Vertical Circulation Research Articles

Low-disturbance land remediation using vertical groundwater circulation well technology: The first commercial deployment in an operational chemical plant

Soil and groundwater contamination by organic pollutants from chemical plants presents significant risks to both environmental and human health. We report a significant field trial where a chemical plant in operation showed soil and groundwater pollution, as verified by sampling and laboratory tests. While many remediation methods are effective, they often require the temporary shutdown of plant operations to install necessary equipment. This paper introduces a novel combination of low-disturbance contaminant remediation technologies, including groundwater circulation well (GCW), pump and treat (P&T), and in-situ chemical oxidation (ISCO) technologies, that can be applied on the premises of an active plant without halting production. The groundwater with dissolved contaminants is removed through P&T and GCW, while GCW enhances ISCO that focus on eliminating the remaining hard-to-pump contaminants. Results show: (1) after two years of remediation effort, the contaminant levels in soil and groundwater were significantly reduced; (2) the average concentration reduction rate of four contaminants, including 1,2-dichloroethane, methylbenzene, ethylbenzene, and M&P-xylene, exceeds 98 %; (3) the presented remediation strategy results in the improvement of remediation efficiency. Specifically, the concentration of 1,2-dichloroethane in observation wells dropped from 40,550.7 μg/L to 44.6 μg/L. This study offers a first-of-its-kind commercial deployment of a GCW-based remediation strategy in an active plant setting. Moreover, the combined remediation approach presented here can serve as a model for designing contaminant remediation projects that require minimal operational disruption.

Understanding thermal stratification and circulation dynamics in Fuxian Lake: Insights from EFDC simulation study

This study aims to provide a comprehensive numerical solution and quantitative analysis of the thermal stratification and circulation in Fuxian Lake, the largest freshwater deep lake in China, utilizing a high-fidelity Environmental Fluid Dynamics Code (EFDC) to build a three-dimensional hydrodynamic model. Simulation results reveal that meteorological conditions and hydrodynamic processes notably influence the spatiotemporal characteristics of the thermocline, with wind and temperature disparities primarily impacting water flow. Maximum water temperature (24.3 °C) and thermocline intensity (0.31 °C/m) typically occur in September. Vertical circulation, driven by wind-induced horizontal divergence and convergence of lake currents, often induces uneven vertical movements, leading to thermocline irregularities. This study also assesses the sensitivity of Fuxian Lake to temperature changes, showcasing the efficacy of EFDC model in accurately reproducing observed spatiotemporal variations. This research not only establishes a foundation for integrating the EFDC model with water quality models but also presents an effective approach for studying hydrodynamics and thermal stratification processes in other deep-water lakes, thereby facilitating lake management and ecological restoration endeavors.

Influences of synoptic circulations on regional transport, local accumulation and chemical transformation for PM2.5 heavy pollution over Twain-Hu Basin, central China

The Twain-Hu Basin (THB), located in Central China, serves as a key juncture where the northerly “polluted” airflows of the East Asian winter monsoon meet the southerly warm and humid airflows. Using the T-PCA (T- Principal Component Analysis) objective synoptic pattern classification, FLEXPART-WRF (Flexible Particle Dispersion Model), and Random Forest model, we investigate the influences of synoptic circulations on regional transport, local accumulation, and chemical transformation of PM2.5 during heavy air pollution over the THB in January of 2015–2022. The results show that the transport-type synoptic pattern accounts for 65.16% of heavy PM2.5 pollution, indicating that regional transport of PM2.5 dominates the THB's heavy air pollution. The PM2.5/CO ratio is higher in the transport-type pattern and positively correlated with PM2.5 concentrations, reflecting a higher efficiency of chemical transformation to secondary PM2.5 in transport-type pollution compared with the accumulation-type pollution. Transport-type heavy PM2.5 pollution is predominantly influenced by upstream anomalous northerly and easterly airflows at the bottom of the high-pressure system, converging with the southern wind in the receptor area over the THB. Accumulation-type heavy pollution exhibits weak wind anomalies in central and eastern China under the control of a uniform pressure field. Furthermore, thermally-induced vertical circulations with sinking airflows in the middle and lower troposphere suppress the vertical air pollutant dispersions. The relative contributions of atmospheric factors for transport-type PM2.5 heavy pollution events are 38.0% for dynamical driver, 26.8% for thermal driver, and 35.1% for chemical transformation, while in accumulation-type, the contribution rates are 33.9%, 36.3%, and 29.7%, respectively. This study elucidates the influences of synoptic patterns on regional transport, local accumulation, and chemical transformation of PM2.5 for heavy air pollution, with implications for understanding changes of air quality in the receptor region of regional transport.

Comparative analysis of spatial transport characteristics of spring cold-front-type sandstorms in the Hexi Corridor

In this study, we investigate the spatial transport characteristics of cold-front-type sandstorms with different intensities in the Hexi Corridor based on the hourly observation data from 13 ground-based meteorological stations in the Hexi Corridor, the data in the upper and lower layers from the Meteorological Information Comprehensive Analysis And Process System, and the three-dimensional aerosol observation data of the Vertical Feature Mask product obtained from the Cloud-Aerosol Lidar with Orthogonal Polarization of the United States. The results show that the influence range and horizontal transport distance of cold-front-type sandstorms in the Hexi Corridor are determined by the intensity, thickness and width of the upper-level troughs and the intensity of cold fronts. Generally, cold fronts pass through the Hexi Corridor from noon to evening and stay in this region for a long time or move slowly, which is favorable to the horizontal long-distance transport of sandstorms. The intensity of the 200 hPa upper-level jets is directly proportional to both the influence range and transport distance of sandstorms which primarily occur on the left side of the exit area of an upper-level jet. The strengthening of upper-level jets induces the formation of the vertical circulation cell at middle and low levels. The ascending branch of the circulation cell lifts sand-dust particles from the surface to the upper layers, and the descending branch transports upper-level momentum to the near-surface. This circulation situation increases the near-surface wind speed and forms sandstorms. The occurrence time and descending branch of the secondary circulation cell caused by upper-level jets are important indicators for predicting the occurrence time and falling area of sandstorms. Dust aerosols are mainly concentrated at a height of 2–6 km,.,and they can reach the height of 12 km. When the dust is concentrated at the height of 2–8 km, and the wind speed of 500 hPa and 300 hPa reaches 28 and 32 m s− 1 or above respectively, the cold front sandstorm can realize the long distance transport of thousands of kilometers.

Air Current Circulation as a Possible Cause of Preseismic Anomalies in the Surface Electric Field

Ground-based measurements of the vertical atmospheric electric field of the Earth sometimes show bay-like anomalies that precede certain earthquakes. In some cases, these anomalies have even been accompanied by a change in the sign of the field under fair weather conditions. Possible causes of this phenomenon are typically attributed to anomalous changes in electrical conductivity in the surface air and increased radon emission from the soil. This paper proposes another mechanism of atmospheric electrical anomalies that involves the entrainment of charged aerosols and light and heavy ions by air flows. Such flows can be produced by small temperature anomalies observed before some seismic events. Theoretical analysis shows that anomalously strong electrical variations may occur even in the presence weak air flows provided that they persist for a long time and there is a specific structure of the velocity field with vertical air circulation and particle exchange between different atmospheric layers. For this type of flows, an analytical solution is derived and spatial distributions of atmospheric electric perturbations are obtained. The results of calculations and estimates confirm that the proposed mechanism can explain the observational data.

Influence of glacial influx on the hydrodynamics of Admiralty Bay, Antarctica - study based on combined hydrographic measurements and numerical modeling

This study investigates the impact of glacial water discharges on the hydrodynamics of a glacial bay in Antarctica, comparing it to well-studied northern hemisphere fjords. The research was carried out in Admiralty Bay (AB) in the South Shetland Islands, a wide bay adjacent to twenty marine-terminating glaciers. From December 2018 until February 2023, AB water properties were measured on 136 days. This dataset showed that a maximally two-layered stratification occurs in AB and that glacial water is always the most buoyant water mass. Using the Delft3D Flow, a three-dimensional hydrodynamical model of AB was developed. During tests, the vertical position and initial velocity of glacial discharges have been shown to be insignificant for the overall bay circulation. Fourteen model scenarios have been calculated with an increasing glacial influx added. The AB general circulation pattern consists of two cyclonic cells. Even in scenarios with significant glacial input, water level shifts and circulation are predominantly controlled by the ocean. Glacial freshwater is carried out of AB along its eastern boundary in a surface layer. Freshwater thickness in this outflow current is maximally 0.27-0.35 m. Within the inner AB inlets, significant glacial influx produces buoyancy-driven vertical circulation. Using an approach combining hydrographic and modeling data, a four-year timeseries of glacial influx volumes into AB has been produced. On average, glacial influx in summer is 10 times greater than in spring and winter and 3 times higher than in autumn. The annual glacial influx into AB was estimated at 0.434-0.632 Gt. Overall, the study demonstrated the unique characteristics of the topography and forcings that influence the hydrodynamics of an Antarctic glacial bay.

Atmospheric and Oceanic Factors Related to the Increasing Summer High Temperature Extremes on the Tibetan Plateau under the Background of Global Warming

Abstract The related atmospheric and oceanic factors are investigated in this analysis to understand the natural attributes responsible for the significant increase of the high temperature extremes (HTEs) on the Tibetan Plateau (TP) in summer. It is found that a stronger-than-normal South Asian high (SAH) and corresponding weaker-than-normal East Asian jet, an anomalous anticyclone and intensified midlevel westerly wind over the TP, and a more extensive, stronger, farther westward- and northward-stretching western Pacific subtropical high motivate more occurrences of HTEs over the TP on the interannual time scale. From 1961 to 2021, these crucial circulation patterns show a significant changing trend favorable for the occurrence of HTEs and thus contribute to its great increase. Further, the significant warmings of sea surface temperature (SST) in the tropical western Indian, northern North Pacific, and western North Atlantic Oceans make great contributions through different air–sea interactive processes as the Matsuno–Gill response, zonal vertical circulation cell, and mid- to high-latitude teleconnection wave train, respectively. Meanwhile, the interdecadal variability plays an important role. A breakpoint at the early twenty-first century is detected in the occurrence of summer HTEs on the TP. Both the crucial circulation patterns and the SST anomalies in the key oceanic regions experienced significant interdecadal transition to favor the occurrence of HTEs. In particular, the Atlantic multidecadal oscillation (AMO) is significantly and positively correlated with the interdecadal variation of summer HTEs on the TP. The zonal teleconnection wave train triggered by AMO forms a stronger-than-normal SAH and strengthened midlevel westerly airflow over the TP, conducive to the increase of summer HTEs on the TP.

A Thermal Regime and a Water Circulation in a Very Deep Lake: Lake Tazawa, Japan

A thermal system in the very deep Lake Tazawa (maximum depth, 423 m) was investigated by estimating the heat budget. In the heat budget estimate, the net heat input at the lake’s surface and the heat input by river inflow and groundwater inflow were considered. Then, the heat loss by snowfall onto the lake’s surface was taken into account. Meanwhile, the lake water temperature was monitored at 0.2 m to the bottom by mooring temperature loggers for more than two years. The heat storage change of the lake from the loggers was calibrated by frequent vertical measurements of water temperature at every 0.1 m pitch by a profiler with high accuracy (±0.01 °C). The heat storage change (W/m2) obtained by the temperature loggers reasonably accorded to that from the heat budget estimate. In the heat budget, the net heat input at lake surface dominated the heat storage change, but significant heat loss by river inflow sporadically occurred, caused by the relatively large discharge from a reservoir in the upper region. How deeply the vertical water circulation in the lake occurs in winter was judged according to the differences between water temperatures at 0.2 m depth and at the bottom and between vertical profiles of dissolved oxygen over winter. It is strongly suggested that the whole water circulation process does not occur every winter, and if it does, it is very weak. A consistent increase in the water temperature at the bottom is probably due to the conservation of geothermal heat by high frequency of incomplete vertical water circulation.

Combined Effects of Multiple Forcing Factors on Extreme Summer Multivariate Compound Heatwaves Over Western Europe

AbstractThe Multivariate compound heatwaves (MCHWs) present a significant risk to human health and ecological diversity, which attract widespread attention from researchers and society. The intensity and variability of summer MCHWs over Western Europe (WE) (MCHWs_WE) have substantially increased over the last two decades. The growing chance of such events is likely related to human activity‐induced climate change. However, the possible contributions from multiple atmospheric boundary forcing remain unclear. This study investigates the combined effects of North Atlantic sea surface temperature (SST), Tibetan Plateau (TP) snow cover (SC), and Arctic sea ice (SIC) on the variability of extreme summer MCHWs_WE. Observational analysis shows that an intensified anticyclonic system prevailing over WE, one of the centers of an atmospheric wave train dominating the North Atlantic‐Europe sector and persists from late spring to summer, is the essential system contributing to the extreme MCHWs_WE. Spring North Atlantic SST anomalies in the form of a dipole pattern persist from spring to summer and contribute to the summer extreme MCHWs_WE by exciting a downward propagating Rossby wave train pattern. Additionally, excessive late spring SC over the western TP and SIC over the Arctic, which are stimulated by the North Atlantic anomalous SST‐related wave train, can intensify the MCHWs_WE‐related anticyclonic system through vertical circulation and wave energy transport. The study further quantifies the relative contributions of the aforementioned factors. The findings of this study could potentially offer valuable insights for improving the prediction skill of summer extreme MCHWs_WE.

Evaluating airflow dynamics in common vertical circulation spaces of a multi-floor apartment building for mitigating airborne infection risks: A CFD modeling study

As more people increasingly inhabit indoor spaces, the importance of interior environment design has grown significantly. The focus of this research is to assess the air flow and air change per hour (ACH) within common service vertical circulation spaces in apartment buildings, emphasizing the potential role of these spaces in mitigating airborne infections. The intricate relationships between the design parameters of these spaces and variables related to air circulation are examined. To achieve this goal, the investigation employed a simulation-based approach, utilizing computational fluid dynamics (CFD) analysis to scrutinize the prevalent design of common vertical circulation spaces. The simulation outcomes unequivocally reveal that the design of these spaces has a direct impact on air circulation patterns, often influencing suboptimal conditions. Armed with these insights, this research advocates for a reevaluation of design considerations of common service vertical circulation in forthcoming housing projects. Furthermore, this research proposes innovative design solutions and strategies aimed at enhancing natural ventilation and overall air flow within common service vertical circulation spaces while evaluating their performance.

Enhancing predictions of remedial reagent transport via a vertical groundwater circulation well with high-resolution aquifer characterization

The vertical groundwater circulation well (GCW) is a commonly used technique in contaminated sites to remove secondary contaminants from low permeable zones. Early GCW studies often used simple subsurface hydraulic properties, such as anisotropic homogeneous aquifers or low conductivity lens/blocks, to mimic the complex subsurface heterogeneity. Although studies based on simplified representations of aquifer heterogeneity provide straightforward flow and transport information for engineering design of a GCW, they may over- or under-estimate contaminant fate and transport in the field. The objective of this study is to identify key heterogeneity factors that control the capture zone extension and to examine the extent to which the accuracy of estimated heterogeneity spatial distributions influences the prediction of remedial reagent transport. To achieve these objectives, we utilized Monte Carlo simulation to investigate the extension of the circulation zone in heterogeneous aquifers and to identify the key factors that contribute most to the variability of the circulation zone. Three commonly used geostatistical approaches (equivalent homogeneous, kriging, and highly parameterized methods) were employed to estimate the spatial distributions of key factors. The reliabilities of these estimated fields were evaluated through their remedial reagent transport predictability. The key factor analysis revealed that the mean porosity value, the variance of lnK, and the correlation length of lnK profoundly influence the lateral expansion of the capture zone. Neglecting the aquifer hydraulic conductivity heterogeneity underestimates the extension of the circulation zone and the spread of remedial reagent. Additionally, utilizing a highly parameterized approach to estimate the high-resolution K field can accurately reproduce the key remedial reagent distributions. The concentration arrival time and peak concentration are significantly improved compared to those predictions based on the equivalent homogeneous and kriged K fields.

The Role of Translation in Enacting Multiscalar Climate Action: Insights from European Christian Faith-Based Actors

Abstract The complex nature of climate change requires action at different scales and in different ways, but questions remain around how to produce climate action that is both multiscalar and joined up. Here we explore this question by adopting a relational approach to studying climate action by faith-based actors, who increasingly play an active role campaigning on climate action. Drawing on qualitative fieldwork with representatives of Christian churches in Sweden, Belgium, Scotland, and England, we identify two interrelated processes that explain how climate action “travels”: first, through horizontal circulation (between faith-based and non-faith-based spheres), and second, through vertical circulation (across individual, local, national, and international levels). However, such processes are not without friction. We demonstrate how processes of “translation” can ensure the integration of climate action into new contexts and result in producing new scalar relations but also exclusions. In doing so, we advance understandings of how multiscalar climate action is produced by nonstate actors.

The effectiveness of the flip technique in vertical ductal stenting.

In this study, the flip technique was compared with the classical method in terms of procedural success and procedure time during ductal stent implantation (DSI) via the carotid artery in patients whose pulmonary blood flow is dependent on the vertical type of ductus arteriosus (DA). Between January 2019 and June 2023, 40 patients (24 males, 16 females; mean age: 15.9±15.4 days; range, 1 to 68 days) with vertical ductus-dependent pulmonary circulation who underwent patent DA stent implantation via the carotid artery were included in the study. Patients were divided into two groups: those who underwent the flip technique (Group 1) and those who did not undergo the flip technique (Group 2). Data were retospectively compiled by reviewing patient files and catheter images. Demographic findings were similar in the groups. The distribution of the DA in terms of tortuosity index was also similar in the groups. The procedure was successful in 18 (90%) patients in Group 1 and 20 (100%) patients in Group 2. There was no procedure-related mortality in both groups. The frequency of procedure-related complications was similar. Procedure duration was 53.6±18.4 min in Group 1 and 41.5±9.1 min in Group 2; the difference was significantly lower in Group 2 (p=0.028). The shorter follow-up in Group 2 was attributed to the flip method starting to be used later in the clinic. During follow-up, stent dilatation was required in two patients in Group 1 and one patient in Group 2, and a second stent implantation was needed in one patient in Group 2. No significant difference was observed between the two groups in terms of reintervention. The success rate of DSI using the carotid artery access is high with both the classical and the flip method in patients with vertical DA. However, the use of the flip technique could be preferred in terms of operator habituation, ergonomic use of the catheter, guidewires, and shorter procedure time.

Моделирование гидродинамики, теплообмена и процесса усреднения гранулированных сред в пневматическом циркуляционном аппарате

The mathematical modeling of hydrodynamics, heat transfer, and averaging of a highly concentrated granular medium in the working area of a vertical pneumatic circulation apparatus is performed. The hydrodynamics of a dense layer of the granular medium is described by a non-Newtonian model with partial slip conditions on solid walls. Such a representation of the granular medium dynamics allows one to approve theoretical calculations with available experimental data for a steady flow in a flat channel. The numerical applicability of the partial slip condition for a non-Newtonian fluid is confirmed by the analytical dependences obtained by the authors for a steady flow in a circular tube and a flat channel, which are transformed into the known analytical formulas under no-slip conditions for a non-Newtonian medium. On the basis of the proposed model, the heat exchange intensity is analyzed when setting the constant heat flux density or the constant temperature on the annular shelves in the apparatus. The intensity of the granular mixture averaging in the bunker with the introduction of additional annular shelves is studied, and the efficiency of granular mixture mixing during rotation is considered. A method for analyzing the mixing of a granular medium in dynamics in each local area of the apparatus is proposed, which is based on the determination of the inhomogeneity coefficient. The results of this study can be used when developing powder technology devices for drying, mixing, dosing, and transport.

Inter-model spread in East Asian Summer Monsoon onset timing linked to the tropical Pacific and Indian oceans' mean state in CMIP6 models

A major challenge for Earth system climate models in simulating the onset of the East Asian summer monsoon (EASM) is the wide inter-model spread of outputs, which causes considerable uncertainty in projections. Based on 31 models of the Coupled Model Inter-comparison Project Phase 6 (CMIP6), this study investigated the inter-model spread of EASM onset biases and its physical connection with simulated atmospheric circulation and tropical Pacific mean state biases. The inter-model leading mode of EASM onset biases exhibits a meridional seesaw pattern, with inverse patterns for South China and the Yangtze–Yellow River basins. The leading mode is closely related to the simulated meridional displacement of the East Asian subtropical westerly jet (EASWJ) and the Northwest Pacific subtropical anticyclone (WNPAC). The northward EASWJ and WNPAC respectively cause ascending or descending motions with moisture convergence or divergence in the Yangtze–Yellow River basins of South China. The leading mode can be attributed to simulated biases in the zonal tripole sea surface temperature (SST) in the tropical Pacific Ocean. Statistical analysis and numerical experiments based on CAM5.0 indicate that the SST bias stimulates “double-loop” zonal vertical circulation in the tropical Pacific and Indian oceans, influencing convection precipitation in the tropical central–western Pacific. The altered convection then triggers a Pacific–Japan-like pattern anomaly, forming meridional seesaw circulation and precipitation anomalies in East Asia. Such meridional seesaw circulation modulates the meridional displacement of the EASWJ and WNPAC, thus affecting EASM onset. Our results provide potential indicators of inter-model uncertainty of EASM onset.

Terrain effects of the Tibetan Plateau on dust aerosol distribution over the Tarim Basin, China

Dust events are frequent in the Tarim Basin because of its underlying desert surface; moreover, meteorological conditions under the influence of the surrounding high terrains, especially the Tibetan Plateau, may also trigger dust events. However, the terrain effect of the Tibetan Plateau on the dust aerosol distribution over the Tarim Basin remains unclear. This study aimed to investigate the impact of the Tibetan Plateau terrain on the dust aerosol variations in three dust events over the Tarim Basin using the Weather Research and Forecasting Chemistry model. With decreasing altitude of the Tibetan Plateau, dust concentration (DC) decreased in the upper layers and increased in the low layers. The DC within the entire atmospheric layers increased by 8.52%, 24.03%, and 43.05% on average during three dust events at Tibetan Plateau altitudes of 3000 m, 2000 m, and 1000 m, respectively, thereby indicating that the DC in the lower layers increasingly dominated the entire atmospheric layers as the Tibetan Plateau altitude decreased. Low-elevation terrain enhanced the planetary boundary layer height, near-surface wind speed, and surface air temperature, but weakened atmospheric stratification stability, all of which are beneficial for strengthening dust emissions and vertical mixing in the lower layers of the Tarim Basin. Furthermore, a decrease in the Tibetan Plateau altitude led to forming a vertical circulation, with the south to rise and the north to sink over the Tarim Basin. Meteorological field and vertical circulation could adequately explain the changes in the distribution of dust aerosols over the Tarim Basin. Overall, this study enhances our understanding of the effect of the Tibetan Plateau terrain on changes in the dust aerosol in the Tarim Basin and surrounding central Asian regions.

Ritmo diario de la fotosintesis, respiración, pigmentos y bacterias heterotróficas (Embalse del Río III, C´órdoba, Argentina)

The results of the variante analysis obtaíned show us the relevando of the diel and day-to-day viriations of the photosyndiesís, ehlorophylba and phaeopigments, specially during summer months, The, short-term variation observed is expiain by displacement of water masses with diffferent amoumts of phytoplankton. In winter, vertical circulation occurs, and the variability of those parameters decrease, Heterotrophic bacteria deosity was the variable with greatest change throughout the observaron period. The establishment of nocturnal eirculaticm and diumal stratification were not observed, being these changes seasonal depend.

Analysis of methods for assimilating fire perimeters into a coupled fire-atmosphere model

Correctly initializing the fire within coupled fire-atmosphere models is critical for producing accurate forecasts of meteorology near the fire, as well as the fire growth, and plume evolution. Improperly initializing the fire in a coupled fire-atmosphere model can introduce forecast errors that can impact wind circulations surrounding the fire and updrafts along the fire front. A well-constructed fire initialization process must be integrated within coupled fire-atmosphere models to ensure that the atmospheric component of the model does not become numerically unstable due to excessive heat fluxes released during the ignition, and that realistic fire-induced atmospheric circulations are established at the model initialization time. The primary objective of this study is to establish an effective fire initialization method in a coupled fire-atmosphere model, based on the analysis of the impact of the initialization procedure on the model’s ability to resolve fire-atmosphere circulations and fire growth. Here, we test three different fire initialization approaches leveraging the FireFlux II experimental fire, which provides a comprehensive suite of observations of the pyroconvective column, local micrometeorology, and fire characteristics. The two most effective fire initialization methods identified using the FireFlux II case study are then tested on the 380,000-acre Creek Fire, which burned across the central Sierra Nevada mountains during the 2020 Western U.S. wildfire season. For this case study, simulated pyroconvection and fire progression are evaluated using plume top height observations from MISR and airborne fire perimeter data, to assess the effectiveness of different initialization methods in the context of establishing pyroconvection and resolving the fire growth. The analyses of both the experimental fire simulation and the wildfire simulation indicate that the spin-up initialization method based on historical fire progression that masks out inactive fire regions provides the best results in terms of resolving the fire-induced vertical circulation and fire progression.

Possible mechanism of the mid-high-latitude synoptic-scale disturbances impact on Meiyu precipitation anomalies

Precipitation during the Meiyu period in East Asia demonstrated a tendency towards increased frequency of rainstorms and escalating disaster-causing potential, exhibiting significant inter-annual variations in recent years. The relationship between Meiyu precipitation (MP) anomalies, related circulation anomalies and mid-high-latitude synoptic-scale disturbances was investigated by observation and reanalysis data from 1979 to 2018 and the regional climate model (RegCM4.6). Based on the observation results, the physical mechanism of disturbance affecting MP was proposed and verified by numerical simulation experiments. The results show that, during the Meiyu periods, the variation of synoptic-scale disturbances over Lake Baikal correlates negatively with MP anomalies, where the abnormal zonal winds and the disturbance anomalies show a strong spatially consistent coherence in the upper troposphere. Compared to drought years, the weaker conversion of disturbance energy to mean flow and the convergence of anomalous Eliassen-Palm (E-P) flux induce mid-high-latitude anomalous easterly flow during the Meiyu period in flood years. The occurrence of such conditions leads to the southward shift of the East-Asian subtropical jet (STJ). Then, anomalous stronger ascending flow over the Meiyu region finally results in stronger MP. In addition, warm temperature anomaly and warm advection anomaly exist at lower latitudes in flood years, while mid-high latitudes exhibit cold temperature anomaly and cold advection anomaly, which is conducive to the southward shift of the East-Asian STJ and the increase of MP. Based on the above diagnosis, sensitivity experiments were conducted using RegCM4.6. When the mid-high-latitude synoptic-scale disturbances are amplified during flood years or flood decades, the MP correspondingly decreases, and vice versa. The simulation results also show that the convergence (divergence) of mid-high-latitude E-P flux results in a weakening (strengthening) of the westerly flow, which leads to the southward (northward) shift of the East-Asian STJ. The alteration of the STJ's position in East Asia alters the position of the ascending branch of the vertical meridional circulation corresponding to the jet stream, subsequently impacting MP. Therefore, both diagnosis and numerical simulation reveal the possible mechanism of synoptic disturbances in mid-high latitude affecting MP in Yangtze River Basin, thus enriching the study of MP anomaly mechanism during Meiyu period.

Direct observations of melting, freezing, and ocean circulation in an ice shelf basal crevasse.

Ocean conditions near the grounding zones of Antarctica's ice shelves play a key role in controlling the outflow and mass balance of the ice sheet. However, ocean observations in these regions are largely absent. Here, we present a detailed spatial survey collected with an underwater vehicle in a basal crevasse located in the ocean cavity at the Ross Ice Shelf grounding zone. The observations depict fine-scale variability in ocean forcing that drives asymmetric melting along the lower crevasse sidewalls and freezing in the upper reaches of the crevasse. Freshwater release from melting at depth and salt rejection from freezing above drives an overturning circulation. This vertical circulation pattern overlays a dominant throughflow jet, which funnels water parallel to the coastline, orthogonal to the direction of tidal currents. Importantly, these data reveal that basal crevasses influence ocean circulation and mixing at ice shelf grounding zones to an extent previously unknown.