Small Plumes Research Articles

Performance of ceiling jet induced by dual unequal strong plumes in a naturally ventilated tunnel

• Thermal property of two unequal flames in a naturally ventilated tunnel is studied. • Temperatures induced by the small plume decay faster than that of the large plume. • A new model for maximum ceiling temperature of two unequal plumes is proposed. • Correlations for ceiling temperature decay profiles of dual plumes are developed. The catastrophic tunnel fire accidents are usually accompanied with multi-source burning. Ceiling gas temperature in tunnel is an important parameter in monitoring the daily operation process and unexpected combustion process. Previous studies are mainly focused on single fire or multiple equal fires in tunnel, while multiple unequal fires burning is common in real tunnel fires. Till now, the law of asymmetrical temperature distribution of multi-source below a ceiling is unknown. This paper aims to experimentally study the thermal performance of two unequal fire sources of propane in a naturally ventilated tunnel. A total of 90 experimental tests were conducted. The side lengths of two burners are fixed at 10 cm and 15 cm. The heat release rate (HRR) of each burner are changed with the HRRs ratio of 1–6. And the spacing between two sources along the longitudinal centerline of tunnel varied from 0–45 cm. Analysis shows that there is only one peak temperature with small spacings, while two peak temperatures appear with large spacings. Then the impingement point position and the maximum ceiling gas temperature of each burner are illustrated. The force analysis is adopted to explain the variation of impingement point position. A parameter α is innovatively introduced to characterize the promoting effect of spacing on maximum temperature at small spacings. Then a new normalized HRR is proposed to establish a unified model for the unequal maximum temperature rises below the ceiling of both sources, which indicates that the maximum temperature rise increases with the normalized HRR and then it maintains at 754 K. By introducing the plume radius, models for asymmetrical temperature decay profiles on both sides of two plumes below the ceiling are proposed, which shows that the temperature in the upstream of the small burner decays faster than that in the downstream of the large burner. The proposed models for maximum temperature and temperature decay profiles can be used to predict the ceiling gas temperatures of two unequal fires in tunnel.

Dispersal of a small wave-protected river plume from drifter observations

Using low-cost surface drifters, this study investigates the influence of the Buranhém River plume on the coastal region of the city of Porto Seguro (in the state of Bahia). The results highlight the importance of small river plumes on the coastal region and their possible influence on tourist beaches and high biodiversity regions. Three drifters, mounted with GPS receivers and temperature and salinity sensors, were simultaneously released into the mouth of the river in six experiments between December 2019 and December 2020, during ebbing spring tides. In each experiment, vertical salinity profiles were measured hourly at the position of the central drifter for 5 h, in order to investigate the along-track stratification of the plume. Results show that there are two distinct dispersion patterns in the Buranhém River plume, and that they are controlled mainly by wind and river discharge. Southward (northward) dispersion with curvilinear shape forced by northeasterly (south and southwesterly) winds were observed during the experiments. The maximum vertical salinity gradient confirmed the shallow character of the river plume (< 3 m in depth), more highly stratified during high river discharge and northward dispersion than in the opposite situation of northeasterly winds and low and medium river discharge. The results suggest that the Buranhém River plume has a larger influence over the northern beaches of Porto Seguro, with its reach being defined by the river discharge. Beaches to the south of the river inlet are less influenced by the river plume. Such unprecedented findings form the background for future studies and for management of this highly visited tourist area in Brazil.

Time-dependent plume front positioning and its dynamics coupled with seasonal river efflux

The time-dependent plume front positioning with respect to different tidal phases and its dynamics coupled with seasonal river efflux on the shelf off Kochi, southwest coast of India, was investigated using Finite Volume Community Ocean Model (FVCOM). This region is linked with a monsoonal estuary, characterised by a mixed semidiurnal tide (1 m) and exhibited features of small and large-scale plumes. The interaction between river efflux and tidal phases modulates plume fronts on the shelf, where the density gradients are fortified or weakened by mixing dynamics. Even though the heavy river efflux in the summer monsoon imparts significant momentum on the shelf, the range of frontal fluctuation was curtailed to 2 km by strong monsoon currents. During the transient phase of the season (fall inter-monsoon), the tidal forcings on plume positioning overwhelm the shelf currents, such that the plume front fluctuates between 5 and 17 km from the inlet (range increasing to ~12 km). During low tides, the region near the inlets was almost homogenised (Rd<1), while during high tides, the region became more stratified due to the transport of high saline coastal water towards the inlet and also by the decreasing kinetic energy (Richardson number, Rd>1). The location of frontal zones suitable for the propagation of internal waves (Froude number, F≤ 1) changes as a result of the competition between river efflux and tide-topography interaction. Strong stratified plume frontal regions with high Brunt Vaisala Frequency (N) could be active zones of internal wave generation when the flow decelerates from supercritical to subcritical during the summer monsoon. The release of accumulated potential energy during the transition from high tide to low tide generates the hydraulic jump. This disturbance in the Nmax zone together with F ≤ 1 condition (supercritical flow changed to subcritical flow) favours the generation and propagation of plume-induced internal waves on the shelf. Satellite imageries demonstrate such propagation of plume-generated internal waves on the shelf off Kochi.

Response of a Small River Plume on Wind Forcing

Wind forcing is the main driver of river plume dynamics. Direction and magnitude of wind determine position, shape, and size of a river plume. The response of river plumes on wind forcing was simulated in many numerical modeling studies; however, in situ measurements of this process are still very scarce. In this study, we report the first direct measurements of frontal movement of a small river plume under variable wind forcing conditions. Using quadcopters, we performed nearly continuous daytime aerial observations of the Bzyb river plume located in the non-tidal Black Sea. The aerial remote sensing was accompanied by synchronous in situ measurements of wind forcing. We assessed spreading patterns of the plume and evaluated movement velocity of its outer border with unprecedentedly high spatial (∼10 m) and temporal (∼1 min) resolution, which was not available in previous studies based on in situ measurements and satellite observations. Based on the collected data, we evaluated the time of response of plume spreading dynamics on changes in wind forcing conditions. The advection velocity of the outer plume border shows linear relation to wind speed with very small response time (10–20 min). The reversal between upstream/downstream plume spreading occurs during several hours under moderate wind forcing conditions. These reversals involve only near-field part of the plume, which cause detachment of the far-field part of the plume. The obtained results are crucial for understanding and simulating spreading dynamics of small river plumes worldwide.

Internal Waves as a Source of Concentric Rings within Small River Plumes

This study is focused on concentric rings, which are regularly observed by remote sensing of small river plumes located in different regions worldwide. We report new aerial observations of these features obtained by quadcopters and supported by synchronous in situ measurements, which were collected during the recent field survey at the Bzyb river plume in the eastern part of the Black Sea. Joint analysis of remote sensing imagery and in situ data suggest that the observed concentric rings are surface manifestations of high-frequency internal waves generated in the vicinity of the river mouth. The obtained results demonstrate that the propagation of these waves does not induce offshore material transport within the plume induced by shear instability, which was hypothesized in a recent numerical modeling study of this process. We provide an explanation for the appearance of misleading material features in the numerical simulations discussed above. Finally, we discuss directions for future research of high-frequency internal waves generated in small river plumes.

Detecting the Surface Signature of Riverine and Effluent Plumes along the Bulgarian Black Sea Coast Using Satellite Data

The clear and reliable detection of effluent plumes using satellite data is especially challenging. The surface signature of such events is of a small scale; it shows a complex interaction with the local environment and depends greatly on the effluent and marine water constitution. In the context of remote sensing techniques for detecting treated wastewater discharges, we study the surface signature of small river plumes, as they share specific characteristics, such as higher turbidity levels and increased nutrient concentration, and are fresh compared to the salty marine water. The Bulgarian Black Sea zone proves to be a challenging study area, with its optically complex waters and positive freshwater balance. Additionally, the Bulgarian Black Sea coast is a known tourist destination with an increased seasonal load; thus, the problem of the identification of wastewater discharges is a topical issue. In this study, we analyze the absorption components of the Inherent Optical Properties (IOPs) for 84 study points that are located at outfall discharging areas, river estuaries and at different distances from the shoreline, reaching the open sea area at a bottom depth of more than 2000 m. The calculations of IOPs take into account all available Sentinel 2 cloudless acquisitions for three years from 2017 until 2019 and are performed using the Case-2 Regional CoastColour (C2RCC) processor, implemented in the Sentinel Application Platform (SNAP). The predominant absorber for each study area and its temporal variation is determined, deriving the specific characteristics of the different areas and tracking their seasonal and annual course. Optical data from the Galata AERONET-OC site are used for validating the absorption coefficient of phytoplankton pigment. A conclusion regarding the possibility of distinguishing riverine, marine and coastal water is derived. The study provides a sound basis for estimating the advantages and drawbacks of optical satellite data for tracking the extent of effluent and fluvial plumes with unknown concentrations of optically significant seawater constituents.

소형 터보젯 엔진 후류의 측정 각도 별 적외선 신호 특성

소형 터보젯 엔진 후류의 측정 각도 별 적외선 신호 특성

Dilution impacts on smoke aging: evidence in Biomass Burning Observation Project (BBOP) data

Abstract. Biomass burning emits vapors and aerosols into the atmosphere that can rapidly evolve as smoke plumes travel downwind and dilute, affecting climate- and health-relevant properties of the smoke. To date, theory has been unable to explain observed variability in smoke evolution. Here, we use observational data from the Biomass Burning Observation Project (BBOP) field campaign and show that initial smoke organic aerosol mass concentrations can help predict changes in smoke aerosol aging markers, number concentration, and number mean diameter between 40–262 nm. Because initial field measurements of plumes are generally &gt;10 min downwind, smaller plumes will have already undergone substantial dilution relative to larger plumes and have lower concentrations of smoke species at these observations closest to the fire. The extent to which dilution has occurred prior to the first observation is not a directly measurable quantity. We show that initial observed plume concentrations can serve as a rough indicator of the extent of dilution prior to the first measurement, which impacts photochemistry, aerosol evaporation, and coagulation. Cores of plumes have higher concentrations than edges. By segregating the observed plumes into cores and edges, we find evidence that particle aging, evaporation, and coagulation occurred before the first measurement. We further find that on the plume edges, the organic aerosol is more oxygenated, while a marker for primary biomass burning aerosol emissions has decreased in relative abundance compared to the plume cores. Finally, we attempt to decouple the roles of the initial concentrations and physical age since emission by performing multivariate linear regression of various aerosol properties (composition, size) on these two factors.

The effect of natural and anthropogenic nutrient and sediment loads on coral oxidative stress on runoff-exposed reefs

Recently, corals on the Great Barrier (GBR) have suffered mass bleaching. The link between ocean warming and coral bleaching is understood to be due to temperature-dependence of complex physiological processes in the coral host and algal symbiont. Here we use a coupled catchment-hydrodynamic-biogeochemical model, with detailed zooxanthellae photophysiology including photoadaptation, photoacclimation and reactive oxygen build-up, to investigate whether natural and anthropogenic catchment loads impact on coral bleaching on the GBR. For the wet season of 2017, simulations show the cross-shelf water quality gradient, driven by both natural and anthropogenic loads, generated a contrasting zooxanthellae physiological state on inshore versus mid-shelf reefs. The relatively small catchment flows and loads delivered during 2017, however, generated small river plumes with limited impact on water quality. Simulations show the removal of the anthropogenic fraction of the catchment loads delivered in 2017 would have had a negligible impact on bleaching rates.

Interpreting Patterns of Concentric Rings within Small Buoyant River Plumes

High-resolution imagery of small buoyant plumes often reveals an extensive pattern of concentric rings spreading outward from near the discharge point. Recent remote sensing studies of plumes from rivers flowing into the Black Sea propose that such rings are internal waves, which form near a river mouth through an abrupt deceleration of the current, or hydraulic jump. The present study, using numerical simulations, presents an alternative viewpoint in which no hydraulic jump occurs and the rings are not internal waves, but derive instead through shear instability. These two differing dynamical views point to a clear need for additional field studies that combine in-water measurements and time-sequential remote sensing imagery.

Volatile Sample Return in the Solar System

We advocate for the realization of volatile sample return from various destinations including: small bodies, the Moon, Mars, ocean worlds/satellites, and plumes. As part of recent mission studies (e.g., Comet Astrobiology Exploration SAmple Return (CAESAR) and Mars Sample Return), new concepts, technologies, and protocols have been considered for specific environments and cost. Here we provide a plan for volatile sample collection and identify the associated challenges with the environment, transit/storage, Earth re-entry, and curation. Laboratory and theoretical simulations are proposed to verify sample integrity during each mission phase. Sample collection mechanisms are evaluated for a given environment with consideration for alteration. Transport and curation are essential for sample return to maximize the science investment and ensure pristine samples for analysis upon return and after years of preservation. All aspects of a volatile sample return mission are driven by the science motivation: isotope fractionation, noble gases, organics and prebiotic species; plus planetary protection considerations for collection and for the sample. The science value of sample return missions has been clearly demonstrated by previous sample return programs and missions. Sample return of volatile material is key to understanding (exo)planet formation, evolution, and habitability. Returning planetary volatiles poses unique and potentially severe technical challenges. These include preventing changes to samples between (and including) collection and analyses, and meeting planetary protection requirements.

The use of noble gas isotopes to trace subsurface boiling temperatures in Icelandic geothermal systems

Geothermal systems are complex environments where geochemical signatures are controlled by the influx of deep mantle fluids as well as near-surface processes that result from the high temperatures. Noble gas isotope ratios (e.g. 3He/4He, 20Ne/22Ne) are well-established tracers of deep mantle fluid provenance, and elemental fractionation of atmosphere-derived isotopes is widely used for tracing shallow processes such as solubility-dependent phase partitioning in groundwater and hydrocarbon fluids. Utilisation of these tracers for the latter purpose has been limited in geothermal systems, where they could be further extended to consider boiling and/or steam condensation. Here we report new noble gas isotope and abundance data for 21 vapour phase geothermal fluid samples collected from geothermal boreholes and naturally degassing fumaroles in Iceland. The samples were collected from active parts of the neovolcanic rift zone and include several key high-temperature geothermal localities of the Northern Rift Zone (NRZ), the Western Rift Zone (WRZ) and the Mid-Iceland Belt (MIB). Helium isotope ratios are MORB-like in the NRZ, whilst samples from the WRZ show values in excess of MORB, up to 15.9 Ra. Neon isotopes plot close to the air value, but may show a small plume mantle contribution. Argon isotopes show distinct mantle-derived 40Ar excesses (40Ar/36Ar up to 361.2), which to our knowledge are the largest measured anomalies in free geothermal fluids from Iceland. The atmosphere-derived noble gas signatures (20Ne, 36Ar, 84Kr) are consistent with high-temperature vapour-liquid phase partitioning. Atmosphere-derived xenon (130Xe) on the other hand is not consistent with the observations from the other atmosphere-derived noble gases, suggesting an additional complexity that likely relates to its unique sorption and bonding behaviour. We show that the abundance of 20Ne, 36Ar, 84Kr in the vapour phase is temperature-dependent, presenting a promising technique that can be used to estimate the temperature at which partitioning occurs in the subsurface. Using multiple noble gas species allows the effects of secondary atmospheric contamination to be corrected when using this method. We predict partitioning temperatures of 229 to 345°C for the samples measured here, consistent with temperatures predicted using conventional geothermometers. The inert nature of the noble gases means that the technique presented here is not reliant on many of the assumptions that underpin conventional geothermometers. We suggest that this technique represents a novel and powerful geochemical tool to investigate the thermal properties of geothermal systems.

Hydrophysical Structure and Current Dynamics of the Kodor River Plume

This work is focused on the river plume generated by the Kodor River which is the largest river of Abkhazia and the northeastern coast of the Black Sea. Based on in situ hydrological data, quadcopter aerial images and satellite observations, hydrophysical structure and circulation in the Kodor plume was studied at different river discharge conditions. Discharge of the Kodor River, which inflows to sea from several deltaic branches forms a relatively shallow plume with large area, as compared to the Mzymta River, the largest estuarine river of the study region, at similar hydrological, meteorological, and oceanographic conditions. Due to its small vertical size and large salinity gradient at the border with the subjacent saline sea, the Kodor plume is characterized by quick response on wind forcing variability. The Kodor plume also has large spatial inhomogeneity, caused by its formation conditions (several closely located freshwater sources prone to abrupt discharge variability), as well as regional bathymetry (interaction between the plume and shoals). During low discharge period, the inflowing Kodor River has relatively low kinetic energy, which causes abrupt deceleration of the jet in the sea area adjacent to the river mouth. As a result, the inertia of the inflowing jet abruptly decreases and large velocity and salinity gradients are formed in vicinity of river estuary, which hinder formation of anticyclonic circulation at the near-field part of the plume. This feature induces transport of freshwater discharge off the river mouth and its accumulation in the far-field part of the small plume under moderate wind forcing conditions that is not typical for large river plumes. The obtained results are important for understanding general aspects of dynamics of buoyant plumes formed by rivers with small discharge rates.

Spatial Structure, Short-temporal Variability, and Dynamical Features of Small River Plumes as Observed by Aerial Drones: Case Study of the Kodor and Bzyp River Plumes

Quadcopters can continuously observe ocean surface with high spatial resolution from relatively low altitude, albeit with certain limitations of their usage. Remote sensing from quadcopters provides unprecedented ability to study small river plumes formed in the coastal sea. The main goal of the current work is to describe structure and temporal variability of small river plumes on small spatial and temporal scales, which are limitedly covered by previous studies. We analyze optical imagery and video records acquired by quadcopters and accompanied by synchronous in situ measurements and satellite observations within the Kodor and Bzyp plumes, which are located in the northeastern part of the Black Sea. We describe extremely rapid response of these river plume to energetic rotating coastal eddies. We reveal several types of internal waves within these river plumes, measure their spatial and dynamical characteristics, and identify mechanisms of their generation. We suggest a new mechanism of formation of undulate fronts between small river plumes and ambient sea, which induces energetic lateral mixing across these fronts. The results reported in this study are addressed for the first time as previous related works were mainly limited by low spatial and/or temporal resolution of in situ measurements and satellite imagery.

First Measurements of Gas Flux with a Low-Cost Smartphone Sensor-Based UV Camera on the Volcanoes of Northern Chile

UV cameras have been used for over a decade in order to remotely sense SO2 emission rates from active volcanoes, and to thereby enhance our understanding of processes related to active and passive degassing. Whilst SO2 column density retrievals can be more accurate/sophisticated using alternative techniques (e.g., Differential Optical Absorption Spectrometer (DOAS), Correlation Spectrometer (COSPEC)), due to their higher spectral resolutions, UV cameras provide the advantage of high time-resolution emission rates, a much greater spatial resolution, and the ability to simultaneously retrieve plume speeds. Nevertheless, the relatively high costs have limited their uptake to a limited number of research groups and volcanic observatories across the planet. One recent intervention in this regard has been the introduction of the PiCam UV camera, which has considerably lowered instrumental cost. Here we present the first data obtained with the PiCam system from seven persistently degassing volcanoes in northern Chile, demonstrating robust field operation in challenging conditions and over an extended period of time, hence adding credence to the potential of these units for more widespread dissemination to the international volcanic gas measurement community. Small and weak plumes, as well as strongly degassing plumes were measured at distances ranging 0.6–10.8 km from the sources, resulting in a wide range of SO2 emission rates, varying from 3.8 ± 1.8 to 361 ± 31.6 td−1. Our acquired data are discussed with reference to previously reported emission rates from other ground-based remotely sensed techniques at the same volcanoes, in particular considering: resolution of single plume emissions in multi-plume volcanoes, light dilution, plume geometry, seasonal effects, and the applied plume speed measurement methodology. The main internal/external factors that influence positive/negative PiCam measurements include camera shake, light dilution, and the performance of the OpenCV and control points post processing methods. A simple reprocessing method is presented in order to correct the camera shake. Finally, volcanoes were separated into two distinct groups: low and moderate SO2 emission rates systems. These groups correlate positively with their volcanological characteristics, especially with the fluid compositions from fumaroles.

Modeling the Dynamics of Small‐Scale River and Creek Plumes in Tidal Waters

AbstractThe fate of discharges from small rivers and mountainous streams are little studied relative to the dynamics of large river plumes. Flows from small watersheds are episodic, forming transient low‐salinity surface plumes that vary tidally due to interaction of outflow inertia with buoyancy and ambient tidal currents. An implementation of the Regional Ocean Modeling System (ROMS v3.0), a three‐dimensional, free‐surface, terrain‐following numerical model, is applied to small river outflows (≤10 m3 s−1) entering a tidal ocean, where they form small plumes of scale ~103 m or smaller. Analysis of the momentum balance points to three distinct zones: (i) an inertia‐driven near field, where advection, pressure gradient, and vertical stress divergence control the plume dynamics, (ii) a buoyancy‐driven midfield, where pressure gradient, lateral stress divergence, and rotational accelerations are dominant, and (iii) an advective far field, where local accelerations induced by ambient tidal currents determine the fate of the river/estuarine discharge. The response of these small tidal plumes to different buoyancy forcing and outflow rate is explored. With increasing buoyancy, plumes change from narrow/elongated, bottom‐attached flows to radially expanding, surface‐layer flows. Weak outflow promotes stratification within the plume layer, and with stronger outflow, the plume layer becomes thinner and well‐mixed. When compared with prototypical large‐river plumes in which Coriolis effects are important, (i) in these small plumes, there is no bulge and no coastal buoyancy current, that is, shore contact is mostly absent, and (ii) the plume is strongly influenced by ambient tidal currents, forming a tidal plume that is deflected upcoast/downcoast from the river mouth.

Temporal-Spatial Evolution of Kinetic and Thermal Energy Dissipation Rates in a Three-Dimensional Turbulent Rayleigh-Taylor Mixing Zone.

In this work, the temporal–spatial evolution of kinetic and thermal energy dissipation rates in three-dimensional (3D) turbulent Rayleigh–Taylor (RT) mixing are investigated numerically by the lattice Boltzmann method. The temperature fields, kinetic and thermal energy dissipation rates with temporal–spatial evolution, the probability density functions, the fractal dimension of mixing interface, spatial scaling law of structure function for the kinetic and the thermal energy dissipation rates in 3D space are analysed in detail to provide an improved physical understanding of the temporal–spatial dissipation-rate characteristic in the 3D turbulent Rayleigh–Taylor mixing zone. Our numerical results indicate that the kinetic and thermal energy dissipation rates are concentrated in areas with large gradients of velocity and temperature with temporal evolution, respectively, which is consistent with the theoretical assumption. However, small scale thermal plumes initially at the section of half vertical height increasingly develop large scale plumes with time evolution. The probability density function tail of thermal energy dissipation gradually rises and approaches the stretched exponent function with temporal evolution. The slope of fractal dimension increases at an early time, however, the fractal dimension for the fluid interfaces is 2.4 at times t/τ ≥ 2, which demonstrates the self-similarity of the turbulent RT mixing zone in 3D space. It is further demonstrated that the second, fourth and sixth-order structure functions for velocity and temperature structure functions have a linear scaling within the inertial range.

Long-term (1999–2019) variability of stratospheric aerosol over Mauna Loa, Hawaii, as seen by two co-located lidars and satellite measurements

Abstract. As part of the Network for the Detection of Atmospheric Composition Change (NDACC), ground-based measurements obtained from the Jet Propulsion Laboratory (JPL) stratospheric ozone lidar and the NOAA stratospheric aerosol lidar at Mauna Loa, Hawaii, over the past 2 decades were used to investigate the impact of volcanic eruptions and pyrocumulonimbus (PyroCb) smoke plumes on the stratospheric aerosol load above Hawaii since 1999. Measurements at 355 and 532 nm conducted by these two lidars revealed a color ratio of 0.5 for background aerosols and small volcanic plumes and 0.8 for a PyroCb plume recorded on September 2017. Measurements of the Nabro plume by the JPL lidar in 2011–2012 showed a lidar ratio of (64±12.7) sr at 355 nm around the center of the plume. The new Global Space-based Stratospheric Aerosol Climatology (GloSSAC), Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) Level 3 and Stratospheric Aerosol and Gas Experiment III on the International Space Station (SAGE III-ISS) stratospheric aerosol datasets were compared to the ground-based lidar datasets. The intercomparison revealed a generally good agreement, with vertical profiles of extinction coefficient within 50 % discrepancy between 17 and 23 km above sea level (a.s.l.) and 25 % above 23 km a.s.l. The stratospheric aerosol depth derived from all of these datasets shows good agreement, with the largest discrepancy (20 %) being observed between the new CALIOP Level 3 and the other datasets. All datasets consistently reveal a relatively quiescent period between 1999 and 2006, followed by an active period of multiple eruptions (e.g., Nabro) until early 2012. Another quiescent period, with slightly higher aerosol background, lasted until mid-2017, when a combination of extensive wildfires and multiple volcanic eruptions caused a significant increase in stratospheric aerosol loading. This loading maximized at the very end of the time period considered (fall 2019) as a result of the Raikoke eruption, the plume of which ascended to 26 km altitude in less than 3 months.

4D surface seismic monitoring the evolution of a small CO2 plume during and after injection: CO2CRC Otway Project study

Time lapse seismic is a vital component of the monitoring and verification of virtually any geosequestration project. Stage 2C of the CO2CRC Otway project is designed to test the limits of land 3D time-lapse (4D) seismic in the monitoring of small-scale CO2 injection. The 4D seismic monitoring program of Stage 2C of the Otway Project includes a baseline survey (BL); three monitor surveys (M1–M3) obtained during the injection of CO2-rich gas into the saline aquifer at a depth of 1.5 km at the injection intervals of 5, 10, and 15 kt; and two post-injection surveys (M4 and M5), acquired one and two years after the end of injection. Reliable time-lapse changes among the 4D surveys were obtained using a buried receiver array. Analysis of the seismic cubes and attributes demonstrates that during and after injection the plume spreads laterally only in southeastern direction. The results demonstrate strong time-lapse signal corresponding to the injection level and the absence of any observed leakage into the overburden. The plume evolution is reliably observed and traced from M1 to M5 surveys with most of the changes occurring between the BL and M4 surveys.

Plume Dynamics of a Lateral River Tributary Influenced by River Discharge From the Estuary Head

AbstractRiver plumes are important pathways for the transportation of terrigenous materials to coastal oceans. This study uses the Regional Ocean Modeling System to investigate the dynamics of a small river plume from a lateral river tributary discharging into an estuary. In particular, the plume is surface advected under buoyancy force alone, and the Earth's rotation helps to increase the plume's spread in a downstream‐biased pattern. Adding tides to the model changes the plume into a bottom‐advected one, and the plume is advected in an alongshore direction, with its spreading more upstream biased. Tide‐induced mixing and tidal advection are responsible for the changes in the plume structure, especially the tidal asymmetry between ebb and flood tides; the tidal residual circulation is insignificant. When river discharge from the estuary head is imposed, the plume is forced to propagate downstream extensively. This study offers insights into the transport and fate of riverine materials in tributaries that flow into semienclosed waterbodies.