This article investigates the snow albedo changes in Colombian tropical glaciers, namely, Sierra Nevada de Santa Marta (SNSM), Sierra Nevada del Cocuy (NSC), Nevado del Ruiz (NDR), Nevado Santa Isabel (NDS), Nevado del Tolima (NDT), and Nevado del Huila (NDH). They are associated with the possible mineral dust deposition from the Sahara Desert during the June and July months using snow albedo (SA), snow cover (SC), and land surface temperature (LST) from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA's Terra and Aqua satellites. And mineral dust (MD) from The Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), both of them during 2000-2020. Results show the largest snow albedo reductions were observed at 39.39%, 32.1%, and 30.58% in SNC, SNSM, and NDR, respectively. Meanwhile, a multiple correlation showed that the glaciers where MD contributed the most to SA behavior were 35.4%, 24%, and 21.4% in NDS, NDC, and NDR. Results also display an increasing trend of dust deposition on Colombian tropical glaciers between 2.81 x 10-3 & mu;g & BULL;m-2 & BULL;year-1 and 6.58 x 10-3 & mu;g & BULL;m-2 & BULL;year-1. The results may help recognize the influence of Saharan dust on reducing snow albedo in tropical glaciers in Colombia. The findings from this study also have the potential to be utilized as input for both regional and global climate models. This could enhance our comprehension of how tropical glaciers are impacted by climate change.

We estimate snow albedo feedback effects of anthropogenic increases in global radiative forcing, which includes carbon dioxide, methane, nitrous oxide, CFC11, CFC12, black carbon, anthropogenic sulfur emissions, total solar irradiance, and local sulfur emissions by compiling annual observations (1972-2008) for radiative forcing, temperature, snow cover, sulfur emissions, and various teleconnections for 255 5 degrees x 5 degrees grid cells in the Northern Hemisphere. Panel DOLS estimates of the long-run relations indicate that the effect of radiative forcing on temperature increases with latitude (consistent with polar amplification), eliminating snow cover increases local temperature by about 2.8 degrees C, and a 1 degrees C temperature increase reduces snow cover by about 1%. These values create a snow albedo feedback (SAF) that amplifies the temperature increase of higher forcing by about 3.4% relative to its direct effect while an increase in sulfur emissions increases the temperature reduction by about 0.4% relative to its direct effect. The 3.4% SAF is smaller than values generated by process-based climate models and may be associated with the empirical estimates for snowmelt sensitivity Delta S-c/Delta T-s To narrow estimates for the SAF from climate models, we conclude with suggestions for a new experimental design that controls for the simultaneous relation between temperature and snow cover.

The snow physical parameters are closely related to the sizes, shapes, and chemical composition of light-absorbing particles (LAPs). By utilizing a computer-controlled scanning electron microscope software called IntelliSEM-EPAS (TM), we first report the measured size-resolved concentration of soot, dust, and fly ash particles in fresh (wet) and aged (dry deposition) snow samples collected at an industrial city in China during and after a snowfall at intervals of 6-8 days. Due to wet scavenging by seasonal snow, soot and dust particles in snow are absorbed by 69.7% and 30.3% at wavelengths of 550 nm, lowering snow albedo by 0.0089 and 0.0039, respectively. Soot particle size increases slightly during dry deposition, whereas size-resolved mineral dust does not undergo a significant shift in particle size. These results indicate the essentiality to involve the effects of accurate size and composition of in-snow LAPs for a better assessment of snow light absorption and reflectance. Plain Language Summary A field survey was undertaken to collect freshly fallen (1) and aged surface (15) snow samples at 1-day intervals in the center of Changchun city, China, which is surrounded by heavy industrial emission sources. We used an advanced computer-controlled scanning electron microscope to determine particle size and number distributions of three major light-absorbing particle types with diameters of 0.2-10 mu m in seasonal snow, namely soot, dust, and fly ash. Soot and dust particles deposited in various ice-grain sizes via wet and dry deposition were also examined in terms of their contributions to light absorption and snow albedo reduction. We report here a first attempt to detect a combination of log-normal soot, dust, and fly ash in seasonal snow, as well as their potential effects on the reduction of snow albedo.

Light-absorbing particles (LAPs) deposited on snow can significantly reduce surface albedo and contribute to positive radiative forcing. This study firstly estimated and attributed the spatio-temporal variability in the radiative forcing (RF) of LAPs in snow over the northern hemisphere during the snow-covered period 2003-2018 by employing Moderate Resolution Imaging Spectroradiometer (MODIS) data, coupled with snow and atmospheric radiative transfer modelling. In general, the RF for the northern hemisphere shows a large spatial variability over the whole snow-covered areas and periods, with the highest value (12.7 W m(-2)) in northeastern China (NEC) and the lowest (1.9 W m(-2)) in Greenland (GRL). The concentration of LAPs in snow is the dominant contributor to spatial variability in RF in spring (similar to 73%) while the joint spatial contributions of snow water equivalent (SWE) and solar irradiance (SI) are the most important (>50%) in winter. The average northern hemisphere RF gradually increases from 2.1 W m(-2) in December to 4.1 W m(-2) in May and the high-value area shifts gradually northwards from mid-altitude to high-latitude over the same period, which is primarily due to the seasonal variability of SI (similar to 58%). More interestingly, our data reveal a significant decrease in RF over high-latitude Eurasia (HEUA) of -0.04 W m(-2) a(-1) and northeastern China (NEC) of -0.14 W m(-2) a(-1) from 2003 to 2018. By employing a sensitivity test, we find the concurrent decline in the concentration of LAPs in snow accounted for the primary responsibility for the decrease in RF over these two areas, which is further confirmed by in situ observations.

Andean glaciers have melted rapidly since the 1960s. While some melting is likely due to anthropogenic climate change driven by increasing greenhouse gases, deposition of light-absorbing particles such as black carbon (BC) may also play a role. We hypothesize that BC from fires in the Amazon Basin and elsewhere may be deposited on Andean glaciers, reducing the surface albedo and inducing further melting. Here we investigate the role of BC deposition on albedo changes in the Andes for 2014-2019 by combining atmospheric chemistry modeling with observations of BC in snow or ice at four mountain sites in Peru (Quelccaya, Huascaran, Yanapaccha, and Shallap) and at one site in Bolivia (Illimani). We find that annual mean ice BC concentrations simulated by the chemical transport model GEOS-Chem for 2014-2019 are roughly consistent with those observed at the site with the longest record, Huascaran, with overestimates of 15%-40%. Smoke from fires account for 20%-70% of total wet and dry deposition fluxes, depending on the site. The rest of BC deposited comes from fossil fuel combustion. Using a snow albedo model, we find that the annual mean radiative forcing from the deposition of smoke BC alone on snow ranges from +0.1 to +3.2 W m(-2) under clear-sky conditions, with corresponding average albedo reductions of 0.04%-1.1%. These ranges are dependent on site and snow grain size. This result implies a potentially significant climate impact of biomass burning in the Amazon on radiative forcing in the Andes.

We quantified the combined effects of mineral dust nonsphericity and size on snow albedo reduction using the MOPSMAP (Modeled optical properties of ensembles of aerosol particles) package and SAMDS (Spectral Albedo Model for Dirty Snow) with the consideration of dust from Sahara, Greenland, San Juan Mountains, and Tibetan Plateau. Results indicate that the dust-induced albedo reduction decreases by up to 30% as the effective radii of dust particles increase in 1-5 mu m. Nonspherical dust enhances snow albedo reduction relative to spherical dust by up to 20%. Stronger enhancements are obtained for higher dust concentration and larger dust size. Furthermore, the dust nonsphericity-induced enhancement of snow albedo reduction is more pronounced for more-absorptive dust. Finally, we develop a new parameterization for quantifying the dependence of snow albedo reduction on dust nonsphericity and size, and provide a convenient way for assessing the climate impacts of dust in snow.

This study employs a fully coupled meteorology-chemistry-snow model to investigate the impacts of light-absorbing particles (LAPs) on snow darkening in the Sierra Nevada. After comprehensive evaluation with spatially and temporally complete satellite retrievals, the model shows that LAPs in snow reduce snow albedo by 0.013 (0-0.045) in the Sierra Nevada during the ablation season (April-July), producing a midday mean radiative forcing of 4.5 W m(-2) which increases to 15-22 W m(-2) in July. LAPs in snow accelerate snow aging processes and reduce snow cover fraction, which doubles the albedo change and radiative forcing caused by LAPs. The impurity-induced snow darkening effects decrease snow water equivalent and snow depth by 20 and 70 mm in June in the Sierra Nevada bighorn sheep habitat. The earlier snowmelt reduces root-zone soil water content by 20%, deteriorating the forage productivity and playing a negative role in the survival of bighorn sheep.

Previous studies have indicated that black carbon (BC) potentially induces snow albedo reductions across northern China. However, the effects of other light-absorbing particles (LAPs, e.g., mineral dust, MD), snow grain shape, or BC-snow mixing state on snow albedo have been largely ignored. Here we evaluate the BC- and MDinduced snow albedo reductions and radiative forcings (RFs) using an updated Snow, Ice, and Aerosol Radiation radiative transfer model, considering all of the potential factors that can be derived from the field observations across northern China. The results highlight that the LAP-induced albedo reductions for nonspherical snow grains are 2%-30% less than those for spherical grains. Furthermore, BC-snow internal mixing can significantly enhance albedo reduction by a factor of 1.42-1.48 relative to external mixing, with snow grain radius ranging from 100 to 1000 mu m. The mean regional BC + MD-induced snow albedo reductions are amplified by the increase of snow grain radius, ranging from 0.012 to 0.123 for fresh snow to 0.016-0.227 for old snow. Finally, we discuss the relative contributions of BC and MD to the albedo reductions and RFs, highlighting the dominant role of BC in reducing snow albedo across northern China.

Light-absorbing impurities (LAIs), including black carbon (BC) and mineral dust (MD), in snow cover reduce snow albedo and accelerate the snow melting rate, thus influencing the regional water resources, ecological environmental security, and climate change. There is still a lack of quantitative assessments of the impacts of BC and MD on snow melt in urban areas. This study was conducted from December 2018 to March 2019. A total of 120 snow samples were collected in Harbin, Northeast China to quantitatively assess the concentration characteristics of BC and MD in snow cover in different urban polluted areas and the impacts on snow albedo, radiative forcing, and snow melting. Average concentrations of BC and MD in snow cover in Harbin were 126,121.03 ng g(-1) and 1419.6 mu g g(-1), respectively. Average concentrations of BC and MD in the industrial area were the highest, which were 4.06 and 3.13 times higher, respectively, than those in the suburban area. BC or MD decreased the average snow albedo by 0.3677 (58.49%) and 0.0583 (18.18%) with radiative forcing of 44.94 W m(-2) and 7.58 W m(-2), respectively. BC and MD in the industrial area, residential area, and suburban area decreased the average albedo by 0.449 (59.55%), 0.3758 (45.86%), and 0.2959 (37.65%), respectively. The impacts on snow melting time in Harbin were mainly attributed to BC, which advanced snow melting by 7.9 +/- 1.16 d, while MD advanced snow melting by 3.7 +/- 0.9 d. Under the combined effect of BC and MD, the industrial area, residential area, and suburban area in the city experienced advanced snow melting by 9.66 +/- 0.38 d, 7.97 +/- 0.31 d, and 6.67 +/- 0.65 d, respectively. The results can be used to assess the contribution of intense human disturbance to snow melting. (C) 2021 Published by Elsevier B.V.

Aerosol-induced snow darkening and its feedback on seasonal snow cover, snowmelt, and runoff were investigated using the Regional Climate Model (RegCM4.6) coupled with SNow, Ice, and Aerosol Radiation (SNICAR) and aerosol modules over the Himalayas during the melting season (March-September). The snow albedo reduction due to the deposition of absorbing aerosols increases the 2 m air temperature (1.47 degrees C) and thus decreases the snow cover (10.6%) over the Himalayas during spring. This aerosol-induced excess warming accelerates the seasonal snowmelt (1.2 mm day(-1)), which reduces the number of snow-covered periods by more than 20 days throughout the Himalayas. The accumulated total snowmelt also increased by 41.3% over the Himalayas during the melting season. The early snowmelt and increase in runoff due to aerosol forcing have significant implications on rivers originating from the western Himalayas (Indus Basin). The change in snowmelt distribution and doubling of snowmelt extremes due to aerosol-induced snow darkening could also translate to an increase in flood risks across the Himalayan river basins. Therefore, the present study highlights the importance of aerosol-induced snow albedo forcing and its feedback on snowmelt and runoff over the Himalayan region, which has further implications on water availability over the South Asian region.