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Radiative forcing (RF) resulting from changes in surface albedo is increasingly recognized as a significant driver of global climate change but has not been adequately estimated, including by Intergovernmental Panel on Climate Change (IPCC) assessment reports, compared with other warming agents. Here, we first present the physical foundation for modeling albedo-induced RF and the consequent global warming impact (GWIΔα). We then highlight the shortcomings of available current databases and methodologies for calculating GWIΔα at multiple temporal scales. There is a clear lack of comprehensive in situ measurements of albedo due to sparse geographic coverage of ground-based stations, whereas estimates from satellites suffer from biases due to the limited frequency of image collection, and estimates from earth system models (ESMs) suffer from very coarse spatial resolution land cover maps and associated albedo values in pre-determined lookup tables. Field measurements of albedo show large differences by ecosystem type and large diurnal and seasonal changes. As indicated from our findings in southwest Michigan, GWIΔα is substantial, exceeding the RFΔα values of IPCC reports. Inclusion of GWIΔα to landowners and carbon credit markets for specific management practices are needed in future policies. We further identify four pressing research priorities: developing a comprehensive albedo database, pinpointing accurate reference sites within managed landscapes, refining algorithms for remote sensing of albedo by integrating geostationary and other orbital satellites, and integrating the GWIΔα component into future ESMs.

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]

The JAXA/Hayabusa2 rendezvoused with the (162 173) Ryugu asteroid from June 2018 to November 2019, performing an artificial impact experiment on 5th April 2019. The goal of this work is to study the photometric properties' variation of the target area (latitude 7–10°N; longitude 303–305°E) after the artificial impact experiment. This is done by applying an empirical method based on the statistical analysis of the Optical Navigation Camera (ONC)'s data set (in particular, of the v band, centred at 0.55  |$\mu$| m), similar to that applied to other asteroids explored by space missions and to the NIRS3 data set of Ryugu. The method was firstly applied on the entire data set acquired between March and April 2019, covering most of the Ryugu surface. The retrieved average phase function of Ryugu is very similar to that obtained on the NIRS3 data set, according to the similar visible and near-infrared albedo values. Nevertheless, this phase function is flatter than other asteroids belonging to the same Ryugu taxonomic class. This can be attributed to the higher spatial resolution of Hayabusa2 observations, which flattens the phase function of dark asteroids by minimizing the effects of shadowing, as confirmed by photometric studies of other asteroids. Then, the photometric properties of the artificial impact crater area revealed a slight phase function steepening and narrowing after the impact: this could indicate that the exposed surface has a larger roughness and more porous particles. [ABSTRACT FROM AUTHOR]

Antarctica is a vital component of Earth’s climate system, influencing global sea level, ocean circulation, and planetary albedo. Major knowledge gaps in critical processes—spanning the atmosphere, ocean, ice sheets, underlying beds, ice shelves, and sea ice—create uncertainties in future projections, hindering climate adaptation and risk assessments of ice intervention strategies. Antarctica’s ice sheet could contribute 28 centimeters to sea level by 2100, and potentially more if we surpass warming thresholds that trigger instabilities and rapid retreat. We review recent advances in understanding the changing stability of the ice sheet margins and identify key processes that require further research. Progress requires high-resolution satellite data, targeted field campaigns, improved modeling, and refined theory. Increased investment and interdisciplinary collaboration are essential to uncovering Antarctica’s hidden processes and reducing uncertainties in future projections. [ABSTRACT FROM AUTHOR]

AbstractWe examine the effect of linear-triplet anisotropic scattering on the solution of transport problems. We consider the albedo problem for a semi-infinite slab with a non-negative scattering kernel that is a linear combination of “linear” and “triplet” scattering. We use two different methods, both of which are based on Case method of singular eigenfunctions, namely the HN method and the SVD method. Case’s eigenfunctions and their orthogonality relations are derived and are used to solve the half-space albedo problem. The results of two methods are in agreement with each other and show that the triplet scattering has only a marginal effect on the solution of the transport problem while the linear scattering has a dominant role. Surprisingly this is true even when the strength of the linear scattering is small. We also report an improvement of the SVD method that allows us to refine the mesh as we please. [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]

The potential dangers of asteroids hitting the Earth are one of the challenges for mankind to preserve the human species. Various missions have been proposed to defend asteroids. Changing the Albedo magnitude by painting asteroids is a suitable and low-cost idea for the asteroid defense plan. Moving away from the Earth requires fuel consumption and the limitations of carrying the necessary materials for painting. Due to these limitations, we are not able to paint the entire asteroid, or for other reasons, we have to paint parts of the asteroid. Therefore, we should find a relative compromise between the variables to get most efficiency from painting parts of the asteroid. In this paper, we present a network structure of Data Envelopment Analysis (DEA) and consider the relationships of all variables including physical and orbital characteristics, spacecraft limitations, effective solar mass, albedo change rate, and elapsed time of the mission. We look for parts of the asteroid's surface where we can get the most displacement by spending the least amount of raw material. One of the advantages of the proposed method is the capability of sensitivity analysis to any of the variables affecting the magnitude of the final displacement. The theorems related to the stability were proven analytically, and we show how to reduce the elapsed time by maintaining efficiency in asteroid painting. The performance of the proposed model was analyzed using real and hypothetical data from asteroid Apophis 99942. [ABSTRACT FROM AUTHOR]

Surface albedo is a key variable influencing ground-reflected solar irradiance, which is a vital factor in boosting the energy gains of bifacial solar installations. Therefore, surface albedo is crucial towards estimating photovoltaic power generation of both bifacial and tilted solar installations. Varying across daylight hours, seasons, and locations, surface albedo is assumed to be constant across time by various models. The lack of granular temporal observations is a major challenge to the modeling of intra-day albedo variability. Though satellite observations of surface reflectance, useful for estimating surface albedo, provide wide spatial coverage, they too lack temporal granularity. Therefore, this paper considers a novel approach to temporal downscaling with imaging time series of satellite-sensed surface reflectance and limited high-temporal ground observations from surface radiation (SURFRAD) monitoring stations. Aimed at increasing information density for learning temporal patterns from an image series and using visual redundancy within such imagery for temporal downscaling, we introduce temporally shifted heatmaps as an advantageous approach over Gramian Angular Field (GAF)-based image time series. Further, we propose Multispectral-WaveMix, a derivative of the mixer-based computer vision architecture, as a high-performance model to harness image time series for surface albedo forecasting applications. Multispectral-WaveMix models intra-day variations in surface albedo on a 1 min scale. The framework combines satellite-sensed multispectral surface reflectance imagery at a 30 m scale from Landsat and Sentinel-2A and 2B satellites and granular ground observations from SURFRAD surface radiation monitoring sites as image time series for image-to-image translation between remote-sensed imagery and ground observations. The proposed model, with temporally shifted heatmaps and Multispectral-WaveMix, was benchmarked against predictions from models image-to-image MLP-Mix, MLP-Mix, and Standard MLP. Model predictions were also contrasted against ground observations from the monitoring sites and predictions from the National Solar Radiation Database (NSRDB). The Multispectral-WaveMix outperformed other models with a Cauchy loss of 0.00524, a signal-to-noise ratio (SNR) of 72.569, and a structural similarity index (SSIM) of 0.999, demonstrating the high potential of such modeling approaches for generating granular time series. Additional experiments were also conducted to explore the potential of the trained model as a domain-specific pre-trained alternative for the temporal modeling of unseen locations. As bifacial solar installations gain dominance to fulfill the increasing demand for renewables, our proposed framework provides a hybrid modeling approach to build models with ground observations and satellite imagery for intra-day surface albedo monitoring and hence for intra-day energy gain modeling and bifacial deployment planning. [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]

The widely used community Noah-MP land surface model currently adopts snow albedo parameterizations that are semiphysical in nature and have systematic biases which impact the accuracy of weather and climate modeling systems that use Noah-MP as the land component. We hypothesized that integrating the snowpack radiative transfer scheme from the latest version of the Snow, Ice, and Aerosol Radiative (SNICAR) model can improve the physical representation of snow albedo processes and reduce corresponding land model uncertainties. Therefore, we evaluate Noah-MP simulations employing the SNICAR scheme and compare model accuracy to a Noah-MP simulation using the default semiphysical Biosphere-Atmosphere Transfer Scheme (BATS) scheme using in situ spectral snow albedo observations at three Rocky Mountain field stations. The agreement between simulated and in situ observed ground snow albedo is significantly enhanced in NoahMP–SNICAR simulations relative to NoahMP–BATS simulations (root-mean-square error reductions from 0.116 to 0.103). Especially, NoahMP–SNICAR improves modeled snow albedo variability for fresh snow and aged snowpack (correlation increase from 0.42 to 0.67). The underestimated variability of snow albedo in NoahMP–BATS is a result of inadequate representation of physical linkages between snow albedo evolution and environmental/snowpack conditions (temperature, snow density, snow water equivalent, and light-absorbing particles), which is substantially improved by the NoahMP–SNICAR scheme. This new development of NoahMP–SNICAR physics provides a means to improve snow albedo accuracy and reduce corresponding uncertainties while providing new modeling capabilities such as hyperspectral snow albedo and effects of snow grain size, snow grain shape, and light-absorbing particles in future studies. Significance Statement: The widely used community Noah-MP land surface model utilizes simplified snow albedo parameterizations that are semiphysical and have large uncertainties that affect the accuracy of weather and climate modeling systems. We aim to reduce uncertainties by incorporating a radiative transfer snow albedo model (i.e., SNICAR) into Noah-MP. The newly coupled NoahMP–SNICAR model shows a significant enhancement in simulating snow albedo at three Rocky Mountain stations when compared to the Noah-MP configuration with the default snow albedo scheme (i.e., BATS). It also introduces new modeling capabilities for future studies, such as hyperspectral snow albedo and the effects of snow grain size, snow grain shape, and light-absorbing particles. [ABSTRACT FROM AUTHOR]

Due to growing interest in the use of bifacial photovoltaic modules this paper analyzes the actual performance of an installation consisting of three types of modules, bifacial monocrystalline silicon among them. An analysis of the operation of the on-grid photovoltaic installation working in the warm summer continental climate of southeastern Poland was carried out in 2021--2022. The roof-top installation with a rated power of 14.04 kWp, consisting of modules made of monocrystalline silicon (mono-Si), polycrystalline silicon (poly-Si) and monocrystalline silicon bifacial (bifacial-Si) delivered 936.76 kWh/kWp in 2021 year and 1070.94 kWh/kWp in 2022 year. In order to predict the optimal configuration of bifacial modules in the tested location, a simulation was performed in the PV-Syst v.7.4 program. Based on a comparison of numerous simulated variants, differing in the orientation of the modules and the reflectivity of the ground surface the best results were found for 1.5 m height above the roof level, 45° inclination angle and albedo coefficient of 0.8. [ABSTRACT FROM AUTHOR]

A long-standing and pervasive problem in climate modeling is the proper representation of cloud albedo over the Southern Ocean (SO). In this study, we investigate the causes of SO cloud albedo biases using phase 6 of the Coupled Model Intercomparison Project (CMIP6) simulations and a cloud-controlling factor approach on daily time scales. Cloud albedo, computed from upwelling and downwelling shortwave radiation at the surface and top of the atmosphere, is averaged into bins of vertical velocity, surface wind, and sea surface temperature. The performance of 15 models in both atmosphere-only and ocean-coupled configurations is evaluated against Clouds and the Earth's Radiant Energy System (CERES) satellite retrievals in combination with ERA5 reanalysis for the 2000–14 period. We find that the SO cloud biases maximize in the 50°–65° oceanic band and that models tend to underestimate SO cloud reflectivity for cold conditions and weak surface winds. In turn, descent (ascent) conditions are consistently underestimated (overestimated) across models for both hemispheres in the same latitude band. With a very similar approach, we evaluate how models represent the observed cloud albedo hemispheric asymmetry over oceans, which also maximizes in the 50°–65° band. The sign of the asymmetry is consistently predicted by all models, many of which also predict a similar magnitude to observations. However, this is also a consequence of compensating global biases as individually most models tend to either overpredict or underpredict cloud albedo in both hemispheres. We propose that surface temperatures less than 4°C are important in explaining SO bias in cloud albedo and that they also partly explain the observed hemispheric asymmetry. Further, we hypothesize that the 4°C threshold sets a hemispheric asymmetry in cloud phase. [ABSTRACT FROM AUTHOR]

The UK Global Ocean and Sea Ice configuration version 9 (GOSI9) is a new traceable hierarchy of three model configurations at 1, 1/4 and 1/12° based on version 4.0.4 of the NEMO code. GOSI9 has been developed as part of the UK's Joint Marine Modelling Programme (JMMP), a partnership between the Met Office, the National Oceanography Centre, the British Antarctic Survey, and the Centre for Polar Observation and Modelling. Following a seamless approach, it will be used for a variety of applications across a wide range of spatial and temporal resolutions: short-range coupled numerical weather prediction (NWP) forecasts, ocean forecasts, seasonal and decadal forecasts, and climate and Earth system modelling. The GOSI9 configurations are described in detail with a special focus on the updates since the previous version (GO6-GSI8). Results from 30-year ocean–ice integrations forced by CORE2 fluxes are presented for the three resolutions, and the impacts of the updates are assessed using the 1/4° integrations. The upgrade to NEMO 4.0.4 includes a new sea ice model SI3 (Sea Ice modelling Integrated Initiative) and faster integration achieved through the use of partially implicit schemes that allow a significant increase in the length of the time step. The quality of the simulations is generally improved compared to GO6-GSI8. The temperature and salinity drifts are largely reduced thanks to the upgrade to NEMO 4.0.4 and the adoption of fourth-order horizontal and vertical advections helping to reduce the numerical mixing. To improve the representation of the Southern Ocean, a scale-aware form of the Gent–McWilliams parameterization and the application of a partial-slip lateral boundary condition on momentum in the Southern Ocean have been added, resulting in a stronger and more realistic Antarctic Circumpolar Current (ACC) transport and a reduction in the temperature and salinity biases along the shelf of Antarctica. In the Arctic, the representation of sea ice is improved, leading to a reduction in surface temperature and salinity biases. In particular, the excessive and unrealistic Arctic summer sea ice melt in GO6-GSI8 is significantly improved in GOSI9 and can be attributed to the change in the sea ice model and to the higher albedos that increased sea ice thickness. [ABSTRACT FROM AUTHOR]

The Aerosol Layer Height (ALH), from the Sentinel-5P/TROPOMI L2__AER_LH product, is based on an optimal estimation (OE) approach, fitting cloud-free measurements to synthetic reflectances in the strongest oxygen absorption band, provided by a neural network trained with high resolution simulated reflectances. The ALH has been continuously improved since its release in 2019, focusing especially on (bright) land surfaces, over which the ALH product showed underestimated aerosol layer heights (biased towards the surface). This paper describes the latest updates of the ALH product, that includes first the introduction of the Directional Lambertian-Equivalent Reflectance (DLER) climatology to improve the surface albedo characterisation over land. Second, the paper describes a further improvement, adding the surface albedo in the feature vector of the OE inversion, using the DLER as prior information. Using this approach, the retrievals over land largely match the retrievals over ocean, which have shown a good comparison with validation data since its release, most notably with CALIOP weighted extinction heights. The albedo is fitted for both land and ocean surfaces, but the implementation is different over land and ocean because of the large range of land surface albedos. Over land, the a priori surface albedo values are relaxed so the fitting procedure can incorporate the albedo effects in the retrieval over land. Over ocean, the retrievals are optimised by tuning the a priori error settings. The current implementation improves retrievals over land with about 1.5 times more converged results, and decreases land-ocean contrasts in the aerosol layer height retrievals. The average difference between CALIOP weighted extinction height decreased for selected cases from about −1.9 km to −0.9 km over land and from around −0.8 km to +0.1 km over ocean. [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]

Eccentric planets may spend a significant portion of their orbits at large distances from their host stars, where low temperatures can cause atmospheric CO2 to condense out onto the surface, similar to the polar ice caps on Mars. The radiative effects on the climates of these planets throughout their orbits would depend on the wavelength-dependent albedo of surface CO2 ice that may accumulate at or near apoastron and vary according to the spectral energy distribution of the host star. To explore these possible effects, we incorporated a CO2 ice-albedo parameterization into a one-dimensional energy balance climate model. With the inclusion of this parameterization, our simulations demonstrated that F-dwarf planets require 29% more orbit-averaged flux to thaw out of global water ice cover compared with simulations that solely use a traditional pure water ice-albedo parameterization. When no eccentricity is assumed, and host stars are varied, F-dwarf planets with higher bond albedos relative to their M-dwarf planet counterparts require 30% more orbit-averaged flux to exit a water snowball state. Additionally, the intense heat experienced at periastron aids eccentric planets in exiting a snowball state with a smaller increase in instellation compared with planets on circular orbits; this enables eccentric planets to exhibit warmer conditions along a broad range of instellation. This study emphasizes the significance of incorporating an albedo parameterization for the formation of CO2 ice into climate models to accurately assess the habitability of eccentric planets, as we show that, even at moderate eccentricities, planets with Earth-like atmospheres can reach surface temperatures cold enough for the condensation of CO2 onto their surfaces, as can planets receiving low amounts of instellation on circular orbits. [ABSTRACT FROM AUTHOR]

Characterized by a composition that highlights extensive geochemical differentiation processes, basaltic asteroids are considered fragments of differentiated bodies. To study the smallest bodies in this population, an important tool is the photometric phase curve that can exhibit different behaviours according to the surface properties of the body. We present here the phase curves obtained for 10 V-type asteroids, nine belonging to the main belt population and one a near-Earth object, with observations acquired at the Observatório Astronômico do Sertão de Itaparica (Brazil). Different behaviours of the phase curves were found, as already obtained by studies of polarimetric curves. Adding to our results in the phase curves of 20 V-types from the literature, we found behaviours not expected for objects of moderate to high albedo in the opposition effect region. We attribute this result to the way regoliths are distributed on the surface of small asteroids, which are different from those of larger objects, although the surface composition is the same. [ABSTRACT FROM AUTHOR]

Current issues such as global warming and energy conservation are being discussed more than ever worldwide. Today's pavement sustainability evaluation methods recognize the complicated nature of pavement thermophysical characteristics but do not address albedo-related indicators or outcomes. Pavement infrastructure sustainability assessment systems that objectively prescribe certain thermophysical qualities and albedo criteria relating to "cool pavement," "urban heat island," and other cleaner production effects targets are required. The aim of this study was to quantitatively analyze the thermophysical properties and albedo of urban roads to validate the thermal models used in AASHTOWare Pavement ME (PaveME) version 2.3 Design software. Core samples of both portland cement concrete pavement (PCC) and asphalt pavement (AC) were drilled at 10 locations in a number of sites. In the central and eastern United States, seven field sample locations in different cities were chosen to represent a diversity of local aggregate types, pavement varieties and years of age, and environments. New test methods were then developed and used to quantify the thermal properties of pavements, including thermal conductivity (k), specific heat capacity (SH), emissivity, and albedo. The pavement thermal properties from the literature were summarized and compared to the experimental data. The pavement thermal performance varies greatly in different regions. Thermal conductivity values of PCC and AC cores from northern PCC and AC pavement samples were lower than those found in southern samples. Further endeavors are needed to enhance the accuracy of measuring thermal conductivity value and heat capacity value by utilizing pavement samples. Doing so would enable state highway agencies to document the thermal properties of their pavements and determine the appropriate thermal input values to reduce the negative impact of pavement sustainability and achieve cleaner production goals for pavement infrastructure. [ABSTRACT FROM AUTHOR]

Hydrous minerals are significant indicators of the ancient aqueous environment on Mars, and orbital hyperspectral data are one of the most effective tools for obtaining information about the distribution of hydrous minerals on the Martian surface. However, prolonged weathering, erosion, and other external forces result in complex mixing effects, often weakening the spectral absorption features of individual minerals. This study proposes a quantitative inversion method for Martian hydrous minerals by integrating a radiative transfer model with a deep learning network. Based on the physics of the Hapke radiative transfer model, the single-scattering albedo spectra of mineral end members were obtained. Additionally, the Linear Spectral Mixture Model was employed to generate a large number of fully constrained mineral mixture samples, providing theoretical support for experimental data. An LSTM-1DCNN model was trained to establish a data-driven quantitative inversion framework. CRISM data were applied to the Eberswalde Crater region to retrieve the abundances of 21 hydrous minerals, including tremolite, opal, and serpentine. The average abundance of hydrous minerals was calculated to be 0.018, with a total area proportion of approximately 8%. Additionally, by analyzing the distribution areas of hydrous silicates, hydrous sulfates, and hydrous hydroxides, the water activity history of the region was inferred. The results align with findings from related studies and mineral spectral index results. By incorporating deep learning into traditional mixing models, this study identifies the distribution of various low-abundance hydrous minerals, enhancing the accuracy of Martian hydrous mineral inversion. It is expected to provide valuable references for the selection of landing sites for Tianwen-3 and support the smooth implementation of China's Mars exploration mission. [ABSTRACT FROM AUTHOR]

In this study, the global land surface albedo namely GAC43 was retrieved for the years 1979 to 2020 using Advanced Very High Resolution Radiometer (AVHRR) global area coverage (GAC) data onboard National Oceanic and Atmospheric Administration (NOAA) and Meteorological Operational (MetOp) satellites. We provide a comprehensive retrieval process of the GAC43 albedo, followed by a comprehensive assessment against in situ measurements and three widely used satellite-based albedo products, the third edition of the CM SAF cLoud, Albedo and surface RAdiation (CLARA-A3), the Copernicus Climate Change Service (C3S) albedo product, and MODIS BRDF/albedo product (MCD43). Our quantitative evaluations indicate that GAC43 demonstrates the best stability, with a linear trend of ±0.002 per decade at nearly all pseudo invariant calibration sites (PICS) from 1982 to 2020. In contrast, CLARA-A3 exhibits significant noise before the 2000s due to the limited availability of observations, while C3S shows substantial biases during the same period due to imperfect sensors intercalibrations. Extensive validation at globally distributed homogeneous sites shows that GAC43 has comparable accuracy to C3S, with an overall RMSE of approximately 0.03, but a smaller positive bias of 0.012. Comparatively, MCD43C3 shows the lowest RMSE (~0.023) and minimal bias, while CLARA-A3 displays the highest RMSE (~0.042) and bias (0.02). Furthermore, GAC43, CLARA-A3, and C3S exhibit overestimation in forests, with positive biases exceeding 0.023 and RMSEs of at least 0.028. In contrast, MCD43C3 shows negligible bias and a smaller RMSE of 0.015. For grasslands and shrublands, GAC43 and MCD43C3 demonstrate comparable estimation uncertainties of approximately 0.023, with close positive biases near 0.09, whereas C3S and CLARA-A3 exhibit higher RMSEs and biases exceeding 0.032 and 0.022, respectively. All four albedo products show significant RMSEs around 0.035 over croplands but achieve the highest estimation accuracy better than 0.020 over deserts. It is worth noting that significant biases are typically attributed to insufficient spatial representativeness of the measurement sites. Globally, GAC43 and C3S exhibit similar spatial distribution patterns across most land surface conditions, including an overestimation compared to MCD43C3 and an underestimation compared to CLARA-A3 in forested areas. In addition, GAC43, C3S, and CLARA-A3 estimate higher albedo values than MCD43C3 in low-vegetation regions, such as croplands, grasslands, savannas, and woody savannas. Besides the fact that the new GAC43 product shows the best stability covering the last 40 years, one has to consider the higher proportion of backup inversions before 2000. Overall, GAC43 offers a promising long-term and consistent albedo with good accuracy for future studies such as global climate change, energy balance, and land management policy. [ABSTRACT FROM AUTHOR]

Snow cover plays a key role in determining the albedo and thus the shortwave radiation balance of a surface. The effect of snow on albedo is modulated by land use: tree canopies break the uniform snow layer and lower the albedo as compared to an open ground. This results in a higher fraction of shortwave radiation being absorbed in forests. At seasonally snow-covered high latitudes, this lowering of the albedo has been suggested to offset some or all of the climate cooling effect of the carbon stored by forests. We used long-term in situ measurements to study the albedo and shortwave radiation balance of two pairs of sites, each consisting of an open peatland and a forest. One pair is located in northern and one in southern Finland in the boreal zone. We found that both forest sites had a low, constant albedo during the snow-free period. In contrast, both peatland sites had a higher snow-free albedo, with a clear seasonal cycle. The albedo was found to depend on the diffuse fraction of the incoming radiation: during the snow-covered period, higher diffuse fraction was associated with lower albedo, while during the snow-free period it was associated with higher albedo. The thinning of the southern forest site, resulting in a significant reduction of the leaf area index, increased the albedo especially in the snow-covered period. During the snow-covered period, the peatland sites again had higher albedo than the forest sites. The transition between the high and low albedo upon snow accumulation and especially snowmelt was more abrupt at the peatland sites. In the northern pair, the forest site absorbed on average 0.47 GJ m−2 more (around 23 % more) energy from net shortwave radiation than the peatland site annually, whereas in the southern pair, the forest site absorbed on average 0.37 GJ m−2 more (around 14 % more) than the peatland site. The difference in the annual absorbed energy between the peatland site and the forest site was greater in the northern pair due to longer snow-cover duration. This was partially offset by the greater difference in snow-free albedos and higher solar radiation at the southern site pair. The annual difference in the absorbed shortwave radiation between the forest site and the peatland site varied considerably between the years (from 0.37 to 0.61 GJ m−2 for the northern pair and from 0.20 to 0.53 GJ m−2 for the southern pair). The annual variation was mainly controlled by the snow-cover duration in the spring at the peatland sites. These findings have implications for the future climate, as snow cover continues to evolve under global warming. [ABSTRACT FROM AUTHOR]

The rapid climatic and environmental changes observed in the Arctic and across the globe in general call for reliable model projections. In recent years our understanding of ongoing and future changes through ecosystem modelling has increased tremendously. Yet, most ecosystem models do not consider many of the feedback loops at play in natural ecosystems. Particularly those influenced by biota, beyond vegetation and to some extent microbes, are often neglected. As a first step towards a better integration of biotic influences into ecosystem models, we provide a broad overview of the various ways biota may influence feedback loops between the high-latitude biosphere and the atmosphere. We focus specifically on three key feedback loops between tundra and atmosphere (carbon dynamics, albedo and permafrost thaw) and the influences of three key ecosystem compartments (vegetation, decomposers and herbivores) on these. The influences of biota on ecosystem feedback loops are multifaceted and may appear patchy in both space and time. However, biota may still play important roles in modulating ecosystem feedback loops, and by including these dynamics into ecosystem models, magnitude, accuracy and credibility of model projections are likely to improve. [ABSTRACT FROM AUTHOR]

Remote-sensing (RS)-based estimates of Arctic dust are oftentimes overestimated due to a failure in separating out the dust contribution from that of spatially homogeneous clouds or low-altitude cloud-like plumes. A variety of illustrations are given with a particular emphasis on questionable claims of using brightness temperature differences (BTDs) as a signature indicator of Arctic dust transported from mid-latitude deserts or generated by local Arctic sources. While there is little dispute about the presence of both Asian and local dust across the Arctic, the direct RS detectability of airborne dust, as ascribed to satellite (MODIS and AVHRR) measurements of significantly negative brightness temperature differences at 11 and 12 µ m (BTD 11–12) , has been misrepresented in certain cases. While it is difficult to account for all examples of strongly negative BTD11–12 values in the Arctic, it is unlikely that airborne dust plays a significant role. One much more likely contributor would be water clouds in the Arctic inversion layer. The RS detectability of the impact of Arctic dust (notably due to Arctic dust from local sources) can, however, be of significance. Sustained dust deposition can substantially decrease (visible to shortwave IR) snow and ice reflectance albedo (pan-chromatic reflectance) and the signal measured by satellite sensors. Significantly negative BTD11–12 values would, however, only represent a limited area near the drainage basin sources according to our event-level case studies. The enhanced ice-nucleating particle (INP) role of local Arctic dust can, for example, induce significant changes in the properties of low-level mixed-phase clouds (cloud optical depth changes <∼ 1) that can readily be detected by active and passive RS instruments. It is critical that the distinction between the RS detectability of airborne Arctic dust versus the RS detectability of the impacts of that dust be understood if we are to appropriately parameterize, for example, the radiative forcing influence of dust in this climate-sensitive region. [ABSTRACT FROM AUTHOR]

Recently it was proposed that a sudden drainage of accumulated Arctic sea ice could have caused cold climate events during the last deglaciation. To explore this mechanism, we performed numerical experiments with an atmosphere–ocean–sea ice model. In these experiments, the impact of a large flush of Arctic sea ice was compared to a reference glacial state of the climate. In our results, the sea ice flush produces a major surface freshening of the North Atlantic Ocean and a 17% weakening of the strength of the Atlantic Meridional Overturning Circulation. Together with an increase in surface albedo, this weakening in ocean circulation leads to a cooling over the North Atlantic, extending to the downwind continents. Compared to our reference glacial state, the cooling reaches 5°C and lasts about 80 years. This climate anomaly is similar in magnitude and duration to relatively short cooling events during the last deglaciation, such as the Older Dryas, the Inter‐Allerød cold period and the Preboreal Oscillation. We thus conclude that the sea‐ice flush mechanism is consistent with the occurrence of such cooling events in the North Atlantic region. However, longer cooling events such as the Younger Dryas would require additional mechanisms. [ABSTRACT FROM AUTHOR]

Background. The albedo of the earth's surface is an important indicator that determines the energy balance that exists between our planet and the atmosphere. The issues of optimization of albedometric measurements carried out by spectrometric equipment installed on board an unmanned aerial vehicle (UAV) are considered. The aim of the work is to solve the problem of optimizing albedometric measurements, taking into account the logarithmic relationship between the raw primary digital readings (DN) and the real indicator of reflection of natural and artificial terrestrial objects in the red, green and blue spectral ranges. The object of the study is albedometric measurements carried out by UAVs. The subject of the study is the optimization of albedometric measurements in narrow spectral ranges. Materials and methods. Using the variational method, the optimal dependence of the reflection index of terrestrial objects on the zenith angle of the UAV position relative to the object under study is investigated. The optimization criterion is the target functional in the form of an integrated value DN over the entire range of the change in the specified zenith angle. In the optimal mode, this functionality should reach its maximum if some restrictive condition is imposed on the specified dependence. Results. Using the variational optimization method, the optimal type of the specified dependence is calculated. It is shown that the results of the optimization are indirectly confirmed by the data of well-known experimental studies. Conclusion. Choosing the optimal ratio between the specified zenith angle and the reflection index of objects makes it possible to increase the efficiency of using UAVs for search purposes.

This paper focuses on the analytical modeling of albedo reflection in bifacial photovoltaic modules, with particular emphasis on the backside. First, we critically examine the approaches proposed in the literature, presenting them with a tutorial style and a uniform nomenclature. These approaches are demonstrated to yield physically meaningless results, as they erroneously assume that the ground area shaded by the module acts as a source of reflected irradiance independent of the portion of sky dome visible to such an area. Then we introduce a correction based on the view factor between the shaded area and the sky. The result is a comprehensive and accurate analytical model that also describes the case of suspended panels and can be easily implemented into PV plant simulators.

The albedo and solar reflectance of surrounding surfaces, such as roads, pavements, and building façades, influence urban microclimate and outdoor thermal comfort. This study investigates the cumulative effect of pavements and facades’ albedo on the microclimate and outdoor thermal comfort in hot climates, trying to find the correlation between the urban surface albedo ratios and their thermal effects. Using the ENVI-Met software, nine scenarios with different albedo values (0.2 to 0.8) for pavements and buildings’ façades were simulated to encounter concrete in three colours. The clustering technique for the results was performed using the K-Means clustering method and correlation analysis using the orange data mining tool. The results indicate strong correlations between façade-pavement albedo ratio (FPR), air temperature, and UTCI values in both seasons, as well as a greater effect of the pavement on thermal conditions compared to the façade. Furthermore, the impact of high-albedo materials on air temperature and outdoor thermal comfort is the opposite, as the L-L scenario presents the highest UTCI values and the lowest air temperature in summer. Overall, the results indicate complex correlations between FPR, air temperature, and UTCI values. [ABSTRACT FROM AUTHOR]

While paleoclimate simulations have been a priority for Earth system modelers over the past three decades, little attention has been paid to the period between the mid-Holocene and the Last Millennium, although this is an important period for the emergence of complex societies. Here, we consider the climate of 2500 BP (550 BCE), a period when compared to late preindustrial time, greenhouse gas concentrations were slightly lower, and orbital forcing led to a stronger seasonal cycle in high latitude insolation. To capture the influence of land cover on climate, we asynchronously coupled the NASA GISS ModelE Earth system model with the LPJ-LMfire dynamic global vegetation model. We simulated global climate and assessed our results in the context of independent paleoclimate reconstructions. We also explored a set of combinations of model performance parameters (bias and variability) and demonstrated their importance for the asynchronous coupling framework. The coupled model system shows substantial vegetation albedo feedback to climate. In the absence of a bias correction, while driving LPJ-LMfire in the coupling process, ModelE drifts towards colder conditions in the high latitudes of the Northern Hemisphere in response to land cover simulated by LPJ-LMfire. A regional precipitation response is also prominent in the various combinations of the coupled model system, with a substantial intensification of the Summer Indian Monsoon and a drying pattern over Europe. Evaluation of the simulated climate against reconstructions of temperature from multiple proxies and the isotopic composition of precipitation (δ18Op) from speleothems demonstrated the skill of ModelE in simulating past climate. A regional analysis of the simulated vegetation-climate response further confirmed the validity of this approach. The coupled model system is sensitive to the representation of shrubs and this land cover type requires particular attention as a potentially important driver of climate in regions where shrubs are abundant. Our results further demonstrate the importance of bias correction in coupled paleoclimate simulations. [ABSTRACT FROM AUTHOR]

The Two-streAm Radiative TransfEr in Snow (TARTES) model computes the spectral albedo and the profiles of spectral absorption, irradiance, and actinic fluxes for a multi-layer plane-parallel snowpack. Each snow layer is characterized by its specific surface area, density, and impurity content, in addition to shape parameters. In the landscape of snow optical numerical models, TARTES distinguishes itself by taking into account different shapes of the particles through two shape parameters, namely the absorption enhancement parameter B and the asymmetry factor g. This is of primary importance as recent studies working at the microstructure level have demonstrated that snow does not behave as a collection of equivalent ice spheres, a representation widely used in other models. Instead, B and g take specific values that do not correspond to any simple geometrical shape, which leads to the concept of the "optical shape of snow". Apart from this specificity, TARTES combines well-established radiative transfer principles to compute the scattering and absorption coefficients of pure or polluted snow, as well as the δ -Eddington two-stream approximation to solve the multi-layer radiative transfer equation. The model is implemented in Python, but conducting TARTES simulations is also possible without any programming through the SnowTARTES web application, making it very accessible to non-experts and for teaching purposes. Here, after describing the theoretical and technical details of the model, we illustrate its main capabilities and present some comparisons with other common snow radiative transfer models (AART, DISORT-Mie, SNICAR-ADv3) as a validation procedure. Overall the agreement on the spectral albedo, when in compatible conditions (i.e., with spheres), is usually within 0.02 and is better in the visible and near-infrared range compared to longer wavelengths. [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]

The article "Energy Flows at Earth's Surface" discusses the convergence of two energy flows at Earth's surface: one from the Sun and the other from Earth's interior. Solar energy controls surface temperature and processes involving the atmosphere, oceans, and biosphere, while endogenous heat is responsible for processes in Earth's interior. Solar energy is about 2800 times greater than endogenous heat and has no effect on internal processes, while endogenous heat is irrelevant for surface temperature and processes. The article also highlights the impact of thermal evolution on planets with higher surface temperatures, such as Venus. [Extracted from the article]

Increasing the albedo of urban surfaces, through strategies like white roof installations, has emerged as a promising approach for urban climate adaptation. Yet, modeling these strategies on a large scale is limited by the use of static urban surface albedo representations in the Earth system models. In this study, we developed a new transient urban surface albedo scheme in the Community Earth System Model and evaluated evolving adaptation strategies under varying urban surface albedo configurations. Our simulations model a gradual increase in the urban surface albedo of roofs, impervious roads, and walls from 2015 to 2099 under the SSP3‐7.0 scenario. Results highlight the cooling effects of roof albedo modifications, which reduce the annual‐mean canopy urban heat island intensity from 0.8°C in 2015 to 0.2°C by 2099. Compared to high‐density and medium‐density urban areas, higher albedo configurations are more effective in cooling environments within tall building districts. Additionally, urban surface albedo changes lead to changes in building energy consumption, where high albedo results in more indoor heating usage in urban areas located beyond 30°N and 25°S. This scheme offers potential applications like simulating natural albedo variations across urban surfaces and enables the inclusion of other urban parameters, such as surface emissivity. Plain Language Summary: Higher albedo surfaces reflect more sunlight, which helps cool down cities. Yet, research into how altering the albedo of urban surfaces on a global scale can aid climate adaptation is limited. It either relies on empirical analysis, oversimplifying urban physical processes, or assumes that urban surface albedo remains constant over time. These limitations hinder our understanding of how changes in urban surfaces can impact the urban thermal environment. In this study, we developed a new option that allows urban surface albedo to vary over time within a global climate model. By gradually increasing global urban surface albedo, we quantified the cooling effects of implementing high urban albedo in a more realistic way. This new option sets the stage for future exploration of scenarios like painting roofs white or how materials age, shedding light on effective urban climate adaptation strategies. Key Points: We developed a new representation scheme of transient urban surface albedo in Community Earth System Model (CESM) to improve urban climate adaptation modelingThe new scheme enables CESM to assess evolving adaptation strategies for roofs, impervious roads, and walls over timeSimulations show increasing roof albedo cools cities more effectively than increasing wall or impervious road albedo [ABSTRACT FROM AUTHOR]