized. The academic buoyancy scale was applied to (243) university students (male-female). Data were statistically analyzed using correlation coefficient, arithmetic mean, and two-way ANOVA. Results demonstrated that students have a high level of academic buoyancy, there was a significant correlative relationship between academic buoyancy and academic average, and there were no significant differences in the academic buoyancy level due to gender (male-female), academic discipline (theoretical-practical). The research recommended increasing students' academic buoyancy level to help them encounter academic pressures and challenges and to solve the problems they face in their academic lives effectively.
 
 Keywords: Academic buoyancy; academic average; demographic variables; university students

Social comparison and academic buoyancy among freshmen in one selected public university

The study examined the relationship between social comparison and academic buoyancy among freshmen in one selected public university in Kenya. The study adopted cross-sectional survey research design. The social comparison and academic buoyancy scales were used to collect data. The sample size of the study consisted of 213 freshmen from one selected public university in the western part of Kenya. The data collected were analyzed using descriptive statistics, and inferential statistics, such as Pearson correlation coefficient and regression analysis statistical techniques. It was established, that there was a low positive (r=0.187, n=213, p=0.006) relationship between social comparison and academic buoyancy among the first year university students. The social comparison regression model was adequate to predict the level of academic buoyancy among first year university students, [F (1, 211)=7.641, p=0.006, accounting for 3.5 % (R2=0.035)] of the variation in academic buoyancy levels. The study recommends that counseling staff at universities should develop specific orientation programmes to enhance the academic buoyancy of freshmen with inappropriate social comparisons. Future studies could also focus on institutional based factors, influencing academic buoyancy among freshmen at universities.

Dynamics of sediment-laden plumes in the ocean

We present a series of experiments to illustrate the dynamics of positively or negatively buoyant particle-laden plumes in a cross-flow, with relevance for the discharge of sediment into the ocean during deep-sea mining operations. In an unstratified ambient fluid, our experiments identify three different regimes, corresponding to (i) a dense particle-laden plume, host to relatively dense saline fluid, in which the particles separate from the descending plume as the flow speed falls below the particle settling speed; (ii) a dense particle-laden plume, host to buoyant fluid, in which the fluid gradually rises from the sinking plume of particles, to form a second rising plume of source fluid; and (iii) a buoyant particle-laden plume, host to buoyant fluid, which rises from the discharge pipe, and from which particles gradually sediment. Classical models of single-phase plumes describe the initial motion of the plumes in cases (i) and (iii), but as the flow speed falls below the particle fall speed, sedimentation leads to a change in the averaged buoyancy, and, hence, the plume speed. Our data also suggest that the sedimentation leads to a reduction in the rate of entrainment of ambient fluid, compared with the classical single-phase plumes. We also show that with a density stratified ambient fluid, the stratification may arrest the plume prior to significant particle sedimentation, and in this case, the plume tends to spread downstream at the level of neutral buoyancy where particle sedimentation proceeds. The bulk density of the residual plume fluid may then remain intermediate between the density of the upper and lower layer fluid, or may become less dense than the upper layer fluid, in which case, following sedimentation, the plume fluid rises through the upper layer. While the dynamics of deep-sea mining plumes in the ocean are more complex, for example, owing to background turbulence and mixing, the results of our new laboratory experiments highlight the range of flow processes which may influence the initial dispersion and sedimentation of particles in such plumes following release into the water, depending on the initial conditions, the ambient density and the particle fall speed. We also discuss the relevance of our work in the context of ash dispersal by volcanic plumes.

Lightning forecasting in Bangladesh based on the lightning potential index and the electric potential

This work documents the performances of diagnostic and explicit lightning forecasts for selected high impact weather events over Bangladesh. The lightning flashes are calculated by three methods: (1) a diagnostic lightning parameterization that bases its algorithm on the level of neutral buoyancy from a convective parameterization scheme, (2) lightning potential index (LPI) using local graupel and ice contents, and (3) explicit prediction of electric fields and lightning initiation from WRF-ELEC. Five lightning events that occurred on 02 April 2019, 17 May 2019, 20 April 2020, 26 May 2020, and 20 May 2021 were examined to evaluate the forecasting capability of each scheme for the lightning over a 24-h forecast period. Prior to diagnosing lightning activity, the composite radar reflectivity and the neighborhood score metrics (ETS, FSS) for hourly rainfall were analyzed to determine if the simulated precipitation structure is consistent with the observations. Analyses based on performance diagrams were also included for a better illustration of how simulations perform on predicting precipitation. The spatial distribution of LPI and lightning flashes is compared against the NASA Lightning Imaging Sensor (LIS) dataset. The qualitative results show that in most of the studied cases, there is a good agreement between the observations and the WRF-ELEC-based simulations in terms of detecting the primary regions of lightning activity. The LPI based predictions perform also considerably well. The results from this endeavor constitute an essential initiative towards the implementation of an effective operational lightning warning system to mitigate lightning-related hazards in Bangladesh and northeast India.

Fractional crystallization of a basal lunar magma ocean: A dense melt-bearing garnetite layer above the core?

In the wake of its accretion, the Moon was likely partially or fully molten, forming a lunar magma ocean (LMO). A fully molten Moon may crystallize neutrally buoyant olivine, whose accumulation may form a barrier leading to a separation into two independently evolving melt reservoirs. This study investigates the crystallization of such a putative basal lunar magma ocean, ranging from the core mantle boundary (with radius r = 380 km) to the level of neutral olivine buoyancy (r = 600 km). Consecutive crystallization experiments determine liquidus temperatures and crystallize 10–30 wt% minerals, before conceptually segregating these according to their buoyancy, and then stepping to a new bulk composition that corresponds to the residual melt after removal of the cumulate minerals.The first olivine to crystallize from a Taylor Whole Moon composition (twm, XMg = Mg/(Mg + Fe2+) = 0.83) has XMg = 0.94 and is neutrally buoyant at 3.8 GPa according to the melt density model of Lange and Carmichael (1990). Crystallization begins at the core mantle boundary, but early olivine floats and re-dissolves until the magma ocean cools to the liquidus temperature at the depth of neutral buoyancy (1850 °C). At this point a > 500 km thick olivine-only layer could form, mainly fed from the upper magma shell. The crystallization sequence in the basal magma ocean is olivine-only at 1850–1675 °C, 0–26 pcs (wt% percent solidified) → olivine + opx (to 1600 °C, 42 pcs) → opx + cpx + garnet (to 1580 °C, 60 pcs) → cpx + garnet (to 1520 °C, 73 pcs) → cpx + garnet + olivine leaving 11 wt% residual melt at 1450 °C.Cooling this last melt to 1300 °C leads to 80% garnet + cpx + olivine + Ti-spinel, the residual liquid corresponding to 2.2% of the basal magma ocean. Olivine, opx and cpx remain buoyant over the entire crystallization interval and various pyroxenite layers are added to the olivine layer. Garnet and the final cotectic cpx + garnet + olivine + FeTi-oxide assemblage instead form a 70 km thick basal layer on the core-mantle boundary. Such a layer provides a gravitationally stable high-density lowermost lunar mantle, which would concur with a recent re-analysis of the lunar seismic data. The lowest temperature experiment at 1300 °C, not much above the 1250 °C proposed for the core-mantle boundary from inversion of geophysical data, had about 20% of a highly evolved, dense Fe-rich melt. It is feasible that this melt has remained in its liquid state to present day, providing an explanation for the proposed low vp and vs layer and high dissipation just above the core-mantle boundary.

Experimental settling, floatation and compaction of plagioclase in basaltic melt and a revision of melt density

Centrifuge-assisted piston cylinder experiments were conducted on plagioclase in basaltic melt at 1140–1250 °C, 0.42–0.84 GPa and mostly 1000 g. One set of experiments assesses the settling velocity of a dilute plagioclase suspension; a second sinks or floats plagioclase in a MORB-type melt exploring conditions of neutral buoyancy; and a third set examines floatation of plagioclase from an evolved lunar magma ocean composition. A compaction rate for plagioclase cumulates is established. The experiments demonstrate that neutral density of plagioclase An74 in a MOR-type tholeiitic basalt occurs at 0.59 ± 0.04 GPa (1200 °C), contrasting predictions by present models on melt density which yield a density inversion pressure at 0.10–0.15 GPa. In nature, the level of neutral buoyancy depends on melt composition; nevertheless, for the onset of plagioclase crystallization in dry tholeiitic basalts, our result is robust. As the molar volume of plagioclase is well known, the experimentally determined pressure of neutral buoyancy indicates a correction of -1.6% to previous density models for silicate melts. It follows that for (tholeiitic) layered mafic intrusions, plagioclase is negatively buoyant for early, relatively primitive, parent melts. In contrast, the extreme Fe enrichment of a fractionating lunar magma ocean leads to melt densities that let anorthite always float. Compaction φ/φ0 of experimental plagioclase cumulates is quantified to φ/φ0 = − 0.0582 log (Δρ·h·a·t) + 1.284, where φ0 is the porosity after settling (67 ± 2%), h the cumulate pile height, a acceleration and φ porosity as a function of time t. Gravitational-driven compaction in tens of m-thick plagioclase cumulate in basaltic magmas reaches down to ~ 40% porosity within hundreds of years, a timescales competing with characteristic cooling times of cumulate layers of mafic intrusions. To achieve plagioclase modes > 80% due to compaction, an additional overload of ~ 100 m (layers) of mafic minerals would be required. Compaction of a lunar anorthosite crust of 35 km to 20% porosity (i.e. ~ 90% plagioclase after crystallization of the interstitial melt) would require 30 kyrs.

Two‐Point Mixing, Buoyancy Sorting, and Updraft Dilution in the RACORO Campaign

AbstractAircraft measurements of shallow cumulus cases from the Routine Atmospheric Radiation Measurement (ARM) Aerial Facility (AAF) Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) campaign are studied in a transformed Paluch diagram. Previous studies have interpreted samples in Paluch diagrams in terms of two‐point mixing and buoyancy sorting. The two‐point mixing behavior is frequently seen in the RACORO observations and can be unambiguously distinguished from buoyancy sorting. The latter is not found in the RACORO observations and is also rare in a large‐eddy simulation (LES) of a RACORO case. As opposed to often assumed gradual dilution of updrafts, around half of the instances of two‐point mixing show no clear evidence of updraft dilution. We also find substantial spread in the properties of parcels that have adjusted to their level of neutral buoyancy and that a LES with horizontally homogeneous surface underestimates this spread. The inclusion of surface heterogeneity in the LES improves the agreement of its horizontal moisture variations with the aircraft measurements.

A Pressure-Invariant Neutral Density Variable for the World's Oceans

AbstractWe present a new method to calculate the neutral density of an arbitrary water parcel. Using this method, the value of neutral density depends only on the parcel’s salinity, temperature, latitude, and longitude and is independent of the pressure (or depth) of the parcel, and is therefore independent of heave in observations or high-resolution models. In this method we move the parcel adiabatically and isentropically like a submesoscale coherent vortex (SCV) to its level of neutral buoyancy on four nearby water columns of a climatological atlas. The parcel’s neutral density γSCV is interpolated from prelabeled neutral density values at these four reference locations in the climatological atlas. This method is similar to the neutral density variable γn of Jackett and McDougall: their discretization of the neutral relationship equated the potential density of two parcels referenced to their average pressure, whereas our discretization equates the parcels’ potential density referenced to the pressure of the climatological parcel. We calculate the numerical differences between γSCV and γn, and we find similar variations of γn and γSCV on the ω surfaces of Klocker, McDougall, and Jackett. We also find that isosurfaces of γn and γSCV deviate from the neutral tangent plane by similar amounts. We compare the material derivative of γSCV with that of γn, finding their total material derivatives are of a similar magnitude.

An Observational Comparison of Level of Neutral Buoyancy and Level of Maximum Detrainment in Tropical Deep Convective Clouds

AbstractTropical deep convective clouds are important drivers of large‐scale atmospheric circulation representing the main vertical transport pathway through the depth of the troposphere for heat, momentum, water, and chemical species. The strength and depth of this transport are impacted by the convective updraft size and intensity that are driven by buoyancy, dynamical forcing, and mixing of environmental air, that is, entrainment. In this study, we identify tropical deep convective systems with well‐defined forward anvils using Atmospheric Radiation Measurement (ARM) ground‐based profiling radars, at three ARM fixed sites in the Tropical Western Pacific (TWP; i.e., Manus, Nauru, and Darwin) and three ARM Mobile Facility deployments in Niamey, Niger; Gan Island, Maldives; and Manacapuru, Brazil. We use the difference between the level of neutral buoyancy (LNB) and the level of maximum detrainment (LMD) as a proxy for the effective bulk convective entrainment (εproxy). The LNB, the theoretical height that a parcel raised above the level of free convection would reach with no mixing, is calculated based on preconvection radiosonde measurements using parcel theory. The LMD is the height of the maximum reflectivity observed in forward anvil clouds by profiling radars. Deep convective systems over the TWP show higher LNBs that extend to 16.3 km on average and larger εproxy (median value of LNB minus LMD up to 6.5 km) compared to their continental counterparts in the Amazon and West Africa. Oceanic conditions show larger convective available potential energy (CAPE) coupled with higher moisture at low levels, which favors larger εproxy. In contrast, continental cases initiate and develop, under high convective inhibition, steeper environmental lapse rate, and high wind shear conditions, which show smaller offset between LNB and LMD. Deep convective cases that promote significant cold pools at the surface experience less εproxy. Using a Random Forest regression algorithm, CAPE is associated with the highest feature importance score for predicting convective εproxy, followed by low‐level relative humidity. For continental cases, the low‐level wind shear also indicates higher importance.

An Analysis of Plastic Barrels as a Platforms Material of Floating House in Coastal Areas

Housing is a very basic necessity for human life, so it is needed by considering its comfort of the environment and constituent materials. For people who live on the coastal areas which have narrow land and low environmental arrangement, a floating house can be the solution. The floating house is a building that stands or floats on water by relying on the weight and area of the field that is submerged as load parameters that are able to be borne by the structure. The house can float and be placed on the edge of the beach and above the sea water front. There are various materials that can be utilized as the footing of this floating house; one of which is plastic barrels. This research aims at analyzing the level of buoyancy, the amount of materials and the cost needed for the construction of a simple floating house unit using plastic barrels as the platforms. The results showed that the buoyancy level (Fa) of plastic barrels as the platforms material is 549.814 Newton, the number of plastic barrels needed as platforms materials is 232 pieces costing for IDR 358,270, 000.

Driving engagement: investigating the influence of emotional intelligence and academic buoyancy on student engagement

ABSTRACT Available evidence suggests that learners’ level of emotional intelligence and academic buoyancy are associated with components of behavioural and emotional engagement. Recent work has provided preliminary evidence that the relationship between emotional intelligence and student engagement is mediated by academic buoyancy. Therefore, the current study was designed to determine if the association between emotional intelligence, behavioural engagement, emotional engagement, behavioural disaffection, and emotional disaffection is mediated by academic buoyancy. A sample of 253 undergraduate and graduate students completed self-report measures of the primary constructs of interest. Results of an a priori path analysis indicated that emotional intelligence had a significant direct effect on behavioural and emotional engagement and behavioural and emotional disaffection. Our results also revealed academic buoyancy shared a direct relationship with behavioural and emotional engagement and emotional disaffection. Critically, our results provided additional evidence that the relationship between components of student engagement – behavioural engagement, emotional engagement, and emotional disaffection – was partially mediated by academic buoyancy. Discussion concerns the potential benefits of implementing interventions designed to enhance emotional intelligence in an effort to increase learners coping potential, engagement, and overall academic success.

Changes in Convective Available Potential Energy and Convective Inhibition under Global Warming

AbstractAtmospheric convective available potential energy (CAPE) is expected to increase under greenhouse gas–induced global warming, but a recent regional study also suggests enhanced convective inhibition (CIN) over land although its cause is not well understood. In this study, a global climate model is first evaluated by comparing its CAPE and CIN with reanalysis data, and then their future changes and the underlying causes are examined. The climate model reasonably captures the present-day CAPE and CIN patterns seen in the reanalysis, and projects increased CAPE almost everywhere and stronger CIN over most land under global warming. Over land, the cases or times with medium to strong CAPE or CIN would increase while cases with weak CAPE or CIN would decrease, leading to an overall strengthening in their mean values. These projected changes are confirmed by convection-permitting 4-km model simulations over the United States. The CAPE increase results mainly from increased low-level specific humidity, which leads to more latent heating and buoyancy for a lifted parcel above the level of free convection (LFC) and also a higher level of neutral buoyancy. The enhanced CIN over most land results mainly from reduced low-level relative humidity (RH), which leads to a higher lifting condensation level and a higher LFC and thus more negative buoyancy. Over tropical oceans, the near-surface RH increases slightly, leading to slight weakening of CIN. Over the subtropical eastern Pacific and Atlantic Ocean, the impact of reduced low-level atmospheric lapse rates overshadows the effect of increased specific humidity, leading to decreased CAPE.

Undrained bearing capacity of skids/pedrails during trenching for buried submarine pipelines

The paper investigates the undrained bearing capacity of an underwater trencher used for installation of buried submarine pipelines. The underlying soil is assumed to have an undrained strength that increases linearly with depth. The paper presents charts for the bearing capacity of these systems as a function of trench geometry, loading distance (i.e., the distance between the trencher skid/pedrail and the crest of trench wall), surface strength and the gradient of strength increasing with depth. These charts can guide engineers in the level of buoyancy needed for safe trenching operations. All calculations are performed using finite element limit analysis (FELA) and the parametric studies reveal five principal failure modes. At last, the paper includes an engineering example to demonstrate the use of the charts for practice.

A 1D RCE Study of Factors Affecting the Tropical Tropopause Layer and Surface Climate

Abstract There are discrepancies between global climate models regarding the evolution of the tropical tropopause layer (TTL) and also whether changes in ozone impact the surface under climate change. We use a 1D clear-sky radiative–convective equilibrium model to determine how a variety of factors can affect the TTL and how they influence surface climate. We develop a new method of convective adjustment, which relaxes the temperature profile toward the moist adiabat and allows for cooling above the level of neutral buoyancy. The TTL temperatures in our model are sensitive to CO2 concentration, ozone profile, the method of convective adjustment, and the upwelling velocity, which is used to calculate a dynamical cooling rate in the stratosphere. Moreover, the temperature response of the TTL to changes in each of the above factors sometimes depends on the others. The surface temperature response to changes in ozone and upwelling at and above the TTL is also strongly amplified by both stratospheric and tropospheric water vapor changes. With all these influencing factors, it is not surprising that global models disagree with regard to TTL structure and evolution and the influence of ozone changes on surface temperatures. On the other hand, the effect of doubling CO2 on the surface, including just radiative, water vapor, and lapse-rate feedbacks, is relatively robust to changes in convection, upwelling, or the applied ozone profile.