Temporal Variation Of Temperature Research Articles

Dynamic Response of Surface Water Temperature in Urban Lakes under Different Climate Scenarios-A Case Study in Dianchi Lake, China.

Lake surface water temperature is a fundamental metabolic indicator of lake ecosystems that affects the exchange of material and energy in lake ecosystems. Estimating and predicting changes in lake surface water temperature is crucial to lake ecosystem research. This study selected Dianchi Lake, a typical urban lake in China, as the research area and used the Air2water model combined with the Mann-Kendall mutation statistical method to analyze the temporal and spatial variation in the surface water temperature of Dianchi Lake under three climate models. The research results show that, under the RCP 5-8.5 scenario model, the surface water temperature change rate for Dianchi Lake from 2015 to 2100 would be 0.28 ℃/10a, which was the largest change rate among the three selected scenarios. The rate of change during 2015–2100 would be 9.33 times higher than that during the historical period (1900–2014) (0.03 °C/10a). Against the background of Niulan River water diversion and rapid urbanization, the surface water temperature of Dianchi Lake experienced abrupt changes in 1992, 2016, 2017, and 2022. Against the background of urbanization, the impact of human activities on the surface water temperature of urban lakes will become greater.

Efficacy of inertial confinement fusion experiments in light ion fusion cross section measurement at nucleosynthesis relevant energies

Inertial confinement fusion (ICF) experiments create a unique laboratory environment in which thermonuclear fusion reactions occur within a plasma, with conditions comparable to stellar cores and the early universe. In contrast, accelerator-based measurements must compete with bound electron screening effects and beam stopping when measuring fusion cross sections at nucleosynthesis-relevant energies. Therefore, ICF experiments are a natural place to study nuclear reactions relevant to nuclear astrophysics. However, analysis of ICF-based measurements must address its own set of complicating factors. These include: the inherent range of reaction energies, spatial and temporal thermal temperature variation, and kinetic effects such as species separation. In this work we examine these phenomena and develop an analysis to quantify and, when possible, compensate for their effects on our inference. Error propagation in the analyses are studied using synthetic data combined with Markov Chain Monte Carlo (MCMC) machine learning. The novel inference techniques will aid in the extraction of valuable and accurate data from ICF-based nuclear astrophysics experiments.

Investigation of seepage near the interface between an embankment dam and a concrete structure: monitoring and modelling of seasonal temperature trends

Seasonal subsurface temperature monitoring, which exploits the fact that increased seepage flow may locally alter the temperature distribution, is a useful approach for leakage monitoring and evaluation within embankment dams and their foundations. At the Mactaquac Generating Station, New Brunswick, Canada, spatial and temporal variations of temperature have been monitored and modelled at the steeply inclined interface between the compacted clay till core of the embankment dam and an abutting concrete diversion sluiceway. Over a 4-year period, two seasonally recurring anomalies at different depths were observed by fibre optic distributed temperature sensing in the concrete structure close to the interface. A 3D coupled flow and heat transport model was developed in FEFLOW to simulate temperature distribution within the dam resulting from seasonal variations in air and reservoir temperature. Leakage zones near the interface were simulated in the concrete and embankment. At a depth of 13 m below the crest, the significant lag time between temperature variations in the reservoir and dam core shows that the leakage responsible for an observed temperature anomaly must be limited to enhanced flow within the concrete. At much shallower depths, where seasonal reservoir and dam core temperatures fluctuate nearly in phase, seepage paths are more challenging to determine.

City-wide monitoring and contributing factors to shallow subsurface temperature variability in Nanjing, China

Shallow temperatures down to a depth of 100 m were measured over one year in 19 closed boreholes located in Nanjing, China, to reveal the conditions and factors influencing the subsurface thermal regime. A monitoring concept with distributed temperature sensing, fiber Bragg grating-based sensor, and a type of Resistance Temperature Detectors, is implemented, providing spatial distribution characteristics of subsurface temperatures. The results show that temperatures near the surface are most dynamic, influenced by the air temperature. The temperature remains stable at the depth of 10–20 m. The mean transition temperature is 18.1 °C. Borehole measurements are interpolated by using satellite images and surface temperature records to obtain large-scale surface temperature distributions and temporal variations of subsurface temperature. Geological and hydrological conditions are primary factors by affecting subsurface upward heat flux and heat loss. Urban land cover change and enhanced heat release from urbanization contribute to a subsurface urban heat island with intensities of 1.0–4.4 °C. The altered subsurface thermal regime is of primary concern for the management of shallow geothermal energy use. The monitoring concept in this study can provide spatially-temporally continuous profiles of subsurface temperature and become a reference for city-wide geothermal monitoring in other urban areas.

Temporal and Spatial Variation of Land Surface Temperature and Its Driving Factors in Zhengzhou City in China from 2005 to 2020

Rapid urbanization is an important factor leading to the rise in surface temperature. How to effectively reduce the land surface temperature (LST) has become a significant proposition of city planning. For the exploration of LST and the urban heat island (UHI) effect in Zhengzhou, China, the LST was divided into seven grades, and the main driving factors of LST change and their internal relations were discussed by correlation analysis and gray correlation analysis. The results indicated that LST showed an upward trend from 2005 to 2020, and a mutation occurred in 2013. Compared with 2005, the mean value of LST in 2020 increased by 0.92 °C, while the percentage of LST-enhanced areas was 22.77. Furthermore, the spatial pattern of UHI was irregularly distributed, gradually spreading from north to south from 2005 to 2020; it showed a large block distribution in the main city and southeast in 2020, while, in the areas where woodlands were concentrated and in the Yellow River Basin, there was an obvious “cold island” effect. In addition, trend analysis and gray correlation analysis revealed that human factors were positively correlated with LST, which intensified the formation of the UHI effect, and the influence of Albedo on LST showed obvious spatial heterogeneity, while the cooling effect of vegetation water was better than that of topography. The research results can deepen the understanding of the driving mechanism of the UHI effect, as well as provide scientific support for improving the quality of the urban human settlement environment.

A zonal and segmentation analysis of the relationships between variations in sea-surface temperatures of the western Pacific Ocean and Southeast Asian rainfall

Abstract With the objective of understanding how terrestrial precipitation in Southeast Asia (SEA) responds to both temporal and spatial variations in sea-surface temperature (SST) of the western Pacific Ocean, we first used the North–South and zonal SST variation analyses for the data set named A Group for High-Resolution Sea-Surface Temperature (GHRSST) Level 4 Multiscale Ultrahigh Resolution (MUR). Second, we applied a localized correlation analysis to the SST data set and rainfall data (Integrated Multi-satellitE Retrievals for Global precipitation measurement (IMERG)) in order to determine the boundaries and characteristics of the complex interactions between SST and rainfall variations. The zonal SST variation analysis result suggested that the warm pool in the North of western Pacific zones close to SEA (120 °E–150 °E) was more sustained and less varied than that in the South zones. In terms of the western Pacific SST impact on rainfall in SEA, the correlation analysis confirmed the well-established concept that the SST of the ocean part close to the SEA land, in general, has more influence on SEA rainfall than does the SST of the ocean part far away from SEA. Still, there were some parts of SEA whose rainfall was not governed by the sea–land juxtaposition.

Temporal and Spatial Variation of Land Surface Temperature in Recent 20 Years and Analysis of the Effect of Land Use in Jiangxi Province, China

Under the background of global warming, it is of great significance to study the temporal and spatial evolution of land surface temperature (LST) on long-time scale and the impacts of land use in the fields of urban thermal environment and regional climate change. Based on MODIS LST long time series remote sensing data, the temporal and spatial evolution characteristics of pixel-wise LST in Jiangxi Province, the middle inland province of China from 2000 to 2020 were analyzed by using Theil-Sen + Mann-Kendall, coefficient of variation and Hurst index, and the response of LST to land use was identified by combining the contribution and diversity index. The results showed as follows: (1) LST was generally distributed as "high in Middle-East-West-South and low in North-northwest-southeast direction". LST showed an overall downward trend, indicating a weakening of the warming trend. The dynamic trend of LST was characterized by more descending than ascending tendency. The dynamic stability showed a coexistence of high and low fluctuation tendency, with a higher proportion of medium and low fluctuation areas having obvious spatial differences. The overall dynamic sustainability was characterized by uncertainty of future change trend. (2) The LST were strongly affected by land use in the past 20 years. Firstly, the areas of high LST were mostly located in construction land and unused land, while the areas of low LST were mostly in water area and forest land. However, forest land and water area of high temperature were gradually turned to construction land later on. Secondly, the land use structure and pattern had an strong effects on LST. With the increase of the area proportion of different land use, the LST showed significant differences. The more complex the spatial pattern of land use, the more obvious its impact on LST. The research results will provide some reference for the regions with the same characteristics as Jiangxi Province to deal with LST under the background of global climate change.

Assessment of spatial and temporal variations of land surface temperature (LST) due to elevation changes in Yazd Province, Iran

Assessment of spatial and temporal variations of land surface temperature (LST) due to elevation changes in Yazd Province, Iran

Intracellular Heat Transfer and Thermal Property Revealed by Kilohertz Temperature Imaging with a Genetically Encoded Nanothermometer.

Despite improved sensitivity of nanothermometers, direct observation of heat transport inside single cells has remained challenging for the lack of high-speed temperature imaging techniques. Here, we identified insufficient temperature resolution under short signal integration time and slow sensor kinetics as two major bottlenecks. To overcome the limitations, we developed B-gTEMP, a nanothermometer based on the tandem fusion of mNeonGreen and tdTomato fluorescent proteins. We visualized the propagation of heat inside intracellular space by tracking the temporal variation of local temperature at a time resolution of 155 μs and a temperature resolution 0.042 °C. By comparing the fast in situ temperature dynamics with computer-simulated heat diffusion, we estimated the thermal diffusivity of live HeLa cells. The present thermal diffusivity in cells was about 1/5.3 of that of water and much smaller than the values reported for bulk tissues, which may account for observations of heterogeneous intracellular temperature distributions.

Three-Dimensional Dynamic Variations of Ground/Air Surface Temperatures and Their Correlation with Large-Scale Circulation Indexes in Southwest China (1980–2019)

Air/soil temperatures play important roles in land–atmosphere interactions. The three-dimensional (temporal, spatial, and vertical) variations of maximum, mean, and minimum ground soil temperature at 0 cm (GSTx, GSTm, and GSTn, respectively), surface air temperature at 2 m (SATx, SATm, and SATn, respectively), and soil–air temperature difference (SATDx, SATDm, and SATDn, respectively) and their potential linkages with large-scale indexes in Southwest China during 1980–2019 were analyzed. Variations of GST and SAT at the majority of stations (pixels) exhibited significant (p ≤ 0.05) warming, albeit at different rates; consequently, SATD exhibited different variation. Moreover, the period of GST, SAT, and SATD was similar in intra-annual and interannual oscillation but was different in interdecadal oscillation. The variation rate of GST, SAT, and SATD exhibited significant (p ≤ 0.05) correlation with elevation, but with different variation gradient. Notably, asymmetric variation of SATDx (downward trend) and of SATDn (upward trend) with elevation was found at elevations >3 km. Wavelet coherence showed that the Atlantic Multidecadal Oscillation is the dominant factor affecting GST and SAT, whereas the Pacific Decadal Oscillation and the North Atlantic Oscillation make the greatest contributions to SATD. It was found that GST, SAT, and SATD exhibit different variations under the effects of global warming, the driving mechanism of which requires further study.

Unsteady MHD Flow through Porous Media with Temporal Variation in Temperature and Concentration at the Plate

The present analysis aims at to the free convective unsteady MHD flow of a viscous fluid through a saturated porous medium, considering the radiative heat loss and chemical reaction of the diffusing species in the presence of an exponential time varying cross flow. The novelties of the present analysis are that the electrically conducting fluid is made to flow through saturated porous medium subjected to transverse magnetic field; the presence of constant volumetric heat source acts as an internal thermal power within the boundary layer; the principle of superposition underlying basis of method of analytical solution. Some important findings of the study are that the flow model acts as a surface-coolant and it lowers down the bounding surface-concentration also; the imposed magnetic field, thermal radiation, porosity of the saturated porous medium and the destructive chemical reaction of the diffusing species have effects on progressive thinning of the boundary layer.

Measurement-based investigation of subway station tunnel thermal environment

Compared with the interval tunnel, the subway station tunnel has higher temperature. Therefore, more attention should be paid. In order to study the thermal environment characteristics of station tunnels, this paper selects four typical stations in Guangzhou, China. The station tunnel air temperature, tunnel exhaust duct temperature, and air inlet temperature of train air conditioning condenser were tested. The results show that the subway station tunnel has a temperature rise of about 4 °C from the opening to the operation scale. Temporal variations of temperature are determined by the passenger flow and train density; however, it has nothing to do with the operation year. The TEF (Tunnel Exhaust Fan) plays a clear role in ensuring the normal operation of the train air conditioner; when the fan is turned off, the instantaneous air inlet temperature of the train air conditioning condenser frequently exceeds 45 °C during the evening peak, and fails to work. Once the fan is turned on, the air conditioner can operate normally. The effect of the TEF on reducing the tunnel temperature is limited with a reduction range within 1 °C. In addition, the heat removal effect of TEF was quantitatively analyzed. The research results describe the characteristics of the thermal environment of the station tunnel in the hot summer and warm winter climate area. Moreover, the results also provide a reference for the design and operation of the TEF system.

A spatio-temporal temperature-based thresholding algorithm for underground coal fire detection with satellite thermal infrared and radar remote sensing

Coal fire is a global catastrophe that causes resource waste, economic loss, and environmental pollution. Accurate detection of surface abnormalities induced by coal fires (such as thermal anomalies and land deformation) is critical for coal fire monitoring and extinguishment. However, the conventional thermal anomaly detection methods do not consider the temporal variation of land surface temperature (LST). Moreover, previous studies have not applied the polarimetric persistent scatterer interferometry(PolPSI) technique for coal-fire-related ground deformation monitoring, which is supposed to have better performance than conventional persistent scatterer interferometry (PSI) approaches. To this end, in this study, a spatio-temporal temperature-based thresholding (STTBT) algorithm is proposed to detect thermal anomalies, firstly. Then, the ground deformation obtained by the PolPSI method is combined with the detected thermal anomalies for the coal fire detection. Besides, a two-stage bandpass filter is employed to assist in detecting the suspected coal fire. The results in the Fukang coal fire area, China, demonstrate that, compared with the conventional methods, the proposed STTBT mothed achieves higher accuracy of thermal anomalies detection, thereby can able to detect coal fire areas more effectively. In addition, PolPSI has better performance than PSI in ground deformation monitoring over coal fire areas. The proposed STTBT combined with PolPSI can serve as a powerful tool for detecting and monitoring underground coal fires.

In-situ thermography revealing the evolution of internal short circuit of lithium-ion batteries

The demand for lithium-ion batteries is ever increasing while its safety is arousing great public concerns. The feature of a defective cell that may evolve to catastrophic failure is difficult to characterize, given the observation of the cell's internal structure is hard to make. Herein, this paper proposes a new method using thermography to characterize the evolution process from internal short circuit to thermal runaway inside a lithium-ion cell. The spatial and temporal temperature variation around the initiation point of the internal short circuit as well as the voltage and surface temperature are recorded in high frequency. The internal short circuit is triggered by the magnet and wax. The results show that the aluminum-anode-type internal short circuit can lead to thermal runaway by a sequence of the hot spot, gas generation, and combustion. Inadequate internal short circuit heat generation contributes to a temporary hot spot that gradually cools down to ambient temperature. Thermal runaway tends to occur when the hot spot above 150 °C reaches the area of 50 mm2 and the majority of the exothermic side reaction heat in the hot spot area is released within ca. 2s. These results are expected to guide the design of safer lithium-ion batteries.

Ignition and combustion characteristics of boron agglomerates under different oxygen concentrations

Boron is widely used in solid ramjets and powder engines due to its high gravimetric and volumetric calorific values. It mostly exists in the form of agglomerates in the combustion chamber. The present study investigates the ignition and combustion characteristics of amorphous boron agglomerates under different oxygen concentrations in comparison with those of single-particle crystalline boron. The surface morphology evolution of boron particles during the combustion process was directly examined, and the flame morphology and spectral data were analyzed. For the residual condensed-phase products after the boron particles were extinguished, the micro-morphology of the surface was observed by field-emission scanning electron microscope (FE-SEM), the micro-area elementary composition was analyzed with X-ray energy dispersive spectrum (EDS). Temporal variation of the agglomerate surface temperature was also obtained by applying a fitting procedure based on the Planck law. According to the experimental results, the agglomerates gradually shrank due to the discharge of voids during the ignition and combustion processes. After the outer surface of the boron agglomerate reached a molten state, residual boron oxide and voids still remained inside the agglomerates. Under high oxygen concentrations, the experimental results revealed presence of ejection and micro-explosion phenomena in the boron agglomerates combustion. These phenomena occurred when the internally vaporized boron oxide dominated the liquid film resistance and expelled the molten agglomerates. After completion of melting process, the agglomerates formed spherical geometries and burned in the form of droplets. By increase of the oxygen concentration from 20% to 100% during laser loading, the average temperature of boron agglomerates was increased from 2312 K to 2732 K, and the self-sustaining combustion time of single-particle crystalline boron was increased from 170 ms to 419 ms, while the self-sustaining combustion time of boron agglomerates was first increased from 183 ms to 242 ms and then decreased to 84 ms. The current study indicated that ejection and explosion phenomena are likely to exist in the local high-oxygen regions of the combustion chamber.

Design and Characterization of an RF Applicator for In Vitro Tests of Electromagnetic Hyperthermia.

The evaluation of the biological effects of therapeutic hyperthermia in oncology and the precise quantification of thermal dose, when heating is coupled with radiotherapy or chemotherapy, are active fields of research. The reliable measurement of hyperthermia effects on cells and tissues requires a strong control of the delivered power and of the induced temperature rise. To this aim, we have developed a radiofrequency (RF) electromagnetic applicator operating at 434 MHz, specifically engineered for in vitro tests on 3D cell cultures. The applicator has been designed with the aid of an extensive modelling analysis, which combines electromagnetic and thermal simulations. The heating performance of the built prototype has been validated by means of temperature measurements carried out on tissue-mimicking phantoms and aimed at monitoring both spatial and temporal temperature variations. The experimental results demonstrate the capability of the RF applicator to produce a well-focused heating, with the possibility of modulating the duration of the heating transient and controlling the temperature rise in a specific target region, by simply tuning the effectively supplied power.

Temporal Temperature Variation in Urban Gardens Is Mediated by Local and Landscape Land Cover and Is Linked to Environmental Justice

The urban heat island (UHI) effect remains a major threat to society as cities densify and sprawl. Urban greening through local to landscape management is a proposed strategy to combat UHI and improve environmental justice in city neighborhoods. For example, urban community gardens are multifunctional green spaces that play an important role for biodiversity and for civic engagement. But the role of urban gardens in urban cooling and relieving UHI remain unclear, specifically how temperatures fluctuate within gardens in relation to garden management factors and city landscape context, and how this relates to urban heat in city neighborhoods. We investigated diurnal and nocturnal temperature ranges, and daily maximum and minimum temperatures in 18 urban gardens over the peak of the summer agricultural growing season. We then analyzed how temperatures were correlated to local land cover factors within the garden, to surrounding landscape imperviousness at various spatial scales, and to environmental justice indicators (stressors) of garden neighborhoods. We found that nocturnal temperature range is negatively correlated to landscape imperviousness, and that the relationship decreases in strength with increasing spatial scale. This result supports the importance of evapotranspiration processes of surrounding green areas for nocturnal cooling. Some local land cover factors were important for temperatures, indicating heating or cooling management mechanisms from within urban gardens. Finally, the mean number of environmental stressors in neighborhoods negatively related to temperature variation. The results of this work can inform resource use and crop selection in urban agriculture, as well as how temperature-related ecosystem services of gardens relate to environmental justice of city neighborhoods.

Relationships between air temperature and ice conditions on the southern Baltic coastal lakes in the context of climate change

Shallow, lagoonal coastal lakes of the Southern Baltic are exceptionally susceptible to atmospheric factors. This work examines the influence of winter air temperatures in Ustka on ice parameters (dates of first ice occurrence and last ice disappearance, ice season duration, number of days with ice, and maximum ice thickness) on Southern Baltic coastal lakes (Jamno, Bukowo, Gardno, Łebsko), and trends displayed by changes in these parameters over the period spanning 1960/61-2019/20. The research data was retrieved from the archives of Institute of Meteorology and Water Management – National Research Institute. As a first step of the analysis, we investigated the statistical relationships in spatial and temporal variations in winter air temperature and coastal lake ice parameters. Correlation and regression method was employed to determine the influence of air temperature on coastal lake ice conditions. Correlation and determination coefficients were calculated, and linear regression equations were determined. The statistical significance of the observed relationships was assessed using Fisher-Snedecor test. Additionally, linear trend models were constructed. Our analysis indicates that from 1960/61 to 2019/20, the average rate of increase in winter temperature (December-March) in Ustka equalled 0.04°C ⋅year-1. The correlation coefficients for air temperature versus ice parameters were highly statistically significant (p<0.001). The strongest relationships (with correlation coefficients below -0.90) occurred between air temperature and number of days with ice. Ice season duration and number of days with ice are both closely linked with last ice disappearance date and ice thickness. Our analysis shows that a 1°C increase in average seasonal air temperature will result in the number of days with ice on the studied coastal lakes becoming reduced by 16-17 days. All trends in ice parameters indicate a mildening of ice conditions. Most of the assessed trends are statistically significant. The strongest trends were observed for ice season duration, and indicate its shortening toward the east, from 0.66 day ⋅year-1 (Lake Jamno) to 1.16 day ⋅year-1 (Lake Łebsko). All correlation coefficients for ice trends were found to increase eastward, which could be explained by an increasing influence of the warming climate over the Southern Baltic in this direction. The strong relationships between air temperature and Southern Baltic coastal lake ice parameters, and the determined rate of changes may have a significance for forecasting, as the shifting dates of ice formation and disappearance on lakes are highly important for the lake hydrodynamics, and the functioning of aquatic ecosystems.

Why are 'suboptimal' temperatures preferred in a tropical intertidal ectotherm?

In thermally extreme environments, it is challenging for organisms to maximize performance due to risks associated with stochastic variation in temperature and, subsequently, over evolutionary time minimizing the exposure to risk can serve as one of the mechanisms that result in organisms preferring suboptimal temperatures. We tested this hypothesis in a slow-moving intertidal snail on tropical rocky shores, where temperature variability increases with time from 30min to 20hr when recorded at 30min intervals (due to short-term environmental autocorrelation where temperatures closer in time are more similar as compared to temperatures over a long period of time). Failure to accommodate temporal variation in thermal stress by selecting cool habitats can result in mortality. Thermal performance curves for different traits (heart rate and locomotion) were measured and compared to the snail's thermal preferences in both the field and laboratory. Predicted performances of the snails were simulated based on thermal performance curves for different traits over multiple time-scales and simulated carryover effects. A strong mismatch was found between physiological and behavioural thermal maxima of the snails (physiological thermal maximum being higher by ~7°C), but the snails avoided these maxima and sought temperatures 7-14°C cooler. Such a risk-averse strategy can be explained by their predicted performances where the snails should make decisions about preferred temperatures based on time periods ≥5hr to avoid underestimating the temporal variation in body temperature. In extreme and stochastic environments, where the temporal variation in environmental conditions can lead to substantial divergence between instantaneous and time-averaged thermal performances, 'cooler is better' and 'suboptimal' body temperatures are preferred as they provide sufficient buffer to reduce mortality risk from heat stress.

Thermal Management of Photovoltaics Using Porous Nanochannels

The photoelectric conversion efficiency of a solar cell is dependent on its temperature. When the solar radiation is incident on the photovoltaics (PV) panel, a large portion of it is absorbed by the underlying material which increases its internal energy leading to the generation of heat. An overheated PV panel results in a decline in its performance which calls for an efficient cooling mechanism that can offer an optimum output of the electrical power. In the present numerical work, thermal management with a porous nanochannels device capable to dissipate high heat flux is employed to regulate the temperature of a commercial PV panel by integrating the device on the back face of the panel. The spatial and temporal variation of the PV surface temperature is obtained by solving the energy balance equation numerically. By evaluating the steady-state PV surface temperature with and without thermal management, the extent of cooling and the resulting enhancement in the electrical power output is studied in detail. The nanochannels device is found to reduce the PV surface temperature significantly with an average cooling of 31.5 oC. Additionally, the enhancement in the electrical power output by ~33% and the reduction in the response time to 1/8th highlight the potential of using porous nanochannels as a thermal management device. Furthermore, the numerical method is used to develop a universal curve which can predict the extent of PV cooling for any generic thermal management device.