Variability Of Physical Processes Research Articles

Quantifying the statistical dependence of mid-latitude heatwave intensity and likelihood on prevalent physical drivers and climate change

Abstract. Recent heatwaves such as the 2021 Pacific Northwest heatwave have shattered temperature records across the globe. The likelihood of experiencing extreme temperature events today is already strongly increased by anthropogenic climate change, but it remains challenging to determine to what degree prevalent atmospheric and land surface conditions aggravated the intensity of a specific heatwave event. Quantifying the respective contributions is therefore paramount for process understanding but also for attribution and future projection statements conditional on the state of atmospheric circulation or land surface conditions. We here propose and evaluate a statistical framework based on extreme value theory, which enables us to learn the respective statistical relationship between extreme temperature and process variables in initial-condition large ensemble climate model simulations. Elements of statistical learning theory are implemented in order to integrate the effect of the governing regional circulation pattern. The learned statistical models can be applied to reanalysis data to quantify the relevance of physical process variables in observed heatwave events. The method also allows us to make conditional attribution statements and answer “what if” questions. For instance, how much would a heatwave intensify given the same dynamic conditions but at a different warming level? How much additional warming is needed for the same heatwave intensity to occur under average circulation conditions? Changes in the exceedance probability under varying large- and regional-scale conditions can also be assessed. We show that each additional degree of global warming increases the 7 d maximum temperature for the Pacific Northwest area by almost 2 ∘C, and likewise, we quantify the direct effect of anti-cyclonic conditions on heatwave intensity. Based on this, we find that the combined global warming and circulation effect of at least 2.9 ∘C accounts for 60 %–80 % of the 2021 excess event intensity relative to average pre-industrial heatwave conditions.

Coastal vulnerability assessment of India's Purba Medinipur-Balasore coastal stretch: A comparative study using empirical models

The 90.20 km coastal stretch extending from India's Subarnarekha estuary (Balasore District, Odisha) to the mouth of the Haldi River (Purba Medinipur, West Bengal) was evaluated. The evaluation was for vulnerability to climate extremes and variabilities (e.g. tropical cyclones, storm surges, and eustatic sea-level rise) resulting in coastal erosion, inundation, salinization and increased biophysical and socio-economic impacts. Coastal vulnerability mapping with respect to coastal hazards was applied to identify and implement risk reduction policies. In order to understand the spatial distribution of physical vulnerability along this coastal stretch, the Coastal Vulnerability Index (CVI) using Gornitz's CVI model and the Analytical Hierarchy Process (AHP) method were applied. These models were run in ArcGIS ver. 10.5 using six geological parameters viz., elevation, slope, bathymetry, coastal geomorphology, shoreline change, and coastal land use and four physical process variables viz. Mean sea level (MSL), mean tidal range, significant wave height, and storm surge height. Both of the models produced very good results. Based on Gornitz's CVI model, it was found that 13.56% of the coastline is highly vulnerable to these hazards, while the AHP model indicated 11.29% of the coast was at high vulnerability. When both models were simulated the same probable inundation extent of two different storm surge scenarios of wave height, viz. ≤ 3 m and≤5 m, the areas estimated to be affected by the surge were 255.22 and 779.59 sq. km, respectively. The coastal blocks of Nandigram-I, Contai-I, Deshopran, and Bhograi were identified as highly vulnerable due to landward erosion and inundation. The study inferred that the combined effect of cyclonic activities and storm surge along with high tide made the coast highly susceptible. This study could help coastal planners, decision-makers, and administrators to prepare a risk management plan for long-term coastal conservation and management.

Physics-based detection of cyber-attacks in manufacturing systems: A machining case study

The overlap between operational technologies and information technology has resulted in profound improvements in the manufacturing ecosystem, but it increases the risk of a non-conventional class of cyber-attacks capable of inflicting physical damages on manufacturing processes and/or products. If successful in penetrating traditional cyber-only defenses, such attacks may not be detected timely, leading to financial losses, and potentially endangering human safety. However, malicious alterations of products and/or processes intended by these attacks can be manifested as anomalous changes in process dynamics. Hence, monitoring physical process variables such as vibration and power consumption (known as side-channels in cybersecurity literature) can provide a physical-domain defense layer to detect such attacks. Focusing on product-oriented attacks, we propose a method to connect the product design, process design, and in situ monitoring to identify the physical manifestations of these attacks. The proposed approach can verify the geometric integrity of a machined part by observing cutting power signals during machining. We utilize the process and product knowledge to segment the power signal into the cutting cycles corresponding to specific geometrical features and extract process-related information accordingly. This work primarily focuses on extracting machining times for individual geometric features in parts. Next, we use the extracted information to construct quality control charts to use in detecting geometric integrity deviations of machined parts. Finally, we demonstrate our proposed method using a case study of cyber-physical attacks on machining processes aiming to tamper with different product's dimensional and geometrical features.

Better interactive astronomy lectures using the Laser-Assisted Student Engagement Routine

In support of teaching astronomy as a human enterprise, modern astronomy teaching often emphasizes visuals—whether heavenly telescope images of the cosmos or graphs depicting the relationships between physical process variables. Well-known suggestions of how to have students individually interact with images and graphics pepper earlier AstroNotes columns: teaching strategies that challenge students to provide missing labels to diagrams or to create their own graphical representations using small, individual whiteboards. We suggest here a method of intellectually engaging large groups of students with a large image or graphic that is projected in the front of the room.

Synthesis of interannual variability in spatial demographic processes supports the strong influence of cold-pool extent on eastern Bering Sea walleye pollock (Gadus chalcogrammus)

Attributing variability in fish demographic processes to environmental conditions is helpful when assessing population status and forecasting changes in ecosystem function. Empirical orthogonal function (EOF) analysis has long been used to explore variability in physical processes, but has been only recently employed to study variability in biological processes. EOF analysis estimates dominant modes of variability (indices) and produces maps representing the spatial response for the dependent variable to each of these indices. In the eastern Bering Sea (EBS), research has linked demographic processes to the spatial extent of bottom temperatures less than or equal to 2 °C (the “cold-pool extent” or “CPE”), but has generally not compared effects among different demographic processes. We applied EOF analysis to four types of data measuring the outcome of demographic processes for EBS walleye pollock (Gadus chalcogrammus) over the period 1982–2019: numerical density (outcome of movement), morphometric condition (outcome of bioenergetics), length-at-age (outcome of growth), and prey-biomass-per-predator-mass (a proxy for stomach contents; outcome of consumption). We first designed exploratory factor analysis (EFA) models that did not include a CPE effect. We then applied confirmatory factor analysis (CFA), which differed from EFA by attributing observed patterns to a spatially varying response of demographic processes to CPE. We inferred that CPE was a proxy for demographic variability when there was a strong correlation between (1) the first or second mode of variability in the EFA and CPE or (2) the spatial map associated with the positive phase of the first or second mode of variability from the EFA model and the spatially varying response of CPE from the CFA model. Results showed that prey-biomass-per-predator-mass had the strongest correlation with CPE, numerical density and morphometric condition were also strongly correlated with CPE, and length-at-age was moderately correlated with CPE. The models also identified several anomalous years: 1999 and 2010, which were characterized by a very large CPE and high indices for variables related to demographic processes; and 2016–2019, which were characterized by a small CPE and low indices for variables related to demographic processes. We conclude that demographic processes for EBS walleye pollock show the finger-print of bottom-up environmental variation. Future research can employ CPE projections to forecast spatio-temporal changes in variables related to demographic processes, thereby informing estimates such as weight-at-age that are used in stock assessment models.

Non-conventional CO2 sequestration via Vitamin C promoted green reaction: Yield evaluation

Carbon dioxide increase in the atmosphere is a relentless rise process. Many mitigation measures aimed at the reduction of carbon dioxide emissions coupled with capture in variously stable sequestration systems have been proposed over time.In a previous paper (Pastero, 2019), we proposed a new and green method to capture carbon dioxide avoiding the usage of hazardous reagents and the production of harmful compounds. The method involves the application of an aqueous solution of calcium ascorbate (vitamin C) as the only reagent and the precipitation of calcium oxalate as the main reaction product.The role of the chemical and physical process variables controlling the reaction has been investigated in order to increase significantly and stabilize the reaction yield in terms of CO2-sequestration capacity. In the present paper, we evaluated the performance of our method quantitatively, referring to two simple experimental setups: the maximum carbon dioxide yield exceeded 60 %, meaning that every 100 mol of carbon dioxide fed to the capturing system, 60 mol are removed and stored into a stable solid phase. This boost in the method’s performance was obtained optimizing the key-parameters of the reaction and increasing the exchange surface.

Application of a Coastal Vulnerability Index. A Case Study along the Apulian Coastline, Italy

The coastal vulnerability index (CVI) is a popular index in literature to assess the coastal vulnerability of climate change. The present paper proposes a CVI formulation to make it suitable for the Mediterranean coasts; the formulation considers ten variables divided into three typological groups: geological; physical process and vegetation. In particular, the geological variables are: geomorphology; shoreline erosion/accretion rates; coastal slope; emerged beach width and dune width. The physical process variables are relative sea-level change; mean significant wave height and mean tide range. The vegetation variables are width of vegetation behind the beach and posidonia oceanica. The first application of the proposed index was carried out for a stretch of the Apulia region coast, in the south of Italy; this application allowed to (i) identify the transects most vulnerable to sea level rise, storm surges and waves action and (ii) consider the usefulness of the index as a tool for orientation in planning strategies. For the case study presented in this work, the most influential variables in determining CVI are dune width and geomorphology. The transects that present a very high vulnerability are characterized by sandy and narrow beaches (without dunes and vegetation) and by the absence of Posidonia oceanica.

Hybrid fuzzy-PID control of a nuclear Cyber-Physical System working under varying environmental conditions

In real-time control of Cyber-Physical Systems (CPSs), physical process variables are monitored and processed by intelligent controllers for keeping the values of safety parameters between given thresholds. Environmental conditions can affect the system dynamics and also the controller function. This paper presents a hybrid fuzzy-PID (Proportional-Integral-Derivative) controller, which learns the optimal PID controller parameters and adapts them according to the environmental parameters and process variables values.The proposed intelligent controller is applied to respond to the changes and transients in the environmental inlet air temperature of the secondary loop of a Lead-Bismuth Eutectic eXperimental Accelerator Driven System (LBE-XADS), for keeping the secondary average coolant temperature in a range of values between two safety thresholds.

Multiscale modeling of oxide RRAM devices for memory applications: from material properties to device performance

RRAM devices have been subjected to intense research efforts and are proposed for nonvolatile memory and neuromorphic applications. In this paper we describe a multiscale modeling platform connecting the microscopic properties of the resistive switching material to the electrical characteristics and operation of RRAM devices. The platform allows self-consistently modeling the charge and ion transport and the material structural modifications occurring during RRAM operations and reliability, i.e., conductive filament creation and partial disruption. It allows describing the electrical behavior (current, forming, switching, cycling, reliability tests) of RRAM devices in static and transient conditions and their dependence on external conditions (e.g., temperature). Thanks to the kinetic Monte Carlo approach, the inherent variability of physical processes is properly accounted for. Simulation results can be used both to investigate material properties (including atomic defect distributions) and to optimize stack and bias pulses for optimum device performances and reliability.

Effects of model physics on hypoxia simulations for the northern Gulf of Mexico: A model intercomparison

AbstractA large hypoxic zone forms every summer on the Texas‐Louisiana Shelf in the northern Gulf of Mexico due to nutrient and freshwater inputs from the Mississippi/Atchafalaya River System. Efforts are underway to reduce the extent of hypoxic conditions through reductions in river nutrient inputs, but the response of hypoxia to such nutrient load reductions is difficult to predict because biological responses are confounded by variability in physical processes. The objective of this study is to identify the major physical model aspects that matter for hypoxia simulation and prediction. In order to do so, we compare three different circulation models (ROMS, FVCOM, and NCOM) implemented for the northern Gulf of Mexico, all coupled to the same simple oxygen model, with observations and against each other. By using a highly simplified oxygen model, we eliminate the potentially confounding effects of a full biogeochemical model and can isolate the effects of physical features. In a systematic assessment, we found that (1) model‐to‐model differences in bottom water temperatures result in differences in simulated hypoxia because temperature influences the uptake rate of oxygen by the sediments (an important oxygen sink in this system), (2) vertical stratification does not explain model‐to‐model differences in hypoxic conditions in a straightforward way, and (3) the thickness of the bottom boundary layer, which sets the thickness of the hypoxic layer in all three models, is key to determining the likelihood of a model to generate hypoxic conditions. These results imply that hypoxic area, the commonly used metric in the northern Gulf which ignores hypoxic layer thickness, is insufficient for assessing a model's ability to accurately simulate hypoxia, and that hypoxic volume needs to be considered as well.

Unstructured-grid model for the North Sea and Baltic Sea: Validation against observations

A new unstructured-grid model and its application to the North Sea and Baltic Sea are described. The research focus is on the dynamics in the two basins and in the multiple straits connecting them and more specifically on how the model replicates the temporal and spatial variability of physical processes. The comparison against observed data indicates the realism in the simulations of the exchange flows. The simulations demonstrated that in contrast to the tidal variability which decreases in the strait, the role of the barotropic forcing due to weather systems increases. In this zone reversal of transport is well manifested by the increased difference between the surface and bottom salinity values. Small sub-basins like Arkona and Bornholm play the role of reservoirs for denser water which under specific conditions cascades on its way to the Gotland Deep. Unlike the intermediate and deep water salinity in the Baltic Sea, which is strongly affected by fluxes in the straits, the simulated winter-refill and evolution of cold intermediate water are rather driven by surface cooling and processes in the upper mixed layer.

Variability in transport pathways on and around the South Georgia shelf, Southern Ocean: Implications for recruitment and retention

The waters around South Georgia are among the most productive in the Southern Ocean, with zooplankton populations close to the island, in particular Antarctic krill, supporting vast colonies of higher predators. However, our understanding of the processes governing variability in the supply of these food resources is limited by the poor spatial and temporal resolution of available data. Here, we use a numerical modeling approach to examine the underlying physical processes driving the recruitment and retention of zooplankton to the South Georgia shelf. Variability in the magnitude and spatial distribution of recruitment was dominated by the proximity and orientation of the southern Antarctic Circumpolar Current front to the shelf edge. Shelf retention was highest for source sites on the southwest shelf, with the main transport routes off the shelf to the north and northwest. Retention was lowest in the austral summer and winter; in summer increased glacial melt drives stronger off‐shelf near‐surface currents, while in winter, stronger winds lead to an increase in off‐shelf transport. Of particular note was the prediction of a significant increase in retention for particles released throughout the shelf in April and July 2000. This period coincided with the development of pronounced anticlockwise shelf flows, associated with horizontal density gradients due to reduced wind mixing of shelf waters, and differences between shelf and oceanic waters, which significantly reduced off‐shelf transport rates. Such findings are crucial for understanding the influence of variability in physical processes on the ecosystem at South Georgia.

Multi-scale patterns of spatial variability in sessile assemblage structure do not alter predictably with development time

Patterns of benthic community structure are driven by a range of biological and physical processes that act over multiple spatial and temporal scales. Settlement panels were deployed in relatively ‘pristine’ subtidal habitats off southwest Australia, to examine spatial variability in assemblage structure at multiple spatial scales, from centimetres to 100s of kilometres. Panel assemblages were harvested after 3, 9 and 14 months of maturation, to test the following hypotheses: (i) that the magnitude of variability at large spatial scales increases with assemblage development time, (ii) that variability at the smallest spatial scales is consistently high regardless of assemblage development time, and (iii) that patterns of spatio-temporal variability differ between taxa. No clear trends in the magnitude of variability at each spatial scale examined, in relation to assemblage development time, were recorded. Sessile assemblages were highly variable at all spatial scales examined, and variability at the smallest-spatial scale (cms) was consistently high. As predicted, the magnitude of variability at the largest spatial scales (i.e. between locations 100s of km apart) was lowest for immature assemblages, but overall patterns of large-scale variability did not alter predictably with maturation time. Subtidal sessile assemblages in southwest Australia, like elsewhere, are structured by a complex, interacting suite of biological and physical processes that vary in their relative importance throughout assemblage maturation. As such, understanding variability patterns is challenging, and requires greater appreciation of variability in physical processes across multiple spatial and temporal scales and improved knowledge of the life histories and population structures of key taxa.

Statistical optimization of physical process variables for bio-plastic (PHB) production by Alcaligenes sp.

In the present study, efforts have been made to optimize the three physical process variables viz; pH, temperature and agitation speed for enhanced polyhydroxybutyrate (PHB) production in batch cultivation by Alcaligenes sp. which serves as precursor for bio-plastic (PHB) production. Strain selection was done by viable staining method using nile blue A dye. Agro-industrial by products; cane molasses and urea were used as carbon and nitrogen source for PHB production. Optimization of physical process variables was done by central composite rotatable design (CCRD) using design expert (DX 8.0.6) software. Shake flask cultivation performed under optimum physical condition viz; 34.5 °C temperature, 6.54 pH and agitation speed of 3.13 Hz, gave PHB mass fraction yield of 76.80% on dry molasses substrate and showed 98.0% resemblance with the predicted percentage yield of 77.78%. Batch cultivation further performed in 7.5 L lab scale bioreactor (working volume: 5.6 L) under optimized condition gave maximum cell biomass of 11 ± 0.5 g L−1 with a PHB content of 8.8 ± 0.4 g L−1 after 48.0 h of fermentation. Scale up study on bioreactor gave maximum PHB yield (YP/x) and productivity of 0.78 and 0.19 g L−1 h, which are higher than previous reports under similar condition. Characterization of PHB was done by FTIR.

Product and process understanding of a novel pediatric anti-HIV tenofovir niosomes with a high-pressure homogenizer

A variety of factors were systemically evaluated in order to establish the characteristics of the niosomes obtained with a high-pressure homogenizer. The vesicular sizing parameters, electrical properties, drug entrapment data and drug release characteristics were investigated using two groups of factors. The first group presented the physical process variables such as pressure of the homogenizer and the times that the samples were processed (cycles). The second group encompassed the compositional variables such as the drug loading, surfactant chain length, cholesterol level and the level of the charge imparting agent. The obtained data showed that the drug distributed within both the aqueous and lipid phases of the formed niosomes. Saturation-like behaviors for both the effect of homogenization cycles on the produced size and the effect of the pressure on the size homogeneity were recorded. In contrast to the drug entrapment and conductivity of the niosomal suspension, the vesicular size parameters as well as the zeta potential were inversely proportional with the homogenization parameters. Drug release was significantly affected by the compositional factors rather than the physical ones. The current study demonstrated the usefulness of the microfluidization for the production and further scale-up of anti-HIV niosomes with very small mean vesicular sizes.

Modeling the interactions between the seasonal and diel migration behaviors of Calanus finmarchicus and the circulation in the Gulf of St. Lawrence (Canada)

The Gulf of St.-Lawrence (GSL) is a dynamic region supporting a productive pelagic ecosystem. This environment presents unique opportunities to study the interactions between the population dynamics of planktonic species and the variability of physical processes. The copepod Calanus finmarchicus is a dominant component of zooplankton biomass and abundance in the GSL. We developed a 3-D coupled physical–biological numerical model in order to study the population dynamics of C. finmarchicus in the GSL for the year 1999. We coupled a life cycle model of C. finmarchicus representing the average properties of the population in terms of egg production, development, migration behavior and mortality to a regional circulation model driven by realistic atmospheric, hydrological and oceanic forcing. The distribution and abundance patterns of C. finmarchicus were sensitive to the migration behavior owing to the strong vertical and horizontal shears in the circulation. Both the timing of seasonal ontogenetic vertical migrations and the diel vertical migrations appeared to be essential to produce simulation results similar to the observations and to ensure the perennial presence of a local population in the GSL.

Regionalization of the Gulf of Mexico from space-time chlorophyll-a concentration variability

Regions in the Gulf of Mexico are determined based on the statistical behavior of the long-term monthly means of chlorophyll-a concentration from SeaWiFS satellite estimations. An analysis based on the four largest modes of an empirical orthogonal decomposition, which account for 84.9% of the variance, results in nine spatial patterns with different statistical behavior representing 14 connected regions. The time evolution (or principal component) of the first two modes resemble the annual cycle, but each one with a different phase; the third mode represents a semiannual period and the fourth mode shows three maxima and minima. A map of the resulting regions is obtained and the oceanographic processes taking place in each region are discussed. The largest region covers most of the deep Gulf and the continental slope. Other regions in the deep Gulf are located southeast of the Mississippi River mouth and off-shelf of southern Texas and Tabasco, all associated with seasonal offshore cross-shelf transports. The shelves are associated with specific regions, but in wide shelves the inner and outer continental platforms are separated. Among the causes that determine different regions are topographic characteristics and the seasonal variability of physical processes, mainly entrainment caused by heat and momentum fluxes, upwelling, river plumes, and cross-shelf transports associated with the convergence of the along-coast currents.

Coastal and mesoscale dynamics characterization using altimetry and gliders: A case study in the Balearic Sea

Dynamics along the continental slopes are difficult to observe given the wide spectrum of temporal and spatial variability of physical processes which occur (coastal currents, meanders, eddies, etc.). Studying such complex dynamics requires the development of synergic approaches that use integrated observing systems. In this context, we present the results of an observational program conducted in the Balearic Sea combining coastal gliders and altimetry. The objectives of this experiment are to study regional dynamics using new technologies, such as gliders, in synergy with satellite altimetry and to investigate the limitations and potential improvement to altimetric data sets in the coastal zone. In this regard, new methodologies have been developed to compute consistent altimetric and glider velocities, and a novel technique to estimate absolute glider velocities, combining surface glider geostrophic velocities with integrated currents estimated from the glider GPS positioning, has been applied. In addition, the altimetric velocity computation has been improved, especially in the coastal zone, using high‐frequency along‐track sampling associated with new filtering and editing techniques. This approach proves efficient for homogenizing the physical contents of altimetry and glider surface currents (percentage of standard deviation explained is >40) and characterizing regional dynamics in the Balearic Sea through a combined analysis of a high‐resolution observing system, such as the appearance of anomalous intense mesoscale features missing in the classical circulation scheme of the Balearic Sea.

Cascaded two-degree-of-freedom control of seeded batch crystallisations based on explicit system inversion

Simple structures and robustness against disturbances are important attributes of chemical productions controllers. The present contribution considers these aspects for seeded batch cooling crystallisations. A new cascaded control scheme is presented. It combines consistent feedforward control with classic feedback control of the main physical process variables, which are the crystalliser temperature, the supersaturation and the crystal mean size. The calculation of the feedforward trajectories uses an explicit inversion of the crystalliser model which is based on the Methods of Moments. A state observer is used to determine online the respective moments of the crystal size distribution. An additional observer is included to estimate unmeasurable heat disturbances and to update the temperature feedforward trajectories. The present contribution summarises the model derivation, system inversion, feedforward and feedback controller design and the design of the observers. Numerical simulations and experimental results from a laboratory plant at BASF Ludwigshafen prove the applicability of the proposed control concept.

Patterns and processes in the California Current System

The California Current System (CCS) is forced by the distribution of atmospheric pressure and associated winds in relation to the west coast of North America. In this paper, we begin with a simplified case of winds and a linear coast, then consider variability characteristic of the CCS, and conclude by considering future change. The CCS extends from the North Pacific Current (∼50°N) to off Baja California, Mexico (∼15–25°N) with a major discontinuity at Point Conception (34.5°N). Variation in atmospheric pressure affects winds and thus upwelling. Coastal, wind-driven upwelling results in nutrification and biological production and a southward coastal jet. Offshore, curl-driven upwelling results in a spatially large, productive habitat. The California Current flows equatorward and derives from the North Pacific Current and the coastal jet. Dominant modes of spatial and temporal variability in physical processes and biological responses are discussed. High surface production results in deep and bottom waters depleted in oxygen and enriched in carbon dioxide. Fishing has depleted demersal stocks more than pelagic stocks, and marine mammals, including whales, are recovering. Krill, squid, and micronekton are poorly known and merit study. Future climate change will differ from past change and thus prediction of the CCS requires an understanding of its dynamics. Of particular concern are changes in winds, stratification, and ocean chemistry.