Surface Temperature Dependence Research Articles

Long-term climatological trends driving the recent warming along the Angolan and Namibian coasts

AbstractThe coastal regions off Angola and Namibia are renowned for their highly productive marine ecosystems in the southeast Atlantic. In recent decades, these regions have undergone significant long-term changes. In this study, we investigate the variability of these long-term changes throughout the annual cycle and explore the underlying mechanisms using a 34-year (1982–2015) regional ocean model simulation. The results reveal a clear seasonal dependence of sea surface temperature (SST) trends along the Angolan and Namibian coasts, with alternating positive and negative trends. The long-term warming trend in the Angolan coastal region is mainly explained by a pronounced warming trend in the austral spring and summer (November-January), while the decadal trend off Namibia results from a counterbalance of an austral winter cooling trend and an austral summer warming trend. A heat budget analysis of the mixed-layer temperature variations shows that these changes are explained by a long-term modulation of the coastal currents. The Angolan warming trend is mainly explained by an intensification of the poleward coastal current, which transports more warm equatorial waters towards the Angolan coast. Off Namibia, the warming trend is attributed to a reduction in the northwestward Benguela Current, which advects cooler water from the south to the Namibian coast. These changes in the coastal current are associated with a modulation of the seasonal coastal trapped waves that are remotely-forced along the equatorial waveguide. These long-term changes may have significant implications for local ecosystems and fisheries.

Why Are Mountaintops Cold? The Transition of Surface Lapse Rate on Dry Planets

AbstractUnderstanding surface temperature is important for habitability. Recent work on Mars has found that the dependence of surface temperature on elevation (surface lapse rate) converges to zero in the limit of a thin CO2 atmosphere. However, the mechanisms that control the surface lapse rate are still not fully understood. It remains unclear how the surface lapse rate depends on both greenhouse effect and surface pressure. Here, we use climate models to study when and why “mountaintops are cold.” We find the tropical surface lapse rate increases with the greenhouse effect and with surface pressure. The greenhouse effect dominates the surface lapse rate transition and is robust across latitudes. The pressure effect is important at low latitudes in moderately opaque (τ ∼ 0.1) atmospheres. A simple model provides insights into the mechanisms of the transition. Our results suggest that topographic cold‐trapping may be important for the climate of arid planets.

Electrokinetic ion rectification coupled with surface charge and thermal dependence in the conical nanochannel

With the further development of nanotechnology, electrokinetic ion rectification (ICR) is receiving increasing attention. Since the chemical equilibrium boundary is more suitable for expressing the wall charging characteristics and the coincidence of asymmetric temperature with ICR, we first propose an ICR ion transport model that couples the chemical equilibrium boundary with asymmetric temperature. In this work, ICR under different electrical boundary conditions is studied. The effects of membrane thermal conductivity, solution pH, and geometric conditions on the rectification performance are further explored in combination with surface charge and temperature dependence. The results show that the rectification ratio of the constant σ model and constant ζ model has a significant deviation compared to the multi-ion model, and the electrical boundary conditions can be simplified by changing the external conditions. By controlling the thermal conductivity of the membrane, the distribution of temperature difference within the reservoir or nanochannel can be determined, which affects the enrichment or depletion of ions in the nanochannel and ultimately achieves the goal of optimizing the rectification ratio. The optimal ICR ratio can be obtained by adjusting pH, and optimizing geometric conditions can significantly improve rectification performance. These studies provide helpful information for ion transport control and optimization of micro/nanofluid devices.

Effects of greenhouse gases on Earth, Venus, and Mars: Beyond the one-blanket model

I present a discussion of the effect of increasing carbon dioxide on planetary climate, at a level suitable for insertion as a module into an upper-level Physics course. The treatment includes two key ingredients that are often missing from more elementary discussions, yet are amenable to analytic methods: First, that convection implies a dependence of surface temperature on the height of the outermost infrared-thick layer; and second, that increasing the level of CO2 closes spectral windows of absorption. These themes are applicable not only to an industrializing Earth but also to our neighboring planets.

Parameterizations for sea spray aerosol production flux

Sea spray aerosols (SSA) are important contributors to the global aerosol load, and they have a significant impact on the global climate system and chemical processes. To better assess the environmental impact of SSA emissions, it is important to quantitatively characterize the parametric dependence of SSA production fluxes on other environmental variables, and assess their role in global climate models (GCMs) and chemical transport models (CTMs). There are currently significant differences in the simulation of global SSA production fluxes in various models, and these differences are mainly attributed to the differences in the sea spray source functions (SSSFs). Research in the literature over the last decade has greatly broadened the knowledge of SSSFs and improved our understanding of SSA production fluxes and how they are applied in models. This paper clarifies the derivation process of different SSSFs, and provides a critical review of the application progress of different SSSFs in different models, which plays an important role in improving the accuracy of model simulations to evaluate the impact of SSA. More specifically, we review the studies related to the parameterization of sea spray aerosol production fluxes in the last decade, mainly focusing on the influencing factors of SSA production, the research progress of SSSFs, and the application of SSSFs in the models. The main environmental factors that alter the production flux in SSA include wind speed, sea surface temperature, wave state, salinity, surface active organic matter, etc. To better parameterize the SSA production flux, different expressions of SSSFs have been proposed. This paper mainly summarizes from different variables such as particle size distribution dependence, whitecap coverage, sea surface temperature dependence and wave state dependence. Moreover, many studies have incorporated different SSSFs in different GCMs and CTMs to evaluate the reasonableness of SSSFs and the climate impact of SSA emissions. Finally, we summarize the current results and inadequacy of SSA production flux parameterization, and put forward the prospect of future research direction.

Rotational-Energy Transfer in H2 Ortho-Para Conversion on a Metal Surface: Interplay between Electron and Phonon Systems.

Clarifying energy transfer processes in molecular adsorption on solid surfaces is essential to understand the gas-surface interaction. Unlike the vibrational-energy transfer processes, which are thought to be well understood in detail, the rotational-energy transfer process still remains unclear. Considering the interconversion between ortho and para states of H2 is accompanied by the nuclear spin flip and the rotational-energy transfer, the surface-temperature dependence of the ortho-to-para conversion of molecularly chemisorbed H2 on Pd(210) is studied. The conversion rate is accelerated with an increase in surface temperature. Based on the conversion model proposed for metal surfaces, we analyze the temperature dependence of the conversion rate, taking into account both electron and phonon systems of the substrate. The rotational-energy transfer is most likely mediated by surface electrons with the assistance of the substrate phonons.

Investigation of the Temperature Dependence of a Product Dried in a Solar Dryer on Its Moisture Content

This paper presents the results of liquid-viscous temperature studies of agriculture products during in drying process in a solar-drying installation of a radiation-convective type. And also, the results of the temperature of the glass coating of the drying chamber during the day at different periods of the year. The outer surface temperature dependences of the drying chamber glass enclosure in July and October on the density of solar radiation and from the ambient air temperature are given. Research indicators have been determined that, other things being equal, the temperature of the dried product is significantly affected by their absorption capacity. The indicators of the research that in other equal conditions their observing feature significantly effects on temperature of drying products are defined absorption capacity.

A Review of Recombination Coefficients of Neutral Oxygen Atoms for Various Materials

Relevant data on heterogeneous surface recombination of neutral oxygen atoms available in the scientific literature are reviewed and discussed for various materials. The coefficients are determined by placing the samples either in non-equilibrium oxygen plasma or its afterglow. The experimental methods used to determine the coefficients are examined and categorized into calorimetry, actinometry, NO titration, laser-induced fluorescence, and various other methods and their combinations. Some numerical models for recombination coefficient determination are also examined. Correlations are drawn between the experimental parameters and the reported coefficients. Different materials are examined and categorized according to reported recombination coefficients into catalytic, semi-catalytic, and inert materials. Measurements from the literature of the recombination coefficients for some materials are compiled and compared, along with the possible system pressure and material surface temperature dependence of the materials' recombination coefficient. A large scattering of results reported by different authors is discussed, and possible explanations are provided.

Surface Hydroxyl Chemistry of Titania- and Alumina-Based Supports: Quantitative Titration and Temperature Dependence of Surface Brønsted Acid-Base Parameters.

Surface hydroxyl groups on metal oxides play significant roles in catalyst synthesis and catalytic reactions. Despite the importance of surface hydroxyls in broader material applications, quantitative measurements of surface acid-base properties are not regularly reported. Here, we describe direct methods to quantify fundamental properties of surface hydroxyls on several titania- and alumina-based supports. Comparing commercially available anatase, rutile, P25, and P90 titania, thermogravimetric analysis (TGA) indicated that the total surface hydroxyl density varied by a factor of 2, and each surface hydroxyl is associated with approximately one weakly adsorbed water molecule. Proton-exchange site densities, determined at 25 °C with slurry acid-base titrations, led to several conclusions: (i) the intrinsic acidity/basicity of surface hydroxyls were similar regardless of the titania source; (ii) differences in the surface isoelectric point (IEP) were primarily attributable to differences in the surface concentration of acid and base sites; (iii) rutile has a higher surface concentration of basic hydroxyls, leading to a higher IEP; and (iv) P25 and P90 titania have slightly higher surface concentrationsof acidic hydroxyls relative to anatase or rutile. Temperature effects on surface acid-base properties are rarely reported yet are significant: from 5 to 65 °C, IEP values change by roughly one pH unit. The IEP changes were associated with large changes to the intrinsic acid-base equilibrium constants over this temperature range, rather than changes in the composition or concentration of the surface sites.

Evaluation of the small particle adhesion force on low temperature surface in high vacuum using atomic force microscopy

The adhesion force of small particles on a substrate surface depends on various parameters, including the surface roughness, temperature, and surrounding environment. In this study, atomic force microscopy was used to investigate the surface temperature dependence of the adhesion force of small silica particles on relatively smooth and rough Al substrates at temperatures below room temperature in high vacuum. The adhesion force did not depend on the temperature of the rough substrate. On the smooth substrate with a temperature decrease from 298 K, the adhesion force increased and was the largest at 273 K. Moreover, the adhesion force decreased from 273 to 213 K and remained almost constant below 213 K. The change in adhesion force was explained in terms of the surface diffusion of water molecules that formed capillaries. Its activation barrier was deduced to be 96 meV in the range of 273–213 K.

Effects of doping ceria on flame quenching in a narrow channel with zirconia-based functional coatings

Wall coating modification has been a potential solution to organize the combustion process in space-constrained system. For this purpose, CeO2 doping effects on the flame stability of premixed methane/air mixtures confined within an adjustable-gap narrow channel with coating ZrO2-based ceramics are experimentally investigated. A series of characterization means are utilized to analyze these prepared composite coatings. Results elaborate that the catalytic activities of CeO2-ZrO2 solid solution correlate with the ratio of CeO2 dopant in bulk. Phase structural stabilities can be strengthened through increasing the CeO2 content, which is due to the significant increase in the ratio of tetragonal phase to monoclinic phase of ZrO2. X-ray photoelectron spectroscopy and H2 temperature-programmed reduction analysis outcomes show that the concentration of formed oxygen vacancies increases significantly with richer CeO2 phase doped, which promotes the exaltation of lattice oxygen activity and fluidity. Flame quenching tests demonstrate that the wall surface temperature dependence of the quenching distance is changed substantially by doping CeO2 into the ZrO2 coating wall, eliminating the negative temperature effect observed for a pure ZrO2 case at the medium temperature ranges of 673–773 K. The cases of higher-CeO2-content doping provide a lower flame quenching distance, especially at slightly fuel-rich conditions, which arises from the enhancement of the storage and release functions of highly active oxygen ions through Ce4+/Ce3+ redox cycles. Comparing of OH planar laser-induced fluorescence images near the extinction limit indicates that in addition to flow rate and air–fuel ratio, different coating materials also have dramatic effects on the post flame characteristic and flame oscillation. In general, this paper not only provides a good overview of the chemical interaction between the wall and flame, but also makes an implication for the design of high-stability small-scale combustors by reasonably manufacturing this type of CeO2-ZrO2 coating functional materials.

Thermal relaxation of dark matter admixed neutron star

ABSTRACT Motivated by the various theoretical studies regarding the efficient capturing of dark matter by neutron stars, we explore the possible indirect effects of captured dark matter on the cooling mechanism of a neutron star. The equation of states for different configurations of dark matter admixed star at finite temperature is obtained using the relativistic mean-field formalism with the IOPB-I parameter set. We show that the variation in the dark matter momentum vastly modifies the neutrino emissivity through specific neutrino generating processes of the star. The specific heat and the thermal conductivity of a dark matter admixed star have also been investigated to explore the propagation of cooling waves in the interior of the star. The dependence of theoretical surface temperature cooling curves on the equation of state and chemical composition of the stellar matter has also been discussed along with the observational data of thermal radiation from various sources. We observed that the dark matter admixed canonical stars with $k_{f}^{\rm DM} \gt 0.04$ comply with the fast cooling scenario. Further, the metric for internal thermal relaxation epoch has also been calculated with different dark matter momentum and we deduced that increment of dark matter segment amplify the cooling and internal relaxation rates of the star.

Ku- and Ka-Band Ocean Surface Radar Backscatter Model Functions at Low-Incidence Angles Using Full-Swath GPM DPR Data

This paper presents the results of the first characterization of coincident Ku- and Ka-band ocean surface normalized radar cross section measurements at earth incidence angles 0°–18° using one year of wide swath Global Precipitation Measurement (GPM) mission dual frequency precipitation radar (DPR) data. Empirical geophysical model functions were derived for both bands, isotropic and directorial sensitivity were assessed, and finally, sea surface temperature (SST) dependence of radar backscatter, at both bands, were investigated. The Ka-band exhibited higher vector wind sensitivity for a low-to-moderate wind speeds regime, and the SST effects were also observed to be substantially larger at Ka-band than at Ku-band.

Vibrationally inelastic scattering of HCl from Ag(111).

Using molecular beam cooled samples and quantum state-selective detection, we observe v = 0 → 1 vibrational transitions when HCl (v = 0) collides with an Ag(111) surface and derive both the incidence energy and surface temperature dependence of the transition probability. Our observations reveal that both electronically adiabatic and non-adiabatic mechanisms are at play in this inelastic process. A comparison to other systems shows similarities and trends that are consistent with an electron transfer mechanism forming a transient HCl-. For example, the electronically nonadiabatic coupling is stronger than for HCl scattering from Au, where the solid's work function is higher. HCl differs from other systems in that dissociation is possible over a low barrier. Vibrationally inelastic v = 1 → 2 transitions could not be seen when HCl (v = 1) collides with an Ag(111) surface. We suggest that scattering events, where HCl (v = 1) is subject to dynamical influences that increase its vibrational energy, lead efficiently to dissociation before the HCl (v = 2) molecule can escape the surface. This system appears to be an excellent candidate to study electronically nonadiabatic effects in dissociative adsorption.

Temperature dependence of surface and grain boundary energies from first principles

In this study we systematically study the temperature dependence of interface energies in W using first principles. To that purpose, we compute interface free energies and consider different contributions, i.e., from lattice expansion, vibrational contribution from harmonic and quasiharmonic approximation with explicit phonon calculations, and electronic contribution. We find that interface energies decrease with temperature and that in most cases the harmonic approximation to the free energy is sufficient. The relative decrease of the interface energy at 2000 K for the surfaces varies from $\ensuremath{-}20$% to $\ensuremath{-}30$%, while for grain boundaries, the interface energies decrease from $\ensuremath{-}30$% to $\ensuremath{-}55$%. Our results are compared to models on temperature dependence of interface energies available in literature. We find that they are in qualitative agreement also exhibiting a general decrease with higher temperatures. However, most models neglect anisotropy effects and are not in quantitative agreement. The equilibrium crystal shape matches with experimentally observed particle and pore shapes.

A new and simple prescription for planet orbital migration and eccentricity damping by planet–disc interactions based on dynamical friction

ABSTRACT During planet formation, gravitational interaction between a planetary embryo and the protoplanetary gas disc causes orbital migration of the planetary embryo, which plays an important role in shaping the final planetary system. While migration sometimes occurs in the supersonic regime, wherein the relative velocity between the planetary embryo and the gas is higher than the sound speed, migration prescriptions proposed thus far describing the planet–disc interaction force and the time-scales of orbital change in the supersonic regime are inconsistent with one another. Here we discuss the details of existing prescriptions in the literature and derive a new simple and intuitive formulation for planet–disc interactions based on dynamical friction, which can be applied in both supersonic and subsonic cases. While the existing prescriptions assume particular disc models, ours include the explicit dependence on the disc parameters; hence, it can be applied to discs with any radial surface density and temperature dependence (except for the local variations with radial scales less than the disc scale height). Our prescription will reduce the uncertainty originating from different literature formulations of planet migration and will be an important tool to study planet accretion processes, especially when studying the formation of close-in low-mass planets that are commonly found in exoplanetary systems.

MID-TERM FORECAST FOR THE ICE CONDITIONS IN THE BERING SEA

Application of CICE ice model for the mid-term (days) forecasting in the Bering Sea is considered, with short description of the model. Dependence of the sea surface temperature on the air temperature forecasted by GFS (Global Forecasting System) is determined. The ice concentration, ice cover, and the dates of ice formation are forecasted for the winter 2018/2019 using the model; its practical applicability is concluded.

Relationship between land surface temperature and fraction of anthropized area in the Atlantic forest region, Brazil.

There is growing evidence that modification of tropical forests to pasture or other anthropic uses (anthropization) leads to land surface warming at local and regional scales; however, the degree of this effect is unknown given the dependence on physiographic and atmospheric conditions. We investigated the dependence of satellite land surface temperature (LST) on the fraction of anthropized area index, defined as the fraction of non-forested percentual area within 120m square boxes, sampled over a large tropical forest dominated ecosystem spatial domain in the Atlantic Forest biome, southeastern Brazil. The LST estimated at a 30 m resolution, showed a significant dependence on elevation and topographic aspect, which controlled the average thermal regime by 2~4°C and 1~2°C, respectively. The correction of LST by these topographic factors allowed to detect a dependence of LST on the fraction of non-forested area. Accordingly, the relationship between LST and the fraction of non-forested area showed a positive linear relationship (R2 = 0.63), whereby each 25% increase of non-forest area resulted in increased 1°C. As such, increase of the maximum temperature (~4°C) would occur in the case of 100% increase of non-forested area. We conclude that our study area, composed to Atlantic forest, appears to show regulatory characteristics of temperature attenuation as a local climatic ecosystem service, which may have mitigation effects on the accelerated global warming.

Unconventional Josephson junctions with topological Kondo insulator weak links

Proximity-induced superconductivity in three dimensional (3D) topological insulators forms a new quantum phase of matter and accommodates exotic quasiparticles such as Majorana bound states. One of the biggest drawbacks of the commonly studied 3D topological insulators is the presence of conducting bulk that obscures both surface states and low energy bound states. Introducing superconductivity in topological Kondo insulators such as SmB$_6$, however, is promising due to their true insulating bulk at low temperatures. In this work, we develop an unconventional Josephson junction by coupling superconducting Nb leads to the surface states of a SmB$_6$ crystal. We observe a robust critical current at low temperatures that responds to the application of an out-of-plane magnetic field with significant deviations from usual Fraunhofer patterns. The appearance of Shaphiro steps under microwave radiation gives further evidence of a Josephson effect. Moreover, we explore the effects of Kondo breakdown in our devices, such as ferromagnetism at the surface and anomalous temperature dependence of supercurrent. Particularly, the magnetic diffraction patterns show an anomalous hysteresis with the field sweep direction suggesting the coexistence of magnetism with superconductivity at the SmB$_6$ surface. The experimental work will advance the current understanding of topologically nontrivial superconductors and emergent states associated with such unconventional superconducting phases.

Skin Layer Effects on Adhesion Forces of PVA Brushes and Its Temperature Dependence

In this study, the adhesion forces between PVA (PolyVinyl Acetal) brushes and solid surfaces were measured directly using a highly responsive load cell. The adhesion forces were compared based on contact time, and the influence of skin layer existence on PVA brush surface was investigated. In addition, the surface temperature dependence of the adhesion forces was also studied. Results showed that the adhesion force increased with increasing surface contact time. For a PMMA surface, significantly large adhesion forces were observed. It was also seen that the adhesion force decreased with increasing temperature. However, by using the present setup, the adhesion forces in all experimental conditions without skin layer brush cases could not be measured.