Transport Of Mass Research Articles

Migration of Accreting Planets and Black Holes in Disks

Nascent planets are thought to lose angular momentum (AM) to the gaseous protoplanetary disk via gravitational interactions, leading to inward migration. A similar migration process also applies to stellar-mass black holes (BHs) embedded in the disks of active galactic nuclei. However, AM exchange via accretion onto the planet/BH may strongly influence the migration torque. In this study, we perform 2D global hydrodynamic simulations of an accreting planet/BH embedded in a disk, where AM exchange between the planet/BH and disk via gravity, accretion, pressure, and viscosity are considered. When accretion is turned off, we recover the linear estimate for Type I migration torque. However, for the two planet masses we investigated with our accreting simulations, we find outward migration due to the positive AM deposited onto the accreting body by the disk gas. Our simulations achieve the global steady state for the transport of mass and AM: The mass and AM fluxes are constant across the disk except for jumps ( ΔṀ and ΔJ̇ ) at the planet’s location, and the jumps match the accretion rate and torque on the planet. Our findings suggest that caution is needed when applying the standard results of disk migration to accreting planets and BHs.

Filling in Munk’s ‘orbital gap’ in climate and sea-level variability

Abstract This study explores the linkage between lunar precessions, solar activity, plus their interactions, and the interannual variability of climate indices and Australian sea level. The focus is on variability longer than the lunar nodal cycle (18.6 years), but shorter than millennia, also known as orbital gap. Climate indices include the Pacific Decadal Oscillation, El Niño-Southern Oscillation, the Southern Oscillation Index, the Indian Ocean Dipole, and the Southern Annular Mode. Long-term (> 100 years) sea-level data were examined at Fremantle (Western Australia) and Fort Denison (Sydney, Eastern Australia). Periodicities associated with gravitational and radiational forces were fitted to 3-yr- and 5-yr-filtered records of each climate index and of sea-level records. All fits, 10 for climate indices and 12 for sea level, explained the variance of all filtered records remarkably well (>60%). Findings suggest that lunar precessions and their interactions with solar activity may be connected to interannual variations in oceanic mixing. Mixing leads to climate variability through transport of heat, mass and solutes in the atmosphere and ocean, and ultimately relates to interannual sea-level variability. This study represents the possibility of astronomic effects on Earth’s environmental variables, beyond the internal variability of the ocean-atmosphere system.

Numerical study of multi-phase flow in ultrashort pulse laser processing

Ultrashort pulse laser processing is highly valued due to its enormous potential for high micromachining quality while it comprises complicated physical mechanisms especially when the pulse width falls in the regime about 10 ps. This study presents a complete mathematical modeling on multi-phase phenomena in ultrashort pulse laser processing, such as melting, vaporization, and solidification. The volume of fluid (VOF) technique is used to capture the interface during phase transition. Based on this hybrid model, the transport of energy and mass are investigated to study the influence of laser parameters on the formation of laser ablation hole. This work develops the incompressible multiphase laser ablation solver based on PIMPLE algorithm. The calculation results are validated by different references under different laser processing parameters which emphasize the importance of mechanism on thermal ablation and hydrodynamics in picosecond laser processing. More calculation results about the trends in hole depth over pulse laser width, laser fluence, and the number of pulses show the intricate influence of laser parameters.

Modeling with generalized flux theory for computational investigation of thermal enhancement in fluid with tri‐, di‐, and mono‐nanoparticles

AbstractTo study the influence of several factors (tri‐nanoparticles and relaxation time related to momentum, thermal, and concentration) on non‐Fourier transport of heat and mass, mathematical models are developed. The cases of tri‐, di‐, and mono‐nanofluids are considered. Flow and transport scenarios are translated into mathematical equations for which conservation laws and correlations for thermophysical properties are used. Boundary layer simplifications are used to approximate these mathematical models. The nondimensional set of problems is numerically solved using the finite element method (FEM). The solutions that are convergent and mesh‐free are obtained. The outcomes are compared to existing benchmarks. There is excellent consistency between the current and published results. The viscoelastic behaviors related to momentum, thermal, and solutal relaxation times are examined. It is also investigated how tri‐nanoparticles improve heat transmission in flow. The wall shear stresses for the mono‐, di‐, and tri‐nanofluids are calculated against momentum relaxation time. It is observed that tri‐nanofluid exerts the highest stress on the surfaces over which it flows. Therefore, while using these fluids, the surface should be ensured to bear the stresses; otherwise, failure of the system may take place. Thus, industrial applications and additional capability of surface be ensured. This looks at influence the Deborah number on the fluid motion. Deborah number is straightforwardly connected with relaxation time and it is found that higher is Deborah number lower will be the speed of fluid. As a consequence, viscous region will be narrow down. Thus, viscous dominant region is controllable by the using fluid of higher relaxation time. A significant enhancement in the thermal performance of Maxwell fluid occurs via the dispersion of tri‐nanoparticles ().

A computational study of Eyring‐Powell fluid model over a rotating cone with magnetic field and joule heating effect

AbstractIn this research, we investigate mixed convection transport of mass and heat transfer in the unsteady boundary layer flow of the Eyring‐Powell fluid around a rotating cone in the presence of Brownian and thermophoresis effects. Rotating cones are widely used in conical diffusers, medical devices, Aerospace Engineering and a variety of rheometric and viscosimetry applications. Specifically, we focus on the flow of the Eyring‐Powell fluid around the cone in the presence of magnetohydrodynamics and nanofluid. The modeled momentum, energy, and concentration equations of the problem are transformed into nonlinear dimensionless, nonlinear ordinary equations by utilizing the similarity variables. These nonlinear coupled ordinary differential equations are solved numerically via Bvp4c, and the outcomes for important physical parameters on momentum, energy, and concentration equations are presented graphically. The computational outcomes of physical parameters for skin friction coefficient, local Nusselt number, and Sherwood are also presented in tabular form.

Direct Entrainment as a Measure of Dilution

Abstract The turbulent transport of mass, energy, moisture, and momentum between the clouds and the surrounding environment plays a central role in determining the vertical structure of the troposphere. This article investigates the connection between net entrainment, defined here as the net transport of air into individual clouds, and net dilution, defined as the tendencies of passive tracers such as static energy or total water mixing ratio. Entrainment and detrainment rates for 2.6 × 106 individual cloud samples are obtained from a large-eddy simulation of shallow convective boundary layer atmosphere that explicitly calculates the turbulent fluxes across the cloud boundaries. The equations describing the tendencies of cloud mass and tracer concentrations are derived as a function of directly calculated entrainment and detrainment rates of the individual clouds, and used to calculate net entrainment and dilution rates. Directly calculated net entrainment and dilution rates agree well with cloud mass and tracer tendencies and give a dilution time scale of 13 min. In contrast, the traditional bulk-plume approximation overestimates the effect of entrainment and detrainment on the dilution of cloud field properties due to the differential tracer transport through the moist shell surrounding the cloud. Using direct measures of entrainment and detrainment for individual clouds separates different processes that influence the turbulent mass transport between the clouds and their environment.

Examples of entropy: from physics to nature

Abstract This paper aims to give a short history of how the concept of entropy has been developed and how it is used today in diverse scientific disciplines in our quest for understanding ourselves and our environment. The first part of the paper gives a historical perspective, which starts with the invention of the first heat engines, continues with the verbal formulation of the laws of thermodynamics and ends with the formulation of the mathematical equations that tell the complete story of thermodynamics by describing the transport of mass, momentum, energy and entropy. The second part of the paper focusses on the use of entropy beyond heat engines and shows how entropy has influenced the thinking in scientific disciplines such as chemistry, biology, ecology, communication, economy and sociology. Both a historical summary and the examples presented in this paper are limited to within the domain of classical mechanics. Although entropy has ignited powerful ideas and has many uses in both relativistic and quantum mechanics, these are not within the scope of this paper.

Low-temperature reactivity, extinction, and heat release rate of non-premixed cool flame at elevated pressures

Understanding the fundamental characteristics of high-pressure cool flames is crucial for the development of advanced and efficient low-temperature combustion engine technologies. The pressure dependency of multi-oxygen addition branching reactions in low-temperature chemistry significantly influences the dynamics, structure, and reactivity of cool flame. This study investigates the non-premixed cool flame of diethyl ether (DEE) at elevated pressures. The results show that pressure rise promotes low-temperature chemistry and significantly extends the extinction limit of cool flame. It is found that the cool flame heat release rate is correlated with the product of pressure and the square root of the pressure-weighted strain rate, Q∼aP·P, which is different from that of hot flames, Q∼aP. The radical index concept for atmospheric cool flames is extended to high-pressure cool flames allowing to decouple the mass and thermal transports from the chemical kinetics term to evaluate the fuel reactivity at elevated pressures. The radical index shows that the low-temperature reactivity of DEE is enhanced with the pressure and is higher than n-dodecane by a factor of 19, 18.3, and 16.4 for 1, 3, and 5 atm, respectively. Kinetic analysis reveals that pressure rise results in QOOH stabilization and promotions of the second O2 addition and the chain-branching reaction pathway for multiple OH radical productions.

Modelling the ejection of primary aerosols during the fast pyrolysis of biomass anisotropic particles

A model for the fast pyrolysis of anisotropic biomass particles is presented which considers bubbling dynamics within the liquid intermediate phase (metaplast) and aerosol ejection from this phase. The model employs the population balance equation and the method of moments to estimate the production rate and resultant size distribution of aerosol ejections, incorporating a detailed CRECK reaction mechanism, and considers the effect of anisotropic biomass microstructure on the intraparticle transport of mass and energy. This study investigates the impact of particle size, heating rate (heat transfer coefficient), and lignocellulosic composition on aerosol ejection. The model predicts that, at high heating rates (convective heat transfer coefficient of 359 W/m2.K), aerosols can contribute over 20% to the heavy fraction yield in bio-oil for small particles (1 mm diameter, 4 mm length). The model can predict aerosol size distribution and surface area, indicating an average size of 20 μm for bubbles and 5 μm for aerosols during increased bubble production and aerosol ejection rates. These findings are consistent with prior experimental results and provide essential information for future modeling of extra-particle reactions of the aerosols as they progress through the reactor.

Magnetically Arrested Circumbinary Accretion Flows

Binary systems with comparable masses and a surrounding accretion disk can accrete gas through spiral accretion streams penetrating the central cavity formed by tidal interactions. Using three-dimensional Newtonian magnetohydrodynamics simulations, we investigate the possibility of a magnetically arrested accretion flow through the cavity. Rather than solely continuously feeding the binary through spiral accretion streams, the accretion is regulated by the strong magnetic field inside the cavity. Transport of mass and angular momentum onto the binary then proceeds largely periodically in magnetic flux eruption episodes. The ejected flux tubes carry angular momentum outward and away from the binary, inject hot plasma into the disk, and can launch flares. This likely intermittent scenario could have potential implications for the emission signatures of supermassive black hole binaries and shed light onto the role magnetic fields play in the binary’s orbital evolution.

Thermal Imprints of Mesoscale Eddies in the Global Ocean

Abstract Mesoscale eddies have been widely documented for their significant role in regulating oceanic heat absorption and redistribution. However, our understanding of their thermal impacts on a global scale has been hampered by the scarcity of eddy-targeted observations. Here, we perform a comprehensive global analysis of over 2 million historical hydrographic profile measurements collocated with satellite-based eddy observations between 1993 and 2019, revealing rich geographical variability in the intensity, vertical extent, and asymmetry of the temperature anomalies induced by eddies. In tropical and subtropical oceans, temperature anomalies within eddies are dominated by eddy pumping and heavily influenced by near-surface vertical stratification, resulting in a relatively shallow extent of eddy effects (around 500 m) with subsurface maximum temperature anomalies occurring near 100 m. In midlatitude main current systems with sharp horizontal temperature gradients, the impact of eddy trapping becomes evident, leading to temperature anomalies extending to depths of 1000 m, with vertical peak values exceeding 4°C between 300 and 700 m, equivalent to perturbations in the local mean-state temperature of nearly 30%. This process also results in substantial temperature anomalies on isopycnal surfaces, indicating notable cross-frontal transport of heat and water mass with varying properties. The estimated meridional heat transport by eddy movement is on the order of O(1) MW, generally one order of magnitude smaller than previous estimates of the time-varying meridional heat transport (). However, this does not imply that they are unimportant, as this long-range cross-frontal heat transport may have significant consequences on regional temperature extremes and biogeochemical environments. Significance Statement Mesoscale eddies with a horizontal scale of O(100) km play a crucial role in modulating oceanic heat absorption and redistribution. However, their activities vary significantly across the global ocean, and our understanding of their thermal impacts remains incomplete. In this study, we conduct a global analysis of the influence of eddies on ocean temperature using over 2 million historical in situ temperature and salinity profile measurements combined with satellite-based eddy observations. Our analysis reveals substantial regional variability in the intensity, vertical extent, and asymmetry of temperature anomalies within eddies of different polarities and discusses the underlying mechanisms. Additionally, we estimate the meridional heat transport caused by eddy movement within each 2° × 2° grid, providing insights into the efficient pathways for eddy heat transport in western boundary currents and their extensions. These results enhance our understanding of the global-scale thermal impact of eddies and provide valuable references for assessing their biogeochemical and ecological consequences.

Local and Remote Atmosphere‐Ocean Coupling During Extreme Warming Events Impacting Subsurface Ocean Temperature in an Antarctic Embayment

AbstractCoastal ocean temperatures can respond to different atmospheric and oceanic processes at local spatial scales or through remote teleconnections. This study focused on subsurface ocean temperatures (subT) at 10 m depth in Maxwell Bay, northern Antarctic Peninsula from February 2017 and January 2022. It investigated extreme warming events during austral summers and their interaction with atmospheric and oceanic conditions regionally and locally. The analysis identified active and extreme Marine Heat Waves (MHWs) in March 2017 and January‐February 2020 associated with a significantly negative Southern Annular Mode index observed 3–4 months before the temperature increase. In March 2017, temperatures exceeded the climatological mean by over 1°C. This anomaly was linked to a strengthened Amundsen Sea Low and a blocking anticyclone moving between the Scotia Sea and the South‐West Atlantic Ocean that deflected westerly winds and facilitated the anomalous transport of warmer northern air masses to the AP. In January‐February 2020, the highest recorded subT was observed (2.97°C), although air‐sea heat fluxes did not show a similar pattern. In February 2020, one of the most intense atmospheric heatwaves ever recorded in West Antarctica was observed. This heatwave corresponded with maximum subT and positive sea surface temperature anomalies extending throughout the western region of the Southern Ocean, related to an extremely negative Southern Annular Mode. This study provides valuable insights into the impact of strong MHWs, a phenomenon that has been less documented in Antarctic coastal regions.

Fungal aerosols over the Northwest Pacific to Arctic Ocean: The influence of air mass and environmental factors

Bioaerosols, prevalent in the atmosphere, serve as carriers for microbe transmission and can also act as Cloud Condensation Nuclei (CCN) and Ice Nuclei (IN), exerting significant influence on cloud microphysics, radiative forcing, precipitation processes, and global climate dynamics. In this study, we conducted a comprehensive study of airborne fungi from the Northwest Pacific to the Arctic Ocean. During the 9th Chinese National Arctic Research Expedition (Chinare, 2018) cruise, total suspended particulate matter (TSP) samples were collected, followed by high-throughput sequencing to determine the microbial community's structure. Ascomycota and Basidiomycota are widespread in marine fungal aerosols along this route, with a notably higher abundance of Epicoccum and Cladosporium in fungal aerosols from the low-latitude Northwest Pacific compared to the high-latitude Arctic Ocean region. The composition of fungal communities depended on air mass transport processes and environmental factors. Long-range transport of terrestrial air masses not only enriches the abundance of fungal aerosols but also increases the relative abundance of dominant genera such as Basidiomycota, Epicoccum and Cladosporium. The knowledge gap about fungal aerosols over the Arctic route from the Northwest Pacific to the Arctic Ocean was filled in part by this work. This study deepens our understanding of how environmental factors and terrestrial air masses influence the composition and distribution of fungal community, offering valuable insights into the interconnections between marine and terrestrial ecosystems and their potential impacts on climate and atmospheric processes.

Statistical Distributions of Plasma Density and Pressure in the Jovian Plasma Sheet

The Jovian plasma sheet is a key region of the Jovian magnetosphere populated by a mix of warm and hot plasma. It is the main channel for radial transport of mass and energy in the Jovian magnetosphere and provides a favorable environment for magnetic reconnection and wave–particle interactions although the understanding of its plasma properties is incomplete. This study combines observations from the Jovian Auroral Distributions Experiment and Juno Energetic Particle Detector Instrument on board the Juno spacecraft during its first 31 orbits to analyze the plasma properties of the Jovian plasma sheet from 20 R J to 100 R J. Our results indicate that the plasma number density decreases from 1 cm−3 at 20 R J to 0.005 cm−3 at 100 R J, while the plasma pressure decreases from 2 nPa at 20 R J to 0.02 nPa at 100 R J. The plasma pressure inside the plasma sheet is comparable to the magnetic pressure in the lobe region, suggesting a rough balance between the two. In the plasma sheet with r > 70 R J, the H+ density and pressure remain relatively constant, likely due to other plasma sources such as the solar wind. Additionally, we find that the pressure (density) ratios for heavy ions between the center and the edge of the plasma sheet are generally an order of magnitude, while that for H+ decreases with radial distance. These findings contribute to a more comprehensive understanding of the plasma properties of the Jovian plasma sheet.

Non-Fourier heat and mass transport enhancement by hybrid nanofluid-flow over a non-linearly stretchable surface having variable thickness

This article uses non-classical Fick's law, non-Fourier's law, and conservation laws for mass and thermal transport. The hybrid nanoparticles Cu and Al2O3 are considered. The new correlations among the thermo-physical properties of base fluid, Cu and Al2O3 are coupled with simplified nonlinear mathematical models. The resulting models are solved numerically by the finite element method (FEM). The linear shape functions are chosen for the approximation of residual equations. This approximation leads to a nonlinear algebraic system that is linearized by the Picard scheme. The numerical results are ensured to be grid-independent, and convergence is analyzed. The results are validated, and an excellent agreement is obtained between available benchmarks and current outcomes. Thermal solutal relaxation phenomena are responsible for a significant reduction in the transport of heat and mass in Newtonian fluids. These non-Fourier's and non-classical Fick's laws are capable of capturing thermal and solutal elastic phenomena, respectively. Cu and Al2O3 simultaneously act as good conductors of heat, and their simultaneous dispersion in base fluid results in a significant rise in thermal conductivity. Numerical experiments have shown that the transport of heat can be optimized by simultaneous suspension of Cu and Al2O3.

Evolution Characteristics of PM2.5 and O3 and Their Synergistic Effects on Atmospheric Compound Pollution in Tangshan

The concentrations of atmospheric pollutants PM2.5, O3, SO2, NO2, and CO together with the meteorological factors of temperature （T）, relative humidity （RH）, wind speed, and other relevant data in Tangshan from 2015 to 2021 were collected to study the variation characteristics of PM2.5 and O3 at different periods in Tangshan City in the past seven years and their influencing factors, to discuss the contributions of air mass transport to PM2.5 and O3 pollution, and to reveal the synergistic influence mechanism of PM2.5 and O3 on atmospheric compound pollution by using correlation analysis and backward trajectory cluster analysis techniques. The results showed that PM2.5 concentrations in Tangshan decreased year by year from 2015 to 2021, whereas O3 concentration showed a unimodal trend, with the peak appearing in 2017. Both PM2.5 and O3 concentrations showed obvious seasonal variation trends； PM2.5 was characterized by the highest concentration in winter and the lowest concentration in summer, whereas O3 was characterized by the highest concentration in summer and the lowest concentration in winter. In addition, the diurnal variation in PM2.5 showed a bimodal distribution, with the peak occurring during the morning and evening on weekdays, and O3 showed a unimodal distribution, with the peak value appearing during the period with strong ultraviolet radiation in the afternoon. PM2.5 had a significant positive correlation with SO2, NO2, and CO, whereas O3 had a significant positive correlation with radiation and temperature. Under the different pollution conditions, PM2.5 and O3 were affected by air mass transports from different directions. Being impacted by various factors, the synergistic effect of PM2.5 and O3 on atmospheric compound pollution showed an obvious negative effect in winter, whereas there was an obvious positive effect in spring, summer, and autumn. Under the backgrounds of different pollutions, when the concentration of PM2.5 exceeded 150 μg·m-3, the synergistic effect of PM2.5 and O3 showed an obvious negative effect.

The impact of evolving synoptic weather patterns on multi-scale transport and sources of persistent high-concentration ozone pollution event in the Yangtze River Delta, China

High-concentration ozone pollution pose threats to ecosystems and human health. However, there is limited research on the impact of the alternating evolution of synoptic weather patterns (SWPs) on the multi-scale transport processes and sources of ozone. From June 14 to 18, 2018, a rare consecutive ozone pollution plagued in Hefei and broader Yangtze River Delta region (YRD). This study investigates the meteorological factors and sources using in-situ observational data and WRF-Chem model simulations. Analysis reveals a northeastern low-pressure system moving from north to south generated a cold front. This moving cold front facilitated the vertical transport of warm air masses carrying high-concentration ozone originating from North China. Subsequently, Ozone-rich air masses (ORMs) were transported over the YRD, influenced by the eastward movement of the Mongolian high-pressure system. Based on WRF-Chem model with NOx tagging mechanisms and WRF-FLEXPART backward simulations, it is confirmed that a notable atmospheric transport originated from North China region (NCR) to Hefei, especially on June 15. As the Mongolian high-pressure weakens and shifts east-southward, it carried ORMs generated by NOx emissions from the YRD, accumulating over the sea within the range of 120°E to 126°E and 25°N to 30°N. Both WRF-chem model results and TRopospheric Ozone and Precursors from Earth System Sounding (TROPESS) Chemistry Reanalysis dataset Version 2 (TCR-2) revealed the existence of ORMs in this geographic range. Subsequently, the ORMs carried out to sea by the weakened high-pressure system were reintroduced inland, influenced by southeast winds brought about by the peripheral circulation of typhoon “Gaemi”. In summary, the alternating evolution of SWPs significantly influences multi-scale ozone transport from both the NCR and the YRD regions, making substantial contributions to this prolonged episode. These findings offer valuable insights for improving regional ozone pollution prevention and control mechanisms.

Microscopic state equation for oscillator chains

Systems allowing anomalous transport of mass, momentum energy, etc., such as low-dimensional particles systems or highly confining media, are hard to characterize thermodynamically. Indeed, local thermodynamic equilibrium may not be established and their behaviour often strongly depends on many microscopic parameters, including the symmetry of the interaction potentials. Thermodynamic state equations, on the other hand, involve a small set of observables, which are obtained averaging in time and over the large number of particles that populate mesoscopic cells in which local equilibrium can be realized. In this work we show that a linear relation discovered earlier, that connects the average distance between pairs of consecutive particles with their kinetic energy, applies to quite a large set of 1-dimensional particle systems known to produce anomalous transport. This relation is microscopic in nature, since the quantities involved are neither averaged over many particles, neither over very large times. Nevertheless, its robustness is under variations of the external parameters, and the limited set of quantities it involves qualify it as a state equation, analogously to thermodynamic relations. We provide conditions for which the relation can be violated within a limited range of parameters values, and we find that it can be extended to two-dimensional networks of coupled oscillators. The validity of this relation further shows that the states of aggregation of matter in low-dimensional systems are often different from standard macroscopic ones.

Evidence of a dual African and Australian biomass burning influence on the vertical distribution of aerosol and carbon monoxide over the southwest Indian Ocean basin in early 2020

Abstract. During the 2020 austral summer, the pristine atmosphere of the southwest Indian Ocean (SWIO) basin experienced significant perturbations. This study examines the variability of aerosols and carbon monoxide (CO) over this remote oceanic region and investigates the underlying processes in the upper troposphere–lower stratosphere (UT-LS). Aerosol profiles in January and February 2020 revealed a multi-layer structure in the tropical UT-LS. Numerical models – the FLEXible PARTicle dispersion model (FLEXPART) and the Modèle Isentropique de transport Mésoéchelle de l'Ozone Stratosphérique par Advection (MIMOSA) – indicated that the lower-stratospheric aerosol content was influenced by the intense and persistent stratospheric aerosol layer generated during the 2019–2020 extreme Australian bushfire events. A portion of this layer was transported eastward by prevailing easterly winds, leading to increased aerosol extinction profiles over Réunion on 27 and 28 January. Analysis of advected potential vorticity revealed isentropic transport of air masses containing Australian biomass burning aerosols from extratropical latitudes to Réunion at the 400 K isentropic level on 28 January. Interestingly, we found that biomass burning (BB) activity in eastern Africa, though weak during this season, significantly influenced (contributed up to 90 % of) the vertical distribution of CO and aerosols in the upper troposphere over the SWIO basin. Ground-based observations at Réunion confirmed the simultaneous presence of African and Australian aerosol layers. This study provides the first evidence of African BB emissions impacting the CO and aerosol distribution in the upper troposphere over the SWIO basin during the convective season.

Contrasting extremely warm and long-lasting cold air anomalies in the North Atlantic sector of the Arctic during the HALO-(𝒜 𝒞)3 campaign

Abstract. How air masses transform during meridional transport into and out of the Arctic is not well represented by numerical models. The airborne field campaign HALO-(𝒜𝒞)3 applied the High Altitude and Long-range Research Aircraft (HALO) within the framework of the collaborative research project on Arctic amplification (𝒜𝒞)3 to address this question by providing a comprehensive observational basis. The campaign took place from 7 March to 12 April 2022 in the North Atlantic sector of the Arctic, a main gateway of atmospheric transport into and out of the Arctic. Here, we investigate to which degree the meteorological and sea ice conditions during the campaign align with the long-term climatology (1979–2022). For this purpose, we use the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis v5 (ERA5), satellite data, and measurements at Ny-Ålesund, including atmospheric soundings. The observations and reanalysis data revealed two distinct periods with different weather conditions during HALO-(𝒜𝒞)3: the campaign started with a warm period (11–20 March 2022) where strong southerly winds prevailed that caused poleward transport of warm and moist air masses, so-called moist and warm air intrusions (WAIs). Two WAI events were identified as atmospheric rivers (ARs), which are narrow bands of strong moisture transport. These warm and moist air masses caused the highest measured 2 m temperatures (5.5 °C) and daily precipitation rates (42 mm d−1) at Ny-Ålesund for March since the beginning of the record (1993). Over the sea ice northwest of Svalbard, ERA5 indicated record-breaking rainfall. After the passage of a strong cyclone on 21 March 2022, a cold period followed. Northerly winds advected cold air into the Fram Strait, causing marine cold air outbreaks (MCAOs) until the end of the campaign. This second phase included one of the longest MCAO events found in the ERA5 record (19 d). On average, the entire campaign period was warmer than the climatological mean due to the strong influence of the ARs. In the Fram Strait, the sea ice concentration was well within the climatological variability over the entire campaign duration. However, during the warm period, a large polynya opened northeast of Svalbard, untypical for this season. Compared to previous airborne field campaigns focusing on the evolution of (mixed-phase) clouds, a larger variety of MCAO conditions was observed during HALO-(𝒜𝒞)3. In summary, air mass transport into and out of the Arctic was more pronounced than usual, providing exciting prospects for studying air mass transformation using HALO-(𝒜𝒞)3.