Shallow Flow Research Articles

Flow Evolution and Vertical Accelerations in Wave‐Swash Interactions

AbstractWe report on a laboratory study of wave‐swash interactions, which occur in the very nearshore environment of a beach when the shallow swash flow of a breaking wave interacts with a subsequent wave. Wave‐swash interactions have been observed in the field, hypothesized to be important for nearshore transport processes, and categorized into different qualitative types, but quantitative descriptions of their dynamics have remained elusive. Using consecutive solitary waves with different wave heights and separations, we generate a wide variety of wave‐swash interactions with large flow velocities and vertical accelerations. We find that wave‐swash interactions can be quantitatively characterized in terms of two dimensionless parameters. The first of them corresponds to the wave height ratio for consecutive waves, and the second is a dimensionless measure of the time separation between consecutive wave crests. Using measurements of bed pressure and free‐surface displacement, we estimate the total vertical accelerations and focus on the peak upward‐directed acceleration. We find that wave‐swash interactions can generate vertical accelerations that can easily exceed gravity, despite occurring in very shallow water depths. The large vertical accelerations are upward‐directed and are quickly followed by onshore‐directed horizontal velocities. Together, our findings suggest that wave‐swash interactions are capable of inducing large material suspension events of sediment or solutes in sediment pores, and transporting them onshore. While the data are from a single location making it difficult to generalize the findings across the swash zone, the results clearly demonstrate the importance of large vertical accelerations in wave‐swash interactions.

Molten pool behaviors and printability of tungsten anti-scattering grids with extremely thin wall thickness fabricated via laser powder bed fusion

It is challenging for laser powder bed fusion (LPBF) technique to fabricate metal parts with a wall thickness below 100 μm. This work investigated the critical conditions for achieving extremely thin wall thickness in tungsten grids fabricated via LPBF. Specifically, the impact of low energy density on the printability of tungsten single tracks and grids via LPBF was comprehensively examined. A computational fluid dynamics approach was employed to develop a thermal fluid flow model for single tracks with multilayers in LPBF. The findings demonstrate that at low energy densities, single tracks exhibit four different morphologies, i.e., balling, discontinuity and winding, discontinuity but straightness, as well as continuity and straightness. The simulation model effectively elucidates the continuity of single tracks and provides insights into the governing mechanism of molten pool defects. Due to high thermal diffusion properties of tungsten, the continuity of its track relies on the connection of neighboring molten pools and is sensitive to scanning speed. The tungsten molten pools with low energy density can be categorized into shallow flows affected by surface morphology and deep flows influenced by internal voids of the powder bed. After multi-layer stacking, the track fluctuations and defects in single tracks accumulated into greater surface roughness and deteriorate thin-walled morphology. The critical conditions required for printing extremely thin walls were achieved, ensuring minimal merging of tracks between two layers by maintaining the energy density of 57J/mm3. Based on these findings, an ultra-thin-walled anti-scattering tungsten grid with a wall thickness of 86 μm and a wall roughness below 3.3 μm (Ra) was fabricated by LPBF. This work provides valuable theoretical insights and presents a viable methodology for determining the minimum energy density threshold and wall thickness essential for LPBF processing of thin-walled components.

Effects of initial soil moisture on rill erodibility and critical shear stress factors in the WEPP model across diverse soil types

Rill erosion, a significant issue in agricultural regions, is intricately linked to initial soil moisture conditions, affecting the development of concentrated flow erosion processes. However, understanding its dynamics amidst varying soil moisture conditions remain challenging. This study aimed to assess the impact of different soil moisture levels on rill erodibility parameters in the Water Erosion Prediction Project (WEPP) model and to evaluate soil cohesion across a spectrum of soils. Through laboratory experiments employing a small V-shaped rill channel, we investigated rill erodibility (Kr) and critical hydraulic shear stress (τcr), under three soil moisture scenarios: initially dry, saturated, and drainage, with incremental surface inflow rates. Additionally, we examined the efficiency of soil cohesion obtained from an Automated Soil Cohesion Measurement Apparatus in predicting Kr and τcr across various soil textures. Our analysis encompassed twenty soils representing nine texture classes, revealing significant correlations between basic soil properties, cohesion parameters, and WEPP model rill erodibility. Notably, initial soil moisture conditions exerted substantial influence on erodibility potentials. Soils with higher silt contents demonstrated better fits in terms of Nash-Sutcliffe model efficiency, particularly under initially dry and saturated conditions. However, predictions for initially drained soils yielded poor fits, emphasizing the intricate interplay between soil properties and hydrological conditions. In conclusion, our findings emphasize the critical role of topsoil water dynamics in rill erodibility. We propose that soil cohesion serves as a valuable predictor, complementing friction forces within the soil and enhancing simulations of rill erodibility under shallow flow conditions in rills, particularly in next-generation process-based modeling approaches.

Combined dam-break modes between upper and lower reservoirs of pumped storage hydropower stations and associated flood risk assessment

ABSTRACT With the increasing construction of pumped storage hydropower projects in China, dam-break risk has become a matter of great concern. Typical pumped storage hydropower stations have relatively small storage capacity but are vulnerable to complicated combinations of dam breaks between their upper and lower reservoirs. This paper provides basic principles for determining different dam-break classes that could initiate at a pumped storage hydropower station and summarizes these in terms of risk source. After idealizing the breach development process, a simple dam-break model and a planar two-dimensional depth-averaged shallow flow model are used to calculate the discharge hydrograph of the dam-break flood and simulate the temporal and spatial characteristics of downstream inundation. Taking a montane rockfill-pumped storage project as an example, 12 dam-break schemes are used to examine different types of combined flow patterns driven by upper and lower dam breaks with modes that are gradual and/or instantaneous. It is found that predicted dam-break discharge hydrographs and downstream inundation indexes under adverse schemes fit common features of dam-break floods in mountain rivers. Downstream disaster losses are evaluated and flood evacuation routes are recommended. The findings of this study should be useful in ensuring the safe management of pumped storage hydropower stations.

Forest catchment structure mediates shallow subsurface flow and soil base cation fluxes

Hydrologic behavior and soil properties across forested landscapes with complex topography exhibit high variability. The interaction of groundwater with spatially distinct soils produces and transports solutes across catchments, however, the spatiotemporal relationships between groundwater dynamics and soil solute fluxes are difficult to directly evaluate. While whole-catchment export of solutes by shallow subsurface flow represents an integration of soil environments and conditions but many studies compartmentalize soil solute fluxes as hillslope vs. riparian, deep vs. shallow, or as individual soil horizon contributions. This potentially obscures and underestimates the hillslope variation and magnitude of solute fluxes and soil development across the landscape. This study determined the spatial variation and of shallow soil base cation fluxes associated with weathering reactions (Ca, Mg, and Na), soil elemental depletion, and soil saturation dynamics in upland soils within a small, forested watershed at the Hubbard Brook Experimental Forest, NH. Base cation fluxes were calculated using a combination of ion-exchange resins placed in shallow groundwater wells (0.3 – 1 m depth) located across hillslope transects (ridges to lower backslopes) and measurements of groundwater levels. Groundwater levels were also used to create metrics of annual soil saturation. Base cation fluxes were positively correlated with soil saturation frequency and were greatest in soil profiles where primary minerals were most depleted of base cations (i.e., highly weathered). Spatial differences in soil saturation across the catchment were strongly related to topographic properties of the upslope drainage area and are interpreted to result from spatial variations in transient groundwater dynamics. Results from this work suggest that the structure of a catchment defines the spatial architecture of base cation fluxes, likely reflecting the mediation of subsurface stormflow dynamics on soil development. Furthermore, this work highlights the importance of further compartmentalizing solute fluxes along hillslopes, where certain areas may disproportionately contribute solutes to the whole catchment. Refining catchment controls on base cation generation and transport could be an important tool for opening the black box of catchment elemental cycling.

Asymmetric vertical transport in weakly forced shallow flows

In this paper, we report on an investigation of the vertical transport of tracer particles released within a shallow, continuously-forced flow by means of numerical simulations. The investigation is motivated by the shallow flows encountered in many environmental situations and inspired by the laboratory experiments conducted in electromagnetically forced shallow fluid layers. The flow is confined to a thin fluid layer by stress-free top and no-slip bottom walls. The dynamics and the transport properties of the shallow flow are investigated under various flow conditions characterized by a Reynolds number related to the forcing, ReF, and the aspect ratio of vertical and horizontal length scales δ. The forcing generates an array of vortices that becomes unsteady when ReFδ2≳10. These vortices are accompanied by upwellings in their cores which are surrounded by narrower, stronger downwellings. Hence, upwellings occur where the horizontal flow is vorticity-dominated, while downwellings where it is strain-dominated. The magnitude of the asymmetry in strength and size of the vertical flows and their correlation with horizontal structures depends on the flow conditions and significantly influences the vertical spreading of particles within the fluid volume. Under conditions leading to a large asymmetry, particles within updrafts are transported slowly upwards, while particles within downdrafts rapidly move downwards. In addition, particles are trapped for longer within the updrafts than downdrafts because of their correlation with vorticity-dominated regions. However, when the flow becomes fully three-dimensional and highly unsteady for large ReFδ2 values, this transport asymmetry subsides because the updrafts and downdrafts exhibit similar strength and size in such flow conditions. Consequently, similar amounts of particles are transported upwards and downwards at similar rates.

Flow and coherent structures generated by a circular array of rigid, emerged cylinders in a shallow channel

The study investigates the flow structure, dynamics of the large-scale coherent structures, drag forces and sediment entrainment mechanisms generated by a circular array of diameter D containing rigid emerged circular cylinders of diameter d placed in a smooth-bed channel of depth h under strong shallow flow conditions (D/h = 20, d/D = 0.0125 and 0.025). Eddy resolving simulations are conducted with different values of the solid volume fraction 0.025 ≤ SVF ≤ 0.1 and non-dimensional frontal area per unit volume (2.56 ≤ aD ≤ 10.2, where for the present configuration, a = SVF(1/d)4/ ${\rm \pi}$ ) and a fixed channel Reynolds number (Reh = 10 000). The flow conditions are such that a vortex street (VS)-type of shallow wake is expected to form for a solid cylinder of diameter D. Findings are compared with previous results obtained for cases with moderately shallow conditions 2.5 ≤ D/h ≤ 3.5 and with the limiting case of flow past a solid cylinder with D/h = 20. For moderately shallow conditions, the core of the main horseshoe vortex (HV) forming around the array occupies a small fraction of the water column and its coherence is the largest in front of the array. By contrast, for very shallow conditions, multiple HVs form around the array and their cores occupy a large fraction of the water column. Moreover, the coherence of most of these HVs peaks close to the sides of the array. Only for relatively large aD values, the main HV extends over the whole upstream face of the array, similar to the limiting case of a solid cylinder. For sufficiently high aD, a secondary instability is present inside the near wake that leads to the formation of parallel horizontal vortices in the vicinity of the wake roller vortices. The changes in the wake structure with decreasing SVF and aD are qualitatively similar to those observed for cases with moderately shallow flow conditions, with the antisymmetric wake shedding mode being suppressed for aD ≤ 2.5. However, the Strouhal number associated with the shedding of wake rollers, which is still close to 0.2 for a solid cylinder with D/h = 20, can be as high as 0.4 for aD = 2.5. The paper also discusses how the steady wake and total wake lengths and the strength of the bleeding flow vary with the SVF. Simulation results show that the capacity of the flow to entrain sediment inside and around the array peaks for SVF = 0.05 and aD = 5.2, with sediment entrainment monotonically increasing with the SVF outside the array and monotonically decreasing inside the array. Despite the differences in the flow structure next to and inside the array, the variation of the mean, time-averaged streamwise drag coefficient of the solid cylinders ${\bar{C}_d}$ with aD is close to that observed for arrays with moderately shallow flow conditions. The combined drag coefficient for the array decreases with increasing flow shallowness, with the decay being stronger for relatively large values of aD.

Investigating drug-gut microbiota interactions: reductive and hydrolytic metabolism of oral glucocorticoids by in vitro artificial gut microbiota

Elucidation of the role of gut microbiota in the metabolism of orally administered drugs may improve therapeutic effectiveness and contribute to the development of personalized medicine. In this study, ten different artificial gut microbiota (AGM), obtained by culturing fecal samples in a continuous fermentation system, were challenged for their metabolizing capacity on a panel of six glucocorticoids selected from either prodrugs or drugs. Data from metabolic stability assays highlighted that, while the hydrolysis-mediated conversion of prodrugs to drugs represented only a minor metabolic pathway, significant differences in the stability of parent compounds and in their conversion rates to multiple reductive metabolites were obtained for the selected drugs. In the latter case, a taxonomic composition-dependent ability to convert parent drugs to metabolites was observed. Indeed, the artificial microbial communities dominated by the genus Bacteroides showed the maximal conversion of parent glucocorticoids to several metabolites. Furthermore, the effect of drugs on AGM was also evaluated through shallow shotgun sequencing and flow cytometry-based total bacterial cell count highlighting that these drugs can affect both the taxonomic composition and growth performances of the human gut microbiota.

Characterization of wind effect on environmental dispersion for a shallow wetland flow

The present work focuses on the dispersion of pollutants under the influence of wind and ecological degradation in a fully developed steady flow for a shallow wetland. The dispersion coefficient is determined by Aris’ method of moments and Meis’ multi-scale analysis. Based on the comparison study, the concentration profiles obtained using multi-scale analysis converge with Aris’ method of moments, indicating that both analytical approaches provide reliable and consistent descriptions of pollutant dispersion in the system. In first-order degradation reaction rates, high degradation rates lead to lower mean concentrations and potentially more pronounced concentration gradients, while low degradation rates result in higher mean concentrations. The critical length of the region influenced by the contaminated cloud is computed analytically. It shows that for the common contaminant constituent lead (Pb), initially, it increases gradually to reach the maximum; after that as time increases, it decreases to zero under wind conditions.

A Numerical Approach to Analyzing Shallow Flows over Rough Surfaces

The hydraulic characteristics (such as velocity profiles, near-bed velocity profile, bed shear stress, and resistance coefficients) of shallow flows over rough surfaces were investigated using numerical simulations. A novel method is presented to simulate shallow flows over rough surfaces in a two-dimensional (2D) numerical domain, where the physical numerical domain represents bed topography. Results reveal that the model can accurately predict spatially averaged velocity profiles, turbulence characteristics, shear stresses, and uniform flow depths. The analysis identified two distinct flow regions based on mean and turbulent flow profiles. Results show that the turbulent shear stress profiles provide a more accurate estimation of the bed shear stresses. Resistance coefficients (friction factor or Manning’s roughness coefficient) vary with Froude number and submergence ratio (depth divided by roughness height).

A vertically non-uniform temperature approach for the friction term computation in depth-averaged viscoplastic lava flows

Recently, depth-averaged shallow flow models have been adapted to modelling liquefied lava flows, generally characterized by a marked temperature-dependent non-Newtonian rheology. Modelling these complex flows requires to include the effects of the depth-averaged temperature gradients in the governing equations. The most significant term to correctly predict the lava mobility is the flow resistance term, which is widely estimated using the linear viscoplastic Bingham model. This non-Newtonian model allows to relate the bed shear stress to the depth-averaged lava flow features by means of a cubic equation with analytical solution when assuming a uniform temperature distribution along the vertical profile. Nevertheless, the lava temperature is non-uniform along the vertical due to the heat transfer at the bottom and the free surface, and hence the classical cubic Bingham model is not valid anymore. In this work, a depth-averaged shallow flow model is adapted for realistic lava flows considering influence of the non-uniform vertical temperature profile in the non-Newtonian resistance. This requires to modify the rheological viscoplastic models for ensuring the coupling between flow dynamics and temperature evolution. Three non-uniform temperature vertical distributions are considered: linear, piece-wise and diffusion profiles. Synthetic tests are used to show the influence of the temperature vertical profile on the numerical results. Furthermore, laboratory experimental data are used to validate this novel viscoplastic resistance formulation and to show that the calibration of its parameters is possible.

Pairwise balancing of forces in traveling granular waves

A survey is given of the forces at work inside traveling roll waves and monoclinal flood waves in dry granular matter. By numerically solving the generalized Saint-Venant equations for shallow granular flow, we find a hierarchy of pairwise near-balancing forces, which together are responsible for sustaining the shape of the nonlinear waves in question. The leading force pair is gravity vs. friction, followed by inertia vs. pressure, while the minor imbalance left by the aforementioned pairs is settled by a (small though essential) diffusive force.

A thermal infrared imaging observation system for the measurement of overland flow velocities under controlled laboratory conditions

Flow velocity is an important physical parameter in characterizing the hydraulics of water flow. The accurate measurement of overland flow velocities has great significance for understanding and modeling sediment transport and soil erosion. In this study, a Thermal Infrared Imaging Observation System (TIIOS) based on thermal infrared imaging techniques and computer vision recognition technology was established to measure overland flow velocities under controlled laboratory conditions. TIIOS has three subsystems including thermal tracer control, image acquisition and transmission, and image storage and processing. It can be used to dynamically monitor changes in shallow flow velocity by means of automatic control of thermal tracer, instantaneous image acquisition, image correction, noise removal and centroid determination. The observation precision was high with a standard deviation of 0.004 m·s−1 for flow velocity, a temporal resolution of 1/9th s, and a spatial resolution of 2 mm. The new system achieved higher accuracy compared to the traditional dye tracing and salt tracing techniques in observing the dynamic transport process of thermal tracer movement. The relative errors of the centroid velocity measured by the TIIOS ranged from −9.83 % to 6.40 %; whereas the relative errors of centroid velocity measured by salt tracer ranged from −21.36 % to 17.22 %. Measurements by the established TIIOS under different hydraulic conditions demonstrate that the relative errors of the centroid velocity are all smaller than those of the leading-edge velocity. This observational system provided a reliable way to measure shallow flow velocity for better understanding the mechanisms of water erosion processes and showed its potential to be used in field experiments under natural conditions.

Factors influencing seasonal chemistry patterns in Virginia mountain streams

The relative influence of seasonal patterns in hydrological flow and seasonal differences in biological and geochemical activity on stream chemistry patterns is difficult to discern because they covary; temperate systems are characterized by lower mean flow in the summer (i.e. corresponding to deeper flow paths, elevated temperature, and biological activity), and higher mean flow in the winter (i.e. corresponding to shallower flow paths, depressed temperature, and biological dormancy). Using 2018 data, when seasonal stream flow conditions reversed, and two prior conventional water years, the relationship between monthly acid-relevant analyte concentrations and streamflow were compared within and between winter and summer to provide insight into controls on characteristic seasonal chemistry patterns at two mid-Appalachian sites with distinct geology (weatherable mafic and weather resistant siliciclastic). Acid neutralizing capacity (ANC) increased (1) with lower flow, in both seasons and (2) in summer, for all flow conditions. The compounding impacts resulted in a doubling of concentration from typical winter with high flow to summer with low flow at both sites. Base cation patterns tracked ANC at the mafic site, resulting in an ~ 60% increase of from winter with high flow to summer with low flow; distinctions between summer and winter contributed more to the seasonal pattern (72%) than changes in flow. Sulfate increased at the mafic site (1) with higher flow, in both seasons and (2) in winter, for all flow conditions, resulting in an ~ 50% increase from summer with low flow to winter with high flow; distinctions between winter and summer conditions and flow contributed similarly (40–60%) to the typical seasonal chemical pattern. The biogeochemical mechanism driving differences in stream chemistry between summer and winter for the same flow conditions is likely increased rates of natural acidification from elevated soil respiration in summer, resulting in greater bedrock weathering and sulfate adsorption. Findings highlight the significance and consistency of growing vs dormant season variations in temperature and biological activity in driving intra-annual patterns of stream solutes. This data set informs parameterization of hydro-biogeochemical models of stream chemistry in a changing climate at a biologically relevant, seasonal, timescale.

Sensitivity of Coastal Squall-Line Evolution to Numerical Sea-Breeze Initialization Method

Abstract This study employs 3D idealized numerical experiments to investigate the physical processes associated with coastal convection initiation (CI) as an offshore-moving squall line traverses a mountainous coastal region. A squall line can propagate discretely as convection initiates over the lee slope downstream of the primary storm as the cold pool collides with a sea breeze. Intensity of the initiating convection, thus the downstream squall line, is sensitive to the sea-breeze numerical initialization method, since it influences sea-breeze and cold pool characteristics, instability and vertical wind shear in the sea-breeze environment, and ultimately the vertical acceleration of air parcels during CI. Here, sea breezes are generated through four commonly used numerical methods: a cold-block marine atmospheric boundary layer (MABL), a prescribed surface sensible heat flux function, a prescribed surface sensible plus latent heat flux functions, and radiation plus surface-layer parameterization schemes. For MABL-initialized sea breezes, shallow weak sea-breeze flow in a relatively low instability environment results in weak CI. For the remainder, deeper stronger sea-breeze flow in an environment of enhanced instability supports more robust CI. In a subset of experiments, however, the vertical trajectory of air parcels is suppressed leading to weaker convection. Downward acceleration forms due to the horizontal rotation of the sea-breeze flow. Accurate simulations of coastal convective storms rely on an accurate representation of sea breezes. For idealized experiments such as the present simulations, a combination of initialization methods likely produces a more realistic representation of sea breeze and the associated physical processes.

NUMERICAL COMPUTATION OF ONE- AND TWO-LAYER SHALLOW FLOW MODEL

In this research, we study a proficient computational model designed to simulate shallow flows involving one- and two-layer shallow flow. This numerical model is built upon the Saint Venant equations, which are widely used in hydraulics to depict the behavior of shallow water flow. The numerical scheme used here is constructed based on the conventional leapfrog technique implemented on a staggered grid framework, referred to as MCS. The primary objective of this research is to re-examine and implement the MCS in accurately modelling the free surface and interface waves produced by different flows passing through irregular geometries. Unlike the conventional MCS, we modify the momentum conservation principle to be more general, accommodating a non-negative wet cross-sectional area due to irregular geometry. We successfully conduct numerous numerical simulations by examining various scenarios involving one-layer and two-layer flow through irregularly shaped channels or structures. Our results show that the correct surface wave profile generated by a one-dimensional dam break through the triangular obstacle in the open channel can be simulated very well. Comparison with the existing experimental data seems promising although some disparities are being found due to dispersive phenomena with RMSE less than 5%. Furthermore, our scheme is successfully extended to simulate the steady sub-maximal exchange in two-layer flows using specific boundary conditions. The alignment between the submaximal numerical results with exchange flow theory is noticeable in the interface profile, characteristics of flow conditions and the flux values achieved when the steady situation occurs. These satisfying results indicate that our proposed numerical model can be used for practical needs involving various flow situations both one and two-layer cases

Extension of Iber for Simulating Non–Newtonian Shallow Flows: Mine-Tailings Spill Propagation Modelling

Extension of Iber for Simulating Non–Newtonian Shallow Flows: Mine-Tailings Spill Propagation Modelling

Shallow groundwater quality around the area Kaligending final processing site in Kebumen Regency, Central Java Province

Abstract The location of the Kaligending final Processing site is in Kraminan, Kaligending Village, Karangsambung District, Kebumen Regency which is the place for final waste processing. The Kaligending final processing site which is located in the hills can have an environmental impact on the area located below it. One of the impacts is the condition of groundwater in the area. The purpose of this study is to determine the condition and quality of shallow groundwater in the area. To find out groundwater conditions especially position and the pattern of shallow groundwater flow in the area is measured in the shallow ground water level which is then made a map of shallow groundwater and shallow groundwater flow direction patterns, while groundwater quality is measured by electrical conductivity and total dissolve solid (TDS) shallow groundwater in several wells. The results of the map pattern of shallow groundwater flow directions in the area come from the east and northeast, groundwater quality based on electrical conductivity is still suitable for use. The quality of shallow groundwater in residents’ wells in the Kraminan area is based on total dissolved solids, there are 4 wells that exceed the upper limit of drinking water quality standards (wells 3, 4, 5 and 6) which are located close to the Krembeng River

Identification of Shallow Groundwater Facies and Flow Patterns in Batang Regency, Central Java, Indonesia

Abstract Population growth as a result of a subsequent increase in the economic center and industrial complex construction has also proven to influence the shallow groundwater occurrence in Batang Regency, Central Java, Indonesia. The region per se, had a minimum amount of observation and literature, especially regarding the issue namely groundwater flow pattern and facies distribution. This research discussed hydrogeological assessment through systematic mapping to investigate shallow groundwater occurrence, including 90 observation & measurement points consisting of 89 dug well and one water spring. Based on purposive random sampling with upstream-downstream consideration, 73 of 90 samples were analyzed in the laboratory to determine groundwater hydrochemistry. The results indicated that the shallow groundwater pattern in Batang Regency generally flows from south to north with a dominant southwest-northeast pattern. Based on the trilinear piper diagram, shallow groundwater facies in the study area are characterized by calcium bicarbonate, alkaline chloride, alkaline bicarbonate, and mixed types. The distribution of calcium bicarbonate facies is widely spread in the southern part of the study area. In contrast, alkaline bicarbonate is mainly found between the coastline and hilly in the south. On the other hand, alkaline chloride is distributed evenly along the coastal area. Intermixing of different groundwater facies is expected due to its positive correlation between TDI and major ions plot in the composition diagram.

Mechanical and Thermal Forcing for Upslope Flows and Cumulus Convection over the Sierras de Córdoba

Abstract The upslope flow processes affecting the vertical extent of orographic cumulus convection are examined using observations from the Cloud, Aerosol, and Complex Terrain Interactions (CACTI) Field Campaign. Specifically, clear-air returns from the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) C-band radar (CSAPR2) are used to characterize the structure and variability of the ridge-normal (i.e., up/downslope) flow components, which transport mass to the crest of Argentina’s Sierras de Córdoba and contribute to convective initiation. Data are compiled for the entire CACTI period (Oct-Apr), including days with clear skies, shallow cumuli, cumulus congestus, and deep convection. To examine shared variability amongst >70,000 radar scans we use (a) a principal component analysis (PCA) to isolate modes of variability in the upslope flow, and (b) composite analysis based on convective outcomes, determined from GOES16 satellite observations. These data are contextualized with observed surface sensible heat fluxes, thermodynamic profiles, and synoptic-scale analysis. Results indicate distinct thermally and mechanically forced upslope flow modes, modulated by diurnal heating and synoptic-scale variations, respectively. In some instances, there is a superposition of thermal and mechanical forcing, yielding either deeper or shallower upslope flow. The composite analyses based on satellite data show that successively deeper convective outcomes are associated with successively deeper upslope flow layers that more readily transport mass to the ridge crest in conjunction with lower lifting condensation levels, facilitating convective initiation. These results help to isolate the forcing mechanisms for orographic convection, and thus provide a foundation for parameterizing orographic convective processes in coarse resolution models.