Spatiotemporal Temperature Patterns Research Articles

Can urban shrinkage contribute to mitigating surface air temperature warming?

In recent years, urban areas are increasingly experiencing intense warming. Although urbanization is an important driver of warming in urban environments, it remains unclear whether depopulation trends in shrinking cities mitigate this warming effect. Here, we explored the relationship between shrinking cities and observed warming in China. Of the 356 Chinese cities, 95 were identified as shrinking between 2000 and 2010. We categorized 2419 observation stations into three groups—rural, shrinking, and non-shrinking—and generated a surface air temperature (SAT) anomaly series for each group from 1961 to 2014. Temperature differences between the shrinking and non-shrinking urban stations were investigated. Using segmented generalized least squares regression, the spatiotemporal temperature patterns across the mean (Tmean), maximum (Tmax), and minimum temperatures (Tmin), diurnal temperature range (DTR) indicators, and across seasons—spring, summer, autumn, and winter—were explored. Results revealed a cooling effect in shrinking cities, with decadal decreases of 0.042 °C (–0.078 to –0.005 °C), 0.083 °C (–0.126 to –0.039 °C), and 0.029 °C (–0.062 to –0.005 °C) in regional Tmean, Tmax, and Tmin anomalies, respectively. Moreover, pronounced seasonality was identified in this phenomenon—the cooling effect was most notable for Tmean in spring and Tmax in autumn, less significant in summer, and negligible in winter. These results suggested that the population decline in shrinking cities could alleviate regional warming, having implications that could influence urban planning and climate mitigation policies.

Gold Nanostructures for an Effective Bone Cancer Therapy: Numerical Simulation and Experimental Investigation

AbstractGold nanostructures play a crucial role in medical applications, harnessing size and shape‐dependent properties. A prominent area of research is cancer treatment through the photothermal approach. Here, numerical simulation is explored to study the impact of gold nanostructure size, shape, and laser parameters on spatiotemporal temperature patterns during photothermal therapy (PTT). Spherical, rod, star, bipyramid, and cubic nanostructures in small, medium, and large sizes underwent 150 s of laser irradiation. COMSOL software, incorporating bioheat physics, precisely gauged thermal variations. The structural characteristics notably influence the temperature profiles, with medium‐sized rod, star, and bipyramid gold nanoparticles exhibiting superior thermal properties. Experimental validation of simulations focuses on the optimal nanostructure, synthesizing through the seed growth method. Transmission electron microscopy, UV‐visible spectroscopy, and X‐ray diffraction analysis confirm its proposed characteristics. Results demonstrate a robust correlation between experimental and simulation parameters, affirming precision. Findings showcase photothermal properties in line with theoretical predictions. The aim of this study is to determine the optimal gold nanostructure for bone cancer treatment using PTT, addressing the challenges presented by the dense and resilient nature of bone tissue and deep tumor locations. By utilizing multi‐physical modeling and simulations facilitated by COMSOL software, a novel method for pre‐clinical estimation is introduced. This research provides insights into each nanoparticle‐based PTT process prior to ex vivo and in vivo studies, offering a comprehensive understanding of the interplay between nanostructure characteristics and PTT outcomes. The approach contributes to advancing the field of cancer treatment by enhancing the predictability and effectiveness of nanoparticle‐mediated PTT.

Spatial and temporal evolution of heatwaves in Taiwan in a changing climate using multi-dimensional complementary ensemble empirical mode decomposition

Recent decades have witnessed noticeable warming in highly developed cities. Taiwan, a densely populated island characterized by its monsoon-dominated climate and unique mountainous topography, has experienced an average temperature increase of 1.0–1.4 °C in the last century, significantly exceeding the global average. This research introduces the Multi-dimensional Complementary Ensemble Empirical Mode Decomposition (MCEEMD) algorithm, providing a novel approach for analyzing gridded climate data and uncovering spatiotemporal temperature patterns in Taiwan. This methodology offers valuable insights into the localized impacts of climate change. The spatiotemporal evolution of temperature from 1960 to 2020 is analyzed to estimate the warming trend associated with climate change. Essential factors related to the urban heat island (UHI) effect, which leads to temperature disparities between urban and rural areas, are also examined. Warming and the UHI effect are critical components of climate change, increasing the likelihood of extreme weather events in urban areas. The study investigates extreme weather events from 1960 to 2020, focusing on heatwaves. It projects changes in the frequency and duration of heatwaves for the mid (2046–2065) and late 21st century (2081–2100). Notably, Taipei experienced a warming trend exceeding 1.5°C in the 2010s, which was likely influenced by urbanization. Additionally, areas experiencing the sharpest increase in heatwave events (more than 1.5 events) by 2000 were predominantly in highly developed cities across northern and southern Taiwan. Further analysis under the RCP8.5 scenario suggests that, by the end of the 21st century, heatwave events could last for at least 20 days in many regions, with the potential to extend to nearly a month during the summer.

Effects of hydropeaking by an upstream dam on thermal mixing in a riverine lake

The hydropeaking operations of a hydropower dam can significantly affect the flow and thermal regimes in riverine reservoirs, and this effect is very complex, both in space and time. In this study, we used a 3D hydrodynamic model, calibrated with field datasets, to investigate the thermal mixing resulting from hydropeaking within Paldang Lake (PL) in South Korea. The spatiotemporal temperature patterns revealed that density currents critically affected thermal mixing in the reservoir and developed differently based on upstream dam operations and flooding events. Notably, the confluence of the North Han River (NHR) and South Han River (SHR) played a key role in shaping the thermal regime. During the hydropeaking release from the upstream dam in the NHR, the colder water of the NHR from the deep-water discharge of the upstream dam plunged beneath the warmer water of the SHR, leading to three-dimensional mixing. Consequently, the thermal mixing patterns varied depending on the discharge patterns from the upstream dam. Additionally, diurnal variations in the dam discharge frequently affected areas of the reservoir exhibiting high Schmidt stability. During the non-operation period of the upstream dam, the SHR flow backflowed into the downstream section of the NHR, resulting in the confluent area exhibiting the poorest vertical mixing. Secondary currents also played a crucial role in influencing the flow and thermal regimes, with the intensity of the secondary flow varying along the longitudinal mainstream of the reservoir. The thermal mixing state was predominantly weakened to partial mixing within a curved reach owing to the secondary current. Overall, this study demonstrates that the complexity of flow and thermal processes in the PL is significantly influenced by hydropeaking events. These findings emphasize the importance of understanding density currents and secondary flows according to dam operation in managing riverine reservoirs for enhanced ecological health and sustainable water resource management.

Influence of low frequency variability modes on spatiotemporal patterns of temperature and precipitation in Northwestern North America

ABSTRACT This study performs a comprehensive analysis of the influence of low-frequency variability modes (LFVMs) on the average and extreme temperature and precipitation in the extended winter (November–February) over Northwestern North America (NWNA). Maximum covariance analysis is applied to quantify the covariability between LFVMs and regional climate variables, followed by composite analysis to assess the influence of each LFVM on extremes at local scales using high-resolution gridded observations. This study extends previous analyses by characterizing the spatial patterns of regional climate variations associated with a suite of LFVMs. This includes the associations between negative phases of North Atlantic Oscillation (NAO) and extreme precipitation over western NWNA and the central Columbia basin and the positive phase of the North Tropical Atlantic (NTA) with increases in the minimum and maximum temperature of NWNA except for the western Fraser basin. Overall, the analyses show that LFVM effects are more pronounced over the eastern and southcentral parts of NWNA during extended winter.

Thermal Perception for Information Transmission: Theoretical Analysis, Device Design, and Experimental Verification.

Information transmission is a fundamental issue for human-computer interaction (HCI). Traditional interaction methods through visual, voice, and force haptics are very mature. However, the thermal perception (TP) for HCI is not studied in depth. This work proposes the TP-based information transmission framework. Firstly, we investigated the human hand-object contact heat transfer model and the temperature perception resolution of the hand and verified the feasibility of spatiotemporal temperature stimulation for information transmission by simulations. Then, a thermal device was designed, which utilized a 7×5 Peltier array, a water cooler, temperature sensors, and a control module to realize various static and dynamic spatiotemporal temperature patterns stimulation. Finally, we implemented a device prototype and recruited 20 subjects for experimental studies. The results show that the device can display various temperature patterns and provide thermal stimulations with high precision and speed. Furthermore, the subjects can accurately recognize different temperature values, icons, codes, and waveforms with their palm and fingers after a few times of training, which validates the TP-based information transmission method. Therefore, people can apply this method to interact with machines for information feedback, virtual reality, augmented reality, etc.

Retracted: The impact of a boundary layer height formulation on the GEOS‐5 model climate

AbstractPlanetary boundary layer (PBL) processes are important for the estimation of surface‐atmosphere exchanges that impact global climate. One way of characterizing the strength of these processes is the PBL depth. In the Goddard Earth Observing System (GEOS‐5) atmospheric general circulation model, the PBL depth is also used in calculating the turbulent length scale, which, in turn, is used in estimating the turbulence and vertical mixing within the model. Therefore, changing the PBL depth definition directly affects the model climate. This study evaluates the climatological model response of two long‐term simulations using different PBL depth definitions. The first definition is based on a bulk Richardson number; the second uses a combination of the same bulk Richardson number definition over land plus a definition based on the turbulent eddy diffusion coefficient over water. The two simulations produce different spatiotemporal patterns of temperature, specific humidity, and wind speed related to the differences in turbulence. The largest differences, as expected, are present over water. Due to differences in atmospheric stability, the relationship between the two PBL depth estimates differ among the majority of the oceans and off the west coasts of continents, affecting the climatic response. Due to its optimization of the climatic response while maintaining a realistic diurnal cycle of PBL depth, the mixed PBL depth configuration is preferred.

Two-dimensional modelling of hydrodynamics and water quality of a stratified dam reservoir in the southern side of the Mediterranean Sea

A vertical two-dimensional, laterally averaged hydrodynamic and water quality model CE-QUAL-W2 was used to simulate water temperature, dissolved oxygen, electrical conductivity, chlorophyll a, total suspended solids, alkalinity, ammonium, phosphate, and total iron in the Sejnane Dam (North Tunisia) in response to external forcings that characterize main features of climate in the southern side of the Mediterranean Sea. The hydrodynamic modelling results show that the model is able to reproduce accurately the measured water surface elevation, spatio-temporal patterns of temperature, dissolved oxygen and other state of variables and to capture most of the seasonal changes in the reservoir. Three scenarios involving the impacts of severe drought season, summer rainfall and total suspended solids load on hydrodynamics and water quality are analyzed. Severe drought reduces the thickness of hypoxic waters from 10 to 2–4 m and shifts the temperature of the entire water column up to 5 °C during summer and about 1.2 °C in winter. The thermocline takes place 1 month before that of the reference and sinks to the bottom faster by 1–2 m per month. Summer rainfall dilutes the first waves of the autumn rains and disrupts the thermal gradient in the water column, which may show complex thermal structures. TSS load has the most negative effects on water quality in that it shifts the phosphorus concentration by 1–3 mg/l and promotes an early warming of surface water in spring and an early cooling since late summer by up to 1 °C. During summer stratification, it contributes to the cooling of the metalimnion by 2 °C on average, which may alter its structure and dynamics as an aquatic biotope.

A Low-Cost Wireless Temperature Sensor: Evaluation for Use in Environmental Monitoring Applications

Abstract A wide range of environmental applications would benefit from a dense network of air temperature observations. However, with limitations of costs, existing siting guidelines, and risk of damage, new methods are required to gain a high-resolution understanding of spatiotemporal patterns of temperature for agricultural and urban meteorological phenomena such as the urban heat island. With the launch of a new generation of low-cost sensors, it is possible to deploy a network to monitor air temperature at finer spatial resolutions. This study investigates the Aginova Sentinel Micro (ASM) sensor with a custom radiation shield (together less than USD$150) that can provide secure near-real-time air temperature data to a server utilizing existing (or user deployed) Wi-Fi networks. This makes it ideally suited for deployment where wireless communications readily exist, notably urban areas. Assessment of the performance of the ASM relative to traceable standards in a water bath and atmospheric chamber show it to have good measurement accuracy with mean errors <±0.22°C between −25° and 30°C, with a time constant in ambient air of 110 ±15 s. Subsequent field tests also showed the ASM (in the custom shield) had excellent performance (RMSE = 0.13°C) over a range of meteorological conditions relative to a traceable operational Met Office platinum resistance thermometer. These results indicate that the ASM and radiation shield are more than fit for purpose for dense network deployment in environmental monitoring applications at relatively low cost compared to existing observation techniques.

Climatic trends and different drought adaptive capacity and vulnerability in a mixed Abies pinsapo–Pinus halepensis forest

The projected temperature rise, rainfall decrease and concentration of rainfall in extreme events could induce growth decline and die-off on tree populations located at the geographical distribution limit of the species. Understanding of adaptive capacity and regional vulnerability to climate change in Mediterranean forests is not well developed and requires more focused research efforts. We studied the relationships between spatiotemporal patterns of temperature and precipitation along the southwestern edge of the Betic range (southern Spain) and measured basal area increment (BAI) and carbon isotope (Δ) in tree ring series of Abies pinsapo and Pinus halepensis, two Mediterranean conifer trees with contrasting drought adaptive capacity. Climatic information was obtained from a network covering a wide range of elevations and distances from the Atlantic and Mediterranean coasts. Temperature trends were tested by the Mann–Kendall test, and precipitation was thoroughly analyzed by quantile regression. Climatic data showed a warming trend, enhanced since the 1970s, while quantile regressions revealed that drought events worsened during the course of the twentieth century. Long-term decrease of A. pinsapo BAI was related to regional warming and changing precipitation patterns, suggesting increasing drought stress on this species. Both temperature and precipitation in the summer influenced wood Δ in P. halepensis, whereas negative correlation between wood Δ and current autumn temperature was yielded for A. pinsapo. Increased intrinsic water use efficiency was inferred from wood Δ in both species; however, A. pinsapo showed sudden growth reductions under drier conditions, while pine trees were able to maintain almost constant BAI values and lower water costs under increasing long-term water stress.

Temperature and conversion patterns in a network of catalytic reactors for methanol synthesis with different switch strategies

A network of connected catalytic reactors with periodically switched inlet and outlet sections is numerically studied for reversible exothermic reactions. The methanol synthesis is selected as representative process example and two different switch strategies are compared with the objective of overcoming the conversion limits imposed by thermodynamic equilibrium. The first strategy, which is the most considered in literature, consists of periodically switching the feed to the second reactor of the current reactor sequence while the second strategy is implemented by periodically switching the feed to the last reactor of the current sequence. Periodic regimes corresponding to single square-like temperature waves travelling over the catalytic bed and characterized by comparable methanol conversion values are detected for both the considered strategies. These regimes exhibit, however, a significantly larger domain of existence for the second strategy. Moreover, the second strategy gives rise to other periodic regimes corresponding to spatiotemporal temperature patterns characterized by different spatial and temporal periodicity. These patterns arise in the form of temperature wave trains and ensure methanol conversion values significantly larger than those found under periodic regimes characterized by single temperature waves.

How much influence does landscape-scale physiography have on air temperature in a mountain environment?

Spatio-temporal patterns of temperature in mountain environments are complex due to both regional synoptic-scale and landscape-scale physiographic controls in these systems. Understanding the nature and magnitude of these physiographic effects has practical and theoretical implications for the development of temperature datasets used in ecosystem assessment and climate change impact studies in regions of complex terrain. This study attempts to quantify the absolute and relative influence of landscape-scale physiographic factors in mediating regional temperatures and assess how these influences vary in time. Our approach was to decompose the variance in in situ temperature measurements into components associated with regional free-air temperature estimates and local physiographic effects. Near-surface air temperature data, collected between 1995 and 2006 from 16 meteorological stations in the Lake Tahoe region of California, USA were regressed against free-air temperature (North American Regional Reanalysis dataset) for the same period. Residuals from this fit represent spatial deviations from the regional mean and were modeled as a function of physiographic position on the landscape using variables derived from terrain analysis techniques. Linear models relating temperature residuals to physiographic variables explained roughly 10–90% of the variance in temperature residuals and had root mean squared error of 1.2–2.0 °C, depending upon the type of measurement and time of year. Results demonstrate that: (1) regional temperature patterns were the principle driver of surface temperatures explaining roughly 70–80% of the variance in in situ measurements; (2) the remaining variance was largely explained by spatial variability in landscape-scale physiographic variables; (3) the influence of physiographic drivers varied seasonally and was influenced by regional conditions. Periods of well-mixed atmospheric conditions lend themselves to the use of simple elevation-based lapse rate models for temperature estimation whereas other physiographic effects become more prominent during periods of enhanced atmospheric stability; and lastly (4) small differences in temperature due to landscape position, when integrated over time, can have a prominent effect on water balance and thus hydrologic and ecologic processes.

Transversal Hot Zones Formation in Catalytic Packed-Bed Reactors

Spatiotemporal patterns reported to form in the cross sections of packed-bed reactors (PBRs) may pose severe safety hazard when present next to the reactor wall. Understanding what causes their formation and dynamic features is essential for the rational development of design and control strategies that circumvent their generation. We review the current knowledge and understanding about the formation of these transversal temperature patterns. Simulations and model analysis revealed that the formation of the hot spots and their dynamics are sensitive to the assumed kinetic and reactor models. Under practical conditions, stable symmetry-breaking bifurcation to nonuniform states, from stable, stationary, transversally uniform states cannot be predicted by common PBR models with a rate expression that depends only on the surface temperature and concentration of the limiting reactant. However, analysis and simulations reveal that transient nonuniform transversal temperatures may emerge in an upstream moving traveling front under practical conditions. Microkinetic oscillatory reactions predict the formation of a plethora of intricate spatiotemporal temperature patterns and temperature front motions that are sensitive to the reactor operating conditions and properties such as diameter and initial conditions. The predicted temperature patterns may be rather intricate as a result of conjugation of several modes. The nonlinear coupling between the states at different axial positions, that is, the interaction among the local temperature and concentrations at different cross-sections of the bed, may explain the intricate conjugation of several modes and modulation of the observed spatiotemporal patterns. While some simulations predicted spatiotemporal pattern evolution in PBRs, there is a need to understand which reaction mechanisms may lead to their formation. Most previous simulations and analysis utilized two-dimensional reactor models. However, hot zones are three-dimensional structures, often very small, and difficult to detect in large reactors. A 3-D simulation, although tedious, is necessary to provide full information about the size, shape and dynamic features of small hot zones. Moreover, common PBR models may have to be modified to account for the impact of local states such as flow distribution and nonuniform packing. Verification of the various model predictions requires in situ measurements of 3-D hot zones.

Reactor diameter impact on hot zone dynamics in an adiabatic packed bed reactor

AbstractRecent analysis revealed that a pseudohomogeneous model of a uniformly active, adiabatic packed bed reactor can predict formation of stable hot zones in the cross‐section of the reactor if the kinetic rate expression can lead to isothermal rate oscillations. This prediction was confirmed by simulations of CO oxidation. We show that hot zone formation in a shallow reactor can be predicted also for C2H4 hydrogenation, the kinetic model of which is structurally different from that of CO oxidation. Qualitatively different spatiotemporal temperature patterns may form under the same operating conditions. Their number increases as the reactor diameter is increased. An increase in the reactor diameter increases the time constant of the transversal heat dispersion and decreases the temperature synchronization among points on the same reactor cross‐section. The interaction and conjugation among qualitatively different moving temperature patterns can lead to formation of complex motions. © 2007 American Institute of Chemical Engineers AIChE J, 2007

Evolution of spatiotemporal temperature patterns in monolithic catalytic reactor

Experimental data on dynamic evolution of spatiotemporal temperature patterns and temporal conversion patterns for CO and hydrocarbon oxidation and NO reduction in a monolithic catalytic reactor reflecting variations of inlet conditions are presented. Possibility of increasing conversion of NO x reduction by periodic variation of inlet conditions is experimentally documented.

Periodic, quasiperiodic and chaotic spatiotemporal patterns in a tubular catalytic reactor with periodic flow reversal

Periodic, quasiperiodic and chaotic symmetric and unsymmetric spatiotemporal temperature patterns arise in the heterogeneous (two-phase) model of the catalytic reactor with periodic flow reversal. Coexistence of various types of stable solutions was observed. Chaotic solutions arising via the torus breaking route were also observed. The transitions among individual types of spatiotemporal patterns and their development are studied by means of Poincaré maps of the associated model represented as a one-parameter family of discrete dynamical systems derived from the simulation results of the original continuous model.

Spatiotemporal temperature patterns during hydrogen oxidation on a nickel disk

AbstractSpatiotemporal temperature patterns on a polycrystalline nickel disk were recorded using infrared video imaging during atmospheric hydrogen oxidation and characterized by the proper orthogonal decomposition pattern analysis technique. The system was studied at two different residence times, 3.2 s and 6.4 s. At moderate feed temperatures, steady‐state multiplicity and rate oscillations were found. Oscillations at a residence time of 6.4 s were periodic and essentially spatially uniform. At a residence time of 3.2 s, however, the surface temperature became nonuniform, and rate oscillations occurred via traveling temperature waves which emanated from “pacemakers” (locally active regions) on the edge of the catalyst. During periodic oscillations, the waves were emitted synchronously from the pacemakers, while during chaotic oscillations, the pacemakers were desynchronized and emitted waves independently of each other. Nonlocal gas‐phase coupling between distance surface elements caused spatial desynchronization during rate oscillations.

Patterns of temperature pulses on electrically heated catalytic ribbons

A rich and intricate variety of spatiotemporal temperature patterns is predicted to exist on the surface of a thin catalytic ribbon, the average temperature of which is kept by electrical heating at a preset value, when the catalytic surface undergoes slow activation-deactivation. The control of the average temperature introduces an integral constraint that generates patters that are not observed in its absence. This one-dimensional system exhibits (in addition to a chaotic behavior) four basic motions: unidirectional pulses, back-and-forth pulses, antiphase oscillation, and a source point from which two pulses emanate and move in opposite directions. Other motions we observed are combinations and transitions among these four. Several of the motions have already been observed experimentally. At some transitions, spatial structures appear to change discontinuosly and without hysteresis, suggesting global bifurcations.

Pattern selection in controlled reaction–diffusion systems

When a chemical reaction is carried out on a catalytic ribbon, the spatial average temperature of which is kept constant by electrical heating, spatiotemporal temperature patterns form when the uniform steady state is unstable at the set temperature. Numerical simulations reveal periodic and aperiodic patterns of moving pulses, ‘‘breathing’’ pulses, or stationary and oscillatory fronts. The transitions between some of these patterns are intricate and proceed via global bifurcations. Bifurcation maps of parameter regions leading to specific patterns are used to gain insight into pattern formation and organization of these parameter regions. The relations among the dynamics of the uncontrolled system, the ribbon length, and the selected pattern are discussed. Similar patterns are expected to evolve in other reaction–diffusion systems subject to control of space-averaged properties.

Spatiotemporal temperature patterns on an electrically heated catalytic ribbon

Oscillatory and chaotic variations in the overall reaction rate were observed during the oxidation of propylene in air on a thin platinum ribbon, the average temperature (resistance) of which was kept at a preset value via electrical heating. A thermal image showed that back and forth movement of a high-temperature wave on the ribbon and the dynamic change in the length and temperature of the ignited zone were the cause of the variation in the overall reaction rate