Experimental measurements of collision-induced absorption (CIA) cross-sections for CO-H2 and CO2-CH4 complexes were performed using Fourier transform spectroscopy over a spectral range of 100-500 cm and a temperature range of 200-300 K. These experimentally derived CIA cross-sections agree with the spectral range and temperature dependence of the calculation by Wordsworth (2017), however the amplitude is half of what was predicted. Furthermore, the CIA cross-sections reported here agree with those measured by Turbet (2019). The CIA cross-sections can be applied to planetary systems with CO2-rich atmospheres, such as Mars and Venus, and will be useful to terrestrial spectroscopists. Additionally, radiative transfer calculations of the early Mars atmosphere were performed and showed that CO2-CH4 CIA would require surface pressure greater than 3 bar for a 10% methane atmosphere to achieve 273 K at the surface. CO2-H2, however, liquid water is possible with 5\% hydrogen and less than 2 bar of surface pressure.

In an effort to better represent aerosol transport in meso- and global-scale models, large eddy simulations (LES) from the NCAR Turbulence with Particles (NTLP) code are used to develop a Markov chain random walk model that predicts aerosol particle vertical profiles in a cloud-free marine atmospheric boundary layer (MABL). The evolution of vertical concentration profiles are simulated for a range of aerosol particle sizes and in a neutral and an unstable boundary layer. For the neutral boundary layer we find, based on the LES statistics, that there exist temporal correlation structures for particle positions, meaning that over short time intervals (T= 500 s, or T/Tneut= 0.25), particles near the bottom of the boundary are more likely to remain near the bottom of the boundary layer than being abruptly transported to the top, and vice versa. For the unstable boundary layer, a similar time interval of T= 500 s (T/Teddy= 0.39) exhibits weaker temporal correlation compared to the neutral case due to the strong non-local convective motions. In the limit of a large time interval, T= 2000 s (T/Teddy= 1.56), particles have been mixed throughout the MABL and virtually no correlation exists. We leverage this information to parameterize a Markov chain random walk model that accurately predicts the evolution of vertical concentration profiles for the range of particle size and stability tested in LES, even over short time intervals which exhibit substantial correlation. The new methodology has significant potential to be applied at the subgrid level for coarser-scale weather and climate models.

Observations by several cameras on the Perseverance rover showed a 22° scattering halo around the Sun over several hours on the morning of sol 292 (15 December 2021). Such a halo has not previously been seen off Earth. The halo occurred during the aphelion cloud belt season and the cloudiest time yet observed from the Perseverance site. The halo required crystalline water-ice cloud particles in the form of hexagonal columns large enough for refraction to be significant, at least 11 µm in diameter and length. Near 44 km altitude, fall speeds would have been 0.3-1 m/s for the smallest allowed particles. Over the 3.3-hour duration of the halo, particles could have fallen 3-12 km, causing downward transport of water and dust. Halo-forming clouds are likely rare due to the high supersaturation of water that is required but may be more common in northern subtropical regions during mid-northern summer.

The Barents Sea attracts year-around human activity as the winter sea ice cover retreats, creating a need for short and long term prediction of environmental conditions in the region. Previous studies have shown that local ocean heat content and heat transport at the Barents Sea Opening provide interannual to decadal predictability of Barents Sea ice cover. Part of this predictability is suggested to originate from thermodynamic anomalies propagating along the Norwegian Atlantic Current. To better understand this source of predictability, and the relevant timescales, we use models (Coupled Model Intercomparison Project Phase 6; CMIP6) and satellite observations, to study the linear response of the monthly mean Barents Sea ice cover to downstream sea surface temperature anomalies. We show that in March the sea ice response is strongest on short lead times (<2 year), vanishing towards ~7 year timescale and that the linear sea ice response function can be reconstructed using an advective-diffusive ‘leaky-pipe’ model with multiple propagation timescales. The sea surface temperature based sea ice predictability is linked to decadal and longer timescale variability. Our results also show that sea surface temperatures close to the sea ice edge provide the best predictability at short timescales, but with a skill that approaches that of the sea surface temperatures further away at long timescales.

To investigate CO2 sink capacity in the western Arctic Ocean (north of 65°N), we conducted underway, ship-based observations of partial pressures of CO2 (pCO2) and total dissolved inorganic carbon (TCO2) in surface seawater in early winter (November 2018). From these two properties of the seawater inorganic carbon system, we calculated total alkalinity (TA). In the early winter, surface seawater pCO2 in most places was lower than atmospheric pCO2. The weighted mean of the air-sea fluxes of CO2 were calculated to be -7.5 ± 1.6 mmol m−2 d−1. The calculated fluxes implied that the area acted as a moderate sink for atmospheric CO2 in early winter, and its rate of CO2 uptake was comparable to that (-8.0 ± 1.7 mmol m−2 d−1) in summer (late August-September 2017). Spatial variations of surface seawater pCO2 in the early winter could be attributed mostly to conservative changes of TCO2 and TA, which together accounted for more than 70% of the pCO2 variations. In the marginal ice zone, however, there was a drawdown of surface seawater pCO2 by 70-90 matm due to horizontal advection of water with an anomalously high temperature from the Pacific Ocean and its subsequent cooling. We found that TA was an important determinant of the spatial variations of pCO2 in the western Arctic Ocean because of the conservative nature of the changes of TA and TCO2 during mixing of water masses. This conservative behavior was observed in both the early winter and summer.

Different lithofacies of shale oil reservoir invole different lithology（mineral composition）, structure(laminated and interbedded crack), pore type and permeability. One of our objectives is to explore the frequency dependent elastic properties and attenuation of the rocks with different lithofacies characteristics for shale oil reservoir. For another significant purpose, we attempt to explain the possible dispersion and attenuation mechanisms in shale using existing theoretical models. We first executed two sets of stress–strain oscillation experiments on partially white-oil saturated samples with different lithofacies, which comes from Inter-Salt shale oil in QianJiang Sag, to investigate the dispersion of elastic moduli, elastic and anelastic parameters, anisotropy and attenuation from seismic to ultrasonic frequencies. Assuming that the formation conforms to the characteristics of VTI medium, the experiments were carried out at a confining pressure range between 5 and 30MPa in the frequency range 1 to 1000Hz using two samples drilled in vertical and parallel directions to the formation bedding. And then we not only evaluate the applicability of the anisotropic Gassmann theory to the Inter-Salt shale, but also discuss the experimental phenomenon at mesoscopic and microscopic scales. The results of our broad-frequency experiment study illustrated that the dispersion and attenuation for compression/extension vertical to bedding is larger than that parallel to bedding in partial fluid saturation, and exhibiting different attenuation characteristic peaks. The increase of shear stiffness tensor with frequency seems to indicate the inapplicability of anisotropic Gassmann theory. The interpretation of the attenuation measurements in terms of well-established theoretical models which depict the wave-induced flow of pore fluid at the mesoscopic scale was discussed in terms of the Lithofacies characteristics, include intergranular pores and horizontal interlayer fractures,et al.

Past sea-level changes in the Mediterranean Sea are highly non-uniform and can deviate significantly from both the global average sea-level rise and changes in the nearby Atlantic. Understanding the causes of this spatial non-uniformity is crucial to the success of coastal adaptation strategies. This, however, remains a challenge owing to the lack of long sea-level records in the Mediterranean. Previous studies have addressed this challenge by reconstructing past sea levels through objective analysis of sea-level observations. Such reconstructions have enabled significant progress towards quantifying sea-level changes, however, they have difficulty capturing long-term changes and provide little insight into the causes of the changes. Here, we combine data from tide gauges and altimetry with sea-level fingerprints of contemporary land-mass changes using spatial Bayesian methods to estimate the sources of sea-level changes in the Mediterranean Sea since 1960. We find that sea level in the Mediterranean rose slowly until 1990 (0.4±0.5 mm yr-1), at which point it started accelerating significantly, driven by both sterodynamic changes and land-ice loss, reaching an average rate of 3.4±0.3 mm yr-1 in the period 2000-2018. The rate of sea-level rise shows considerable spatial variation in the Mediterranean Sea, primarily reflecting changes in the large-scale circulation of the basin. Since 2000, sea level has been rising faster in the Adriatic, Aegean, and Levantine Seas than anywhere else in the Mediterranean Sea.

Accurate space weather forecasting requires advanced knowledge of the solar wind conditions in near-Earth space. Data assimilation (DA) combines model output and observations to find an optimum estimation of reality and has led to large advances in terrestrial weather forecasting. It is now being applied to space weather forecasting. Here, we use solar wind DA with in-situ observations to reconstruct solar wind speed in the ecliptic plane between 30 solar radii and Earth’s orbital radius. This is used to provide solar wind speed hindcasts. Here, we assimilate observations from the Solar Terrestrial Relations Observatory (STEREO) and the near-Earth dataset, OMNI. Analysis of two periods of time, one in solar minimum and one in solar maximum, reveals that assimilating observations from multiple spacecraft provides a more accurate forecast than using any one spacecraft individually. The age of the observations also has a significant impact on forecast error, whereby the mean absolute error (MAE) sharply increases by up to 23% when the forecast lead time first exceeds the corotation time associated with the longitudinal separation between the observing spacecraft and the forecast location. It was also found that removing coronal mass ejections from the DA input and verification time series reduces the forecast MAE by up to 10% as it removes false streams from the forecast time series. This work highlights the importance of an L5 space weather monitoring mission for near-Earth solar wind forecasting and suggests that an additional mission to L4 would further improve future solar wind DA forecasting capabilities.

A new Aitken mode aerosol scheme is developed for a large eddy simulation (LES) model in order to better investigate cloud-aerosol interactions in the marine boundary layer and to study the Aitken buffering hypothesis of McCoy et al. (2021). This scheme extends the single-mode two-moment prognostic aerosol scheme of Berner et al. (2013). Nine prognostic variables represent accumulation and Aitken log-normal aerosol modes in air and droplets as well as 3 gas species. Scavenging of interstitial aerosol by cloud and rain drops and coagulation of dry aerosol are treated using the scheme described in B13. The scheme includes a simple chemistry model with gas phase H2SO4, SO2, and DMS as prognostic variables to capture basic influences of sulfur chemistry on the model aerosols. Primary nucleation of H2SO4 aerosol particles from gas-phase H2SO4 is neglected. A deep, precipitating stratocumulus case (VOCALS RF06) is used to test the new scheme. The presence of the Aitken mode aerosol increases the cloud droplet concentration through activation of the larger Aitken particles and delays the creation of an ultraclean, strongly precipitating cumulus state. Scavenging of dry accumulation and Aitken particles by cloud and precipitation droplets accelerates the collapse. Increasing either the above-inversion Aitken concentration or the surface Aitken flux increases the Aitken population in the boundary layer and prevents the transition to an ultraclean state.

Flood risk assessment and the design of protection measures often require the estimation of high water levels of a given probability of exceedance, i.e. design flood levels. The common approach for the estimation of design flood levels has typically three main steps. First, direct measurements of annual maximum water levels in a river cross-section are converted into annual maximum flows by using a rating curve. Second, a probability distribution function is fitted to these annual maximum flows to derive discharges of a desired probability of exceedance, i.e. design peak flows. Third, a hydraulic model is applied to derive the corresponding design flood levels. Each of the three steps is associated with significant uncertainties, affecting the accuracy of estimated design flood levels. In this study, we compare this common approach with an alternative one based on the statistical analysis of time series of annual maximum water levels. The rationale behind this study is that high water levels are directly measured and often come along with higher precision and accuracy than peak flows. While the direct use of high water levels is typical in coastal flood hazard and risk assessment, the potential of this approach in the context of river flooding has not been sufficiently explored. In this study we compare the common approach with an alternative approach based on statistical analysis of annual maximum water levels.

Asthenospheric shear causes some minerals, particularly olivine, to develop anisotropic textures that can be detected seismically. In laboratory experiments, these textures are also associated with anisotropic viscous behavior, which should be important for geodynamic processes. To examine the role of anisotropic viscosity for asthenospheric deformation, we developed a numerical model of coupled anisotropic texture development and anisotropic viscosity, both calibrated with laboratory measurements of olivine aggregates. This model characterizes the time-dependent coupling between large-scale formation of lattice-preferred orientation (i.e., texture) and changes in asthenospheric viscosity for a series of simple deformation paths that represent upper-mantle geodynamic processes. We find that texture development beneath a moving surface plate tends to align the a-axes of olivine into the plate-motion direction, which weakens the effective viscosity in this direction and increases plate velocity for a given driving force. Our models indicate that the effective viscosity increases for shear in the horizontal direction perpendicular to the a-axes. This increase should slow plate motions and new texture development in this perpendicular direction, and could impede changes to the plate motion direction for 10s of Myrs. However, the same well-developed asthenospheric texture may foster subduction initiation perpendicular to the plate motion and deformations related to transform faults, as shearing on vertical planes seems to be favored across a sub-lithospheric olivine texture. These end-member cases examining shear-deformation in the presence of a well-formed asthenospheric texture illustrate the importance of the mean olivine orientation, and its associated viscous anisotropy, for a variety of geodynamic processes.

A broad statistical study addresses for the first time an evolution of ultra-low frequency (ULF) waves/fluctuations in the terrestrial foreshock around the Moon generated through the interaction between the back-streaming particles reflected from the bow shock and the incoming solar wind. They propagate sunward but are convected by the solar wind flow back toward the bow shock and their amplitudes grow. However, our study shows that waves could be growing as well as decaying towards the bow shock under the quasi-radial interplanetary magnetic field. We demonstrate that the statistically determined growth rate is positive and larger for compressive variations of the density and magnetic field strength than for its components. We show that even if a possible influence of the Moon and its wake is excluded, the growth rate is decreased by non-linear effects leading to saturation of the wave amplitude.

Fracture characterization is essential to hydrocarbon and geothermal exploration and production as well as carbon geo-sequestration. Active and passive measurements have been extensively applied to map fractures across various scales. Active and passive measurements have inherent advantages and limitations that complement each other. In this study, to improve the mapping of embedded fractures and the surrounding geomechanically altered regions, we integrate active shear-wave transmission measurement with passive acoustic-emission measurement collected during a lab-scale hydraulic-fracturing experiment. The proposed approach leverages the advantages of the two modalities of measurements, while minimizing the limitations. Polarized shear-wave transmission (active) measurement was collected before and after the hydraulic fracturing, and the acoustic emission (passive) measurement was collected during hydraulic fracturing. Two sets of two-dimensional maps of fracture and fracture-induced damage in axial, median and frontal planes were obtained by separately processing the physics-informed transformations of active and passive measurements. These 2D maps are then fed to wavelet-based image-fusion technique to integrate the two sources of information for the reliable mapping/imaging of the embedded fractures and the surrounding geomechanically altered regions. Plain word summary Fractures and geomechanical alterations embedded in a solid material can be characterized using active or passive measurements. Signal type, timing, duration and location of the source is controlled during an active measurement to allow optimal interactions of the propagating wave and the fractured material, whereas the signals due to waves generated by the processes of fracturing and geomechanical alterations are captured during a passive measurement. Active and passive measurements have advantages and limitations that complement each other. In this study, physics-informed transformations and wavelet-based image fusion are used to integrate the active and passive measurements to get the best of the two measurement modalities for purposes of reliable imaging of fractures and the surrounding geomechanically altered regions. Key points  Integration of active and passive measurements will leverage their strengths and minimize the limitations of individual measurement techniques.  To the best of authors’ knowledge, no reference exists where the two modalities are combined to characterize the fractures either in the field or laboratory scale.  We integrate active ultrasonic measurements with passive acoustic-emission measurements using physics-informed transformations and data fusion techniques.  The proposed method improves the imaging of embedded fractures and the surrounding geomechanically altered regions.  Two-dimensional maps of fracture and fracturing-induced damage is generated in axial, median and frontal planes.

The Canada Basin has exhibited a significant trend toward a fresher surface layer and thus a more stratified upper ocean over the past three decades. Here, we explore the extent to which the Community Earth System Model (CESM) accurately simulates the observed surface freshening and seasonal processes that contribute to the freshening. We examine 30 simulations from CESM1 (used in the IPCC AR5), 3 simulations from CESM2 (IPCC AR6), and ocean observations from 1975 and 2006-2012. In contrast to the observations, the models simulate salinity profiles that show relatively little variation between 1975 and 2012. We demonstrate that this bias can be partly attributed to the model’s tendency to mix freshwater too deep, creating a surface layer that is saltier than observed. The results provide insight for climate model improvement that could have wide-reaching implications because upper-ocean stratification influences the vertical transport of heat and nutrients.

Soil moisture is important for sub-seasonal and seasonal climate prediction. However, biases and uncertainties of soil moisture in climate models affect the accuracy of climate prediction. Here we evaluate biases in climate model soil moisture across different time scales in the frequency domain. Based on our findings, compared to observations, soil moisture variability in the models is found to be underestimated at frequencies smaller than the seasonal time scale and overestimated at frequencies larger than the seasonal time scale. In addition, for the total effect of evapotranspiration and precipitation variability on soil moisture, models also underestimate frequencies smaller than the seasonal time scale and overestimate frequencies larger than it. Furthermore, no matter which factor (evapotranspiration or precipitation) is most affecting soil moisture, models underestimate its effect on soil moisture in the corresponding frequency range. Finally, at a global scale, biases in climate models can be related to the mean climate and not to soil properties. This study provides new insights into climate models deficiencies, and contributes to a better understanding of soil moisture and climate.

This paper describes a method for analyzing the kinematic properties of ions composing the solar wind. The core technology is a velocity analysis performed by dual rotating electric field (REF) units arranged coaxially in tandem, where the electric field in the downstream unit is set in the opposite direction to the upstream one. When the solar wind flies freely through the REF units, ions diverge outwards in the upstream unit and converge inwards in the downstream unit. Since the degree of diversion and conversion correspond to each ion’s velocity, ions separate into multiple groups flying through the REF units, terminate their flights on an image sensor placed on the tail end, and create sorted patterns that exhibit the velocity distribution of ions. As the REF units act on ions only by dynamic lateral electric force, the initial velocity and charge state of the ions remain invariant during the analysis process, which can be advantageous for solar wind analysis. This paper introduces a proposed instrument equipped with multiple functions, including an energy analysis, an overall velocity analysis, and a detailed ion velocity analysis. The kinematic properties of the measured ions correspond to energy levels ranging from 300 eV to 20 keV, velocities from 20 km/s to 1,900 km/s, and mass numbers from 1 to 200.

Modern bedrock streams and rivers emerged in the Midwestern United States in response to glacial outwash floods ~19,000 years ago and continued to adjust to new drainage patterns over the landscape formed by Wisconsin glaciation events. The Illinois River and corresponding tributaries form a fascinating landscape with canyons carved 50-200 m deep into the St. Peter Sandstone. These geomorphic features are preserved and open to visitors as Starved Rock State Park in Central Illinois. Free access to the state parks and close proximity to the large Chicago metropolitan area result in frequent visitation to this natural attraction. Recently, the rates of natural stream incision appear to be overprinted by direct human influences on the landscape. The St. Peter Sandstone is a weakly cemented, extremely friable quartz arenite, making it susceptible to human disturbance and rapid natural erosion. This study explores how quickly present day changes occur along bedrock surfaces using photogrammetric Structure-from-Motion (SfM). Repeat photographic data were collected once per month from two sites within the park where canyon walls contained human carvings that served as reference features to align photos and monitor change. Photos were merged in Agisoft PhotoScan Pro to construct 3D point clouds and imported into CloudCompare to measure changes to rock surfaces between monthly visits. The photogrammetric SfM analysis detected measurable change on a centimeter to millimeter scale. Changes along footpaths were observed when visitor traffic was high. During winter months when visitor traffic decreased, rainfall and snowmelt runoff primarily caused mobilization and removal of loose sediments covering bedrock surfaces. Bedrock thin sections from each site were studied to assess the influence of cement on erosion rates. Lower cement concentrations were observed at the outcrop site with the greatest measured surface change. Changes detected with SfM analyses demonstrate that human interactions can influence erosion processes in a short time. While both natural and human caused changes occurred on bedrock surfaces, precipitation created greater measurable differences.

Ground-based VLF transmitters located around the 2 world generate signals that leak through the bottom side of the 3 ionosphere in the form of whistler mode waves. Wave and particle 4 measurements on satellites have observed that these man-made 5 VLF waves can be strong enough to scatter trapped energetic 6 electrons into low pitch angle orbits, causing loss by absorption in 7 the lower atmosphere. This precipitation loss process is greatly 8 enhanced by intentional amplification of the whistler waves using 9 a newly discovered process called Rocket Exhaust Driven 10 Amplification (REDA). Satellite measurements of REDA have 11 shown between 30-and 50-dB intensification of VLF waves in 12 space using a 60-second burn of the 150 g/s thruster on the Cygnus 13 satellite that services the International Space Station (ISS). This 14 controlled amplification process is adequate to deplete the 15 energetic particle population in the radiation belts in a few minutes 16 rather than the multi-day period it would take naturally. 17 Numerical simulations of the pitch angle diffusion for radiation 18 belt particles use the UCLA quasi-linear Fokker Planck model 19 (QLFP) to assess the impact of REDA on radiation belt 20 remediation (RBR) of newly injected energetic electrons. The 21 simulated precipitation fluxes of energetic electrons are applied to 22 models of D-region electron density and bremsstrahlung x-rays for 23 predictions of the modified environment that can be observed with 24 satellite and ground-based sensors. 25 26 Index Terms-Active Space Experiments, Parametric