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The theory of radiative transfer in the atmosphere is crucial in the study of climate, because radiative exchanges are at the origin of the atmospheric dynamics. It is therefore important to evaluate this phenomenon in order to be able to take effective measures to tackle climate change. The objective of this work is to evaluate the capability of the RegCM5 climate model to reproduce radiative transfer over Central Africa. The analysis is carried out over a 10‐year period, from January 2002 to December 2011 preceded by 1 year as spin‐up. RegCM5 model were evaluated using the ERA5 dataset for the radiative transfer parameters (the shortwave radiation [SWR], longwave radiation [LWR], cloud cover [CLT], surface albedo [ALB] and surface temperature), as well as CHIRPS dataset for precipitation. Three subregions were identified for more specific analysis of the model, namely the Sahel, Congo basin and Cameroon highlands. Two radiative schemes were used: the radiative scheme of the community climate model (CCM) and Rapid Radiative Transfer Model (RRTM). The assessment of radiative transfer parameters was carried out by examining their seasonal variability and annual cycles using data from two RegCM5 experiments, RegCM5‐CCM3 and RegCM5‐RRTM. Before this assessment, a sensibility analysis to convective schemes carried out with the default RegCM5 radiative scheme (CCM3) shows that Grell scheme with Arakawa and Shulber closure is the best scheme to represent key radiation parameters (LWR and SWR). This convective scheme is therefore used for assessing the two Radiative transfer schemes. Results show that both RegCM5 experiments simulate relatively well the variables linked to radiative transfer for the four seasons of the year. However, RegCM5 with RRTM as radiative scheme depicts better performance over all subregions and seasons, suggesting that the choice of this scheme does not depend on land cover, topography and rainfall regimes in a complex region such as Central Africa. [ABSTRACT FROM AUTHOR]

AbstractWe examine the effect of linear anisotropic scattering on the solution of spherical geometry transport problems. We consider the albedo problem of a solid homogeneous sphere with linearly anisotropic scattering and write two matrix equations to solve the albedo problem with the HN and SVD methods in pseudo slab geometry. These methods are based on Case method of singular eigenfunctions. The numerical results of both methods are in agreement with each other. [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]

A laboratory study was performed using the Visible Oxford Space Environment Goniometer in which the broadband (350–1250 nm) bidirectional reflectance distribution functions (BRDFs) of two representative Apollo regolith samples were measured, for two surface roughness profiles, across a range of viewing angles—reflectance: 0–70°, in steps of 5°; incidence: 15°, 30°, 45°, and 60°; and azimuthal: 0°, 45°, 90°, 135°, and 180°. The BRDF datasets were fitted using the Hapke BRDF model to (1) provide a method of comparison to other photometric studies of the lunar regolith and (2) to produce Hapke parameter values which can be used to extrapolate the BRDF to all angles. Importantly, the surface profiles of the samples were characterized using an Alicona 3D® instrument, allowing two of the free parameters within the Hapke model, φ and θ¯, which represent porosity and surface roughness, respectively, to be constrained. The study determined that, for θ¯, the 500–1000 μm size‐scale is the most relevant for the BRDF. Thus, it deduced the following "best fit" Hapke parameters for each of the samples: Apollo 11 rough—w = 0.315 ± 0.021, b = 0.261 ± 0.007, and hS = 0.039 ± 0.005 (with θ¯ = 21.28° and φ = 0.41 ± 0.02); Apollo 11 smooth—w = 0.281 ± 0.028, b = 0.238 ± 0.008, and hS = 0.032 ± 0.006 (with θ¯ = 13.80° and φ = 0.60 ± 0.02); Apollo 16 rough—w = 0.485 ± 0.155, b = 0.155 ± 0.083, and hS = 0.135 ± 0.007 (with θ¯ = 21.69° and φ = 0.55 ± 0.02); Apollo 16 smooth—w = 0.388 ± 0.057, b = 0.063 ± 0.033, and hS = 0.221 ± 0.011 (with θ¯ = 14.27° and φ = 0.40 ± 0.02). Finally, updated hemispheric albedo functions were determined for the samples, which can be used to set laboratory measured visible scattering functions within thermal models. [ABSTRACT FROM AUTHOR]

High-precision lunar scene 3D data are essential for lunar exploration and the construction of scientific research stations. Currently, most existing data from orbital imagery offers resolutions up to 0.5–2 m, which is inadequate for tasks requiring centimeter-level precision. To overcome this, our research focuses on using in situ stereo vision systems for finer 3D reconstructions directly from the lunar surface. However, the scarcity and homogeneity of available lunar surface stereo datasets, combined with the Moon's unique conditions—such as variable lighting from low albedo, sparse surface textures, and extensive shadow occlusions—pose significant challenges to the effectiveness of traditional stereo matching techniques. To address the dataset gap, we propose a method using Unreal Engine 4 (UE4) for high-fidelity physical simulation of lunar surface scenes, generating high-resolution images under realistic and challenging conditions. Additionally, we propose an optimized cost calculation method based on Census transform and color intensity fusion, along with a multi-level super-pixel disparity optimization, to improve matching accuracy under harsh lunar conditions. Experimental results demonstrate that the proposed method exhibits exceptional robustness and accuracy in our soon-to-be-released multi-scene lunar dataset, effectively addressing issues related to special lighting conditions, weak textures, and shadow occlusion, ultimately enhancing disparity estimation accuracy. [ABSTRACT FROM AUTHOR]

Highly efficient bifacial organic solar cells (OSCs) have not been reported due to limited thickness of the active layer in conventional configurations, not allowing for efficient harvesting of front sunlight and albedo light. Here, bifacial OSCs are reported with efficiency higher than the monofacial counterparts. The incorporation of pyramid-based asymmetrical optical transmission (AOT) array to a transparent silver electrode suppresses the escaping of front sunlight without sacrificing the harvesting of albedo light. Parasitic absorption induced by the excitation of surface plasmons in an AOT electrode is further reduced by doping organic emitter in electron transport layer and capping high dielectric constant film to silver. The rear electrode achieves a front transmittance of 7% and a rear transmission of 86%. At a conventional albedo of 0.2, the synergistic effect of AOT and minimized optical loss endow the bifacial OSCs with power conversion efficiency of 20.4%. This work paves the way for the utilization of albedo light in OSCs. [ABSTRACT FROM AUTHOR]

Naturally treeless ecosystems are being replaced by native and non‐native trees worldwide, often through deliberate afforestation using forestry tree species. By introducing species having novel traits, such as relatively rapid growth, many afforestation efforts also produce numerous changes in ecosystems, at the landscape scale.Trees are considered critical for climate change mitigation; indeed, many current carbon sequestration strategies rely on trees. Planting trees or allowing trees to naturally colonize through range expansions can be seen as an ideal way to increase atmospheric carbon capture. For example, a snapshot approach may show that introducing trees into treeless ecosystems enhances aboveground accumulation of carbon, helping increase ecosystem carbon storage.However, considering other impacts such as reductions in soil carbon or albedo and increased fire severity (through increases in fuel loads and connectivity) reduces the effectiveness of afforestation strategies for climate change amelioration. Additional negative impacts of afforestation are also likely, such as the reduction of native biodiversity and productivity, substantial water yield losses, and changes in nutrient cycles, which can exacerbate other global change drivers. Further, tree invasions originating from afforestation can exacerbate these negative impacts.Synthesis. This review highlights that the positive and negative impacts of planting trees in naturally treeless ecosystems as a strategy to mitigate climate change are idiosyncratic, depending on the location where trees are introduced, the time period trees are allowed to grow, and risks of spread and impacts associated with specific tree species. Although planting trees can potentially be a tool to fight climate change, a greater consideration of their impacts is required to minimize the unexpected negative consequences of afforestation efforts. [ABSTRACT FROM AUTHOR]

In current land surface models or satellite remote sensing retrievals, clear‐sky surface albedo (α) is usually assumed to be symmetrical and relies only on the solar elevation angle (SEA). Based on 1‐min high‐resolution measurements of surface radiation fluxes, this study demonstrated that the diurnal variations of clear‐sky surface albedo exhibited a significant asymmetrical pattern in both summer and winter seasons over a semi‐arid grassland of the China's Loess Plateau. The results indicated that α values in the morning were generally larger than those in the afternoon at the same SEA, and diurnal asymmetry of surface albedo was distinctly prominent with SEA <40° in summer (before 9:30 a.m.) or SEA <20° in winter (before 10:00 am), and tended to diminish at midday. The averaged morning/afternoon albedo differences under sunny days were 0.05 (30.4%) and 0.09 (37.8%) in summer and winter seasons, respectively. Air relative humidity was positively correlated with the diurnal asymmetry of surface albedo, ascribed to probable formation of dew in the morning. Depression of the dew point was negatively linked to the morning/afternoon albedo differences, which was attributed to the strong scattering of incident sunlight by dewdrops could enhance the morning surface albedo. Such diurnal asymmetry of surface albedo should be included in the parameterization scheme of mesoscale and region‐scale climate models in the semi‐arid areas of China's Loess Plateau. [ABSTRACT FROM AUTHOR]

Earth's Northern and Southern Hemispheres reflect essentially equal amounts of sunlight. How—and whether—this hemispheric albedo symmetry is maintained remains a mystery. We decompose Earth's hemispheric albedo symmetry into components associated with the surface, clear‐sky atmosphere, and different cloud types as defined by cloud effective pressure and optical thickness. Climatologically, greater reflection by the surface, aerosols, and high clouds in the Northern Hemisphere is balanced by greater low and mid‐level cloudiness in the Southern Hemisphere. Both hemispheres have darkened at similar rates over the past two decades; whether the darkening from more rapidly declining aerosol in the Northern Hemisphere is causing a departure from all‐sky symmetry remains uncertain. Natural experiments including long‐term trends, sea ice loss, and volcanic eruptions provide strong evidence against the hypothesis that extratropical low clouds compensate changing clear‐sky asymmetries on annual‐to‐decadal timescales but some evidence that tropical high cloud shifts may do so. Plain Language Summary: Mysteriously, the Northern and Southern Hemispheres reflect the same amount of sunlight as each other, but scientists are not yet sure why, how, or even whether this phenomenon is sustained by the Earth system. The Northern Hemisphere is brighter in clear skies because it contains more pollution particles in the atmosphere and has more land area, whereas the Southern Hemisphere is cloudier. We break down this cloudiness contrast into components related to different cloud types defined by their height and thickness. Tropical high‐altitude clouds increase reflection preferentially in the Northern Hemisphere but are overcompensated by low‐ and mid‐level clouds in the Southern Hemisphere, especially in the subtropics and midlatitudes. Both hemispheres have darkened over the past two decades, but whether the Northern Hemisphere is darkening faster than the Southern Hemisphere due to decreasing particulate pollution or if they are darkening at the exact same rate remains uncertain. Based on long‐term trends and "natural experiments" like sea ice loss and volcanic eruptions, we can rule out the hypothesis that low‐level clouds in the Southern Ocean act to balance out clear‐sky asymmetries at yearly‐to‐decadal timescales, but we cannot rule out the hypothesis that high‐altitude tropical clouds do so. Key Points: Greater reflection from Northern Hemisphere clear‐skies and high clouds is balanced by Southern Hemisphere low and mid‐level cloudsEvidence points against extratropical low cloud adjustments compensating for clear‐sky albedo changes on decadal timescalesLimited and conflicting evidence for whether shifts in tropical high clouds compensate clear‐sky changes at annual to decadal timescales [ABSTRACT FROM AUTHOR]

In this study, we assess the homogeneity of aerosol optical depth (AOD) between two sun photometer networks, the Global Atmosphere Watch-Precision Filter Radiometer (GAW-PFR) and the European SKYNET radiometers network (ESR), at the common wavelengths of their main instruments (500 and 870 nm). The main focus of this work is to evaluate the effect of the improved Langley plot calibration method (ILP) used by SKYNET and to investigate the factors affecting its performance. We used data from three intercomparison campaigns that took place during 2017–2021. Each campaign was organized at two locations (mountainous rural – Davos, Switzerland; urban – Rome, Italy). Our analysis shows that differences in AOD due to post-processing and instrument differences are minor. The main factor leading to AOD differences is the calibration method. We found a systematic underestimation of AOD in ESR compared to in GAW-PFR due to underestimation of the calibration constant calculated with the ILP method compared to the calibration transfers using the PFR as a reference. The calibration and AOD differences are smaller in Davos, where the traceability criteria are satisfied at 870 nm and where the median differences are below 0.01 at 500 nm. In Rome, the AOD median differences at 500 nm were in the 0.015–0.034 range. We conducted a sensitivity study, which shows that part of the difference can potentially be explained by errors in the assumed surface albedo and instrument solid-view angle provided as inputs to the ILP code (based on Skyrad pack 4.2). Our findings suggest that the ILP method is mainly sensitive to the measured sky radiance. The underestimation in calibration is probably caused by an error in the retrieved scattering AOD (sc-AOD) through the sky radiance inversion. Using an alternative retrieval method (Skyrad MRI pack version 2) to derive sc-AOD and to recalibrate the instruments with the ILP method, we found no significant differences between the retrieved sc-AOD and no systematic increase in the ILP-derived calibration constant when using the MRI pack for sc-AOD inversion instead of the Skyrad 4.2. The potential error may be a result of the model assumptions used for the sky radiance simulations. In conclusion, the on-site calibration of sun photometers has several advantages, including the fact that instrument shipments and data gaps can be avoided. However, it has also the disadvantages of a larger uncertainty and significant systematic differences compared to the traditional Langley calibration performed under low- and constant-AOD conditions at high-altitude sites. The larger uncertainty of the ILP method can be attributed to the required modelling and input parameters. [ABSTRACT FROM AUTHOR]

Surface albedo is an important parameter in radiative-transfer simulations of the Earth's system as it is fundamental for correctly calculating the energy budget of the planet. The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA's Terra and Aqua satellites continuously monitor daily and yearly changes in reflection at the planetary surface. The MODIS Surface Reflectance Black-Sky Albedo dataset (version 6.1 of MCD43D) provides detailed albedo maps for seven spectral bands in the visible and near-infrared range. These albedo maps allow us to classify different Lambertian surface types and their seasonal and yearly variability and change, albeit only into seven spectral bands. However, a complete set of albedo maps covering the entire wavelength range is required to simulate radiance spectra and correctly retrieve atmospheric and cloud properties from remote sensing observations of the Earth. We use a principal component analysis (PCA) regression algorithm to generate hyperspectral albedo maps of the Earth. By combining different datasets containing laboratory measurements of hyperspectral reflectance for various dry soils, vegetation surfaces, and mixtures of both, we reconstruct albedo maps across the entire wavelength range from 400 to 2500 nm. The PCA method is trained with a 10-year average of MODIS data for each day of the year. We obtain hyperspectral albedo maps with a spatial resolution of 0.05° in latitude and longitude, a spectral resolution of 10 nm, and a temporal resolution of 1 d (day). Using the hyperspectral albedo maps, we estimate the spectral profiles of different land surfaces, such as forests, deserts, cities, and icy surfaces, and study their seasonal variability. These albedo maps will enable us to refine calculations of the Earth's energy budget and its seasonal variability and improve climate simulations. [ABSTRACT FROM AUTHOR]

Glacier meltwater is an indispensable water supply for billions of people living in the catchments of major Asian rivers. However, the role of glaciers on river runoff regulation is seldom investigated due to the lack of annual glacier mass balance observation. In this study, we employed an albedo-based model with a daily land surface albedo dataset to derive the annual glacier mass balance over the Tuotuo River Basin (TRB). During 2000–2022, an annual glacier mass balance range of −0.89 ± 0.08 to 0.11 ± 0.11 m w.e. was estimated. By comparing with river runoff records from the hydrometric station, the contribution of glacier mass change to river runoff was calculated to be 0.00–31.14% for the studied period, with a mean value of 9.97%. Moreover, we found that the mean contribution in drought years is 20.07%, which is approximately five times that in wet years (4.30%) and twice that in average years (9.49%). Therefore, our results verify that mountain glaciers act as a significant buffer against drought in the TRB, at least during the 2000–2022 period. [ABSTRACT FROM AUTHOR]

Vegetation can modify the planetary surface albedo via the Charney mechanism, as plants are usually darker than the bare surface of the continents. We updated ESTM (Earth-like surface temperature model) to incorporate the presence, distribution and evolution of two dynamically competing vegetation types that resemble grasslands and trees (the latter in the double stages of life: adults and seedlings). The newly developed model was applied to estimate how the climate-vegetation system reaches equilibrium across different rocky planetary configurations, and to assess its impact on temperature and habitability. With respect to a world with bare granite continents, the effect of vegetation-albedo feedback is to increase the average surface temperature. Since grasses and trees exhibit different albedos, they affect temperature to different degrees. The ultimate impact on climate depends on the outcome of the competition between these vegetation types. The change in albedo due to vegetation extends the habitable zone and enhances the overall planetary habitability beyond its traditional outer edge. This effect is especially relevant for planets that have a larger extension of continents than Earth. For Earth, the semimajor axis d  = 1.04 au represents the turning point where vegetation enhances habitability from h  = 0.0 to 0.485 (in the grass-dominance case), to h  = 0.584 (in the case of coexistence between grasses and trees), and to h  = 0.612 (in the tree-dominance case). This illustrates the transition from a snowball state to a planet with intermediate habitability at the outer edge of the circumstellar habitability zone. [ABSTRACT FROM AUTHOR]

The present study aimed to find solutions based on the use of plant-based ingredients that would improve the nutritional quality of meat products as well as ensure sensory and microbiological quality. Two fat replacers, lemon albedo (Citrus lemon) and carob seed gum (Ceratonia siliqua), were investigated by chemical analysis and panel testing to evaluate their effect on the nutritional and sensory quality of beef burgers. The antimicrobial activity of two plant extracts, from nettle (Urtica dioica) leaves and medlar (Eriobotrya japonica) seeds, was studied, evaluating the intensity of inhibitory action and the minimum inhibitory concentration against Pseudomonas spp. and Listeria innocua strains by plate test. In addition, the antioxidant activity of both extracts was evaluated. Based on the results, lemon albedo and medlar seed extracts were validated in a food model (beef burger) by a storage test and a challenge test. The storage test results highlight that medlar seed extract prevents the formation of thiobarbituric acid reactive substances (TBARSs) and ensures microbiological quality, inhibiting Enterobacteriaceae and Pseudomonas spp. Anti-Listeria efficacy was confirmed in situ by challenge test results. In conclusion, although fat replacers ensure nutritional and sensory quality, they do not satisfy microbiological quality. This study clearly demonstrates that the safety of low-fat burgers can only be achieved through the combination of appropriate fat replacers with well-selected natural antimicrobial extracts. [ABSTRACT FROM AUTHOR]

To study the influence of multiple scattering factors on the scattering characteristics, the scattering properties of a sizable double-spherical system at random orientations were analyzed by comparison of the T matrix and simple addition in the S-, C-, and X-bands, including the backscatter section (Cbak), attenuation section (Cext) and scattering section (Csca), asymmetry factor (g), and single scattering albedo (w), with the change in the spherical distance (d) and particle radius (r). It was found that the spacing between the spheres is four times the sphere's radius, which is a clear cut-off point for the influence of multiple scattering in a two-spherical system. Then, by fitting the relative difference multiples of the T matrix method and the simple addition method, the uniform expression of each optical parameter under multiple scattering conditions is obtained. [ABSTRACT FROM AUTHOR]

Limoncella of Mattinata, a rare and ancient Mediterranean citrus fruit, was investigated by sequence analysis of the ribosomal internal transcribed spacer regions, which assigns it as a variety of Citrus medica L. Morphological, chemical, and biomolecular approaches, including light and electron microscopy, HPLC-ESI-MS/MS, and antioxidant and anti-inflammatory assays, were used to characterize the flavedo and albedo parts, usually rich in bioactive compounds. The morphological findings showed albedo and flavedo cellular structures as "reservoirs" of nutritional components. Both albedo and flavedo hydroalcoholic extracts were rich in polyphenols, but they were different in compounds and quantity. The flavedo is rich in p-coumaric acid and rutin, whereas the albedo contains high levels of hesperidin and quercitrin. Antioxidant, anti-inflammatory, and genoprotective effects for albedo and flavedo were found. The results confirmed the health properties of flavedo and highlighted that albedo is also a rich source of antioxidants. Moreover, this study valorizes Limoncella of Mattinata's nutritional properties, cueing its crops' repopulation. [ABSTRACT FROM AUTHOR]

Black carbon (BC) aerosols have attracted wide attention over the world due to their significant climate effects on local and global scales. BC extinction aerosol optical thickness (AOT), scattering AOT, and single scattering albedo (SSA) over China are systematically studied based on the MERRA-2 satellite reanalysis data from 1983 to 2022 in terms of the spatial, yearly, seasonal, and monthly variations. The extinction and scattering AOTs of BC show similar spatial distribution, with high values in eastern and southern China, generally as opposed to BC SSA. A decrease in BC extinction and scattering AOTs has been documented over the last decade. The mean BC extinction AOT, scattering AOT, and SSA over China are 0.0054, 0.0014, and 0.26, respectively. The BC SSA showed small variations during 1983–2022, although a high BC extinction AOT and scattering AOT have been seen in the last two decades. During different decades, the seasonal patterns of BC extinction and scattering AOTs may differ, whereas the BC SSA shows seasonal consistency. Significant monthly variations in the BC SSA are seen over four decades, which are in agreement with their seasonal patterns. The mean BC extinction AOTs are 0.037, 0.033, 0.023, and 0.0054, whereas the average BC scattering AOTs are 0.0088, 0.0082, 0.0060, and 0.0014 in the Pearl River Delta (PRD), Yangtze River Delta (YRD), Beijing–Tianjin–Hebei (BTH) region, and Tarim Basin (TB), respectively. It is interesting to see that BC SSA values in the TB region are generally higher than those over the PRD, YRD and BTH areas, whereas the reverse is true for BC extinction and scattering AOTs. This study provides references for further research on black carbon aerosols and air pollution in China. [ABSTRACT FROM AUTHOR]

Albedo plays a key role in regulating the absorption of solar radiation within ice surfaces and hence strongly regulates the production of meltwater. A combination of Landsat and Sentinel 2 data provides the longest continuous medium resolution (10–30 m) earth surface observatory records. An albedo product (harmonized satellite albedo, hereafter HSA) has already been developed and validated for the Greenland Ice Sheet (GrIS), using harmonized Landsat 4–8 and Sentinel 2 datasets. In this paper, the HSA was validated for various Arctic and alpine glaciers and ice caps using in situ measurements. We determine the optimal spatial window size in point-to-pixel analysis, the best practices in evaluating remote sensing algorithms with groundtruth data, and cross sensor comparison of the Landsat 9 (L9) and Landsat 8 (L8) data. The impact of the spatial window size on measured ice surface homogeneity and albedo validation was analysed at both local and regional scales. Homogeneity statistics calculated from the grey-level co-occurrence matrix (GLCM) suggest that the ice surface becomes more homogeneous as the image resolution becomes coarser. The optimal spatial window size was found to be 90 m, based on maximizing the statistical and graphical measures while minimizing the root mean square error and bias. HSAs generally agree closely with in situ albedo measurements (e.g. Pearson's R ranges from 0.68 to 0.92) across various Arctic and alpine glaciers and ice caps. Cross sensor differences between L9 and L8 are minor, and we suggest that no harmonization is necessary to add L9 to our HSA product. [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]

Absorptive substances (AS) embedded in sea ice can alter irradiance transmission, exerting a significant influence on oceanic biogeochemical processes. Their quantification is thus essential, and a regression model based on the normalized difference index of transmittance (T(λ)) has been widely used for retrieving ice algal biomass. However, the potentials of albedo (α(λ)) and the diffuse attenuation coefficient (Kd(λ)) in AS estimation have not been explored. To fill this gap, sea ice optical properties observed in Liaodong Bay in 2009, 2010, 2013, and 2022 were used to investigate the characteristics of α(λ), T(λ), and Kd(λ) in non‐destructively estimating As through sensitivity analyses based on the Hydrolight radiative transfer model. The effects derived from AS vertical distribution, scattering coefficient and ice thickness were studied specifically. Ultimately, a significant relationship between α(λ) and the total absorption coefficient of AS was derived (R2 = 0.79) for Liaodong Bay sea ice. Sensitivity analyses revealed that it could only retrieve AS in the upper 15–20 cm, which was influenced by variations in ice thickness and scattering coefficient. In contrast, T(λ) could retrieve AS throughout the ice column and is less affected by scattering variation; but it is significantly affected by the vertical distribution of AS in the upper layer. Kd(λ) has the best potential in AS estimation, but for sea ice thinner than 30 cm, the effect of variation in ice thickness could not be neglected, similar to T(λ). Knowledge of this is helpful for the future development of AS estimation. Plain Language Summary: This study focused on the non‐destructive estimation of AS like sediment and ice algae in sea ice, which have an important impact on ecosystems because of their strong absorption of visible light. The potential of reflective and transmitted spectra in AS estimation was systematically explored for applications in different scenarios. Due to the highly variable vertical distribution of AS, scattering intensity and ice thickness, there may be various uncertainties in the AS estimation based on different optical parameters. Through radiative transfer simulations, it was found that the estimation based on reflective spectra could only estimate AS within the upper 15‐20‐cm ice layer and has relatively larger uncertainties for thin ice and under high scattering intensity. Transmitted spectra methods could estimate the AS at any depth of the ice column and were less affected by these variable physical‐optical properties, especially for the spectra of attenuation properties. But for thinner ice with thickeness less than 30 cm, the variation in ice thicknes could not be neglected, whether for reflective spectra or transmitted spectra. Key Points: A significant relationship between albedo and the absorption coefficient of absorptive substances (AS) was constructed for Liaodong Bay sea iceTransmittance is optically superior to albedo in absorptive substance estimation because it is not restricted by its depth and scatteringThe diffuse attenuation coefficient performs best in estimating AS because it is least affected by variations in sea ice [ABSTRACT FROM AUTHOR]

BACKGROUND AND OBJECTIVES: The reflection of solar radiation by pavements is crucial for managing urban heat, enhancing thermal comfort, and supporting sustainable development. Albedo pavements are a key component of modern urban planning. Despite extensive studies on the influence of pavement reflectivity on heat stress in street canyons, there is still a lack of exploration regarding its impact on pedestrian comfort in Thailand during the peak summer months. This study examines thirteen design scenarios and simulations utilizing a microclimate model, with a specific focus on the combined albedos of road surfaces, sidewalks, and plants in a deep street canyon within a residential townhouse project located in Bangkok. METHODS: The utilization of a microclimate simulation model enabled the calculation of climatic conditions within an east-west-oriented street canyon on April 26, which represents a typical summer day in Thailand. By utilizing the simulated microclimatic parameters, hourly physiologically equivalent temperature values were derived to assess human thermal comfort. This analysis helped identify the threshold for comfortable summer conditions in Thailand. Field data validation showed acceptable errors (R² = 0.91, normalized mean square error = 0.17). FINDINGS: For an east-west-oriented deep street canyon with direct overhead sunlight in summer, low-albedo materials for road and sidewalk surfaces are recommended to enhance thermal comfort. The implementation of these albedo strategies has the potential to enhance thermal comfort by 0.34-0.38 percent and alter the threshold values of the Physiologically Equivalent Temperature Index for thermal sensation, transitioning from hot to cold environments. While the percentage increase may seem small, it signifies a substantial advancement in improving thermal comfort for people in urban settings. This finding carries significant importance in densely populated areas with limited natural shade, where even slight improvements in thermal comfort can have a positive effect on public health and well-being. CONCLUSION: Albedo reduction alone may not significantly enhance outdoor comfort within the street canyons. Urban planners and designers should consider integrating additional strategies such as tree planting, Sidewalks facing different directions, exposed to sunlight, instead of pedestrian arcades and overhead shading structures. The thermal environments and comfort of sunlit north-facing sidewalks in an east-west-oriented deep street canyon during the summer, when the sun's path shifts northward, are greatly influenced by the solar tilt and azimuth angles. It is crucial to highlight the substantial impact of these angles. [ABSTRACT FROM AUTHOR]

The measurement of globe temperature (GT) is essential for investigating pedestrian thermal comfort in street canyons. The globe thermometer is the most common instrument used to measure GT; however, its application in scale models has not been thoroughly investigated to date. Therefore, this study explicitly investigates globe thermometer measurements in scale models and analyzes the need for customization of the globe thermometer for more reliable measurements. Scaling down with respect to the size of the globe thermometer and the effect of solar orientation/envelope materials are investigated in this study. The initial experiments were carried out in an outdoor setting using a typical street canyon model (scale 1:100) with an east-west street orientation. The results of the experiment are presented to compare a low solar reflectance street canyon (albedo of 0.4) and a high solar reflectance canyon (albedo of 0.6) in terms of surface temperatures, heat flux, and globe temperature. It is observed that although the wall and road surface temperatures are lower for the high solar reflectance canyon compared to those for the low solar reflectance canyon, the GT (measured at pedestrian height) is higher in a high reflectance canyon during the daytime, which could be due to the combined effect of direct radiation and short-wave reflection. However, for the hours after sunset, a reverse effect is observed, i.e., the GT becomes lower (up to 0.8 °C) in the case of a high reflectance canyon compared to that for the low reflectance canyon. Furthermore, the study emphasizes the impact of solar reflectance of canyon surfaces on GT values, due to the view factors that the globe thermometer on those surfaces. [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]

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]

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]

Albedo is a primary driver of the glacier surface energy balance and consequent melting. As glacier albedo decreases, it further accelerates glacier melting. Over the past 20 years, glaciers on the Tibetan Plateau have experienced significant melting. However, our understanding of the variations in glacier albedo and its driving factors in this region remains limited. This study used MOD10A1 data to examine the average characteristics and variations in glacier albedo on the Tibetan Plateau from 2001 to 2022; the MOD10A1 snow cover product, developed at the National Snow and Ice Data Center, was employed to analyze spatiotemporal variations in surface albedo. The results indicate that the albedo values of glaciers on the Tibetan Plateau predominantly range between 0.50 and 0.60, with distinctly higher albedo in spring and winter, and lower albedo in summer and autumn. Glacier albedo on the Tibetan Plateau decreased at an average linear regression rate of 0.06 × 10−2 yr−1 over the past two decades, with the fastest declines occurring in autumn at an average rate of 0.18 × 10−2 yr−1, contributing to the prolongation of the melting period. Furthermore, significant variations in albedo change rates with altitude were found near the snowline, which is attributed to the transformation of the snow and ice surface. The primary factors affecting glacier albedo on the Tibetan Plateau are temperature and snowfall, whereas in the Himalayas, black carbon and dust primarily influence glacier albedo. Our findings reveal a clear decrease in glacier albedo on the Tibetan Plateau and demonstrate that seasonal and spatial variations in albedo and temperature are the most important driving factors. These insights provide valuable information for further investigation into surface albedo and glacier melt. [ABSTRACT FROM AUTHOR]

Wet and cold biases on the Tibetan Plateau (TP) commonly exist in global and regional climate simulations. Previous studies have explored the possible causes of wet and cold biases and contributed to reducing these biases. However, the connection between wet and cold biases remains insufficiently addressed. Our research indicates that the TP wet bias converts into positive snow amount bias not continually but efficiently and concentratedly, under the control of snow phenology in different regions. Furthermore, the complex relationship between snow amount, snow coverage and surface albedo restricts the transformation of snow amount to surface albedo bias, and thus to cold bias. Our research highlights the spatio‐temporally divergent transformation of wet to cold bias on the TP during snow season, providing a novel perspective to understand the intrinsic connection between wet and cold biases and improve climate simulations on the TP. Plain Language Summary: Due to the harsh environment, observational data are limited on the Tibetan Plateau (TP), so climate model is one of necessary tools for climate researches. However, both global and regional climate models generally overestimate precipitation (wet bias) and underestimate near surface air temperature (cold bias) on the TP. Previous studies have pointed out the possible causes of the wet and cold biases, and partly reduced these biases, leaving the connection between these biases unaddressed. Our study finds that the conversion of wet to cold bias during snow season is divergent in different areas of the TP. Under the control of snow duration in different areas, the wet bias efficiently and concentratedly transforms into larger snow amount. Furthermore, the complex relationship between snow amount, snow coverage and surface albedo restricts the transformation of snow amount to surface albedo bias, and thus to cold bias. We reveal the spatio‐temporally divergent transformation of wet to cold bias on the TP during snow season, and these conclusions will contribute to a better improvement of snow and climate modeling on the TP. Key Points: WRF simulations significantly overestimate snow amount and delay snow phenology on the Tibetan Plateau (TP)Snowfall bias is not always transformable into snow amount bias, depending on snow phenologyComplex relationship between snow amount and surface albedo restricts the transformation of wet to cold bias on the TP [ABSTRACT FROM AUTHOR]

The Jupiter InfraRed Auroral Mapper (JIRAM) instrument onboard the Juno spacecraft performed repeated observations of Jupiter's North Equatorial Belt (NEB) around the time of 12th Juno pericenter passage on 2018 April 1. The data consist of thermal infrared images and show, among other atmospheric features, two bright Hotspots on the boundary between the NEB and the Equatorial Zone. Night-time images of the same areas at different emission angles were used to constrain the trend of the limb-darkening function. Comparison with simulated observations, computed for different emission angles, total opacities, single scattering albedo ω0, and asymmetry parameter g suggests that ω0 ∼ 0.90 ± 0.05 and g ∼ 0.37 ± 0.15 provide best match with data. Subsequently, we computed the ω0 and g resulting from different size distributions, taking into account the complex refractive indices of ammonium hydrosulfide (NH4SH) by Howett et al. [2007] and Ferraro et al. [1980]. Only the former data set is marginally consistent with JIRAM observations. Similarly, ammonia and hydrazine barely reproduce the experimental data. Tholin, although not usually considered a realistic component for Jupiter's aerosols, provides a better match for particle radii between 0.7 and 1 μm, both as a pure material as well as a thick coating over NH4SH cores. Notably, this radius range is consistent with the mean radius of aerosols as estimated by Ragent et al. [1998] on the basis of Galileo entry probe data. Comparison with literature suggests that similar results can be achieved by a large variety of contaminants bearing C–N bounds. [ABSTRACT FROM AUTHOR]

This study examines how photovoltaic (PV) installation parameters—such as tilt angle, azimuth angle, row pitch, height above ground, and albedo impact PV module operating conditions in harsh climates, focusing on irradiance levels and module temperature. It evaluates how these parameters influence degradation rates and the overall lifetime of PV modules. The study correlates variations in module lifetime to lifetime energy generation, economic factors, and environmental impacts. A novel PV optimization strategy is proposed, incorporating lifetime energy yield, levelized cost of electricity, and greenhouse gas emissions, rather than focusing solely on economic metrics. Findings show that installation parameters significantly affect climate stressors and PV module lifetime, making their consideration crucial. For instance, higher tilt angles are recommended to reduce stressor levels and extend the module's lifetime, optimizing energy yield while mitigating losses due to soiling. Height and albedo are identified as particularly sensitive, especially for bifacial modules, where small changes lead to significant differences in lifetime and energy yield. The study highlights an optimal albedo of ≈0.5, aligned with desert sand, suggesting that albedo boosters may not be necessary in desert climates. This approach offers valuable insights for balancing long‐term performance, environmental impact, and economic factors in PV system design. [ABSTRACT FROM AUTHOR]

The impact of a slightly modified broadband snow surface albedo parameterization, which explicitly considers the cloud dependence of the snow albedo, is evaluated in simulations of a coupled regional climate model of the Arctic. The cloud dependence of the snow albedo leads to a more realistic simulation of the variability of the surface albedo during the snowmelt period in late May and June. In particular, the reproduction of lower albedo values under cloud-free/broken-cloud conditions during the snowmelt period represents an improvement and results in an earlier disappearance of the snow cover and an earlier onset of sea-ice melt. In this way, the consideration of the cloud dependence of the snow albedo results in an amplification of the two-stage snow/ice albedo feedback in the model. This finds expression in considerably increased sea-ice melt during the summer months and ends up in a new quasi-stationary equilibrium in sea ice with statistically significant lower sea-ice volume and statistically significant lower summer sea-ice area. [ABSTRACT FROM AUTHOR]

Objectives: To achieve the accurate monitoring of sea ice conditions in the key area of Arctic passage, high resolution sea ice thickness is essential. However, sea ice thickness with kilometer-scale resolution cannot meet the requirement at present. Methods: Considering the relationship between sea ice thickness and image albedo, this paper tried to establish a regression model between the ICESat-2 ATL10 sea ice freeboard product and the high resolution Sentinel-2 optical image albedo by taking advantage of the intensive altimetry data of ICESat-2 along the orbit to obtain dense sea ice freeboard. Based on high resolution sea ice thickness calculated from dense freeboard with the hydrostatic equilibrium model and combined with high resolution sea ice concentration derived from Sentinel-2 image, we classified ice areas into different navigational categories according to the ice-break capability of ship and compared optimal route design at multiple spatial scales. Results: Regression models established from the ATL10 sea ice freeboard and the Sentinel-2 image albedo have good fitting accuracy. The R² of the regression model is higher than 0.5, the average deviation is less than 0.05 m, and the root mean square error of the accuracy validation is less than 0.2 m. High resolution sea ice parameters derived by the proposed method can describe the distribution of fine leads between floating ice which are difficult to be captured by low resolution sea ice parameters. Conclusions: High resolution sea ice parameters can describe the details of sea ice conditions more accurately. Therefore, the proposed high resolution inversion method of sea ice parameters can improve the capability of navigation planning for ships in Arctic passage, further improving the navigation safety. [ABSTRACT FROM AUTHOR]

Surface albedo plays a pivotal role in the Earth's energy balance and climate. This study conducted an analysis of the spatial distribution patterns and temporal evolution of albedo, normalized difference vegetation index (NDVI), normalized difference snow index snow cover (NSC), and land surface temperature (LST) within the Qilian Mountains (QLMs) from 2001 to 2022. This study evaluated the spatiotemporal correlations of albedo with NSC, NDVI, and LST at various temporal scales. Additionally, the study quantified the driving forces and relative contributions of topographic and natural factors to the albedo variation of the QLMs using geographic detectors. The findings revealed the following insights: (1) Approximately 22.8% of the QLMs exhibited significant changes in albedo. The annual average albedo and NSC exhibited a minor decline with rates of −0.00037 and −0.05083 (Sen's slope), respectively. Conversely, LST displayed a marginal increase at a rate of 0.00564, while NDVI experienced a notable increase at a rate of 0.00178. (2) The seasonal fluctuations of NSC, LST, and vegetation collectively influenced the overall albedo changes in the Qilian Mountains. Notably, the highly similar trends and significant correlations between albedo and NSC, whether in intra-annual monthly variations, multi-year monthly anomalies, or regional multi-year mean trends, indicate that the changes in snow albedo reflected by NSC played a major role. Additionally, the area proportion and corresponding average elevation of PSI (permanent snow and ice regions) slightly increased, potentially suggesting a slow upward shift of the high mountain snowline in the QLMs. (3) NDVI, land cover type (LCT), and the Digital Elevation Model (DEM, which means elevation) played key roles in shaping the spatial pattern of albedo. Additionally, the spatial distribution of albedo was most significantly influenced by the interaction between slope and NDVI. [ABSTRACT FROM AUTHOR]

Climate models enable an analysis of observation data related to global warming and climate changes, and they allow making predictions for near the future progress of climate changes. In this study, basics of the climate model, which is used in the analysis of global warming and climate change topics, and the analyses that can be carried out by using these models, are reviewed. Simplified energy balance model considers the balance state between the incoming solar energy from the sun and the radiation energy outgoing from the earth to space. In this perspective, the model allows considering the factors, which can influence global warming, as radiative forces that are acting on the balance state. Thus enabling simplified analyzes of climate changes based on the energy budget even though the climate changes depend on very complex and dynamically changing meteorological and geological factors. In this study, within the framework of basic radiation laws, such as Stefan-Boltzmann and Wien Displacement, the absorption and reflection rates of the solar radiation by the earth, and the atmospheric window concepts, which provide energy escape from the earth's atmosphere to the space within the long-wavelength of the electromagnetic spectrum, were reviewed. In this context, the radiative forcing due to the Albedo effect and the radiative forcing effects due to the accumulation of CO2 molecules in the atmosphere, which have the potential to alter depending on human activities, were explained. Illustrative examples and observation data-based calculations and analyzes are presented to make basic concepts and presented models easy-to-understand. This article is intended to be a tutorial that explains some basic concepts on the topics of global warming and climate change. [ABSTRACT FROM AUTHOR]

Past studies have reported a decreasing planetary albedo and an increasing absorption of solar radiation by Earth since the early 1980s, and especially since 2000. This should have contributed to the observed surface warming. However, the magnitude of such solar contribution is presently unknown, and the question of whether or not an enhanced uptake of shortwave energy by the planet represents positive feedback to an initial warming induced by rising greenhouse-gas concentrations has not conclusively been answered. The IPCC 6th Assessment Report also did not properly assess this issue. Here, we quantify the effect of the observed albedo decrease on Earth's Global Surface Air Temperature (GSAT) since 2000 using measurements by the Clouds and the Earth's Radiant Energy System (CERES) project and a novel climate-sensitivity model derived from independent NASA planetary data by employing objective rules of calculus. Our analysis revealed that the observed decrease of planetary albedo along with reported variations of the Total Solar Irradiance (TSI) explain 100% of the global warming trend and 83% of the GSAT interannual variability as documented by six satellite- and ground-based monitoring systems over the past 24 years. Changes in Earth's cloud albedo emerged as the dominant driver of GSAT, while TSI only played a marginal role. The new climate sensitivity model also helped us analyze the physical nature of the Earth's Energy Imbalance (EEI) calculated as a difference between absorbed shortwave and outgoing longwave radiation at the top of the atmosphere. Observations and model calculations revealed that EEI results from a quasi-adiabatic attenuation of surface energy fluxes traveling through a field of decreasing air pressure with altitude. In other words, the adiabatic dissipation of thermal kinetic energy in ascending air parcels gives rise to an apparent EEI, which does not represent "heat trapping" by increasing atmospheric greenhouse gases as currently assumed. We provide numerical evidence that the observed EEI has been misinterpreted as a source of energy gain by the Earth system on multidecadal time scales. [ABSTRACT FROM AUTHOR]

As photovoltaic (PV) deployment increases worldwide, PV systems are being installed more frequently in locations that experience snow cover. The higher albedo of snow, relative to the ground, increases the performance of PV systems in northern and high-altitude locations by reflecting more light onto the PV modules. Accurate modeling of the snow's albedo can improve estimates of PV system production. Typical modeling of snow albedo uses a simple two-value model that sets the albedo high when snow is present, and low when snow is not present. However, snow albedo changes over time as snow settles and melts and a binary model does not account for transitional changes, which can be significant. Here, we present and validate a model for estimating snow albedo as it changes over time. The model is simple enough to only require daily snow depth and hourly average temperature data, but can be improved through the addition of site-specific factors, when available. We validate this model to quantify its ability to more accurately predict snow albedo and compare the model's performance against satellite imagery-based methods for obtaining historical albedo data. In addition, we perform modeling using the System Advisor Model (SAM) to show the impact of changes in albedo on energy modeling for PV systems. Overall, our albedo model has a significantly improved ability to predict the solar insolation on PV modules in real time, especially on bifacial PV modules where reflected irradiance plays a larger role in energy production. [ABSTRACT FROM AUTHOR]

As photovoltaic (PV) deployment increases worldwide, PV systems are being installed more frequently in locations that experience snow cover. The higher albedo of snow, relative to the ground, increases the performance of PV systems in northern and high-altitude locations by reflecting more light onto the PV modules. Accurate modeling of the snow’s albedo can improve estimates of PV system production. Typical modeling of snow albedo uses a simple two-value model that sets the albedo high when snow is present, and low when snow is not present. However, snow albedo changes over time as snow settles and melts and a binary model does not account for transitional changes, which can be significant. Here, we present and validate a model for estimating snow albedo as it changes over time. The model is simple enough to only require daily snow depth and hourly average temperature data, but can be improved through the addition of site-specific factors, when available. We validate this model to quantify its ability to more accurately predict snow albedo and compare the model’s performance against satellite imagery-based methods for obtaining historical albedo data. In addition, we perform modeling using the System Advisor Model (SAM) to show the impact of changes in albedo on energy modeling for PV systems. Overall, our albedo model has a significantly improved ability to predict the solar insolation on PV modules in real time, especially on bifacial PV modules where reflected irradiance plays a larger role in energy production.

Past studies have reported a decreasing planetary albedo and an increasing absorption of solar radiation by Earth since the early 1980s, and especially since 2000. This should have contributed to the observed surface warming. However, the magnitude of such solar contribution is presently unknown, and the question of whether or not an enhanced uptake of shortwave energy by the planet represents positive feedback to an initial warming induced by rising greenhouse-gas concentrations has not conclusively been answered. The IPCC 6th Assessment Report also did not properly assess this issue. Here, we quantify the effect of the observed albedo decrease on Earth’s Global Surface Air Temperature (GSAT) since 2000 using measurements by the Clouds and the Earth’s Radiant Energy System (CERES) project and a novel climate-sensitivity model derived from independent NASA planetary data by employing objective rules of calculus. Our analysis revealed that the observed decrease of planetary albedo along with reported variations of the Total Solar Irradiance (TSI) explain 100% of the global warming trend and 83% of the GSAT interannual variability as documented by six satellite- and ground-based monitoring systems over the past 24 years. Changes in Earth’s cloud albedo emerged as the dominant driver of GSAT, while TSI only played a marginal role. The new climate sensitivity model also helped us analyze the physical nature of the Earth’s Energy Imbalance (EEI) calculated as a difference between absorbed shortwave and outgoing longwave radiation at the top of the atmosphere. Observations and model calculations revealed that EEI results from a quasi-adiabatic attenuation of surface energy fluxes traveling through a field of decreasing air pressure with altitude. In other words, the adiabatic dissipation of thermal kinetic energy in ascending air parcels gives rise to an apparent EEI, which does not represent “heat trapping” by increasing atmospheric greenhouse gases as currently assumed. We provide numerical evidence that the observed EEI has been misinterpreted as a source of energy gain by the Earth system on multidecadal time scales.

Accurate and reliable measurements of the total solar radiation flux make it possible to evaluate the efficiency of using stand-alone photovaltaic systems in various meteorological conditions. These measurements allow more accurately predict in time the energy production volume, accumulator and capacitive storage devices parameters and the payback period. Research purpose was to study the possibility of creating a photoelectric sensor and a method of uninterrupted measurement based on this sensor which allows to measure total solar radiation flux including its direct, diffused and reflected components simultaneously. The photovaltaic sensor with bifacial photosensitivity was manufactured and applied, which is low-inertia comparing to traditional thermoelectric pyranometers, and its spectral sensitivity is quite close to the same parameter of photovoltaic power supply system. It creates the possibility to estimate the insolation level capable to be completely converted into electrical energy without an ineffective heat-generating long-wavelength part of the solar spectrum. A laboratory measuring stand was made to test the sensor's operability. Modeling and experiments’ the sensor parameters were carried out and confirmed its operability. The bifacial photosensitivity sensor allows to control simultaneously direct, diffused and reflected from the earth's surface components of solar radiation, what gives more complete information about the energy potential of the photovoltaic power supply system location.

Rain‐on‐snow (ROS) events occur when rain falls on snowpack and can have substantial ecological and social impacts. During ROS events, liquid water in the snowpack can decrease the surface albedo, which contributes to the positive snow‐albedo feedback and further accelerates snowmelt. In a warming climate, the frequency and spatial coverage of ROS events are projected to increase in the high‐latitude regions, especially in northern Alaska. Multi‐year ground observations at two northern Alaska sites are utilized to evaluate 59 ROS events from 2012 to 2022. Results show that ROS events lead to dramatic snow albedo changes with a mean decline of −0.04 per day, which is considerably larger than the multi‐year mean of −0.005 in May and −0.008 in June. A snow albedo model is used to simulate the daily snow albedo changes due to snowpack liquid water content. The simulated impact of liquid water content accounts for only 10% of the observed snow albedo changes. In addition, composite synoptic conditions from reanalysis products reveal different moisture sources for ROS events. ROS events in May are associated with anomalous high pressure systems over the site and meridional transport of warm and moist air from lower latitudes. While the June synoptic conditions for ROS events show little deviation from the climatological mean and suggest local moisture contributions. ROS events in June show comparable snow albedo changes as in May despite the difference in moisture sources, which implies a prolonged impact of ROS events on rapid snow deterioration during late spring. Plain Language Summary: Rain‐on‐snow (ROS) events occur when rain falls on a snow‐covered surface, and can decrease surface reflectivity, accelerate snowmelt, exacerbate flooding, and deeply affect the local ecology and society. As global temperature increases, ROS events will become more frequent and intense at high latitudes, especially in northern Alaska. This study leverages a long record of ground observations in northern Alaska from 2012 to 2022 to detect ROS events and evaluate their impacts on snow cover. Results show that ROS events can cause distinct declines in snow reflectivity. The influence of liquid water in the surface snow has been simulated by a model and compared with observations. Additionally, analyses of composite environmental conditions reveal different moisture sources for ROS events. ROS events in May rely on the remote transport of moisture from lower latitudes, while those in June are associated with local moisture sources. Our results have indicated that ROS events will play a more influential role in accelerating surface snow melting at high latitudes in a warming climate. Key Points: Rain‐on‐snow events accelerate albedo decline during May and June at the North Slope of AlaskaSimulated influence of liquid water content explains 10% of the observed snow albedo changesRain‐on‐snow events in May rely on anomalous remote moisture transport, while those in June are associated with local moisture sources [ABSTRACT FROM AUTHOR]

The width of the Inter-Tropical Convergence Zone (ITCZ) affects tropical rainfall, Earth's albedo, large-scale circulation, and climate sensitivity. To better understand the ITCZ width and its effects on global climate, we present a protocol to force changes in ITCZ width in climate models. Starting from an aquaplanet configuration with a slab ocean, adding surface heat fluxes in the deep tropics forces the ITCZ to narrow, and subtracting them causes it to widen. The protocol successfully generates changes in ITCZ width in all four climate models used in this study. ITCZ width in each model responds linearly to forcing magnitude and sign. Comparing across the four climate models, a response to varying ITCZ width that is remarkably consistent among models is the ITCZ strength, which is greater the narrower the ITCZ. On the other hand, the effect of varying ITCZ width on climate sensitivity is divergent among our four models, varying even in sign. Results from this pilot study highlight the connections between surface fluxes, ITCZ width, and the wider climate. A comprehensive model intercomparison project (MIP) has the potential to advance understanding of both the physical processes shaping ITCZ width and its influence on remote atmospheric circulations and global climate. [ABSTRACT FROM AUTHOR]

The albedo of boreal forests depends on the properties of the forest and is a key parameter for understanding the climate impact of forest management practices at high northern latitudes. While high-resolution albedo retrievals from satellites remain challenging, unmanned aerial vehicles (UAVs) offer the ability to obtain albedo corresponding to the typical size of forest stands or even smaller areas, such as forest plots. Plots and pixels of sizes in the typical range of 200–400 m2 are used as the basic units in forest management in the Nordic countries. In this study, the aim was to evaluate the effect of the differences in the footprint size of the measured albedo and fixed-area forest plots on the relationship between albedo and forest attributes. This was performed by examining the correlation between albedo and field-measured forest attributes and metrics derived from airborne laser scanner data using linear regression models. The albedo was measured by a UAV above 400 m2, circular forest plots (n = 128) for seven different flight heights above the top of the canopy. The flight heights were chosen so the plots were always smaller than the footprint of the measured albedo, and the area of a forest plot constituted 30–90% of the measured albedo. The applied pyranometer aboard the UAV measured the albedo according to a cosine response across the footprint. We found the strongest correlation when there was the greatest correspondence between the spatial size of the albedo footprint and the size of the forest plots, i.e., when the target area constituted 80–90% of the measured albedo. The measured albedo of the plots in both regeneration forests and mature forests were highly sensitive (p-values ≤ 0.001) to the footprint size, with a mean albedo difference of 11% between the smallest and largest footprints. The mean albedo of regeneration forests was 33% larger than that of mature forests for footprint sizes corresponding to 90%. The study demonstrates the importance of corresponding spatial sizes of albedo measurements and the target areas subject to measurements. [ABSTRACT FROM AUTHOR]

Ice sheet feedbacks are underrepresented in model assessments of climate sensitivity and their magnitudes are still poorly constrained. We combine a recently published record of Earth's Energy Imbalance (EEI) with existing reconstructions of temperature, atmospheric composition, and sea level to estimate both the magnitude and timescale of the ice sheet‐albedo feedback since the Last Glacial Maximum. This facilitates the first opportunity to quantify this feedback over the most recent deglaciation using a proxy data‐driven approach. We find the ice sheet‐albedo feedback to be amplifying, increasing the total climate feedback parameter by 42% and reaching an equilibrium magnitude of 0.55 Wm−2K−1, with a 66% confidence interval of 0.45–0.63 Wm−2K−1. The timescale to equilibrium is estimated as 3.6 ka (66% confidence: 1.9–5.5 ka). These results provide new evidence for the timescale and magnitude of the amplifying ice sheet‐albedo feedback that will drive anthropogenic warming for millennia to come. Plain Language Summary: During a deglacial transition, ice sheets melt and retreat, decreasing the reflectivity of the land surface and increasing the surface temperature, leading to further melting. It is agreed that this feedback amplifies global warming on millennial timescales, but the exact magnitude and timescale are still very uncertain. This is important because the stronger the feedback, the more sensitive Earth's climate is to carbon dioxide on long timescales. We use proxy data records of the past 25,000 years to quantify the ice sheet‐albedo feedback since the Last Glacial Maximum and estimate the time taken for the feedback to reach equilibrium and stabilize. We find that the ice sheet‐albedo feedback strongly amplifies warming over thousands of years, increasing our understanding of how human activity today will continue to influence our climate for generations into the future. Key Points: Novel proxy data‐driven assessment of the ice sheet‐albedo feedback for the last deglaciation is presentedIce sheet‐albedo feedback is amplifying during a deglacial transition with a best estimate of 0.55 Wm−2K−1 (0.45–0.63 Wm−2K−1)Ice sheet‐albedo feedback reaches equilibrium after approximately 3.6 ka (1.9–5.5 ka) [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]

The shortwave cloud radiative effect (SWCRE) is important for the Arctic surface radiation budget and is a major source of inter‐model spread in simulating Arctic climate. To better understand the individual contributions of various radiative processes to changes in SWCRE, we extend the existing Approximate Partial Radiative Perturbation (APRP) method by adding the absorptivity for the upward beam, considering differences in reflectivity between upward and downward beams, and analyzing the cloud masking effect resulting from changes in surface albedo. Using data from CMIP model experiments, the study decomposes the SWCRE over the Arctic surface and analyzes inter‐model differences in quadrupled CO2 simulations. The study accounts for the influence of surface albedo, cloud amount, and cloud microphysics in the response of SWCRE to Arctic warming. In the sunlit season, CMIP models exhibit a strong, negative SWCRE with a large inter‐model spread. Arctic clouds dampen the surface albedo feedback by reflecting incoming solar radiation and further decrease the shortwave radiation reflected by surface, a fraction of which is scattered back to the surface by clouds. Specifically, this accounts for the majority of the inter‐model spread in SWCRE. In addition, increased (decreased) cloud amount and cloud liquid water reduce (increase) incoming shortwave fluxes at the surface, but they are found to be not critical to the Arctic surface radiation budget and its inter‐model variation. Overall, the extended APRP method offers a useful tool for analyzing the complex interactions between clouds and radiative processes, accurately decomposes the individual SWCRE responses at the Arctic surface. Plain Language Summary: Clouds have a significant impact on how much sunlight reaches the Arctic surface. Here, we refine the method for decomposing sunlight changes into contributions from the variations in surface albedo, cloud amount, and other properties of clouds. The refined method is applied to various climate models in which carbon dioxide is abruptly quadrupled, trying to understand the inter‐model differences in the cloud‐sunlight interaction over the Arctic surface. In the sunlit season, the decrease in surface albedo due to melting sea ice is directly linked to the sunlight reduction by cloud, explaining notable inter‐model differences in total sunlight mediated by the cloud. Cloud reflection reduces incoming solar radiation, thereby mitigating the influence of surface albedo with less solar radiation reaching the surface. Also, clouds reflect less shortwave radiation from the surface due to decreased surface albedo. Changes in cloud amount and liquid water, while affecting incoming shortwave fluxes, are not found to be critical to the changes in the Arctic surface radiation budget produced by climate models. Overall, the refined method proves useful for breaking down the complex interactions between clouds and sunlight. It is a practical tool for understanding individual components of cloud‐sunlight interaction at the Arctic surface. Key Points: A SW radiative decomposition estimates how albedo, cloud fraction, and cloud reflectivity drive responses in SWCRE to increases in CO2Changes in surface albedo mostly determine the magnitude and the inter‐model spread of SWCRE changes observed in the CMIP modelsChanges in cloud fraction and reflectivity in CMIP models show minimal impact on the changes in shortwave cloud radiative effect [ABSTRACT FROM AUTHOR]

It is increasingly recognized that light-absorbing impurities (LAI) deposited on snow and ice affect their albedo and facilitate melting processes leading to various feedback loops, such as the ice albedo feedback mechanism. Black carbon (BC) is often considered the most important LAI, but some areas can be more impacted by high dust emissions. Iceland is one of the most important high latitude sources for the Arctic due to high emissions and the volcanic nature of the dust. We studied optical properties of volcanic dust from Iceland and Chile to understand how it interacts with the Sun's radiation and affects areas of deposition as LAI. Optical properties of dust samples were measured at the laboratory of the Finnish Geospatial Research Institute (FGI) using the latest setup of the FGI's goniospectrometer. We found that, depending on the particle size, the albedo of dry volcanic dust on the visible spectrum is as low as 0.03, similar to that of BC, and the albedo decreases with increasing particle size. Wet dust reduces its albedo by 66% compared to dry sample. This supports the comparability of their albedo reducing effects to BC as LAIs, and highlights their significant role in albedo reduction of snow and ice areas. The potential use of the results from our measurements is diverse, including their use as a ground truth reference for Earth Observation and remote sensing studies, estimating climate change over time, as well as measuring other ecological effects caused by changes in atmospheric composition or land cover. [ABSTRACT FROM AUTHOR]

This study investigates the performance of isotropic and anisotropic diffuse models to estimate the total solar energy received on flat-plate collectors fixed on dual-axis trackers. These estimations are applied at twelve sites selected in both hemispheres with different terrain and environmental conditions. The diffuse (or transposition) models used in this study are the isotropic Liu-Jordan (L&J), Koronakis (KOR), Badescu (BAD), and Tian (TIA), and the anisotropic Hay (HAY), Reindl (REI), Klucher (KLU), Skartveit and Olseth (S&O), and Steven and Unsworth (S&U). These models were chosen because of their simplicity in the calculations and minimum number of input values. The results show that a single transposition model is not efficient for all sites; therefore, the most appropriate models are selected for each site under all, clear, intermediate, and overcast conditions in skies. On the other hand, an increase in the ground albedo in the vicinity of the solar installation can increase the annual inclined solar availability on a two-axis tracker by at least 9% on average. Further, a linear dependence of the annual inclined solar energy on the variation of the ground albedo was found. Also, a linear relationship exists between the annual diffuse-fraction and cloud-modification factor values at the 12 sites. [ABSTRACT FROM AUTHOR]

Surface albedo measures the proportion of incoming solar radiation reflected by the Earth's surface. Accurate albedo retrieval from remote sensing data usually requires sufficient multi-angular observations to account for the surface reflectance anisotropy. However, most middle and high-resolution remote sensing satellites lack the capability to acquire sufficient multi-angular observations. Existing algorithms for retrieving surface albedo from single-direction reflectance typically rely on land cover types and vegetation indices to extract the corresponding prior knowledge of surface anisotropic reflectance from coarse-resolution Bidirectional Reflectance Distribution Function (BRDF) products. This study introduces an algorithm for retrieving albedo from directional reflectance based on a 3 × 3 BRDF archetype database established using the 2015 global time-series Moderate Resolution Imaging Spectro-radiometer (MODIS) BRDF product. For different directions, BRDF archetypes are applied to the simulated MODIS directional reflectance to retrieve albedo. By comparing the retrieved albedos with the MODIS albedo, the BRDF archetype that yields the smallest Root Mean Squared Error (RMSE) is selected as the prior BRDF for the direction. A lookup table (LUT) that contains the optimal BRDF archetypes for albedo retrieval under various observational geometries is established. The impact of the number of BRDF archetypes on the accuracy of albedo is analyzed according to the 2020 MODIS BRDF. The LUT is applied to the MODIS BRDF within specific BRDF archetype classes to validate its applicability under different anisotropic reflectance characteristics. The applicability of the LUT across different data types is further evaluated using simulated reflectance or real multi-angular measurements. The results indicate that (1) for any direction, a specific BRDF archetype can retrieve a high-accuracy albedo from directional reflectance. The optimal BRDF archetype varies with the observation direction. (2) Compared to the prior BRDF knowledge obtained through averaging method, the BRDF archetype LUT based on the 3 × 3 BRDF archetype database can more accurately retrieve the surface albedo. (3) The BRDF archetype LUT effectively eliminates the influence of surface anisotropic reflectance characteristics in albedo retrieval across different scales and types of data. [ABSTRACT FROM AUTHOR]