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The surface color and materials of sidewalk pavements exhibit different albedo characteristics, leading to varied surface urban heat island effects in subtropical regions. To quantify the effect of pavement surface color and material on SUHI, Prefabricated Concrete Structure brick (PCB), Granite brick (GB) and Dutch brick (DB) totaling 14 pavement samples in Hangzhou were placed under unshaded, cloud shaded and tree shaded conditions. CIELAB (International Commission on Illumination L*a*b*) color data, short-wave radiation (incoming and outgoing) and surface temperature were measured. Results showed that L*(lightness) value played a dominant role in the albedo of the pavement surface, and there was a positive correlation in summer and winter. The lower the L* value, the greater the cooling effect of the pavement under cloud and tree shaded conditions. Compared to unshaded condition, tree shade provided the highest cooling benefit of 32.2 °C in summer. Among the 3 types of pavement materials, DB had the lowest average surface temperature in summer and the highest in winter. Therefore, in cities with cold winter and hot summer, it is advised that DB with a high surface L* value be employed. The use of pavement with a low L* value should be accompanied by continuous shading measures to cool the surface temperature. These findings provide a basis for selecting low-energy embodied pavement materials for urban streets and offer important technical support for mitigating the urban heat island effect. [ABSTRACT FROM AUTHOR]

Due to the lack of high-altitude observational datasets, a better understanding of snow cover changes and meteorological forcing for their variation in the Mount Everest region is still insufficient. This study examined changes in snow cover over the Mount Everest region and their relationship to air temperature, albedo (surface and snow), and total precipitation. This study used data from the MERRA2, ERA5-Land, JRA55, FLDAS, and CERES products spanning 41 years (1981–2021). For comparison and evaluation, we also used a ground station, Pyramid, located at a high elevation (5050 masl) at the foot of Mount Everest on the southern slope. The results confirmed a significant decline in snow cover during winter and post-monsoon seasons, which was observed in all datasets. Changes in surface and snow albedo and total precipitation positively correlate with the variation in snow cover; however, this relationship reverses with air temperature. This research suggests that atmospheric warming caused a decline in snow cover in the Mount Everest region. This decline affected snow and surface albedo, causing further warming and contributing to the continued decline in snow cover in the study area. The reduction in precipitation further contributes to the decrease in snow cover in the Mount Everest region. The variations in snow cover in this study correspond to those found in earlier studies on glacier thinning in cryosphere regions. Anthropogenic activities have linked these variations to increasing air temperatures while decreasing snowfall, precipitation, and albedo. [ABSTRACT FROM AUTHOR]

Using an astronomical model of insolation of the polar day and polar night zones of the Earth, the influence of cosmic factors on the ice conditions in them is estimated. It is shown that the temperature increase in the Northern Hemisphere began about 20 000 years ago due to volcanic events that occurred at that time, as well as in connection with the presence of a surplus of solar energy in this area of the planet, caused by the parameters of the Earth’s orbit: the inclination of the rotation axis, eccentricity, and precession angle. The surplus of thermal energy in the Northern Hemisphere has been preserved since then until the present day and will continue for at least 3000 years, after which the next period of glaciation will begin. Similar data are given for the Southern Hemisphere. It is shown that the melting of northern glaciers has been spread over many millennia due to the high heat of ice fusion and a pronounced phase transition. During melting, thermal energy is spent on the destruction of the ice crystal lattice, and the melt temperature does not increase. During freezing, the reverse process occurs: the energy released during ice crystallization prevents the temperature from decreasing. This process also occurs at a constant temperature. The heat-stabilizing properties of ice have manifested themselves in the form of “temperature shelves” on the graphs of the dependence of the average annual temperature on time, constructed based on the results of the analysis of ice cores obtained in the Southern Hemisphere at the Vostok station and in the Northern Hemisphere in central Greenland. At present, ice reserves in the Northern Hemisphere are coming to an end. Accordingly, the ability of glaciers to stabilize temperature is decreasing. As a result, the frequency and power of natural disasters in the world is growing. The problem of preserving the existing climate is becoming urgent. There is less and less time left for preparing and implementing measures to counteract climate change. Decarbonization cannot resist the ongoing process of destruction of the unique mechanism of natural climate stabilization. It is necessary to look for other ways to solve the problem of preserving the current climate. Among them, on the one hand, various methods of increasing albedo can be considered, and on the other hand, methods of reducing the permeability of the atmosphere by spraying special chemicals with short periods of complete decomposition in the upper layers of the atmosphere over certain areas. [ABSTRACT FROM AUTHOR]

Atmospheric dispersion models use mathematical equations to calculate pollution concentrations in the receiving environment; however, there can be variations in the accuracy of a pollutant's calculated concentration among different models due to the nature of the modeling environment and limitations on computational complexities. In this study two types of popular Gaussian pollution dispersion models, AERMOD and ADMS, were investigated to analyze their behavior under specific conditions. Initially, both models were simulated for point and line sources of emission. Subsequently, their output results were compared with passive samplers placed for varying periods (2 weeks, 2 months, and 3 months) at modeled receptor locations. The results indicated that both models underestimate the passive sampler results. However, AERMOD's underestimation was found to be more than ADMS's, resulting in ADMS performing slightly better. Additionally, to study the effectiveness of input parameters such as surface characteristics and solar insolation, a relative sensitivity analysis was conducted under two different atmospheric conditions: convective mixing dominance (CMD) and mechanical mixing dominance (MMD). It was found that AERMOD was relatively more sensitive to surface roughness, especially in MMD conditions than to albedo, surface moisture, and solar insolation. Both models were somewhat insensitive to albedo and Bowen, and solar insolation; however, in CMD conditions, AERMOD was more sensitive to these sunlight-related parameters. Also, both models were more sensitive to surface roughness than other input parameters. The results emphasize the importance of selecting precise parameters, particularly surface roughness, with more care for AERMOD than for the ADMS model. [ABSTRACT FROM AUTHOR]

Impacts of aerosol particles on clouds, precipitation, and climate remain one of the significant uncertainties in climate change. Aerosol particles entrained at cloud top and edge can affect cloud microphysical and macrophysical properties, but the process is still poorly understood. Here we investigate the cloud microphysical responses to the entrainment of aerosol-laden air in the Pi convection-cloud chamber. Results show that cloud droplet number concentration increases and mean radius of droplets decreases, which leads to narrower droplet size distribution and smaller relative dispersion. These behaviors are generally consistent with the scenario expected from the first aerosol-cloud indirect effect for a constant liquid water content (L). However, L increases significantly in these experiments. Such enhancement of L can be understood as suppression of droplet sedimentation removal due to small droplets. Further, an increase in aerosol concentration from entrainment reduces the effective radius and ultimately increases cloud optical thickness and cloud albedo, making the clouds brighter. These findings are of relevance to the entrainment interface at stratocumulus cloud top, where modeling studies have suggested sedimentation plays a strong role in regulating L. Therefore, the results provide insights into the impacts of entrainment of aerosol-laden air on cloud, precipitation, and climate. [ABSTRACT FROM AUTHOR]

Stellar occultations provide a powerful tool to explore objects of the outer solar system. The Gaia mission now provides milli-arcsec accuracy on the predictions of these events and makes possible observations that were previously unthinkable. Occultations return kilometric accuracies on the three-dimensional shape of bodies irrespective of their geocentric distances, with the potential of detecting topographic features along the limb. From the shape, accurate values of albedo can be derived, and if the mass is known, the bulk density is pinned down, thus constraining the internal structure and equilibrium state of the object. Occultations are also extremely sensitive to tenuous atmospheres, down to the nanobar level. They allowed the monitoring of Pluto's and Triton's atmospheres in the last three decades, constraining their seasonal evolution. They may unveil in the near future atmospheres around other remote bodies of the solar system. Since 2013, occultations have led to the surprising discovery of ring systems around the Centaur object Chariklo, the dwarf planet Haumea and the large trans-Neptunian object Quaoar, while revealing dense material around the Centaur Chiron. This suggests that rings are probably much more common features than previously thought. Meanwhile, they have raised new dynamical questions concerning the confining effect of resonances forced by irregular objects on ring particles. Serendipitous occultations by km-sized trans-Neptunian or Oort objects have the potential to provide the size distribution of a population that suffered few collisions until now, thus constraining the history of primordial planetesimals in the 1–100 km range. [ABSTRACT FROM AUTHOR]

Resampling the same satellite image to conduct a multi-scale assessment of desertification can be accompanied by distortion of terrestrial objects and spectral information, which can lead to uncertainty in the generated information. To address this, this study assesses desertification severity in an area of arid and semi-arid climate in the Eastern Mediterranean (Jordan) that is characterised by cloudless scenes using multi-sensor data of the same scene at the same time. To this end, Sentinel-2 at 10 m and 60 m, Landsat-8 at 30 m and MODIS at 250 m and 500 m were collected to extract albedo and modified soil adjusted vegetation index (MSAVI), and subsequently to construct albedo-MSAVI feature space. Using the negative correlation between albedo and MSAVI, desertification degree index (DDI) was generated. The resulting multi-scale DDI maps bear a relative resemblance in terms of spatial distribution, patterns, and proportions. The DDI maps indicate that extremely serious and serious desertification are widespread, accounting for 50% of the study area, primarily in the eastern portions. However, finer DDI maps (10 m, 30 m and 60 m) are essential for detecting small-scale desertification characteristics due to their ability to capture local spatial variabilities, while coarser ones (250 m and 500 m) are better suited for capturing broad-scale desertification patterns driven by climatic factors, in which MODIS data exhibit a relatively higher positive correlation with seasonal average precipitation. Although finer DDI maps show higher accuracy compared to coarser ones, the accuracy of DDI maps of MODIS has shown an increase within a homogeneous landscape. Accordingly, synchronised multi-scale assessment of desertification severity is not only influenced by the spatial resolution but also by the landscape heterogeneity and the type of satellite sensor utilised. The multi-scale approach applied in this study can provide insights on scale-dependent desertification that help in devising overarching mitigation strategies. [ABSTRACT FROM AUTHOR]

The snow cover in the Tibetan Plateau (TP) responds keenly to global climate and hydrological shifts, with snow albedo variation serving as a pivotal indicator of these changes. In this study, we explored snow albedo changes over the period (2001–2022) in the TP combined with the high-resolution near-surface meteorological forcing datasets (2001–2022). The study utilized Ding's method to separate precipitation patterns, and then employed path analysis to evaluate the vertical response of snow albedo to air temperature, rainfall, and snowfall across four periods. The findings are as follows: (1) Snow albedo in area above 4000 m ranged from 0.4 to 0.7, while below 4000 m, snow albedo was primarily below 0.4. Snow albedo was generally higher in the northern TP. (2) During the snow accumulation period (October to December), snow albedo showed a decreasing trend in most areas of the TP. Conversely, snow albedo exhibited overall increasing trends during the snow stable period (January to February), snowmelt period (March to May), and snowless period (June to September). Especially in the central TP, snow albedo showed significant decrease during the snow accumulation period, and it increased significantly in the other periods. (3) Air temperature, rainfall, and snowfall influenced directly and predominantly snow albedo changes in the TP. Especially, air temperature and snowfall were the primary driving factors in most areas. (4) During different periods, air temperature was the main factor driving changes in snow albedo below 5000 m, but snowfall had a stronger influence above 5000 m. Except during the snow accumulation period, the impact of rainfall on snow albedo decreased with increasing altitude. During the snowless period, rainfall affected snow albedo obviously, but snowfall remained the dominant factor in areas above 6500 m. These results provide new insights on climate-driven changes in the snow albedo over the TP. [ABSTRACT FROM AUTHOR]

In this paper, we examined the elevation-dependent warming (EDW) patterns of MODIS LST across different seasons in the Qinling-Daba Mountains, further investigate the connections between the EDW patterns of Land surface temperature (LST) and land surface albedo (ALB) as well as aerosol optical depth (AOD). The key findings include: (1) Our study reveals a robust correlation between LST and air temperature in the Qinling-Daba Mountains, suggesting the feasibility of using MODIS LST to predict the temperature trends (2) During the period from 2001 to 2010, MODIS LST shows a significant EDW trend, primarily in the spring season. In contrast, a negative EDW is observed in the period during 2011–2021, which is contrary to the earlier decade, particularly during the autumn and winter seasons. (3) EDW of MODIS LST is affected by the combination of ALB and AOD. The former has a negative influence on the change of LST, particularly above 2500 m in elevation. However, the latter is negatively correlated with the trend of MODIS LST, primarily at lower and middle altitudes (0–2500 m). This study gives a comprehensive explanation for the EDW of the temporal variations of LST in the Qinling-Daba Mountains to improve our understanding of the complex interactions and potential future climate scenarios in the region. [ABSTRACT FROM AUTHOR]

Tibetan Plateau (TP) is known as the "Third Pole" of the Earth. Any changes in land surface processes on the TP can have an unneglectable impact on regional and global climate. With the warming and wetting climate, the land surface of the TP saw a darkening trend featured by decreasing surface albedo over the past decades, primarily due to the melting of glaciers, snow, and greening vegetation. Recent studies have investigated the effects of the TP land surface darkening on the field of climate, but these assessments only address one aspect of the feedback loop. How do these darkening-induced climate changes affect the frozen ground and ecosystems on the TP? In this study, we investigated the impact of TP land surface darkening on regional frozen ground and ecosystems using the state-of-the-art land surface model ORCHIDEE-MICT. Our model results show that darkening-induced climate changes on the TP will lead to a reduction in the area of regional frozen ground by 1.1×104±0.019×104 km2, a deepening of the regional permafrost active layer by 0.06±0.0004 m, and a decrease in the maximum freezing depth of regional seasonal frozen ground by 0.06±0.0016 m compared to the scenario without TP land surface darkening. Furthermore, the darkening-induced climate change on the TP will result in an increase in the regional leaf area index and an enhancement in the regional gross primary productivity, ultimately leading to an increase in regional terrestrial carbon stock by 0.81±0.001 PgC. This study addresses the remaining piece of the puzzle in the feedback loop of TP land surface darkening, and improves our understanding of interactions across multiple spheres on the TP. The exacerbated regional permafrost degradation and increasing regional terrestrial carbon stock induced by TP land surface darkening should be considered in the development of national ecological security barrier. [ABSTRACT FROM AUTHOR]

In this section of Resonance, we invite readers to pose questions likely to be raised in a classroom situation. We may suggest strategies for dealing with them, or invite responses, or both. "Classroom" is equally a forum for raising broader issues and sharing personal experiences and viewpoints on matters related to teaching and learning science. [ABSTRACT FROM AUTHOR]

In this study, we applied a multivariate logistic regression model to identify deforested areas and evaluate the current effects on environmental variables in the Brazilian state of Rondônia, located in the southwestern Amazon region using data from the MODIS/Terra sensor. The variables albedo, temperature, evapotranspiration, vegetation index, and gross primary productivity were analyzed from 2000 to 2022, with surface type data from the PRODES project as the dependent variable. The accuracy of the models was evaluated by the parameters area under the curve (AUC), pseudo R2, and Akaike information criterion, in addition to statistical tests. The results indicated that deforested areas had higher albedo (25%) and higher surface temperatures (3.2 °C) compared to forested areas. There was a significant reduction of the EVI (16%), indicating water stress, and a decrease in GPP (18%) and ETr (23%) due to the loss of plant biomass. The most precise model (91.6%) included only surface temperature and albedo, providing important information about the environmental impacts of deforestation in humid tropical regions. [ABSTRACT FROM AUTHOR]

Grapefruit albedo is a byproduct obtained from primary processing and is usually discarded as waste. The current study investigated the influence of grapefruit albedo at different concentrations (3, 6, 9, and 12%) on phytochemical, functional, textural, and sensorial quality of semolina pasta. The obtained results showed that the antioxidant activity improved from 17.60 to 38.76% (at the 12% level). The FRAP, TPC, and TFC of the prepared pasta were determined and progressively increased with increasing grapefruit albedo incorporation. Grapefruit albedo addition significantly (P < 0.05) reduced cooking time; however, cooking loss increased from 3.47% to 5.02%, but remained below the technologically acceptable limit, i.e., less than 8%. Higher levels of incorporation decreased L*, while a* and b* increased. FTIR analysis confirmed the presence of functional compounds in the prepared pasta. SEM analysis revealed that albedo powder incorporation affected the structural integrity of the pasta owing to the increased level of fibers, which resulted in a weaker matrix, also confirmed via textural profile analysis (TPA) by decreased hardness. Sensory analysis revealed that the addition of albedo to pasta affected the overall acceptability; however, among the different combinations, pasta with 6% albedo powder concentration was acceptable with the highest overall acceptability score of 7.75. [ABSTRACT FROM AUTHOR]

Highly scattering media, such as milk, skin, and clouds, are common in the real world. Rendering participating media is challenging, especially for high-order scattering dominant media, because the light may undergo a large number of scattering events before leaving the surface. Monte Carlo-based methods typically require a long time to produce noise-free results. Based on the observation that low-albedo media contain less noise than high-albedo media, we propose reducing the variance of the rendered results using differentiable regularization. We first render an image with low-albedo participating media together with the gradient with respect to the albedo, and then predict the final rendered image with a low-albedo image and gradient image via a novel prediction function. To achieve high quality, we also consider the gradients of neighboring frames to provide a noise-free gradient image. Ultimately, our method can produce results with much less overall error than equal-time path tracing methods. [ABSTRACT FROM AUTHOR]

40% of global population, who resides in Asian monsoon region is at high risk from extreme hot summer events, which is expected to increase by 25%/30 years under RCP8.5 scenario. Using Community Earth System Model (CESM) Large-ensemble simulations we assess the relative contribution of external forcings and internal variability on hot extremes over South and East Asia. Climate change projects surface mean temperature to reach 2.0 °C and 5.0 °C by ~2050 and ~2100, respectively, making the region uninhabitable under exposed conditions. Internal variability will partly obscure anthropogenic warming over South and Southeast Asia; however, East Asia will experience a 4–6 fold rise in record breaking hot events in later periods. Nevertheless, beyond 2.35 °C warming internal variability will decrease over South Asia due to weaker albedo feedback on unforced internal variability. Our results contradict the existing hypothesis that warming will increase volatility in weather patterns everywhere, particularly the Asian monsoon regions. [ABSTRACT FROM AUTHOR]

Simulation methods attempt to explain what happens in full-scale environments. However, as simplification procedures, they also have their limitations and opportunities. One of the applications is to use the output data of a physical model to calibrate numerical simulation, or even to use outputs of numerical simulations to analyze urban scale studies. But it is uncertain the error in the interaction between these models. This study aims to analyze the impact of scale analysis and pavements simulation model modification on ambient and surface temperature of asphalt pavement in a physical model of a tropical city street canyons. Therefore, a scaled outdoor experiment was conducted, and a numerical simulation model, using ENVI-met software, was used to investigate the spatiotemporal variation of air and pavement surface temperature, in urban (1:1) and reduced (1:15) scales. For studies on the surface temperature of pavements, within the temperature range of 12 ºC to 37 ºC, it is recommended to calibrate physical models using as input, data derived from numerical simulation models, yielding a mean absolute percentage error (MAPE) of 4.9%. For estimating data in real-world urban scale, within the air temperature range of 15 ºC to 37 ºC, it is proposed to use output data from simulated models in ENVI-met, that presented a mean absolute error (MAE) of ± 0.59 or physical models (MAE = ± 0.66). These results would be useful for the development of urban surface temperatures parametrizations. [ABSTRACT FROM AUTHOR]

There is an urgent need for strategies to reduce the negative impacts of a warming climate on human health. Cooling urban neighborhoods by planting trees and vegetation and increasing albedo of roofs, pavements, and walls can mitigate urban heat. We used synoptic climatology to examine how different tree cover and albedo scenarios would affect heat-related morbidity in Los Angeles, CA, USA, as measured by emergency room (ER) visits. We classified daily meteorological data for historical summer heat events into discrete air mass types. We analyzed those classifications against historical ER visit data to determine both heat-related and excess morbidity. We used the Weather Research and Forecasting model to examine the impacts of varied tree cover and albedo scenarios on meteorological outcomes and used these results with standardized morbidity data algorithms to estimate potential reductions in ER visits. We tested three urban modification scenarios of low, medium, and high increases of tree cover and albedo and compared these against baseline conditions. We found that avoiding 25% to 50% of ER visits during heat events would be a common outcome if the urban environment had more tree cover and higher albedo, with the greatest benefits occurring under heat events that are moderate and those that are particularly hot and dry. We conducted these analyses at the county level and compared results to a heat-vulnerable, working-class Los Angeles community with a high concentration of people of color, and found that reductions in the rate of ER visits would be even greater at the community level compared to the county. [ABSTRACT FROM AUTHOR]

The single scattering albedo (SSA) of aerosol particles is one of the key variables that determine aerosol radiative forcing. Herein, an Algorithm for the retrieval of Single scattering albedo over Land (ASL) is proposed for application to full-disk data from the advanced Himawari imager (AHI) sensor flying on board the Himawari-8 satellite. In this algorithm, an atmospheric radiative transfer model known as the USM (the top of the atmosphere reflectance as the sum of Un-scattered, Single-scattered, and Multiple-scattered components) is used to calculate the SSA instead of predetermining the aerosol model; the USM is constrained by the surface bidirectional reflectance distribution function shape and aerosol optical depth (AOD) in the retrieval process. Combining two consecutive observations and a 2 * 2 pixel window, the optimal estimation algorithm is adopted to obtain the optimal solution for the aerosol SSA. These SSA results are evaluated by comparing with aerosol robotic network (AERONET) data. Linear regression shows that SSAASL = 0.60*SSSAERONET + 0.38, with a correlation coefficient (0.7284), mean absolute error (0.0319), mean bias error (0.00324), root mean square error (0.0427), and ~80.11% of the ASL SSA data within an uncertainty of ±0.05 of the AERONET data. A comparison of the ASL SSA products with collocated Himawari-8 SSA products (Version 03, officially released by the Japan Meteorological Agency (JMA), referred to herein as JMA SSA) shows that the accuracy of the ASL SSA is better than that of the JMA SSA products. For the SSA retrieval in large AODs (>0.4), the validation metrics vs. AERONET data are better. [ABSTRACT FROM AUTHOR]

Aims investigation study to predict the albedo number as a function of latitude and longitude coordinates of the Algeria area, which is situated in North Africa. The estimated range of latitude is between 18.5° and 37.7° whereas the longitude is between –8.5° and 10.5°. The study takes the database as the real data, which is considered comparable values as a reference of the confirmation. An ideal reflector is going to have an albedo of 1, whereas an object that has an albedo of 0 is going to absorb any radiation that strikes it. Albedo is a measure of how much solar radiation, or sunlight, a surface reflects. It can be stated as a percentage or a decimal number, where 0 represents complete absorption of all incoming light and 1 represents a perfect reflector. The prediction model is divided into two parts the first part gives two formulas g1 and g2 which depend on the longitude and latitude of the coordinates of the area, respectively, and then added together g1, and g2, and divided by 2 to take the albedo number. for the second part do the correction between the model and experimental data, which gives us some errors, in this case, create a new correlation of the errors estimate f1, and f2 and add in the old correlation. Finally, a new correlation is corrected and the results give a perfect approximation of the best way. [ABSTRACT FROM AUTHOR]

Rangelands face threats from climate and land-use change, including inappropriate climate change mitigation initiatives such as tree planting in grassy ecosystems. The marginalization and impoverishment of rangeland communities and their indigenous knowledge systems, and the loss of biodiversity and ecosystem services, are additional major challenges. To address these issues, we propose the wilder rangelands integrated framework, co-developed by South African and European scientists from diverse disciplines, as an opportunity to address the climate, livelihood, and biodiversity challenges in the world's rangelands. More specifically, we present a Theory of Change to guide the design, monitoring, and evaluation of wilder rangelands. Through this, we aim to promote rangeland restoration, where local communities collaborate with regional and international actors to co-create new rangeland use models that simultaneously mitigate the impacts of climate change, restore biodiversity, and improve both ecosystem functioning and livelihoods. [ABSTRACT FROM AUTHOR]

Accurate representation of soil and snow state variables in the land surface model is crucial for good simulation results. In order to investigate the potential impacts of the overestimated snow cover over the Tibetan Plateau (TP) on precipitation over China, we designed comparative experiments over TP with and without updated soil texture data, soil hydrological parameters, and the fresh snow density scheme to address this issue with the Weather Research and Forecasting Model (WRF). The results show that snow cover fraction (SCF) and surface albedo in winter on the TP were overestimated in the WRF control experiment (CTL), with albedo bias exceeding 0.4 in the western TP. The SCF in the WRF improved experiment (WRFIM) is about 8% lower than that of the CTL, and the bias is decreased to 0.2–0.3 in the interior of the TP. The thermal and dynamic effects of the TP in winter have a significant impact on the weather and climate of East Asia during summer. Thus, the simulated summer rainfall bias is significantly reduced by WRFIM in North China, and the mid-lower reaches of the Yangtze River, along with the spatial correlation coefficient between the observed-based and WRF-simulated rainfall increased from 0.76 in CTL to 0.88 in WRFIM. The WRFIM-simulated reductions in snow cover and albedo cause a decrease in upward shortwave radiation and eventually increase net surface radiation. The horizontal temperature gradient of the atmosphere is increased in the WRFIM compared to the CTL, and the increased temperature in the lower and middle layers accommodates more water vapor, which is not conducive to precipitation formation. Correspondingly, the Western Pacific Subtropical High at 500 hPa in the middle troposphere weakened. The low-level anticyclonic circulation at 850 hPa also weakened to the east, affecting water vapor transport in eastern China. It leads to a decrease in the water vapor transported northward by southeasterly from the western Pacific Ocean and a decrease in the water vapor flux reaching North China. This work indicates that accurate characterization of soil properties and snow cover on the TP is crucial for improving the simulation bias of summer rainfall in China. [ABSTRACT FROM AUTHOR]

The Jupiter Trojan asteroids are a key population for understanding the chemical and dynamical evolution of the Solar System. Surface compositions of Trojans, in turn, provide crucial information for reconstructing their histories. NASA's Lucy mission will soon complete the first spacecraft reconnaissance of this population. This review summarizes the current state of knowledge of Trojan surface compositions and looks ahead to expected advances in that knowledge from Lucy. Surface compositions of Trojans remain uncertain due to a relative lack of diagnostic absorption features, though dedicated observations have begun to provide some clues to compositions. Trojans have uniformly low albedos, with a population average of ∼5.3%, and red spectral slopes at ultraviolet, visible, and near-infrared wavelengths. A bimodality of spectral slopes has been detected and confirmed across all these wavelengths, and the ratio of "less-red" to "red" Trojans increases with decreasing size. A broad absorption at ∼3.1 μm in some less-red Trojans may indicate the presence of N-H bearing material. Mid-infrared emissivity spectra reveal the presence of fine-grained anhydrous silicates on the surfaces. The meteorite collection contains no identifiable analogs to Trojan asteroids. Among small body populations, some Main Belt asteroids, comets, irregular satellites, and Centaurs provide reasonable spectral matches, supporting some genetic relationships among some members of these groups. The cause of the observed spectral properties remains uncertain, but recent suggestions include a combination of volatile ice sublimation and space weathering or a combination of impact gardening and space weathering. The Lucy mission will provide detailed compositional analysis of (3548) Eurybates, (15094) Polymele, (11351) Leucus, (21900) Orus, and (617) Patroclus-Menoetius, a suite of targets that sample the diversity among the Trojan population along several dimensions. With these flybys, the Lucy mission is poised to resolve many of the outstanding questions regarding Trojan surface compositions, thereby revealing how the Trojans formed and evolved and providing a clearer view of Solar System history. [ABSTRACT FROM AUTHOR]

Lighting is crucial for portrait photography, yet the complex interactions between the skin and incident light are expensive to model computationally in graphics and difficult to reconstruct analytically via computer vision. Alternatively, to allow fast and controllable reflectance and lighting editing, we developed a physically based decomposition through deep learned priors from path-traced portrait images. Previous approaches that used simplified material models or low-frequency or low-dynamic-range lighting struggled to model specular reflections or relight directly without intermediate decomposition. However, we estimate the surface normal, skin albedo and roughness, and high-frequency HDRI maps, and propose an architecture to estimate both diffuse and specular reflectance components. In our experiments, we show that this approach can represent the true appearance function more effectively than simpler baseline methods, leading to better generalization and higher-quality editing. [ABSTRACT FROM AUTHOR]

Restoring tree cover changes albedo, which is the fraction of sunlight reflected from the Earth's surface. In most locations, these changes in albedo offset or even negate the carbon removal benefits with the latter leading to global warming. Previous efforts to quantify the global climate mitigation benefit of restoring tree cover have not accounted robustly for albedo given a lack of spatially explicit data. Here we produce maps that show that carbon-only estimates may be up to 81% too high. While dryland and boreal settings have especially severe albedo offsets, it is possible to find places that provide net-positive climate mitigation benefits in all biomes. We further find that on-the-ground projects are concentrated in these more climate-positive locations, but that the majority still face at least a 20% albedo offset. Thus, strategically deploying restoration of tree cover for maximum climate benefit requires accounting for albedo change and we provide the tools to do so. Restoring tree cover is a prominent climate solution but can cause global warming due to changes in albedo. This paper maps albedo and carbon changes from restoring tree cover to highlight where the greatest net climate benefits can be achieved. [ABSTRACT FROM AUTHOR]

Background: Grasslands in drylands are increasingly influenced by human activities and climate change, leading to alterations in albedo and radiative energy balance among others. Surface biophysical properties and their interactions change greatly following disturbances. However, our understanding of these processes and their climatic impacts remains limited. In this study, we used multi-year observations from satellites and eddy-covariance towers to investigate the response of albedo to variables closely associated with human disturbances, including vegetation greenness (EVI) and surface soil volumetric water content (VWC), as well as snow cover and clearness index (Ta) for their potential relationships. Results: EVI and VWC during the growing season were the primary factors influencing albedo. EVI and VWC were negatively correlated with albedo, with VWC's total direct and indirect impacts being slightly smaller than those of EVI. During the non-growing season, snow cover was the most influential factor on albedo. VWC and Ta negatively affected albedo throughout the year. We estimated the impact of variations in EVI and VWC on climate to be in the range of 0.004 to 0.113 kg CO2 m−2 yr−1 in CO2 equivalent. Conclusions: This study indicates the significant impacts of climate change and human disturbances on vulnerable grassland ecosystems from the perspective of altered albedo. Changes in vegetation greenness and soil properties induced by climate change and human activities may have a substantial impact on albedo, which in turn feedback on climate change, indicating that future climate policies should take this factor into consideration. [ABSTRACT FROM AUTHOR]

In this paper, we describe conversion factors (CF) for the calculation of biologically effective irradiances (BEI) from erythemal irradiance for three effects: photosynthesis of previtamin D3, psoriasis healing, and inactivation of the SARS-Cov-2 virions. CFs were empirically derived from measurements of spectral solar ultraviolet (UV) radiation during all sky conditions at four mid-latitude sites in the Northern Hemisphere, namely Aosta, Belsk, Reading, and San Diego. These CFs were found to depend on solar zenith angle (SZA) and total column ozone, but are largely independent (within ± 5% for SZA < 60°) of local conditions such as surface albedo, visibility and other local atmospheric patterns. The values of these empirical CFs are consistent with analytical CFs derived with radiative transfer calculations (model FastRT) for clear-sky and overcast conditions. To validate these analytical CFs, one-hour radiant exposures for the three biological effects were calculated from erythemal measurements at Reading between 2012 and 2021 and compared with similar exposures calculated directly from the spectral UV measurements. The two datasets agreed within 10% for SZA < 65°, demonstrating the utility of the conversion method. These results suggest that the proposed analytical CFs can be used with confidence to estimate radiant exposures for the three biological effects from measurements of the UV Index at any northern mid-latitude site. [ABSTRACT FROM AUTHOR]

UBVR polarimetric observations of 12 main-belt mostly primitive asteroids located near perihelion heliocentric distances were carried out from December 2022 to April 2023 with Zeiss-2000 telescope at the Terskol Peak observatory. The purpose of the monitoring program was to search for changes in the polarimetric parameters of the asteroids caused by possible sublimation-dust activity, as a result of which the formation of rarefied dust exospheres of asteroids is possible. The objects of the program were asteroids: (1) Ceres, (53) Kalypso, (117) Lomia, (164) Eva, (214) Ashera, (324) Bamberga, (419) Aurelia, (505) Cava, (554) Peraga, (654) Zelinda, (704) Interamnia, (1021) Flammario. Polarimetric observations of asteroids (117) Lomia, (164) Eva and (505) Kava were made for the first time, the remaining asteroids were observed earlier. Only for two asteroids (1) Ceres and (704) Interamnia, according to spectrophotometric observations, temporal spectrophotometric variability was noted earlier. Analysis of temporal changes in the degree of polarization of asteroids and comparison of the results of observations with the data available in the literature showed that the stability of the observed degree of polarization is comparable with measurement errors of % for asteroids of different brightness. Thus, during the observation period, no noticeable polarization signs of temporary sublimation-dust activity of the observed asteroids were detected. Additionally, it is shown that the currently existing variants of the spectral taxonomy of asteroids, based on spectrophotometric data and albedo, demonstrate a significant scattering of the selected classes when compared with their polarimetric phase dependencies. The asteroid (554) Peraga has been confirmed to have a negative degree of polarization at angles less than the inversion angle. Measurements of the polarization of the asteroid (1) Ceres in a wide range of wavelengths did not confirm the previously suspected change in the angle of the polarization plane with the wavelength. [ABSTRACT FROM AUTHOR]

The linkage between elevation and precipitation in the mountainous regions across the world including the Indian Himalayan Region (IHR) is very complex. Various meteorological parameters, viz., albedo, shortwave and longwave radiations, humidity, and mass-energy balance, play a major role in the physical processes occurring in these places. The present study examines the changes in precipitation across the IHR. The precipitation patterns act differently from east to west, and north to south due to the varying elevation. The study employed high-resolution observational gridded precipitation analyses (CHELSA) for the period 1980–2018 and the GTOPO 30 DEM for the analyses. The two major precipitating seasons over the IHR such as the monsoon (JJAS) and winter (DJF) precipitation are considered. Characteristics of the precipitation with altitude over subregions of IHR such as Shivalik's IHR (SH), Lesser IHR (LH) and Higher IHR (HH) are presented. In addition, longitudinal variations over western IHR (WH), central IHR (CH) and eastern IHR (EH) are presented. Further, a non-parametric Mann–Kendall method has been used for trend analysis of precipitation, while the Pettitt test is used for change point detection. A positive precipitation trend is observed over HH and the western part of SH whereas a negative trend is found over the eastern part of SH. In most of the regions in SH, change in mean precipitation is observed during the recent time (1999–2018). However, HH located in the east of CH and west of EH shows a change in mean precipitation quite early (1979–1998). [ABSTRACT FROM AUTHOR]

One of the parameters affecting albedo is snow. Therefore, the effects of snow on albedo can be a tool to understand environmental changes. Moderate Resolution Imaging Spectroradiometer (MODIS) continuously produces snow and albedo products of the land surface on a global scale and with appropriate spatial resolution and makes them available to researchers. In this study, to investigate the relationship between albedo and snow in Iran, first, the daily data of the MODIS sensor MCD43A4 and MOD10A1 products in the area of Iran in the period of 1/1/2001 to 12/30/2021 for 6770 days were downloaded from the NASA website. Since the temperature conditions for snowfall are provided from an altitude of 1700 m, was calculated the seasonal and long-term correlation between albedo and snow at altitudes above 1700 m. These altitudes, which cover 27% of Iran's area, were known as Iran's Mountains (Mts.). The results showed that in the winter and autumn seasons, which are known as Iran's snowy seasons, the land surface albedo also increases with the increase in snow cover. Therefore, in these seasons, the correlation between albedo and snow over Iran's Mts. is strongly positive. In these seasons, positive correlation covers 91 and 81% of Iran's Mts., respectively. In spring, there is a strong positive correlation in high altitudes and a weak positive/negative correlation in low altitudes. The negative correlation in the spring season is due to the delay in the measuring time of the sensor and the conversion of precipitation from solid to liquid. In the summer season, due to the establishment of Subtropical High-Pressure Systems Azores and the increase in air temperature, the snow cover of the Mts. disappears and the albedo was expected to decrease. But with the reduction of snow cover, albedo has increased. As a result, in these seasons, the correlation between albedo and snow over Iran's Mts. is negative. It seems that the increase in albedo in spring and especially summer is caused by the increase in the land surface temperature (LST), which requires separate research. [ABSTRACT FROM AUTHOR]

The present study deals with the normalisation of Hamiltonian for the nonlinear stability analysis in non-resonance case of the triangular equilibrium points in the perturbed restricted three-body problem with perturbation factors as radiation pressure due to first oblate-radiating primary, albedo from second oblate primary, oblateness and a disc. The problem is formulated with these perturbations and Hamiltonian of the problem is normalised up to fourth order by Lie transform technique consequently a Birkhoff's normal form of the Hamiltonian is obtained. The Arnold–Moser theorem is verified for the nonlinear stability test of the triangular equilibrium points in non-resonance case with the assumed perturbations. It is found that in the presence of radiation pressure, stability range expanded, significantly with respect to the classical range of stability; however, because of albedo, oblateness and the disc, it contracted gradually. Moreover, it is observed that alike to the classical problem, in the perturbed problem under the impact of the assumed perturbations, there always exist one or more values of the mass ratio μ within the stability range at which discriminant D 4 = 0 , which means the triangular equilibrium points are unstable in nonlinear sense. [ABSTRACT FROM AUTHOR]

This study delves into the polarization properties of various hair colors using several techniques, including polarization ray tracing, full Stokes, and Mueller matrix imaging. Our analysis involved studying hair in both indoor and outdoor settings under varying lighting conditions. Our results demonstrate a strong correlation between hair color and the degree of linear polarization. Specifically, light-colored hair, such as white and blond, exhibits high albedo and low DoLP. In contrast, dark hair, like black and brown hair, has low albedo and high DoLP. Our research also revealed that a single hair strand displays high diattenuation near specular reflections but high depolarization in areas with diffuse reflections. Additionally, we investigated the wavelength dependency of the polarization properties by comparing the Mueller matrix under illumination at 450 nm and 589 nm. Our investigation demonstrates the impact of hair shade and color on polarization properties and the Umov effect. [ABSTRACT FROM AUTHOR]

The sorption mechanism of cadmium ions is studied using isolated fractions of microgel and pectic substances from pomelo albedo, beet pulp, and sunflower calathides. The sorption capacity of pectic polysaccharides, degree of sorbent affinity for the sorbate, and their binding strength are evaluated. The sorption process is found to obey the Langmuir equation. The thermodynamic parameters of the sorption processes at temperatures from 298.15 to 318.15 K are evaluated. The sorption process is found to have an exothermic mixed character. [ABSTRACT FROM AUTHOR]

Sea ice in its initial formation stages in the nearshore zone can exist in various forms such as grease ice, snow sludge, and pancake ice. These initial ice forms (IIFs) lead to the attenuation of waves on the sea surface, consequently affecting the intensity of microwave scattering on the sea surface. This complicates the identification of areas covered by IIFs that are situated between consolidated ice and open water. This work aims to analyze wave propagation in the presence of IIFs to develop physical models of wave attenuation. The paper presents a description and results of special field experiments to investigate the attenuation of wind waves of various lengths in the presence of ice simulators. Results of numerical simulation of the attenuation of gravitational waves and a comparison with experimental results are also given. One of the significant findings in the studied dependence of the attenuation coefficient on the ice floe size-to-wave length ratio, observed in both field and numerical experiments, is the discovery of a local maximum for waves with lengths of the order of the "ice floe" size. A physical interpretation of the mechanism of gravitational wave attenuation in the presence of ice floes is proposed, taking into account their attached mass. [ABSTRACT FROM AUTHOR]

Conifer forests historically have been resilient to wildfires in part due to thick organic soil layers that regulate combustion and post-fire moisture and vegetation change. However, recent shifts in fire activity in western North America may be overwhelming these resilience mechanisms with potential impacts for energy and carbon exchange. Here, we quantify the long-term recovery of the organic soil layer and its carbon pools across 511 forested plots. Our plots span ~ 140,000 km2 across two ecozones of the Northwest Territories, Canada, and allowed us to investigate the impacts of time-after-fire, site moisture class, and dominant canopy type on soil organic layer thickness and associated carbon stocks. Despite thinner soil organic layers in xeric plots immediately after fire, these drier stands supported faster post-fire recovery of the soil organic layer than in mesic plots. Unlike xeric or mesic stands, post-fire soil carbon accumulation rates in hydric plots were negligible despite wetter forested plots having greater soil organic carbon stocks immediately post-fire compared to other stands. While permafrost and high-water tables inhibit combustion and maintain thick organic soils immediately after fire, our results suggest that these wet stands are not recovering their pre-fire carbon stocks on a century timescale. We show that canopy conversion from black spruce to jack pine or deciduous dominance could reduce organic soil carbon stocks by 60–80% depending on stand age. Our two main findings—decreasing organic soil carbon storage with increasing deciduous cover and the lack of post-fire SOL recovery in hydric sites—have implications for the turnover time of carbon stocks in the western boreal forest region and also will impact energy fluxes by controlling albedo and surface soil moisture. [ABSTRACT FROM AUTHOR]

In this study, we analyze the impact of reduced snow cover in the Northern Hemisphere on the atmosphere and if the atmospheric response depends on the model resolution. We use the atmospheric component of the global climate model EC-Earth and perform three experiments: in the first experiment, we reduce the snow cover in the entire Northern Hemisphere by reducing the snow albedo to a constant value of 0.3, in the second experiment, we reduce the snow albedo only over Eurasia, and the third experiment is the control run using normal snow conditions. All experiments are integrated over the period 1980–2015 at standard resolution (~ 80 km) and high resolution (~ 40 km). Experiments comprise 11 and 5 ensemble members at standard resolution and high resolution, respectively. Reducing the snow albedo in the Northern Hemisphere leads to 5–10% snow cover reduction in winter and spring. Significant warm responses are found over northern Eurasia in spring and summer with a warm response reaching 3 °C. Similar but weaker warm temperature responses are found in the middle and upper troposphere (up to 2 °C) and reversed temperature responses in the stratosphere (up to – 2 °C), particularly over eastern Eurasia. This is closely associated with westerly jet flow response which is enhanced at high-latitude and weakened at low-latitude in winter and spring over eastern Eurasia. Reduced snow cover leads to warmer surface temperatures that accelerate snow-melting and further lead to different snow-hydrological responses in western and eastern Eurasia and more precipitation occurs over eastern Eurasia (increasing 10–20%), particularly in the Siberian region. When the snow albedo is reduced only in the Eurasian sector, the surface response pattern resembles the results of the Northern Hemisphere experiment. The warm response is slightly weakened about 0.25–0.5 °C over Eurasia and significantly weakened outside of Eurasia. However, the upper air circulation response is much less pronounced over Eurasia. The impact of resolution on the mean surface field response is small yet it is more pronounced on the large-scale circulation response, particularly in spring and winter. [ABSTRACT FROM AUTHOR]

Solid precipitation is not only the main supply for glacier mass, but also exerts an important influence on surface albedo and intensifies glacier melting. However, precipitation type observation is very scarce in the high alpine glaciers, which limits the precise simulation of glacier mass balance. This study assessed three discrimination methods of precipitation types including Ding method, Dai method and Froidurot method based on surface albedo observation data on the Laohugou Glacier No. 12 (LHG Glacier) in western Qilian Mountains. The results showed that Ding method had a best applicability on the LHG Glacier, the other two need to calibrate parameters when they are used in the high elevation glacier region. Then we fitted the relationship between snowfall probability and fresh snow albedo, and put forward a revised formula to simulate fresh snow albedo based on Ding method, which is expected to reduce the uncertainty in glacier mass and energy balance model. Finally, we found a best air temperature threshold of 4°C for discriminating monthly precipitation types. In order to accurately simulate the glacier melt, it is necessary to obtain the threshold temperature appropriately in different glacier region with different elevation and humidity. [ABSTRACT FROM AUTHOR]

New measurements from the Arctic ± 40 days around the summer solstice show reflected sunlight from north of 80°N decreases 20–35%. Arctic sea ice coverage decreases 7–9% over this same time period (as reported by the NSIDC) implying Arctic sea ice albedo decreases in addition to the sea ice receding. Similar Antarctic measurements provide a baseline to which Arctic measurements are compared. The Antarctic reflected sunlight south of 80°S is up to 30% larger than the Arctic reflectance and is symmetric around the solstice implying constant Antarctic reflectivity. Arctic reflected sunlight 20 days after solstice is > 100W/m2 less than Antarctic reflected sunlight. For perspective, this is enough heat to melt > 1 mm/hour of ice. This finding should be compared with climate models and in reanalysis data sets to further quantify sea ice albedo's role in Arctic Amplification. The measurements were made with previously unpublished pixelated radiometers on Global Positioning System satellites from 2014 to 2019. The GPS orbits give each radiometer instantaneous and continuous views of 37% of the Earth, two daily full views of the Arctic and Antarctic. Furthermore, the GPS constellation gives full-time full-Earth coverage that may provide data that complements existing limited field of view instruments that provide a less synoptic Earth view. [ABSTRACT FROM AUTHOR]

Global climate change poses significant societal and political challenges. The rapid increase in the near-surface air temperatures and the drastic retreat of the Arctic sea ice during summer are not well represented by climate models. The data sets introduced here intend to help improving the current understanding of the ongoing Arctic climate changes. In particular, this study considers observations from 24 helicopter flights (June–September 2020) and 5 flights with the helicopter-towed probe HELiPOD (May–July 2020) during MOSAiC. Distributions of various surface types (white ice/snow, bright melt ponds, dark melt ponds, open water, and bare ice) were determined using fisheye camera images. They were related to collocated broadband irradiance measurements to analyse the temporal and spatial changes of the surface albedo. Multiple linear regression was applied to assign the measured areal albedo to the corresponding surface-types. The resulting surface-type fractions, the albedo data and respective upward and downward broadband solar irradiances of several flights throughout the melting and refreezing season are provided. [ABSTRACT FROM AUTHOR]

The research presented in this work focuses on investigating the characteristics of equilibrium points within the context of the photogravitational restricted three-body problem. Specifically, the study considers the influences of albedo effect, a straight segment, radiation pressure, as well as small perturbations in the Coriolis and centrifugal forces. The dynamical model proposed in this study reveals the presence of five equilibrium points. Among these, three are collinear with the centers of the massive bodies, while the remaining two are non-collinear. By examining various parameters involved in the system, the effect on the position of the equilibrium points is explored through numerical and graphical analysis. These investigations provide valuable insights into how the positions of these points are affected by changes in the parameters. Another significant aspect addressed in this research is the stability of the equilibrium points. The study finds that the collinear equilibrium points are unstable, irrespective of the parameters involved. On the other hand, the non-collinear points exhibit stability within a specific range of the mass parameter. The precise range of stability depends on the values of the other parameters present in the system. Additionally, the research delves into the study of the permissible and forbidden regions of motion for an infinitesimal body within the system. This analysis is conducted by considering different values of the Jacobian constant and it suggests that the Jacobian constant significantly influences the dynamics of the system and has a direct impact on the permissible regions of motion of the infinitesimal body. [ABSTRACT FROM AUTHOR]

An ensemble of three Regional Climate Models (RCMs) is evaluated over the current climate conditions with the aim of assessing RCMs' skills and limitations in reproducing the near-surface temperature and precipitation over the Subtropical Chile complex terrain region (25 ºS–45 ºS). The simulations driven by ERA-Interim and by GCMs historical scenarios are compared against observational gridded products and ERA5 reanalysis for high and low elevations separately. The RCMs simulate reasonably well the main spatio-temporal characteristics of temperature and precipitation, such as latitudinal climate gradients, orographic uplifts, phase of the seasonal cycle, and realistic inter-annual variability. Although the simulations driven by ERA-Interim show better skills than those driven by GCMs, especially in the case of precipitation, none of the RCMs/simulations performs best or worst in all sub-regions. RCMs and ERA5 have a common prominent cold bias at high elevations north of 35 °S, which is particularly strong above 2000 m.a.s.l. This bias is associated with a strong overestimation of precipitation and an overestimation of surface albedo, likely related to an overestimated snow cover. Because of scarce in-situ observations, this region is also associated with inherent observational uncertainty. Our results emphasize the necessity of improving the density and quality of observational networks over the complex terrain of Subtropical Chile for an accurate assessment and tuning/calibration of RCMs. The assessment of a state-of-the-art RCMs ensemble provided by this study can help in interpreting, bias-correcting, and using the regional climate projections performed with these RCMs for downstream applications and impact studies. [ABSTRACT FROM AUTHOR]

Primary biological aerosol particles (PBAP) play an important role in the climate system, facilitating the formation of ice within clouds, consequently PBAP may be important in understanding the rapidly changing Arctic. Within this work, we use single-particle fluorescence spectroscopy to identify and quantify PBAP at an Arctic mountain site, with transmission electronic microscopy analysis supporting the presence of PBAP. We find that PBAP concentrations range between 10−3–10−1 L−1 and peak in summer. Evidences suggest that the terrestrial Arctic biosphere is an important regional source of PBAP, given the high correlation to air temperature, surface albedo, surface vegetation and PBAP tracers. PBAP clearly correlate with high-temperature ice nucleating particles (INP) (>-15 °C), of which a high a fraction (>90%) are proteinaceous in summer, implying biological origin. These findings will contribute to an improved understanding of sources and characteristics of Arctic PBAP and their links to INP. Primary bioaerosols, important for clouds and climate, were measured at an Arctic mountain site and traced to regional sources. Their seasonality was observed to peak in summer, where they significantly contribute to high-temperature ice nucleating particles. [ABSTRACT FROM AUTHOR]

We have modeled the diffuse background at the Galactic Poles in the far-ultraviolet (FUV: 1536 Å) and the near-ultraviolet (NUV: 2316 Å). The background is well-fit using a single-scattering dust model with an offset representing the extragalactic light plus any other contribution to the diffuse background. We have found a dust albedo of 0.35–0.40 (FUV) and 0.11–0.19 in the NGP ( b > 70 ∘ ) and 0.46–0.56 (FUV) and 0.31–0.33 (NUV) in the SGP ( b < 70 ∘) . The differences in the albedo may reflect changes in the dust-to-gas ratio over the sky or in the dust distribution. We find offsets at zero-reddening of 273–286 and 553–581 photons cm - 2 s - 1 sr - 1 Å - 1 in the FUV and NUV, respectively, in the NGP with similar values in the SGP. [ABSTRACT FROM AUTHOR]

Sharjah-Sat-1 is a 3U cubesat with a CdZnTe based hard X-ray detector, called iXRD (improved X-ray Detector) as a scientific payload with the primary objective of monitoring bright X-ray sources in the galaxy. We investigated the effects of the in-orbit background radiation on the iXRD based on Geant4 simulations. Several background components were included in the simulations such as the cosmic diffuse gamma-rays, galactic cosmic rays (protons and alpha particles), trapped protons and electrons, and albedo radiation arising from the upper layer of the atmosphere. The most dominant component is the albedo photon radiation which contributes at low and high energies alike in the instrument energy range of 20 keV - 200 keV. On the other hand, the cosmic diffuse gamma-ray contribution is the strongest between 20 keV and 60 keV in which most of the astrophysics source flux is expected. The third effective component is the galactic cosmic protons. The radiation due to the trapped particles, the albedo neutrons, and the cosmic alpha particles are negligible when the polar regions and the South Atlantic Anomaly region are excluded in the analysis. The total background count rates are ∼ 0.36 and ∼ 0.85 counts/s for the energy bands of 20 - 60 keV and 20 - 200 keV, respectively. We performed charge transportation simulations to determine the spectral response of the iXRD and used it in sensitivity calculations as well. The simulation framework was validated with experimental studies. The estimated sensitivity of 180 mCrab between the energy band of 20 keV - 100 keV indicates that the iXRD could achieve its scientific goals. [ABSTRACT FROM AUTHOR]

When a light beam enters a scattering-dominated medium, the radiation is isotropized. Part of the radiation goes backwards, leading to non-monotonicity in the radiation energy density profile inside this medium. There arises a local maximum at which the energy density at a scattering albedo is severalfold greater than that without scattering at the same extinction. This effect is studied numerically in one-dimensional and two-dimensional simulations. It is demonstrated that a local maximum of the radiation energy density arises in the medium, whose value depends on the optical depth of the region. This effect can manifest itself, for example, when the radiation from a gamma-ray burst (GRB) enters heated regions in the interstellar medium. The presence of scattering in the GRB radiation generation region, near the front of strong shocks, affects the radiation pattern. The structure of such shocks is remarkable for the presence of a preshock preheating tail. Strong scattering in this region leads to the escape of a significant fraction of the radiation sideways and backwards in the shock reference frame, forming additional tails in the angular distribution of GRB radiation after the relativistic transformation to the laboratory frame. This effect is also studied numerically in three-dimensional simulations. [ABSTRACT FROM AUTHOR]

We proposed a monocular image disentanglement framework based on a compositional model. Our model disentangles the input image into its constituent components of albedo, depth, deformation, pose, and illumination. Instead of relying on any handcrafted priors, we trained our deep neural network to understand the physical meaning of each element by mimicking real-world operations, allowing it to reconstruct images in a self-supervised manner. Our model, trained on multi-frame images of each subject, demonstrates a better understanding of the objects without requiring any supervision or strong model assumptions. We utilized a deformation-free canonical space to align multi-frame images in the same space. This approach enables the understanding of information from multi-frame images in the same space. Our experiments showed that our approach accurately disentangled the physical elements of deformable faces from images with wide variations found in the wild. [ABSTRACT FROM AUTHOR]

Since, in modern high-performance sports, the technical component is decisive, the ski running surface is an important element of cross-country skiing. This paper presents a review of papers on sliding mechanics, discusses modern methods for improving it, and considers the prospects for the development of this area under current energy and environmental conditions. Various factors affecting the sliding mechanics, in particular, snow cover albedo, and microroughness of the ski running surface are analyzed in detail. [ABSTRACT FROM AUTHOR]

Black carbon (BC) in snow plays an important role to accelerate snow melting. However, current studies mostly focused on BC concentrations, few on their size distributions in snow which affected BC's effect on albedo changes. Here we presented refractory BC (rBC) concentrations and size distributions in snow collected from Chinese Altai Mountains in Central Asia from November 2016 to April 2017. The results revealed that the average rBC concentrations were 5.77 and 2.82 ng g−1 for the surface snow and sub-surface snow, which were relatively higher in the melting season (April) than that in winter (November–January). The mass median volume-equivalent diameter of rBC size in surface snow was approximately at 120–150 nm, which was typically smaller than that in the atmosphere (about 200 nm for urban atmosphere). However, there existed no specific mass median volume-equivalent diameter of BC size for sub-surface snow in winter. While during the melting season, the median mass size of rBC in sub-surface snow was similar to that in surface snow. Backward trajectories indicated that anthropogenic sourced BC dominated rBC in snow (70%–85%). This study will promote our understanding on BC size distributions in snow, and highlight the possible impact of BC size on climate effect. [ABSTRACT FROM AUTHOR]

The urban heat island (UHI) under the current climate change scenario could have a major impact on the lives of urban residents. The presence of green areas undoubtedly mitigates the UHI, and modifies some selected anthropized surfaces with particular characteristics (e.g., albedo). Here, we use a university campus as a good template of the urban context to analyze the mitigation effect of different surface types on the air temperature warming. This study provides some of the best practices for the future management of land surface types in urban areas. Through the development of a simple air temperature mitigation index (ATMI) that uses the temperature, water content (WC), and albedo of the investigated surface types, we find the green and anthropized surfaces according to their areal distribution and mitigation effects. The findings address the importance of poorly managed green areas (few annual mowings) and anthropized materials that permit a good balance between water retention capacity and high albedo. In the case of impervious surfaces, priority should be given to light-colored materials with reduced pavement units (blocks or slabs) to reduce the UHI. [ABSTRACT FROM AUTHOR]

The impact of assimilating satellite-retrieved Arctic sea ice thickness (SIT) on simulating sea ice concentration (SIC) climatology in CICE5 is examined using a data assimilation (DA) system based on the ensemble optimal interpolation. The DA of the SIT satellite data of CryoSat-2 and SMOS during 2011–2019 significantly reduces the climatological bias of SIC and SIT in both sea ice melting and growing seasons. Moreover, the response of SIC to SIT change is strongly dependent on the seasons and latitudinal locations. The SIT in the inner ice zone thickens due to the SIT DA during the boreal winter wherein the SIT observation is available; the ice melting throughout the subsequent seasons is attenuated to increase SIC during the boreal summer to reduce the simultaneous SIC bias. In marginal ice zones, the positive SIT bias depicted in the control simulation is significantly reduced by SIT DA, which reduces the positive SIC bias. The idealized experiments of reducing the SIT show that the enhanced ice bottom melting process plays a crucial role in reducing the SIC; the prescribed SIT thinning increases the ice bulk salinity due to the weak gravity drainage of brine and increases the ice bulk temperature due to the decrease of the sea ice albedo. The augmentation of the ice salinity and temperature contributes to the shrinkage of the ice enthalpy, boosting the bottom melting process, which leads to SIC decrease. [ABSTRACT FROM AUTHOR]

Non-line-of-sight (NLOS) imaging aims at reconstructing targets obscured from the direct line of sight. Existing NLOS imaging algorithms require dense measurements at regular grid points in a large area of the relay surface, which severely hinders their availability to variable relay scenarios in practical applications such as robotic vision, autonomous driving, rescue operations and remote sensing. In this work, we propose a Bayesian framework for NLOS imaging without specific requirements on the spatial pattern of illumination and detection points. By introducing virtual confocal signals, we design a confocal complemented signal-object collaborative regularization (CC-SOCR) algorithm for high-quality reconstructions. Our approach is capable of reconstructing both the albedo and surface normal of the hidden objects with fine details under general relay settings. Moreover, with a regular relay surface, coarse rather than dense measurements are enough for our approach such that the acquisition time can be reduced significantly. As demonstrated in multiple experiments, the proposed framework substantially extends the application range of NLOS imaging. The authors propose a confocal complemented signal-object collaborative regularization method for non-line-of-sight (NLOS) imaging without specific requirements on the spatial pattern of measurement points. The method extends the application range of NLOS imaging. [ABSTRACT FROM AUTHOR]