Thermal infrared (TIR) observations from geostationary satellites enable the retrievals of the diurnal variations in land surface temperatures (LST) linked to the land-atmosphere energy exchange and ...water cycle. However, cloud cover obstructs TIR signals and leads to missing gaps that generally account for more than 50% of TIR LST maps. This study proposed an effective method to estimate hourly all-weather LST from the Advanced Geosynchronous Radiation Imager (AGRI) data under the framework of surface energy balance (SEB) theory. An improved temperature and emissivity separation algorithm was first used to obtain the high-quality clear-sky LST, which plays a decisive role in ensuring the accuracy of recovered cloudy-sky LST. Then we proposed a unique way to solve the temperature difference (ΔLST) between the cloudy-sky LST and hypothetical clear-sky LST caused by cloud radiative effects (CRE). The bias (RMSE) of the estimated AGRI hourly cloudy-sky LST is 0.10 K (3.71 K) during the daytime, and -0.20 K (2.73 K) during the nighttime, respectively. The overall bias (RMSE) of the estimated AGRI all-weather LST is 0.02 K (2.84 K). The estimated hourly all-weather LST not only captures the rapid variation in diurnal LST but is also promising for temporal upscaling. The temporally upscaled daily mean LST shows a bias (RMSE) of 0.03 K (1.35 K). This study provides a promising solution to generate diurnal hourly all-weather LST for AGRI and other geostationary satellites.
•Critical applications require materials with superior surface characteristics.•High energy density and cooling rate make lasers suitable for such application.•Laser cladding and surface alloying may ...develop coating with high bonding strength.•Theoretical and experimental result suggest for better clad and surface properties.•Analysis of clad leads to defect free surface with wide industrial acceptance.
Laser cladding and surface alloying are surface modification techniques employed to fabricate thin coating/layer with improved surface properties or to refurbish surface defects by forming highly resistant gradient coatings/layers on the substrate. High energy density and cooling rates make these techniques suitable to process a wide range of materials. In recent years, due to the development of high power lasers, improved controlling and delivery mechanisms have attracted extensive research in laser surface treatment. Researchers have analyzed various process factors to improve process performance. The experimental and theoretical studies show that the performance of laser cladding and surface alloying techniques can be enhanced significantly by the proper selection of input process parameters. This paper summarizes various research works carried out so far in the area of laser cladding and surface alloying of different materials and their applications. It reports the research outcomes of experimental and theoretical studies conducted to improve the process performance. A brief introduction of various laser surface treatment processes is also included. Besides these various problems, their solutions and trend for future works have also been discussed.
This book covers topics ranging from a detailed error analysis of SSTs to new applications employed, for example, in the study of the El Niño–La Niña Southern Oscillation, lake temperatures, and ...coral bleaching. New techniques for interpolation and algorithm development are presented, including improvements for cloud detection. Analysis of the pixel-to-pixel uncertainties provides insight to applications for high spatial resolutions. New approaches for the estimation and evaluation of SSTs are presented. In addition, an overview of the Climate Change Initiative, with specific applications to SST, is presented. The book provides an excellent overview of the current technology, while also highlighting new technologies and their applications to new missions.
Introducing graduate students in physics, optics, materials science and electrical engineering to surface plasmons, this book also covers guided modes at planar interfaces of metamaterials with ...negative refractive index. The physics of localized and propagating surface plasmons, on planar films, gratings, nanowires and nanoparticles, is developed using both analytical and numerical techniques. Guided modes at the interfaces between materials with any combination of positive or negative permittivity and permeability are analyzed in a systematic manner. Applications of surface plasmon physics are described, including near-field transducers in heat-assisted magnetic recording and biosensors. Resources at www.cambridge.org/9780521767170 include Mathematica code to generate figures from the book, color versions of many figures, and extended discussion of topics such as vector diffraction theory.
In this paper, an atmospheric-pressure dielectric barrier discharge is used to modify the surface of the epoxy material and enhance the dissipation of surface charge to reduce the accumulation of ...surface charge. In the experiments, atmospheric-pressure air dielectric barrier discharge is driven by a microsecond pulse generator. Surface properties of epoxy before and after the plasma treatment are characterized by water contact angle, surface potential, and surface/volume conductivity measurements. Atomic force microscope and X-ray photoelectron spectroscopy are used to investigate the changes of the morphology and the chemical composition of the epoxy surface. Experimental results indicate that the surface of epoxy is etched by the plasma and the increase of the surface roughness enhances the surface insulation ability. The O radicals in plasma and the carbonyl groups formed on the surface make the surface charge trap shallower, change the epoxy surface composition then increase the surface conductivity and accelerate surface charge dissipation. When the epoxy is treated for an appropriate time, the epoxy surface insulation performance will be enhanced obviously and the surface charge dissipation will be accelerated.
Intelligent reflecting surfaces can improve the communication between a source and a destination. The surface contains metamaterial that is configured to "reflect" the incident wave from the source ...towards the destination. Two incompatible pathloss models have been used in prior work. In this letter, we derive the far-field pathloss using physical optics techniques and explain why the surface consists of many elements that individually act as diffuse scatterers but can jointly beamform the signal in a desired direction with a certain beamwidth. We disprove one of the previously conjectured pathloss models.
Anthropogenic heat flux (AHF) is a main contributor to the formation of surface urban heat islands (SUHI). Megacities in particular are facing severe problems due to excessive population growth, ...urban area expansion, human activity, increased energy consumption, and increased anthropogenic heat. In this study, a physical modeling approach based on a triple-source surface energy balance (triple-SEB) model was developed to uncover the effect of AHF on land surface temperature (LST) and surface anthropogenic heat island (SAHI) intensity. For this purpose, satellite imagery along with climatic and meteorological data from 1985 to 2019 were studied for six selected megacities: Los Angeles, Atlanta, Athens, Istanbul, Tehran, and Beijing. First, LST and the fraction of different surface covers were calculated by using a single-channel algorithm and a normalized spectral mixture analysis model, respectively. In the second step, impervious surface cover (ISC) and the urban main boundary area (UMBA) of each city were extracted based on the biophysical composite index and city clustering algorithm, respectively. In the third step, anthropogenic LST (ALST) was modeled using a triple-SEB model. In the fourth step, the ALST and UMBA were used together to model SAHI intensity at different dates. Finally, the relationship between the estimated ALST and ISC, as well as between SAHI and ISC, was examined. Results show that the average value of estimated ALST for the megacities increased from 2.02, 0.55, 0.61, 0.64, 0.58, and 0.72 to 2.99, 1.73, 1.66, 1.19, 2.32, and 2.76 °C, respectively. The coefficient of determination between the mean value of ISC and the estimated ALST for all megacities yielded 0.8, which was higher than that between ISC and satellite-derived LST. Moreover, the SAHI intensity for these megacities was found to have increased to 0.73, 0.92, 0.95, 0.98, 0.95 and 1.32 °C, respectively, which can be predicted by ISC with a coefficient of determination of 0.78, 0.79, 0.79, 0.73, 0.71 and 0.52, respectively. This suggests that the triple-SEB model proposed by this study allowed for independent modeling of AHF's influence on SUHI and a better determination of the effect of ISC on LST and SUHI intensity. This approach facilitated comparative analysis of LST and SAHI for a city at different times as well as SAHIs in different cities with different geographic and climate settings.
•A novel method based on triple-source energy balance model developed for LST•LST due to anthropogenic heat flux used to model surface anthropogenic heat island•SAHI and the effect of ISC on SUHI in five global megacities were investigated.•Better determination and modeling of the effect of ISC on LST and SUHI intensity•New method for comparative analysis of LST and SAHI at different times and cities
Abstract
Modeled global warming is often quantified using global near-surface air temperature (
T
as
). Meanwhile, long-term temperature datasets combine observations of
T
as
over land with sea ...surface temperature (SST) over ocean. Modeled ocean
T
as
warms more than SST, which can bias model–observation comparisons. Skin temperature (
T
s
), which is typically warmer than
T
as
, follows SST changes so the ocean surface temperature discontinuity
δT
s
=
T
s
−
T
as
decreases with warming. Here I show that under CO
2
forcing, decreased
δT
s
is consistently simulated for nonpolar ocean within ±60°S/N, but not for other regions. I investigate the causes of oceanic
δT
s
decrease using a LongRunMIP climate simulation, radiative kernels, and standard methods for diagnosing forcing and feedbacks from the CMIP5 ensemble. CO
2
forcing establishes longwave heating of the lower atmosphere and subsequent adjustments that result in a small
T
as
increase, and therefore a
δT
s
decrease. During the subsequent warming in response to CO
2
forcing, the model-mean surface evaporation feedback is 3.6 W m
−2
°C
−1
over oceans, which reduces
T
s
warming relative to
T
as
and further shrinks
δT
s
. Present-day forcing and feedback contributions are of similar magnitude, and both contribute to small differences in model–observation comparisons of global warming rates when these differences are not accounted for.
Significance Statement
Earth’s surface skin temperature is generally warmer than that of the air just above, and this discontinuity drives upward turbulent heat fluxes. Under global warming, climate models consistently show that over oceans, the air above warms more than the water below. This causes issues when comparing model output and observational temperature records, since observational records blend land air and ocean water temperature. It also affects understanding of how surface energy and moisture fluxes will change with warming. Observational data are currently too uncertain to confidently support or refute this model behavior, and the IPCC recently noted that “there is no simple explanation based on physical grounds alone for how this difference responds to climate change.” This study provides such an explanation for changes over ocean, and shows that this result applies only to nonpolar oceans.
Surface flashover is likely to be triggered when a high electric field is applied due to its voltage being much lower than the breakdown voltage of either gas or solid, which restricts the ...development of advanced power electrical and electronic devices. To improve dc surface flashover performances in a vacuum and further explore the effects of deep traps on surface flashover, conductive multiwall carbon nanotubes (MWCNTs) and nonconductive nano-titania (TiO2) particles were incorporated into the epoxy (EP) matrix to tailor the surface deep trap level. Surface trap parameters, surface conductivity, surface charge density, and surface flashover voltage were calculated and measured. It indicates that surface flashover voltage improves by 23.07% and 14.45% compared to pristine EP when solely introducing MWCNTs or nano-TiO2 particles into the EP matrix, while it increases by 36.04% for C0.1T2 as simultaneously introducing both particles. When adding small amounts of particles, the surface charge transport is suppressed due to the introduction of bonded layers in the interfacial region, and the surface deep trap level is improved. As the surface deep trap level increases, charge transport and electron emission processes in the solid surface layer are hindered, which reduces the surface positive charge density and the distortion of the electric field and further results in the reduction of surface conductivity and the improvement of dc surface flashover voltage in a vacuum. The explanation for the effects of surface deep traps on surface flashover is essential for further improvements of surface flashover.
Surface charges have the effect of changing the electric field over spacers in compressed gases, which may affect the stable operation of gas insulated equipment and could possibly trigger a ...catastrophic surface flashover without warning. In this paper, we review the literature on surface charge accumulation and related surface flashover phenomenon on spacers in compressed gases. A summary of experimental research of surface charge accumulation is presented and, the surface charge accumulation mechanism is also summarized, with some newly identified factors in mind that may affect surface charge transport and measurements thereof. Subsequently, the correlation between surface charge accumulation and the surface flashover phenomenon is thoroughly discussed, and the effect of surface charges on surface breakdown under applied voltage pulses of various waveforms is analyzed. Finally, several important research topics in this area are proposed. In addition, some ideas on potential surface charge control methods are presented to aid the design of a better spacer free from surface charges in future studies.
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