Surface Pressure Variations Research Articles

Investigation of seasonal variability of atmospheric columnar CO2 over India in relation to environmental parameters using OCO-2 observation and vertical redistribution model

ABSTRACT This work re-explores the seasonal change of atmospheric carbon dioxide (CO2) concentration, a subject of renewable interest over half a century, in both time and frequency domain and identifies the atmospheric surface pressure and the surface air temperature as key factors for the temporal variation. The annual variability of CO2 dry-air mole fraction derived from the National Aeronautics and Space Administration Jet Propulsion Laboratory (NASA-JPL) Orbiting Carbon Observatory-2 (OCO-2) database for the region bounded by 22° N to 23° N and 86° E to 89° E was found to increase in summer, to decrease in winter and to exhibit a tendency of increase at the end of the year consistently for the years 2016 and 2017 whereas the corresponding variations of solar-induced fluorescence, surface pressure and air temperature showed partial consistency with that. The trends of these findings were cross-checked with the long-time gross variations of CO2, Normalized Difference Vegetation Index, surface pressure and surface temperature for 25 urban regions within approximately 20° N to 29° N and 69° E to 89° E obtained from NASA-Giovanni database for a period of 2010 to 2017. The periodic variations of these parameters were pin-pointed by Fourier transform. Field measurements were carried out for ground level and column-averaged CO2 concentrations in parts per million (ppm) at the region around Kolkata city (22.55° N, 88.35° E). Based on the above findings, a simple atmospheric model is developed for vertical redistribution of CO2 molecules under changed temperature and pressure causing a changed atmospheric path for radiation absorption and an apparent change in the gas concentration at any specific altitude.

Attenuated Interannual Variability of Austral Winter Antarctic Sea Ice Over Recent Decades

AbstractChanges in Antarctic sea ice modify surface circulation, deep‐water formation, and overturning circulation, affecting the ecosystem and the atmosphere‐ocean‐ice interaction. Recent studies focused on long‐term trends of Antarctic sea ice, but whether its variability has changed is less clear. By examining reanalysis data sets, we show an interdecadal attenuation in variability of austral winter Antarctic sea ice since the late 1990s. This mainly arises from declined surface pressure variations in response to a combined effect of El Niño‐Southern Oscillation (ENSO) and the Southern Annular Mode (SAM). Compared to the pre‐1999 period, ENSO and the SAM have reduced variability in the post‐1999 period, and the linkage between them and Antarctic climate has weakened. The decreased level of variability over the 1999–2017 period may facilitate a more sensitive response of Antarctic sea ice to an external forcing, by enhancing the signal‐to‐noise ratio.

Conceptual thermal design of a network of solar-powered Boardsat- and CubeSat-based landed spacecraft on Mars

In this paper, we assess the feasibility of the neoPASCAL thermal design by performing thermal analysis. NeoPASCAL is a network of compact solar-powered landers on Mars which aim to validate Mars General Circulation Models (GCMs) by measuring the diurnal variations in surface pressure. It is a modern revision of the original Pascal mission proposed in 1996, with each science station being ten times smaller in size and mass (a kg or less) by using miniaturised commercial off-the-shelf (COTS) electronic components and satellite platforms (i.e., Boardsat and CubeSat platforms). Despite the harsh thermal environments, the analysis shows that the Boardsat-based model can survive at ≤ ±60° latitude by using a large flexible-solar-cells-attached sail that was originally designed to attain soft landing. If successful, such a network would provide an unprecedented set of global meteorological data that can be used to investigate various meteorological phenomena including the general circulation.

Conceptual thermal design of a network of solar-powered Boardsat- and CubeSat-based landed spacecraft on Mars

In this paper, we assess the feasibility of the neoPASCAL thermal design by performing thermal analysis. NeoPASCAL is a network of compact solar-powered landers on Mars which aim to validate Mars General Circulation Models (GCMs) by measuring the diurnal variations in surface pressure. It is a modern revision of the original Pascal mission proposed in 1996, with each science station being ten times smaller in size and mass (a kg or less) by using miniaturised commercial off-the-shelf (COTS) electronic components and satellite platforms (i.e., Boardsat and CubeSat platforms). Despite the harsh thermal environments, the analysis shows that the Boardsat-based model can survive at ≤ ±60° latitude by using a large flexible-solar-cells-attached sail that was originally designed to attain soft landing. If successful, such a network would provide an unprecedented set of global meteorological data that can be used to investigate various meteorological phenomena including the general circulation.

On pressure perturbations caused by a moving heat source of the frontal type (hydrostatic mode)

The problem of perturbations of the surface pressure caused by a moving nonstationary frontal heat source (localized along one horizontal coordinate) is considered. Pressure disturbances are associated with internal gravity waves (IGWs). It is shown that when a source moves in a finite-height atmospheric layer (atmospheric waveguide) when a discrete set of vertical IGW modes is excited, there are three types of temporal variation of surface pressure at a fixed observation point. These types correspond respectively to the time signal with amplitude modulation, the signal with frequency modulated Doppler type and the signal that occurs only after passing through the source. Each type is implemented for specific values of the oscillation frequency of the source and the Mach number (the ratio of the speed of the source to the phase velocity of the IGW). At Mach numbers less than one, an oscillating source always excites wave precursors disturbances observed before the source arrives. The movement of the source in a semi-infinite atmosphere leads to additional excitation of waves that transfer energy to the upper layers of the atmosphere.

Cholesterol mediates spontaneous insertion of Lycium barbarum polysaccharides in biomembrane model

In this work, the adsorptive behavior of Lycium barabrum polysaccharides (LBP) on 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine(POPC)/1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and POPC/DPPC/Cholesterol (Chol) monolayer films were investigated using the Langmuir films technique and atomic force microscopy (AFM). For the POPC/DPPC system, the π-A isotherms shifted to larger areas and the surface pressure variations (Δπ) in the adsorption curves (10 mN/m and 35 mN/m) increased with the increase in the LBP concentration. For the POPC/DPPC/Chol system, π-A isotherms moved to larger areas with the addition of LBP, and the Δπ values were also lower than those of the POPC/DPPC system. These were ascribed to hydrogen bond network formation between LBP and the lipids. The excess per molecular area (ΔAexc) and the excess Gibbs free energy of mixing ( $$\Delta {\text{G}}_{mix}^{Exc}$$ ) revealed that the repulsion force was the interaction between POPC and DPPC molecules. Meanwhile, the repulsion force increased with the addition of LBP. The addition of cholesterol decreased the force. The interactions among molecules were also evaluated by the values of K (the speed of adsorption of LBP), Ap (the number of each lipid molecule combining with the polysaccharide molecules in the mixed monolayer), Γ (the surface excess concentration) and A (the area per molecule). As shown in AFM images, the morphology of the monolayer films also indicated that LBP was easily adsorbed onto the POPC/DPPC monolayer film via hydrogen bond and the weak Van der Waals interaction. In summary, cholesterol could affect spontaneous insertion of LBP into the POPC/DPPC monolayer films from phosphate buffer solution.

Sensitivity analysis of flowfield modeling parameters upon the flow structure and aerodynamics of an opposing jet over a hypersonic blunt body

Implementation of an opposing jet in design of a hypersonic blunt body significantly modifies the external flowfield and yields a considerable reduction in the aerodynamic drag. This study aims to investigate the effects of flowfield modeling parameters of injection and freestream on the flow structure and aerodynamics of a blunt body with an opposing jet in hypersonic flow. Reynolds-Averaged Navier-Stokes (RANS) equations with a Shear Stress Transport (SST) turbulence model are employed to simulate the intricate jet flow interaction. Through utilizing a Non-Intrusive Polynomial Chaos (NIPC) method to construct surrogates, a functional relation is established between input modeling parameters and output flowfield and aerodynamic quantities in concern. Sobol indices in sensitivity analysis are introduced to represent the relative contribution of each parameter. It is found that variations in modeling parameters produce large variations in the flow structure and aerodynamics. The jet-to-freestream total-pressure ratio, jet Mach number, and freestream Mach number are the major contributors to variation in surface pressure, demonstrating an evident location-dependent behavior. The penetration length of injection, reattachment angle of the shear layer, and aerodynamic drag are also most sensitive to the three crucial parameters above. In comparison, the contributions of freestream temperature, freestream density, and jet total temperature are nearly negligible.

On Pressure Perturbations Caused by a Moving Heat Source of Frontal Type (Hydrostatic Mode)

The problem of surface-pressure perturbations caused by a moving nonstationary heat source (localized along one horizontal coordinate and periodic along the other) is considered. Pressure perturbations are associated with internal gravity waves (IGWs). It is shown that, during the source movement throughout a finite-height atmospheric layer (atmospheric waveguide), when a discrete set of vertical IGW modes is excited, there may be three types of time surface-pressure variations at a fixed observation point. A time amplitude-modulated signal; a Doppler frequency-modulated signal; and a signal that occurs only after the passage of the source correspond to these three types, respectively. Each of these types is implemented for certain source oscillation frequencies and Mach numbers (ratio between the movement rate of source and the phase velocity of IGWs). At $$M < 1$$ , a nonstationary source always excites wave precursors—disturbances observed before the source arrival. The movement of the source in a semi-infinite atmosphere leads to additional generation of waves that transport energy into the upper atmospheric layers.

Wake dynamics and surface pressure variations on two-dimensional normal flat plates

The relationship between vortex dynamics and surface pressure fluctuations on the leeward face of a two-dimensional normal thin flat plate was studied using Direct Numerical Simulations for incompressible flow at a Reynolds number of 1200. The vortex shedding frequency was observed in the spectra of pressure fluctuations on both faces of the plate, while a lower frequency spectral peak was only evident on the leeward pressure fluctuations. Local sharp peaks of low pressure in the separated shear layers coincide with increases in the leeward face pressure fluctuations. These observations are tied to the vortex dynamics using the invariant Q, commonly used for vortex identification. Q is also proportional to the source term for the Poisson equation for the instantaneous pressure. The pressure, which is the only contributor to the plate drag, varies significantly in response to alterations to the vortex shedding, which can be observed in differences of vortex trajectories. At minimum drag, the pressure fluctuations are small, which is attributed to lower values of Q associated with weaker vortices.

Numerical investigation of a pulsed reaction control jet in hypersonic crossflow

This paper presents a numerical study on the flow structures developed when a pulsed reaction control jet is operated in a hypersonic crossflow with a laminar boundary layer. Understanding these flow structures is important to the design of reaction control jets and scramjet fuel injectors. Implicit large-eddy simulations were performed with a round, sonic, perfect air jet issuing normal to a Mach 5 crossflow over a flat plate, at a jet-to-crossflow momentum ratio of 5.3 and a pressure ratio of 251, and with square-wave pulsing at Strouhal numbers of 1/6 to 1/3, based on jet diameter and free-stream velocity. Pulsing the jet allows the shock structure to partially collapse when the jet is off. This shock collapse affects the shedding frequency of shear-layer vortices, the formation of shear-layers downstream of the jet outlet, and the formation of longitudinal counter-rotating vortices. The lead shocks formed at jet start-up allow deeper penetration by increasing the effective jet-to-crossflow momentum ratio near the jet outlet and by preventing interaction between hairpin vortices. Normalised penetration was increased by a maximum of 68% compared with the steady jet. Pulsing also provides a higher jet interaction force per unit mass flow rate compared with a steady jet, with a 52% increase recorded at a 33% duty cycle. Temporal and spatial variations of surface pressure are important for reaction control applications and have been quantified. Pressure distribution depends strongly on duty cycle, and higher interaction force per unit mass flow rate was observed in cases with low duty cycle.

On the relationship between surface pressure, terrain elevation, and air temperature. Part I: The large diurnal surface pressure range at Gale Crater, Mars and its origin due to lateral hydrostatic adjustment

The daily variation of surface pressure observed by the Curiosity Rover Environmental Monitoring Station (REMS) is both significantly larger than observed at other landing sites on Mars and larger than simulated for the Curiosity site by global circulation models (GCM). Mesoscale numerical models are able to simulate the large REMS daily pressure range, but only if they possess sufficiently high horizontal resolution (grid spacing <5 km); low resolution (120–500 km) GCM simulations typically generate daily ranges of about half the observed value. The pressure range in low resolution simulations corresponds to the large-scale thermal tides and the augmentation of this range in high resolution models is associable with mesoscale topographic and surface property variations in the Gale Crater region. We show that the augmentation is due to the lateral redistribution of mass required for the surface pressure distribution over topographic relief to remain approximately hydrostatic as the near-surface air temperature varies through the diurnal cycle. The physical origin and nature of this adjustment flow is explored. We provide a means of predicting the daily surface pressure due to lateral hydrostatic adjustment for any location and further show that this range is slightly reduced by the inability of the atmosphere to completely achieve hydrostaticity and by the thermal effects of induced flows.

Correct Boundary Conditions for the High-Resolution Model of Nonlinear Acoustic-Gravity Waves Forced by Atmospheric Pressure Variations

Currently, an international network of operating high-resolution microbarographs was established to record wave-induced pressure variations at the Earth’s surface. Based on these measurements, simulations are performed to analyze the characteristics of waves corresponding to the observed variations of atmospheric pressure. Such a mathematical problem involves a set of primitive nonlinear hydrodynamic equations considering lower boundary conditions in the form of pressure variations at the Earth’s surface. Selection of upward propagating acoustic-gravity waves (AGWs) generated or reflected at the Earth’s surface requires the Neumann boundary conditions involving the vertical gradients of vertical velocity at the lower boundary. To analyze the correctness of the mathematical problem, linearized equations are used for small-surface wave amplitudes excited near the ground. Using the relation for wave energy, it is proven that the solution of the boundary problem based on the nondissipative approximation is uniquely determined by the variable pressure field at the Earth’s surface. The respective dissipative problem has also a unique solution with the appropriate choice of lower boundary conditions for temperature and velocity components. To test the numerical algorithm, solutions of the linearized equations for AGW modes are used. Developed boundary conditions are implemented into the model describing acoustic-gravity wave propagation from the surface atmospheric pressure source. Atmospheric waves propagating from the observed surface pressure variations to the upper atmosphere are simulated using the obtained algorithms and the computer codes.

Well-Posedness of a Problem of Propagation of Nonlinear Acoustic-Gravity Waves in the Atmosphere Generated by Surface Pressure Variations

Currently there are many international microbarograph networks for high-resolution recording of wave pressure variations on the Earth’s surface. This arouses interest in wave propagation in the atmosphere generated by atmospheric pressure variations. A full system of nonlinear hydrodynamic equations for atmospheric gases with lower boundary conditions in the form of wavelike pressure variations on the Earth’s surface is considered. Since the wave amplitudes near the Earth’s surface are small, linearized equations are used in the analysis of well-posedness of the problem. With the help of a wave energy functional method, it is shown that in the non-dissipative case the solution to the boundary value problem is uniquely determined by the variable pressure field on the Earth’s surface. The corresponding dissipative problem is well-posed if, in addition to the pressure field, appropriate conditions on the velocity and temperature on the Earth’s surface are given. In the case of an isothermal atmosphere, the problem admits analytical solutions that are harmonic in the variables x and t. A good agreement between the numerical and analytical solutions is obtained. The study shows that the temperature and density can rapidly vary at the lower boundary of the boundary value problem. An example of solving the three-dimensional problem with variable pressure on the Earth’s surface taken from experimental observations is given. The developed algorithms and computer programs can be used to simulate atmospheric waves generated by pressure variations on the Earth’s surface.

高密度観測に認められる夏季関東地方の気温と地上気圧の時空間変動の特徴―2014年7～9月の気温と地上気圧データを用いて―

関東地方で実施した高密度観測から得られた夏季の気温と気圧データに対して主成分分析を行い，これらの時空間変動にみられる特徴を明らかにした．気温場と気圧場それぞれの上位3主成分には，海陸風循環，ヒートアイランド現象，北東気流に関係した空間分布が認められ，相互の主成分間に有意な相関関係が存在する．これらの気温と気圧の関係は，いずれも相対的に気温が高い（低い）地域で気圧が低い（高い）傾向を示す．晴天日の気温と気圧の分布には明瞭な日変化が認められ，日中には海風の発達に伴い，関東平野の内陸部で相対的に高温低圧となり，日没後から夜間にかけては，ヒートアイランド現象が顕在化して東京都心から北側郊外にかけての都市部で相対的な高温低圧傾向が認められた．これらの観測事実に基づいた解析から，晴天日の気温と気圧の主要な日変化パターンに，内陸部の高温低圧に伴う海風循環とヒートアイランド現象に伴う高温低圧が認められた．

Effect of temperature-dependent cross sections on O4 slant column density estimation by a space-borne UV–visible hyperspectral sensor

The sensitivities of oxygen dimer (O4) slant column densities (SCDs) were examined by applying temperature-dependent O4 cross sections using the radiative transfer model (RTM) calculation with the linearized pseudo-spherical vector discrete ordinate radiative transfer model. For the sensitivity study, we used a newly developed cross section database in place of the database used in the operational algorithm. Newly investigated O4 cross section databases for 203 K and 293 K were used for the radiance simulation by interpolating temperature for each atmospheric layer based on the vertical profile of standard atmosphere in the RTM. The effect of the temperature-dependent cross sections was a significant O4 SCD increase of 8.3% with dependence on satellite and solar viewing geometries. Furthermore, the O4 SCD generally increased by an estimated 3.9% based on the observation geometries of the Ozone Monitoring Instrument. For the long-term comparison, the O4 SCD estimated from the temperature-dependent cross sections corrects 20% of the total underestimation of O4 SCD between the observation and simulation. Although the surface pressure variation and background aerosol effect also correct the O4 SCD discrepancy, the effect of temperature-dependent cross sections was more important than the effects of surface pressure variation and background aerosols. Therefore, temperature dependence of the cross section in the RTM calculation is essential for the accurate simulation of O4 SCD.

Pressure distribution on rectangular buildings with changes in aspect ratio and wind direction

This study aims to enhance the understanding of the surface pressure distribution around rectangular bodies, by considering aspects such as the suction pressure at the leading edge on the top and side faces when the body aspect ratio and wind direction are changed. We carried out wind tunnel measurements and numerical simulations of flow around a series of rectangular bodies (a cube and two rectangular bodies) that were placed in a deep turbulent boundary layer. Based on a modern numerical platform, the Navier–Stokes equations with the typical two-equation model (i.e., the standard k-e model) were solved, and the results were compared with the wind tunnel measurement data. Regarding the turbulence model, the results of the k-e model are in overall agreement with the experimental results, including the existing data. However, because of the blockage effects in the computational domain, the pressure recovery region is underpredicted compared to the experimental data. In addition, the k-e model sometimes will fail to capture the exact flow features. The primary emphasis in this study is on the flow characteristics around rectangular bodies with various aspect ratios and approaching wind directions. The aspect ratio and wind direction influence the type of wake that is generated and ultimately the structural loading and pressure, and in particular, the structural excitation. The results show that the surface pressure variation is highly dependent upon the approaching wind direction, especially on the top and side faces of the cube. In addition, the transverse width has a substantial effect on the variations in surface pressure around the bodies, while the longitudinal length has less influence compared to the transverse width.

Terrestrial atmospheric responses on Svalbard to the 20 March 2015 Arctic total solar eclipse under extreme conditions.

This article reports on the near-surface atmospheric response at the High Arctic site of Svalbard, latitude 78° N, as a result of abrupt changes in solar insolation during the 20 March 2015 equinox total solar eclipse and notifies the atmospheric science community of the availability of a rare dataset. Svalbard was central in the path of totality, and had completely clear skies. Measurements of shaded air temperature and atmospheric pressure show only weak, if any, responses to the reduced insolation. A minimum in the air temperature at 1.5 m above the ground occurred starting 2 min following the end of totality, though this drop was only slightly beyond the observed variability for the midday period. Eclipse-produced variations in surface pressure, if present, were less than 0.3 hPa.This article is part of the themed issue 'Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse'.

Air–water interfacial properties of enzymatic wheat gluten hydrolyzates determine their foaming behavior

Insight in the link between foaming and interfacial properties of proteins can increase their potential as functional agents in food systems. Here, foaming capacity and stability of structurally different peptic and tryptic wheat gluten hydrolyzates were related to the kinetics of their adsorption at an air–water interface as well as to the properties of a compressed protein film at this interface. Foams from degree of hydrolysis (DH, i.e. the percentage of cleaved peptide bonds) 2 hydrolyzates were more stable than those from their DH 6 counterparts, and this at all protein concentrations tested. However, at protein concentrations from 0.010% to 0.050% (wprot/v), peptic DH 2 and 6 hydrolyzates had better foaming stability than their tryptic counterparts of the same DH. The opposite was observed when protein concentrations ranged from 0.050% to 0.150% (wprot/v). These observations can in part be explained by the molecular mass composition of the samples and, more importantly, by high levels of hydrophobic peptides in the DH 2 samples. The calculation of an average elasticity (up to 20–25 mN/m) from the variation in surface pressure for a variation in surface area in Langmuir isotherms showed that DH 2 samples had higher elasticity than DH 6 samples, which was in agreement with their foaming stabilities at various protein concentrations. Additionally, although not usually considered in literature, it seemed there was a correspondence between surface pressure at different protein surface concentrations and foaming stability at different protein concentrations.

Study of seismic diffractions caused by a fracture zone at In Salah carbon dioxide storage project

The In Salah CO2 storage project in Algeria has injected over 3 million tonnes of carbon dioxide into a water filled tight sand formation. Interferometric Synthetic Aperture Radar (InSAR) range change data revealed a double lobbed pattern of deformation that has been modeled as the opening of a sub-vertical fracture, or damage, zone. The location and geometry of the linear feature were subsequently verified using a seismic reflection survey. The elastic properties of the fracture zone, including anisotropic Poisson ratio (ν), Young's (E) and shear (G) moduli, were estimated from coupled geomechanical and hydrological modeling of surface deformation and pressure variations in the injection well. The elastic moduli reflect the fracture properties after CO2 flow through the fracture zone. Thus, the seismic signature of the fracture zone could be used for monitoring the CO2 plume. Using the estimated fracture model, we built two and three dimensional models consisting of an anisotropic fracture zone embedded within an isotropic background. Finite-difference modeling of seismic shot gathers allows us to estimate the effects of scattering from the fracture zone, potentially further constraining the geomechanical model. From the seismic modeling results, we find diffracted waves, induced by the fracture zone, which behave similar to point source diffractions. This modeling is intended to guide a search for diffraction events in the 3D surface seismic field data. The modeling results indicate that using the moduli estimated from geomechanical modeling, fracture scattered events would be 100 times lower amplitude than the interface reflections, and thus would be hard to detect. While diffracted waves are observed in the field data, which may imply the need for revision of the fracture model, including shape and elastic moduli, we are not able to match the field observation with our modeled events. This work presents a frontier study on the integration of geomechanical and geophysical methods at the In Salah site as a means to test the estimate of the subsurface CO2 flooded fracture properties.

Applying local Green's functions to study the influence of the crustal structure on hydrological loading displacements

The influence of the elastic Earth properties on seasonal or shorter periodic surface deformations due to atmospheric surface pressure and terrestrial water storage variations is usually modeled by applying a local half-space model or an one dimensional spherical Earth model like PREM from which a unique set of elastic load Love numbers, or alternatively, elastic Green's functions are derived. The first model is valid only if load and observer almost coincide, the second model considers only the response of an average Earth structure. However, for surface loads with horizontal scales less than 2500km2, as for instance, for strong localized hydrological signals associated with heavy precipitation events and river floods, the Earth elastic response becomes very sensitive to inhomogeneities in the Earth crustal structure.We derive a set of local Green's functions defined globally on a 1°×1° grid for the 3-layer crustal structure TEA12. Local Green's functions show standard deviations of ±12% in the vertical and ±21% in the horizontal directions for distances in the range from 0.1° to 0.5°. By means of Green's function scatter plots, we analyze the dependence of the load response to various crustal rocks and layer thicknesses. The application of local Green's functions instead of a mean global Green's function introduces a variability of 0.5–1.0mm into the hydrological loading displacements, both in vertical and in horizontal directions. Maximum changes due to the local crustal structures are from −25% to +26% in the vertical and −91% to +55% in the horizontal displacements. In addition, the horizontal displacement can change its direction significantly. The lateral deviations in surface deformation due to local crustal elastic properties are found to be much larger than the differences between various commonly used one-dimensional Earth models.