Moisture Transport Research Articles

Onset of aridification in mid-latitude Asia at 41 Ma linked to the proto-Paratethys Sea retreat

The initial aridification of mid-latitude Asia is thought to be one of the most prominent Cenozoic environmental changes in Asia. However, precisely dated, fine-grained sediments documenting initial aridity beyond central Asia are extremely rare. Here, we reconstruct the history of Middle-Late Eocene (47.8–37.8 Ma) hydroclimate change in northeast China using continuous palynological records from a lacustrine sedimentary sequence in the Fushun Basin. Our results indicate that the onset of aridification occurred concurrently with increased climatic variability at 41.2 Ma, as expressed by a sharp increase in xerophytic Ephedra and mountainous coniferous forest at the expense of an abrupt decrease in broadleaved forest, along with frequent alternations between semi-desert and swamp forest vegetation after 41.2 Ma. The climate changed markedly from a stable, warm-wet climate during the Middle Eocene to a cooler, drier climate with pronounced warm-dry and cold-wet oscillations during the Late Eocene. This finding challenges the previously prevailing idea that the East Asian monsoon was significantly enhanced in northeast China after 41–40 Ma. A comprehensive comparison of records from eastern and central Asia demonstrates that the onset of aridification and enhanced climate variability after 41 Ma were widespread across mid-latitude Asia. This may be explained by reduced moisture transport by the westerlies and strengthening of high- and low-latitude forcing linked to the coeval retreat of the proto-Paratethys Sea.

CloudSat Observations Show Enhanced Moisture Transport Events Increase Snowfall Rate and Frequency Over Antarctic Ice Sheet Basins

AbstractElevated moisture transport over the Antarctic ice sheet can increase snowfall and ice mass. Previous studies used ground‐based observations, reanalysis products, and atmospheric models to evaluate the relationship between extreme moisture transport and snowfall properties. Here, we build on previous studies by combining reanalysis and CloudSat radar snowfall retrievals to examine impacts of extreme moisture intrusions on changes in snowfall frequency and intensity over glacier basins on the Antarctic ice sheet. We examine the impacts of enhanced moisture transport events on snowfall frequency and intensity over two different regions on the Antarctic ice sheet: the Amery Ice Shelf of East Antarctica and the Thwaites and Pine Island glacier basins of West Antarctica. We determine when the median integrated water vapor transport from reanalysis exceeds the 95th percentile within the glacier basins of interest to define enhanced moisture transport events. We then use CloudSat radar snowfall retrievals to evaluate differences between snowfall frequency and intensity during enhanced water vapor transport events compared to the seasonal means for 2007–2010. We find that enhanced moisture transport events over the Amery Ice Shelf and Thwaites and Pine Island glacier basins coincide with higher snowfall frequency and intensity. These enhanced moisture transport events have the potential to alter surface mass balance within glacier basins, with implications for future rates of sea level rise.

Midlatitude Oceanic Fronts Strengthen the Hydrological Cycle Between Cyclones and Anticyclones

AbstractThe Kuroshio‐Oyashio Extension and Gulf Stream oceanic frontal zones are characterized by enhanced activity of synoptic‐scale cyclones and anticyclones and vigorous air‐sea heat and moisture exchange in the cold season. However, the time‐mean air‐sea exchange attributed separately to cyclones and anticyclones has not been assessed. Here we quantify cyclonic and anticyclonic contributions around the frontal zones to surface turbulent heat fluxes, precipitation, and the associated hydrological cycle using atmospheric general circulation model experiments with observed and artificially smoothed sea‐surface temperature gradients. The evaluation reveals that precipitation exceeds evaporation climatologically within cyclonic domains while evaporation dominates within anticyclonic domains. These features as well as the net moisture transport from anticyclonic to cyclonic domains are all enhanced by the sharpness of the frontal zones. Oceanic frontal zones thus climatologically act to strengthen the hydrological cycle. These findings aid our understanding of the relationship between midlatitude air‐sea interactions on synoptic‐ and longer‐time scales.

Adsorption isotherm of building materials at different temperatures: A review and measurement

The temperature dependency of the adsorption isotherm renders its significance as one of the primary input parameters in models dealing with moisture transport. The present study involved the determination of the adsorption isotherm of sixteen building materials from various categories, including cladding, building paper, wood, sheathing boards, and insulations. The measurements were conducted under nine climatic conditions, a combination of three temperatures (3 °C (37.4 °F), 21 °C (69.8 °F), 45 °C (113 °F)) and three relative humidity levels (50%, 70%, 90%). The study indicated that relative humidity increased the building materials’ equilibrium moisture content (EMC). In opposition, an increase in temperature decreased the EMC of the tested materials. It was discovered that cellulose fiber and wood-based materials had a greater capacity to store moisture than others. Conversely, the minimum moisture content was observed in brick, Densglass gold gypsum, and EPS products. Furthermore, we used the ABC model as an adaptable mathematical equation for a novel nonlinear surface fitting of adsorption isotherms of tested materials to make optimal use of the experimental data and effectively analyze the simultaneous impact of all temperatures and relative humidities. Tested against the measured experimental data, we obtained the best R-squared values from the second-order polynomial Equation.

The role of atmospheric rivers and associated circulation patterns in the Arctic warming in boreal winter

AbstractAtmospheric rivers (ARs) serve a narrow, filamentary channels responsible for intense moisture and heat transport, which are vital for the Arctic sea ice loss and surface air warming, particularly in winter. In this study, ERA5 reanalysis data from 1979 to 2020 are used to investigate the evolution of ARs in the Arctic and the corresponding atmospheric circulation patterns in winter. Our findings indicate that atmospheric circulation is a key factor that facilitates the transport and dispersion of ARs. Cyclonic circulation anomalies provide the dynamical support for ARs in the early development stages, while anticyclonic anomalies are essential for maintaining the thermal and moisture conditions of ARs, particularly after their intrusions into the Arctic region. The cooperation between cyclonic and anticyclonic anomalies plays a critical role in the infiltration and dispersion of ARs, governed by distinct circulation modes for regional intrusions. A positive Arctic Oscillation‐like pattern manifests as a cyclonic system over the Arctic, increasing the likelihood of AR intrusion into Baffin Bay. Conversely, a negative pattern induces a more intense anticyclonic system over the Arctic, thereby raising the frequency of ARs in the Bering Strait. The Pacific‐North American pattern not only directly affects ARs entering the Arctic via the Pacific but also has downstream impacts on ARs intruding the Arctic through Baffin Bay.

A micro‐nanohierarchical composite fabric for efficient water transport and outstanding flame retardancy

AbstractTextiles with outstanding moisture transport characteristics and excellent flammability is of vital importance for human beings. In this work, the poly(arylene sulfide sulfone)–polydopamine/polyphenylene sulfide–polydopamine/poly(arylene sulfide sulfone) (PASS‐PDA/PPS‐PDA/PASS) composite fibric with multigradient porous structures from macro to submicron levels prepared via micrometer and nanometer fibers for water transport and evaporation has been fabricated. The introduction of PDA can effectively improve the hydrophilicity of the composite membrane. Meanwhile, superhydrophobic PASS layer with beaded structure was obtained by electrospray as the inner layer. It is found that PASS‐PDA‐72 fabric exhibited outstanding water diffusion property (spreading diameter = 10.47 cm) and ultrafast the water evaporation (0.20 g h−1). Meanwhile, the beaded‐structure PASS fabrics with high hydrophobicity (water contact angle is 130°C) was selected to absorb water from the surface of human skin and transport it to the other side to evaporate quickly, giving the surface of human skin a comfortable and dry environment. What is more, the PASS‐PDA/PPS‐PDA/PASS composite membrane exhibited excellent thermal stability (Tdmax = 544°C) and flame retardancy, which will have potential for the application in the field of fire protection.

Effects of idealized land cover and land management changes on the atmospheric water cycle

Abstract. Land cover and land management changes (LCLMCs) play an important role in achieving low-end warming scenarios through land-based mitigation. However, their effects on moisture fluxes and recycling remain uncertain, although they have important implications for the future viability of such strategies. Here, we analyse the impact of idealized LCLMC scenarios on atmospheric moisture transport in three different Earth system model (ESMs): the Community Earth System Model (CESM), the Max Planck Institute Earth System Model (MPI-ESM), and the European Consortium Earth System Model (EC-EARTH). The LCLMC scenarios comprise of a full cropland world, a fully afforested world, and a cropland world with unlimited irrigation expansion. The effects of these LCLMC in the different ESMs are analysed for precipitation, evaporation, and vertically integrated moisture flux convergence to understand the LCLMC-induced changes in the atmospheric moisture cycle. Then, a moisture tracking algorithm is applied to assess the effects of LCLMC on moisture recycling at the local (grid cell level) and the global scale (continental moisture recycling). By applying a moisture tracking algorithm on fully coupled ESM simulations we are able to quantify the complete effects of LCLMC on moisture recycling (including circulation changes), which are generally not considered in moisture recycling studies. Our results indicate that cropland expansion is generally causing a drying and reduced local moisture recycling, while afforestation and irrigation expansion generally cause wetting and increased local moisture recycling. However, the strength of this effect varies across ESMs and shows a large dependency on the dominant driver. Some ESMs show a dominance of large-scale atmospheric circulation changes while other ESMs show a dominance of local to regional changes in the atmospheric water cycle only within the vicinity of the LCLMC. Overall, these results corroborate that LCLMC can induce substantial effects on the atmospheric water cycle and moisture recycling, both through local effects and changes in atmospheric circulation. However, more research is needed to constrain the uncertainty of these effects within ESMs to better inform future land-based mitigation strategies.

Evaluating the climatic state of Indian Summer Monsoon during the mid-Pliocene period using CMIP6 model simulations

The Indian Summer Monsoon Rainfall (ISMR) plays a critical role in agriculture, thereby significantly affecting the economy of India. Yet, there is a large spread in the ISMR variability for future projections (by the end of 21st century) as simulated by coupled general circulation models. Gaining insight into the variations of the ISMR during warm periods could enhance our ability to understand ISMR variability in the future. In this study, we have selected the mid-Pliocene warm period from 3.0 to 3.3 million years ago (Ma), which has similar external forcing (orbital parameters) comparable to the end of the 21st century. To evaluate the ISMR mean state during the mid-Pliocene, we have used six available Coupled Model Intercomparison Project phase 6 (CMIP6) model simulations and their multi-model ensemble mean. Our analysis suggests that the ensemble of CMIP6 models is better than individual models in capturing the ISM rainfall patterns and its characteristics for the historical period of 1914–2013. During the mid-Pliocene, we find an increase in the JJAS rainfall over most parts of India in comparison to the pre-industrial period with an increase of 34% in seasonal precipitation. This higher precipitation conditions during the mid-Pliocene is accompanied by thermo dynamical (higher CO2 forcing led to higher tropospheric temperature and higher precipitable water) and dynamical (larger tropospheric temperature gradient between Indian landmass and southern Indian Ocean corresponds to enhanced moisture transport, enhanced low-level cross-equatorial flow and intensified Monsoon Hadley Circulation) aspects.

Vegetation changes through stadial and interstadial stages of MIS 4 and MIS 3 based on a palynological analysis of the Girraween Lagoon sediments of Darwin, Australia

A palynological record from Girraween Lagoon sediments (Darwin region of the Northern Territory, Australia) provides detailed long-term insight into tropical savanna vegetation community patterns, climatic and fire relationships, through Marine Isotope Stage 4 (MIS 4: 71–57 thousand years ago, ka) and Marine Isotope Stage 3 (MIS 3: 57–29 ka). Owing to a lack of data in reconstructing northern Australian environments, this paper looks to define and describe to a greater degree the nature and scope of these stadial and interstadial stages for the region. Girraween Lagoon simultaneously provides proximal palaeoecological data for the time and region of Aboriginal people's first arrival into Australia, also encompassing the late Pleistocene continental decline of megafauna. This study provides a dataset enabling full exploration of long-term people-landscape and faunal-floral interactions. Sea levels and associated variations imposed on the transportation of moisture and heat, held implications for MIS 4 and MIS 3 monsoon strength, which was particularly consequential for Girraween regional ecology. Results reveal a prolonged transition from wooded- to grassy-savanna, into a cool drier semi-arid savanna. Increasingly episodic delivery of moisture influenced the permanency of freshwater in the landscape.

Moisture Sources and Pathways of Annual Maximum Precipitation in the Lancang‐Mekong River Basin

AbstractRecent extremely heavy precipitation has led to substantial economic losses and affected millions of residences in the Lancang‐Mekong River Basin (LMRB). This study analyzed the spatial‐temporal characteristics of the annual maximum precipitation (R1X) of the LMRB and identified the moisture sources and pathways conducive to R1Xs using a Lagrangian back trajectory model. Results show that India Ocean and Bay of Bengal (IO/BOB), local evapotranspiration, and West Pacific Ocean and East China (WP/EC) are the three main moisture transport pathways of the R1Xs in LMRB, contributing 68.3%, 20.4% and 11.3% of the trajectories, respectively. R1Xs in the downstream eastern area are affected by tropical cyclones bringing large amounts of moisture from the WP/EC. As tropical cyclones shifted northward under climate change impact, more extreme precipitation occurred over the LMRB due to moisture coming from WP/EC, but those from the IO/BOB had decreased because of the slowdown of flows across the Equator.

Spring tropical cyclones modulate near-surface isotopic compositions of atmospheric water vapour in Kathmandu, Nepal

Abstract. While westerlies are recognized as a significant moisture transport in Nepal during the pre-monsoon season, precipitation is also attributed to moisture from cyclones originating in the Bay of Bengal (BoB) or the Arabian Sea (AS). Tropical cyclones exhibit negative isotopic values in both precipitation and atmospheric water vapour; however, the factors influencing isotopic fractionation during tropical cyclones remain poorly understood. We present the results of continuous measurements of the isotopic composition of atmospheric water vapour (δ18Ov, δDv, and d-excessv) in Kathmandu from 7 May to 7 June 2021 during two pre-monsoon cyclones: cyclone Tauktae, formed over the Arabian Sea, and cyclone Yaas, formed over the Bay of Bengal. Our study reveals that tropical cyclones originating from the BoB and the AS during the pre-monsoon season modulate isotopic signals of near-surface atmospheric water vapour in Nepal. Comparing conditions before and after, we observed a significant depletion of δ18Ov and δDv during both cyclones, attributed to changes in moisture sources (local vs. marine). Convective activity plays a pivotal role in the variability of δ18Ov and δDv during both cyclones, confirmed by the spatial variations of outgoing longwave radiation (OLR) and regional precipitation during both cyclones. We also found a significant negative correlation between δ18Ov and/or δDv and rainfall amount along the trajectories during cyclone Tauktae, probably resulting from integrated upstream processes linked to the earlier Rayleigh distillation of water vapour via rainfall rather than local rainfall. The decrease in δ18Ov and/or δDv during cyclone Yaas is associated with the intensified convection and moisture convergence at the measurement site, while the lower cloud top temperatures (CTTs) and lower cloud top pressure (CTP) during intense convection contribute to higher d-excessv values during the final stage of cyclone Yaas. This characteristic is missing during cyclone Tauktae. Our results shed light on key processes governing the isotopic composition of atmospheric water vapour in Kathmandu with implications for the monsoon moisture transport and paleoclimate reconstructions of tropical cyclone activity.

Modulations of Madden–Julian Oscillation and Quasi-Biweekly Oscillation on Early Summer Tropical Cyclone Genesis over the Bay of Bengal and South China Sea

Abstract The Madden–Julian oscillation (MJO) and the quasi-biweekly oscillation (QBWO) are prominent components of the intraseasonal oscillations over the tropical Indo-Pacific Ocean. This study examines the tropical cyclone (TC) genesis over the Bay of Bengal (BOB) and the South China Sea (SCS) on an intraseasonal scale in May–June during 1979–2021. Results show that the convection associated with the two types of intraseasonal oscillations simultaneously modulates TC genesis in both ocean basins. As the MJO/QBWO convection propagated, TCs form alternately over the two basins, with a significant increase (decrease) in TC genesis frequency in the convective (nonconvective) MJO/QBWO phase. Based on the anomalous genesis potential index associated with the MJO/QBWO, an assessment of the influence of various factors on TC genesis is further assessed. Middle-level relative humidity and lower-level relative vorticity play key roles in the MJO/QBWO modulation on TC genesis. The MJO primarily enhances large-scale cross-equatorial moisture transport, resulting in significant moisture convergence, while the QBWO generally strengthens the monsoon trough and induces the retreat of the western North Pacific subtropical high, increasing the regional lower-level relative vorticity. The potential intensity and vertical wind shear make small or negative contributions. This study provides insights into the neighboring basin TC relationship at intraseasonal scales, which has a potential to improve the short-term prediction of regional TC activity. Significance Statement The Madden–Julian oscillation (MJO) and the quasi-biweekly oscillation (QBWO) are two types of intraseasonal tropical atmospheric oscillations. The development of tropical cyclones (TCs) is often accompanied by intraseasonal convection. This study highlights the distinct roles of MJO and QBWO in TC genesis over the South Asian marginal seas (e.g., Bay of Bengal and South China Sea). The QBWO can co-regulate TC genesis along with the background of the MJO, where the large-scale MJO mainly provides moisture, while the small-scale QBWO mainly contributes to vorticity. These findings provide useful information for subseasonal TCs forecasting. There are many developing countries along the South Asian marginal seacoast; therefore, further research on regional TC climate would help effectively reduce casualties and property damage.

Research on the Characteristics of Raindrop Spectrum and Its Water Vapour Transport Sources in the Southwest Vortex: A Case Study of 15–16 July 2021

This study investigated the convective weather features, precipitation microphysical characteristics, and water vapour transport characteristics associated with a southwest vortex precipitation event that occurred on the eastern edge of the Qinghai–Tibet Plateau, coinciding with a southwest vortex event, from 15 to 16 July 2021, using conventional observations of raindrop spectra, ERA5 reanalysis data, CMORPH precipitation data, and the HYSPLIT_v4 backward trajectory model. The findings aim to provide theoretical insights for improving the forecasting and numerical simulations of southwest vortex precipitation events. The findings revealed that the precipitation event induced by the southwestern vortex at Emeishan Station on 15–16 July 2021 was characterised by high rainfall intensity and significant precipitation accumulation. The raindrop spectrum exhibited a broad distribution with a notable bimodal structure. Both the Sichuan Basin and the Tibetan Plateau were dominated by the South Asian high pressure at higher altitudes, while a pronounced low-pressure system developed at mid and low altitudes within the basin, establishing a meteorological context marked by upper-level divergence and lower-level convergence. Throughout the event, notable vertical uplift velocities were recorded across the Sichuan Basin and Tibetan Plateau, along with distinct positive vorticity zones in the lower and middle strata of the Sichuan Basin, indicating that the atmosphere was in a state of thermal instability. The majority of moisture was in the mid and lower troposphere with evident convergence movements, which played a crucial role in the southwest vortex’s development. WRF numerical simulations of the Emeishan precipitation event more accurately modelled the weather conditions for this precipitation but tended to overestimate the level of precipitation. It was observed that the region around Emei Mountain primarily received moisture influx from the southern Bay of Bengal and the South China Sea, with moisture transport chiefly originating from the Sichuan Basin and in a south-westward trajectory.

Formation mechanisms of persistent extreme precipitation events over the eastern periphery of the Tibetan Plateau: Synoptic conditions, moisture transport and the effect of steep terrain

The eastern periphery of the Tibetan Plateau (EPTP) is prone to frequent and severe Persistent Extreme precipitation (PEP) events in summer. Given the complexity of weather systems and the intricate nature of terrain over this region, the generation and development mechanisms of the PEP in the EPTP remain to be determined. In this study, the formation and persistence mechanisms are further explored from the perspective of the general features of large-scale circulations, moisture source diagnosis and the influence of steep topography by using a thermal-dynamical diagnosis method, a mesoscale numerical simulation and a Lagrangian identification of the main moisture sources. The results show that during PEP events, the corresponding atmospheric circulation systems are characterized by an anomalous Rossby wave train at middle levels, an intensified westerly jet, an eastward extension of the South Asian high and a westward extension of the western Pacific subtropical high, all of which are possible to facilitate the development of potential instability and anticyclonic convergence of water vapor transport. The evaporative moisture sources from the Southeastern Asia (SEA), Bay of Bengal (BOB), and Southern China Sea (SCS) are remarkably enhanced during PEP events, with a contribution of 56.44%, which is 28.5% higher than the climatic mean. The further sensitive experiment indicates that the steep terrain could enhance the continuous transport of positive potential vorticity and the downward propagation of upper-level isentropic potential vorticity disturbances, thereby playing an essential role in the triggering and development of PEP events.

Simulation and experimental study of heat-moisture-solute transfer during drying process of porous media

Fruits and vegetables, being typical porous media, allow for the migration of nutrients (solutes) and the transport of moisture simultaneously during the drying process. To reveal the migration mechanism of heat-moisture-solute during the drying process of porous media, a comprehensive mathematical model was established that accounts for the coupled phenomena of heat and moisture transfer, along with solute migration. The model was simulated using COMSOL to provide insights into these complex interactions. Hot-air drying experiments were conducted using apple slices as the subject to validate the accuracy and reliability of the model. The simulation results and experimental results of temperature, moisture content, and sugar concentration were in good agreement. The findings demonstrate that as the drying process progresses, the interface between temperature, moisture gradients, and sugar concentration shifts from the outer layers toward the inner regions. We investigated the effects of hot air temperature, thickness, and porosity on the heat-moisture-solute transfer in porous media. The results provide support for accurately predicting the migration and transport mechanisms of solutes in porous media.

Temporal variations of stable isotopic compositions in atmospheric water vapor on the Southeastern Tibetan Plateau and their controlling factors

Stable isotopic compositions in atmospheric water vapor (δ18OV, δDV and d-excessV) are effective tracers that provide new insights into the local and regional hydrological cycle on the Tibetan Plateau. One-year continuous measurements of the isotopic compositions in near-surface atmospheric water vapor on the Southeastern Tibetan Plateau are reported. Our results demonstrated the relative impacts of moisture source shifts, large scale moisture transport, and local processes on the variability of the isotopic compositions in atmospheric water vapor. The observed seasonal variations in δ18OV and d-excessV exhibit low values in the monsoon period and high values in the non-monsoon period due to the predominance of large-scale atmospheric circulations. Local processes significantly modulate diurnal cycles of δ18OV and d-excessV. The sharp decrease in δ18OV and increase in d-excessV is related to the synoptic process. Moreover, the seasonality of moisture sources and transport, including moisture uptake and upstream rainout strongly affects the atmospheric moisture and the isotopes. These findings will improve our understanding of the regional hydrological cycle on the Southeastern Tibetan Plateau and provide reference to validate the simulated stable water isotopes.

Infiltration and Leaching Characteristics of Soils with Different Salinity under Fertilizer Irrigation

Salt and nutrient transport and transformations during water infiltration directly influence saline soil improvement and the efficient use of water and fertilizer resources. The effects of soil initial salinity (18.3 g/kg, 25.5 g/kg, 42.2 g/kg, 79.94 g/kg, and 165 g/kg, respectively, labeled S1 to S5) on the infiltration and leaching characteristics of water, salt, and nitrogen were analyzed via a one-dimensional vertical fertilizer infiltration experiment. Meanwhile, the estimation models of cumulative infiltration and wetting front, including the effect of soil initial salinity, were established. The results showed that, with the increase in soil initial salinity, the cumulative infiltration within the same time decreased, and the migration time of wet front to 45 cm was longer. The time required for S5 to reach the preset cumulative infiltration was more than six times that of S1, and, for the wet front migration to 45 cm, the time requirement for S5 was about four times that of S1. In the established Kostiakov model and wetting front model, the coefficients all decreased with the increase in soil initial salinity, and the test index R2 values both reached 0.999. In the Kostiakov model, coefficient K had a linear relationship with the natural logarithm of initial soil salt content, while index a had a direct linear relationship with initial soil salt content. The cumulative leachate volume decreased with the increase in soil initial salinity, and the corresponding data of S3 and S5 were reduced by 37% and 57.3%, respectively, compared with S1. The electrical conductivity values of S1, S3, and S5 were 15.4, 209.8, and 205.6 ms/cm, respectively, being affected by the initial content in soil, soil moisture transport rate, and exogenous potassium nitrate (KNO3) addition. The NO3−-N concentrations in the leachates of S1, S3, and S5 at the end of leaching were 55.26, 16.17, and 3.2 mg/L, respectively. Based on the results of this study, for soil with high initial salinity, the conventional irrigation amount (2250 m3/ha) of the general soil in the study area could not meet the requirements of leaching salt. These results can provide a reference for the formulation of irrigation and fertilization strategies for soils with different salinity and contribute to the sustainable development of saline soil agriculture and the ecological environment.

Differing roles of North Atlantic oceanic and atmospheric transports in the winter Eurasian Arctic sea-ice interannual-to-decadal variability

In recent decades, winter Arctic sea-ice concentration (SIC) has experienced a most prominent decline over Barents-Kara Seas (BKS). However, what regulates the time scale and spatial structure of the SIC variability over the Eurasian Arctic is unclear. Here, we find that the SIC variability over the Eurasian Arctic exhibits two major modes: decadal dipole mode with antiphase variation between the BKS and East Greenland (EG), and interannual monopole mode with in-phase variation between the BKS and EG. This decadal mode mainly results from interdecadal changes in ocean heat transports (OHTs) through Barents Sea Opening (BSO) and EG, lagging the Atlantic Multidecadal Oscillation by 7–16 years. The positive SIC dipole mode with a decrease over the BKS and an increase over the EG is also tied to the negative Arctic Oscillation comprised of Ural blocking and the negative North Atlantic Oscillation (NAO). However, the SIC loss of the interannual monopole mode mainly stems from the positive Arctic dipole comprised of Ural blocking and positive NAO through interannual changes in the BSO OHT and atmospheric moisture or heat transport. We further highlight that interannual atmospheric transports and BSO OHT associated with the Arctic dipole contribute to ~66% and ~34% of the interannual variability of the Eurasian Arctic SIC during 1960-2017, respectively. On decadal timescales, the relative contributions of atmospheric transports associated with Arctic Oscillation and OHT to the Eurasian Arctic SIC variability are ~19% and ~81%, respectively. Especially, the contribution of decadal atmospheric transports is significantly intensified during 2000–2017.

Meso-scale simulation of moisture transport in concrete during wet-dry cycles using 3D RBSM conduit model with variable diffusion model

This paper introduces the 3D RBSM Conduit model, an improved simulation program based on the Rigid Body Spring Model (RBSM), designed to accurately depict the intricate phenomenon of moisture transfer within concrete. This is achieved by incorporating an expanded diffusion model into the simulation framework. The diffusion coefficient is dynamically adjusted at each location and at each time step to accurately represent the precise moisture transfer processes occurring in the concrete. This dynamic adjustment allows the program to efficiently simulate the rate of moisture transport in concrete based on the moisture degree and the dry or wet state of the material. By adapting the diffusion coefficient to the changing conditions in this way, the program achieves simulated moisture transfer rates that align closely with the real-world behavior of moisture in concrete. It offers a dynamic model of the changes in concrete transmission during the switch from drying and wetting conditions. Further, the program exhibits inherent advantages in addressing water transfer problems involving nonlinear boundary conditions and transfer equations. In this study, the program is used to simulate various processes including drying, wetting, local wetting, and combined wet-dry cycles. The results reveal the lag in wet-dry transitions between the interior and exposed surface during the wet-dry conversion process due to retained interior moisture. The simulation captures the moisture variation in the transitional zone.

From tomographic imaging to numerical simulations: an open-source workflow for true morphology mesoscale FE meshes

Full-field techniques such as tomography are becoming progressively more central in the study of complex phenomena, in particular where spatiotemporal evolution is crucial, as in moisture transport or crack initiation in porous media. These techniques provide a unique insight in the local process whose quantification allows the improvement of our understanding and of the models describing them. Nevertheless, the model validation can be pushed further by attempting to explicitly represent the heterogeneities and simulate their role in the processes. Once validated, these models can be used to perform “virtual experiments”, and overcome the limitations of the experiments (e.g., sample size and number, fine control of the boundary and initial conditions). This study proposes a connection between tomography images and mesoscale models through a workflow that mainly employs open-source tools. This workflow is illustrated through the digitization of a Portland cement concrete sample, stemming from neutron tomographies and resulting in a numerical finite element mesh. The proposed workflow is flexible, allowing for the conversion of images from various sources, such as x-ray or neutron tomographies, to different numerical representations of the domain, such as finite element meshes or even a discrete domain required by discrete element methods, while preserving real morphologies with an accuracy proportionate to the specific need of the problem. Beside its generalizability, our method also offers automated labelling of the different domains and boundaries in both the volumetric and surface meshes, which is often necessary for assigning material properties and boundary conditions. Finally, the series of image, geometry and mesh processing steps described in this work are made available on a GitHub repository.