Displays

Possible albedo reduction due to light absorbing impurities (LAI) in snowpack observed at various sites in the world are investigated. Reviewing previously measured black carbon (BC) concentrations, their values distribute in a range of 0.07-0.25 ppbw (ng of BC in g of snow) in Antarctica, 0.55-20 ppbw in Greenland Ice Sheet (GrIS), 4.4-87.6 ppbw for the other Arctic except GrIS, and 4-1221 ppbw for mid-latitudes. As albedo reduction rate by LAI depends on snow grain size, it is more enhanced by larger grain snow such as melt form (melting snow) than smaller grain snow such as precipitation particles (new snow). By assuming two typical snow grain radii r_s = 1000 and 50 µm, respectively for those snow grain shapes, the albedo reduction as a function of BC concentration can be calculated with physically based snow albedo model. The result indicates that albedo in Antarctic snow is not affected by BC in any case of snow grain radius. In GrIS albedo reduction due to BC is small around 0.006 for r_s = 50 µm (new snow) but it rises to 0.026 for r_s = 1000 µm (melting snow), suggesting a few percent of albedo reduction could occur under warmer climate condition due to enhanced snow metamorphism. In the other Arctic except GrIS, the maximum albedo reductions for r_s = 50 µm (1000 µm) are 0.015 (0.064) at the maximum BC concentration (87.6 ppbw). For. mid-latitudes, it is 0.070 (0.24) for r_s = 50 µm (1000 µm) at the maximum BC concentration (1221 ppbw). These results mean albedo reduction in highly polluted area of mid-latitudes cannot be ignored even in case of new snow and is more serious for melting snow.

We have conducted energy budget and snow pit observations at Sapporo (43°N, 141°E, 15 m a.s.l), Japan since 2005. In addition, elemental carbon (EC~BC) and mineral dust concentrations in snowpack were also monitored for snow samples collected twice a week from 2007 by the thermal optical reflectance (TOT) method and gravimetric measurement of a filter. During 10 years from 2007 to 2017, the medians of EC and dust concentrations are 196 ppbw and 2700 ppbw, respectively. Using those data, contribution of LAI to albedo reduction and the radiative forcing (RF) were estimated. The 10-year-mean albedo reduction and RF due to BC+dust are 0.053 and +6.7 Wm^-2, respectively, in which BC effect on albedo reduction is 5.6 times larger than dust. The albedo reduction by BC+dust for only melting period is 0.151, that is 4.8 times larger than that for accumulation period. The effect of LAI on albedo reduction is enhanced by snow grain growth as well as an increase of LAI in melting period compared to that for accumulation season.

How to cite: Aoki, T., Niwano, M., Matoba, S., Tanikawa, T., Kodama, Y., and Hirozawa, Y.: Possible albedo reduction due to light absorbing impurities in snowpack observed at various sites, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8256, https://doi.org/10.5194/egusphere-egu2020-8256, 2020.

Snow contain many insoluble particles, some of which can absorb light (such as mineral dust and black carbon) and are responsible for a large climate forcing, both directly through their influence on snow albedo and indirectly by inducing snow metamorphism – albedo feedbacks.

Light absorbing particles (LAPs) influence snow metamorphism and melting by changing the heat distribution in the snowpack. Conversely, some physical processes in snow influence the size distribution of LAPs in the snowpack: for example, melting partially redistributes the particles and dry metamorphism can induce vertical movement of particles. Yet, few studies investigate those couplings due to the scarcity of detailed physical and chemical characterization of snow.

During two consecutive winters, such detailed characterization of snow was conducted at a high altitude site in the Alps (col du Lautaret, 2058m a.s.l.). The physical properties used here include detailed profiles of snow types enabling to investigate links between LAPs size distribution and snow evolution.

Size distributions analysis shows that for both black carbon (BC) and mineral dust, concentrations are often underestimated due to a significant fraction of particles being too big to be detected by the instruments. The median value of this undetected fraction is at least 20% for dust and at least 5% for BC. In more than 10% of the samples, It even exceeds 60% for dust and 25% for BC.

We then used stratigraphic data to explore the impact of partial melt and refreeze on LAP size distributions through an hypothetic coagulation mechanism induced by freeze-thaw cycles. No visible effect was found for dust, due to the higher variability of deposited particles size distributions. Conversely, freeze-thaw cycles seem to lead to a slight shift of BC size distributions toward the big particles.

How to cite: Voisin, D., Witwicky, J., Tuzet, F., Osmont, D., and Dumont, M.: Dust and Black Carbon size distributions in snow and some links to snow physics., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8723, https://doi.org/10.5194/egusphere-egu2020-8723, 2020.

Light absorbing particles such as black carbon(BC) or mineral dust are known to darken the snow surface when deposited on the snow cover and amplify several snow-albedo feedbacks, drastically modifying the snowpack evolution and the snow cover duration. Mineral dust deposition on snow is generally more variablein time than black carbon deposition and can exhibit both a high inter and intra annual variability. In France, the Alps and the Pyrenees mountain ranges are affected by large dust deposition events originating from the Sahara . The aim of this study is to quantify the impact of these impurities on the snow cover variability over the last 39 years (1979-2018).

For that purpose, the detailed snowpack model Crocus with an explicit representation of impurities is forced by SAFRAN meteorological reanalysis and a downscaling of the simulated deposition fluxes from a regional climate model (ALADIN-Climate). Different simulations are performed: (i) considering dust and/or BC (i.e. explicit representation), (ii) without impurities and (iii) considering an implicit representation (i.e. empirical parameterization based on a decreasing law of the albebo with snow age).

Simulations are compared at point scale to the snow depth measured at more than 200 Meteo-France’s stations in each massif, and spatially evaluated over the 2000-2018 period in comparing thesnow cover area, snow cover duration and the Jacard index to MODIS snow products. Scores are generally better when considering the explicit representation of the impurities than when using the snow age as a proxy for light absorbing particles content.

Results indicate that dust and BC have a significant impact on the snow cover duration with strong variations in the magnitude of the impact from one year to another and from one location to another.We also investigate the contribution of light absorbing particles depositionto snow cover inter-annual variability based on statistical approaches.

How to cite: Réveillet, M., Dumont, M., Gascoin, S., Nabat, P., Lafaysse, M., Nheili, R., Tuzet, F., Menegoz, M., and Ginoux, P.: Role of Saharan dust and black carbon deposition on snow cover in the French mountain ranges over the last 39 years., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15209, https://doi.org/10.5194/egusphere-egu2020-15209, 2020.

Mineral dust plays an important role in the climate of the Tibetan Plateau (TP) by modifying the radiation budget, cloud macro- and microphysics, precipitation, and snow albedo. Meanwhile, the TP with the highest topography in the word can affect intercontinental transport of dust plumes and induce typical distribution characteristics of dust at different altitudes. In this study, we conduct a quasi-global simulation to investigate the characteristics of dust source contribution and transport over the TP at different altitude by using a fully coupled meteorology-chemistry model (WRF-Chem) with a tracer-tagging technique. Generally, the simulation reasonably captures the spatial distribution of satellite retrieved dust aerosol optical depth (AOD) at different altitudes. Model results show that dust particles are emitted into atmosphere through updrafts over major desert regions, and then transported to the TP. The East Asian dust (mainly from Gobi and Taklamakan deserts) transports southward and is lifted up to the TP, contributing a mass loading of 50 mg/m² at 3 km height and 5 mg/m² at 12 km height over the northern slop of the TP. Dust from North Africa and Middle East are concentrated over both northern and southern slopes below 6 km, where mass loadings range from 10 to 100mg/m² and 1 to 10 mg/m² below 3 km and above 9 km, respectively. As the dust is transported to the north and over the TP, mass loadings are 5-10 mg/m² above 6 km.

The imported dust mass flux from East Asia to the TP is 7.9 Tg/year mostly occuring at the heights of 3–6 km. The North African and Middle East dust particles are transported eastward following the westerly jet, and then imported into the TP at West side with the dust mass flux of 7.8 and 26.6 Tg/year, respectively. The maximum mass flux of the North African dust mainly occurs in 0–3 km (3.9 Tg/year), while the Middle East within 6–9 km (12.3 Tg/year). The dust outflow occurs at East side (–17.89 Tg/year) and South side (–11.22 Tg/year) of the TP with a peak value (8.7 Tg/year) in 6–9 km . Moreover, the dust mass is within the size range of 1.25~5.0

How to cite: Hu, Z., Huang, J., Zhao, C., Jin, Q., Ma, Y., and Yang, P.: Modeling dust sources, transport, and radiative effects at different altitudes over the Tibetan Plateau, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12123, https://doi.org/10.5194/egusphere-egu2020-12123, 2020.

Atmospheric Black carbon (BC) strongly affects direct radiative forcing and climate, not only while suspended in the atmosphere but also after deposition onto high albedo surfaces, which are especially sensitive, because the absorption of solar radiation by deposited BC accelerate the snowpack/ice melting. In the Southern Hemisphere, the BC generated in the continents can be transported through the atmosphere from low and mid-latitudes to Antarctica, or it can be emitted in Antarctica by the anthropogenic activities developed in situ.  To assess the potential origin of the BC deposited in the snow of the Antarctic, and establish a possible relationship with the human activities that are carried out there, snow samples were taken in different sites from the Antarctic peninsula during summer periods: Chilean Base O’Higgins (BO), 2014; La Paloma Glacier 2015 and 2016 (at a distance of 6 km separated from BO); close to Chilean Base Yelcho (BY), 2018 and away from Chilean Base Yelcho 2018 (at a distance of 5 km separated from BY). Shallow snow samples were collected in Whirl-Pak (Nasco) plastics bags from the top of the snowpack, in an area of 1 m² and 5 cm thick layer, using a clean plastic shovel and disposable dust-free nitrile gloves. Sample weighed around 1500-2000 g, and they were kept always frozen (-20 °C), during transport and storage, until they could be processed in the laboratory. BC concentration in the snow samples was determined by using a novel methodology recently developed, published and patent by the authors (Cereceda et al 2019, https://doi.org/10.1016/j.scitotenv.2019.133934; US 16/690,013-Nov, 2019 ). The methodology consisted of a filter-based optical method where snow samples were microwave-assisted melted, then filtered through a special filtration system able to generate a uniform BC spot on Nuclepore 47 mm polycarbonate filters (Whatman, UK). BC deposited in filters was analyzed using a SootScan™, Model OT21 Optical Transmissometer (Magee Scientific, USA), where optical transmission was compared between the sample and a reference filter at a wavelength of 880 nm. The BC mass concentration was calculated using a 5-points calibration curve, previously prepared using real diesel BC soot as standard.  Results showed a BC concentration in snow of 1283.8 ± 1240 µg kg^-1. Snow from O’Higgins Base presented the highest BC concentration (3395.7 µg kg^-1), followed by snow from the site close to Yelcho Base (1309.2 µg kg^-1), snow from La Paloma Glacier 2016 (745.9 µg kg^-1), snow from the site away from Yelcho Base (734.5 µg kg^-1) and snow from La Paloma Glacier 2015 (233.6 µg kg^-1). BC values observed in Antarctic snow were higher than others previously reported in the literature (Cereceda et al 2019) and showed the influence that anthropic activities have in the study area, considering that the two highest values of BC concentration in snow were found at sites near the bases, which presented levels comparable to those found in snowy sites in the Andes, continental Chile (Cereceda et al 2019).

How to cite: Cereceda-Balic, F., Ruggeri, M. F., Vidal, V., and Gonzalez, H.: Black Carbon deposition on snow from Antarctic Peninsula , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11669, https://doi.org/10.5194/egusphere-egu2020-11669, 2020.

Assessing the albedo response due to light-absorbing impurities (LAI) in coastal snowpacks has become of great interest in the light of the ‘Antarctic greening’. Reductions in the albedo (triggered by a change in air temperature or by the LAI deposition) can also enhance feedback mechanisms; as the albedo drops, the fraction of absorbed solar energy increases, which leads to additional albedo drops.

Here we assess the presence of Black Carbon (BC) and LAI in coastal snowpacks in the Antarctic Peninsula. The BC-equivalent contentwas assessed by applying the meltwater filtration (MF) technique to snow samples taken at 7 locations in theAntarctic Peninsula, from latitude 62^oS to latitude 67^oS. BC-equivalentconcentrations exhibited significant geographical differences,but were found to be generally lower than 5 ng/g (in the range of those reported for the Arctic Ocean and Greenland). Moreover, the Angstrom coefficients were found to be particularly high at the northern tip of the Antarctic Peninsula,likely due to the snow algae presence. After the onset of melt, red snow algae bloom, significantly affecting the surface albedo, as shown by our measurements.

How to cite: Cordero, R., Damiani, A., Feron, S., Khan, A., Jorquera, J., Sepulveda, E., Carrera, J., and Rowe, P.: Black Carbon and Light-absorbing impurities in the Antarctic Peninsula , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21231, https://doi.org/10.5194/egusphere-egu2020-21231, 2020.

Black carbon (BC) has been pointed as the second largest contributor to climate change after greenhouse gases due to its superior ability to absorb solar radiation. This characteristic is particularly relevant in cryospheric environments, where the presence of BC has been related to a decrease in the albedo of ice/snow surfaces and the acceleration of their melting. In this sense, determination and quantification of BC levels in remote areas can be useful when defining and differentiating emission sources from which they come, considering the importance that the resources of the cryosphere mean for the surrounding populations for drinking water supply, agriculture, hydropower, mining, etc.

In this work, measurements of atmospheric BC from August 2016 to November 2019, carried out in Portillo, Chilean Central Andes, in the "Nunatak" laboratory-refuge (32°50’43’’S, 70°07’47’’W, 3000 m.a.s.l) are presented. This site, located in the highest altitude sector of the Andes mountain range, is very close to “Los Libertadores”, the border between Chile and Argentina. The road connecting both countries has a very high traffic density, with many passenger cars and trucks traveling in both directions. Due to weather, this route has a seasonal operating schedule. During the austral summer (September 1 - May 31) vehicular traffic is allowed 24 hours a day, while in winter (June 1 - August 31) traffic is allowed only from 8 am to 8 pm. Additionally, during heavy snowfalls, the access for vehicles is banned. To establish the impact of vehicular traffic on the atmospheric BC levels in the area, BC concentrations were continuously monitored by a Multi-Angle Absorption Photometer (MAAP) (Model 5012, Thermo). BC was measured in PM2.5, sampled on a glass filter tape an inlet air flow of 1.0 m³ h⁻¹. Measurements were based on the optical attenuation at a wavelength of 637 nm. Data were originally sampled in one-minute resolution, but hourly and monthly means were extracted for further analysis. Results showed a markedly seasonal profile. Summer months presented the highest levels of BC for all the studied years, when the max. values were observed during the night and early morning hours, reaching 2.1 µg m^-3. In turn, during the day there were significant declines in BC concentrations, with min. BC values of 0.2 µg m^-3. Conversely, for all the years studied, winter months had lower average BC values than the summer months, with a markedly different hourly profile, since the max. values (up to 1.7 µg m^-3) were reached in noon and afternoon hours, while the min. values fell up to 0.1 µg m^-3 during night and early morning hours. Furthermore, BC concentration levels in Portillo were measured at an altitude where the main glaciers of central Andes are, showing the impact that BC could cause in the nearby glaciers. This marked seasonal pattern is in line with the traffic operational schedule above-mentioned, suggesting that in the study area, vehicular traffic is the main emission source of atmospheric BC. These findings are key pieces to identifying and implementing successful strategies for mitigation and adaptation on climate change.

How to cite: Ruggeri, M. F., Vidal, V., and Cereceda-Balic, F.: Relationship between atmospheric BC concentration and vehicular traffic in high mountain locations, case of study: Portillo, Chilean Central Andes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11599, https://doi.org/10.5194/egusphere-egu2020-11599, 2020.

We report the first high-resolution record of arsenic (As) observed in Greenland snow and ice for the periods 1711 to 1970 and 2003 to 2009 AD. The results show well-defined large-scale atmospheric pollution by this toxic element in the Northern Hemisphere, beginning as early as the 18th century. The most striking feature is an abrupt, unprecedented enrichment factor (EF) peak in the late 1890s, with a ~30-fold increase in the mean value above the Holocene natural level. Highly enriched As was evident until the late 1910s; a sharp decline was observed after the First World War, reaching a minimum in the early 1930s during the Great Depression. A subsequent increase lasted until the mid-1950s, before decreasing again. Comparisons between the observed variations and Cu smelting data indicate that Cu smelting in Europe and North America was the likely source of early anthropogenic As in Greenland. Despite a significant reduction of ~80% in concentration and ~60% in EF from the 1950s to the 2000s, more than 80% of present-day As in Greenland is of anthropogenic origin, probably due to increasing As emissions from coal combustion in China. This highlights the demand for the implementation of national and international environmental regulations to further reduce As emissions.

How to cite: Lee, K., Han, C., Jun, S.-J., Lee, J. I., and Hong, S.: A 300-year high resolution Greenland ice record of large-scale atmospheric pollution by arsenic in the Northern Hemisphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1645, https://doi.org/10.5194/egusphere-egu2020-1645, 2020.

Currently, little is understood about the deposition and re-volatilisation of organic matter (OM) in snow. Understanding this balance for individual organic compounds has the potential to provide important information about present and past atmospheric conditions. This research investigates in detail the deposition and re-volatilisation rates for specific atmospheric OM that are present in alpine snow. Captured in the blank canvas of snow, any dissolved organic matter (DOM) in surface snow will reflect the relative abundances in the atmosphere once their deposition and revolatilisation rates are known. Likewise, DOM effectively preserved in glacial ice will also express relative atmospheric composition of past climates. A recent pilot study by D. Materić et al.[1] investigates the post-precipitation change of OM in snow near the Sonnblick Observatory in the Austrian Alps. Using proton transfer reaction mass spectrometry, surface snow samples taken over several days were analyzed, and any organics found were grouped by their similar dynamics. This research expands on this study by analyzing snow samples over a larger spatial domain around Sonnblick during the course of five days in conjunction with long-term snow sampling currently underway at the observatory. Together, analysis of these samples will reveal changes in OM in surface snow over the course of the entire melt season. This research also considers both filtered and unfiltered snow samples to differentiate and identify OM of different sizes that are present within each sample. Long-term measurements of post-precipitation OM in surface snow will provide more coherent trends for deposition and re-volatilisation rates of organics, which can be used to tie future measurements of DOM in surface snow to atmospheric OM.

How to cite: Francis, G., Materić, D., Ludewig, E., Röckmann, T., and Holzinger, R.: Deposition of Organic Compounds on Alpine Snow, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10260, https://doi.org/10.5194/egusphere-egu2020-10260, 2020.

Nitrate is naturally deposited in Antarctic snow and is detectable at low concentrations throughout our deepest ice cores. However, nitrate is photoreactive under ultraviolet light and experiences significant post-depositional loss. This nitrate loss favors 14NO3- over 15NO3-, and the resulting isotopic fractionation can be used as a proxy for duration of sunlight exposure. Here, we present nitrate isotope data (δ15N, δ18O, Δ17O) sampled from shallow snow cores and pits across East Antarctica. Our >30 sampling sites extend from coastal Adélie Land onto the high East Antarctic Plateau at Dome C and beyond, covering annual snow mass balances that range from 240 mm/yr to less than 30 mm/yr (water equivalent). The δ15N of nitrate at these sites show an inverse relationship with snow accumulation rate, with δ15N ≈ 20‰ at the coastal sites with the highest accumulations and δ15N ≈ 150-250‰ at the driest inland sites. This relationship develops because newly deposited nitrate is buried below the level of light penetration by new snow relatively quickly at high accumulation sites, but nitrate at drier sites can be exposed to sunlight for several years. After burial below the reach of sunlight, the δ15N signature of nitrate is preserved and thus offers a new proxy for snow accumulation rate in East Antarctic ice cores. In contrast, the oxygen isotopes of nitrate isotopically exchange with surrounding ice after burial, which complicates their interpretation. However, our large sample set allows an estimation of the rate of isotopic exchange at various sites, and the original isotopic values at the time of deposition may be approximated after correcting for this rate of exchange. These oxygen isotope values likely reflect in part the atmospheric oxidation history of the nitrate and its nitrogen oxide progenitor, but further study is needed to fully understand nitrate oxygen isotope dynamics.

How to cite: Akers, P., Savarino, J., and Caillon, N.: Snow accumulation rate and atmospheric oxidation pathway proxies from nitrate isotopes in East Antarctica, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9109, https://doi.org/10.5194/egusphere-egu2020-9109, 2020.

The emission of natural dust particles into the atmosphere from the high-latitude/cold regions is fast-becoming more important than previously thought. Due to land use and climate changes, a vast expanse of land surface previously covered by ice is getting exposed; hence, leading to an increase in dust emissions from these regions. Currently, an estimated 500,000 km² land surface area is contributing up to 100 Tg of dust annually¹. Aside from the direct impact of this dust on the air quality and direct solar radiation budget, it can also influence the cloud glaciation processes. Many studies have clearly established that mineral dust aerosol particles are generally good ice-nucleating particles². However, most of these ice nucleation studies have been conducted on dust from deserts and mid-latitude regions. At present, our understanding of the ice-nucleating abilities of dust from high-latitude regions is highly limited. Here, we report the first comprehensive quantification of ice-nucleating properties of dust obtained from a typical high-latitude region – Iceland. We engaged two laboratory set-ups for this investigation – the Aerosol Interactions and Dynamics in the Atmosphere (AIDA) cloud simulation chamber, and the Ice Nucleation Spectrum of Karlsruhe Institute of Technology (INSEKT). Based on the INAS density calculations which we adopted in quantifying the Icelandic dust ice-nucleating efficiencies, our current results show that dust from Iceland nucleates ice effectively in the range of ~ 10³ – 10¹² m^-2 in the temperature range studied (266 K - 238 K). A preliminary assessment shows that from ~ 250 K its ice-nucleating abilities can compete with that of desert dust and agricultural soil dust. Currently, work is ongoing to understand the role that mineral composition plays in ice nucleation behaviour. Potentially, our new results suggest that the high-latitude dust source could contribute to the INP budget of clouds in the region and may influence precipitation and the climate conditions in high-latitude regions.

How to cite: Umo, N., Schuapp, C., Waldhauserová, P. D., Weidler, P. G., Höhler, K., Arnalds, O., and Möhler, O.: Ice-nucleating properties of Icelandic dust in mixed-phase cloud conditions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14064, https://doi.org/10.5194/egusphere-egu2020-14064, 2020.

Glacier albedo is one of the most important and most variable parameters affecting surface energy balance and directly impacts ice loss. We present preliminary results from a study aiming to quantify the range and variability of spectral reflectance on a glacier terminus and assess the effects of liquid water and impurities on ablation area reflectance. In a second step of the analysis, in-situ data is compared with Landsat 8 and Sentinel 2 surface reflectance products.

In-situ spectral reflectance data was collected for wavelengths from 350-1000nm, using a hand-held ASD spectroradiometer. 246 spectra were gathered along 16 profile lines.

The “brightest” profile has a maximum reflectance of 0.7 and consists of clean, dry ice. At several “dark” profiles, reflectance does not exceed 0.2. At these profiles, liquid water is present, often mixed with fine grained debris. Individual spectra can roughly be grouped into dry ice, wet ice, and dirt/rocks. However, transitions between groups are fluid and in practice these categories cannot always be clearly separated. The spread of reflectance values per profile is generally lower for darker profiles. The reflectance spectra for clean ice exhibit the typical shape found in literature, with highest reflectance values in the lower third of our wavelength range and declining values for wavelengths greater than approximately 580nm. For wet ice surfaces, the spectra follow roughly the same shape as for dry ice, but are strongly dampened in amplitude, with reflectance typically below 0.2.

For the comparison of in-situ and satellite data, we use a Sentinel 2A scene acquired the same day as the ground measurements and a Landsat 8 scene from the previous day. Both scenes are cloud free over the study area. The wavelength range of the in-situ data overlaps with Landsat 8 bands 1-5 and Sentinel 2 bands 1-9 and 8A, respectively.

Neither satellite captures the full range of in-situ reflectance values. In all bands in which both satellites overlap, Sentinel values are shifted up against Landsat, in the sense that the maximum values of the Sentinel data are closer to the maximum values measured on the ground, while the minimum Landsat data are closer to the minimum ground values. Comparing the mean of the spectral reflectances measured on the ground with the associated satellite band values yields Pearson correlation coefficients from 0.53 to 0.62 for Landsat and 0.3 to 0.65 for Sentinel. Correlation coefficients decrease significantly for lower resolution satellite bands.

When binning ground measurements by the associated satellite pixel, the difference between the median/mean ground value and the satellite value tends to decrease with increasing number of ground measurements mapped to unique satellite pixels. While this is expected, the relationship is not obviously linear for our data and differs between the satellites and different bands.

Further in-situ measurements and analysis of satellite data will be carried out to improve understanding of processes governing ablation area reflectance, satellite derived ablation area reflectance products, and the modelling of feedback mechanisms.

How to cite: Hartl, L., Felbauer, L., Schwaizer, G., and Fischer, A.: Small scale spatial variability of spectral Albedo on Jamtalferner, Austria, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2335, https://doi.org/10.5194/egusphere-egu2020-2335, 2020.

A snow pit samples contain information of atmospheric composition and weather condition for recent years. In this study, water isotope ratio and concentrations of major ions and rare earth elements (REE) were determined from a 2 m snow pit sampled at 5 cm intervals at Hercules Neve in northern Victoria Land, Antarctica (73° 03'S, 165° 25'E, 2900m). The water stable isotope ratios range from -45.10 to -29.51 ‰ for δ18O and from 355.8 to -229.2 ‰ for δD. From their clear seasonality, the snow pit is expected to cover the period of 2012–2015. The REE patterns reveal that there exist at least two distinct sources of terrestrial aerosols; One that makes superior contribution when sea salt input is high is likely located closer than another. 

How to cite: Kim, S., Han, Y., Hur, S. D., Hwang, H., Han, C., Hong, S.-B., Jun, S. J., Chang, C., Lee, S., Jung, H., and Lee, J.: Water isotope and chemical records in a recent snow pit from Hercules Neve, northern Victoria Land, Antarctica, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3299, https://doi.org/10.5194/egusphere-egu2020-3299, 2020.

The Aerosol Optical Thickness (AOT) retrieval over the Arctic region is a challenging task due to uncertainties and difficulties in its prerequisites, mainly (i) cloud masking methods and (ii) modeling the underlying snow/ice surface. In the past this led to a large data gap over the Arctic which hampered our understanding of the direct/indirect aerosol effect on Arctic and global climate change. For the purpose of improving our knowledge, we present, for the first time, long-term AOT maps of snow and ice covered areas based on satellite remote sensing.

In this study, a previously developed aerosol retrieval algorithm over snow/ice, (Istomina et al., 2012; in IUP, University of Bremen) is used to retrieve AOT for a period of 10 years, 2002-2012, over the Arctic and to analyze its spatial and temporal changes. This algorithm is based on a multi-angle approach and uses pre-computed look-up tables to retrieve AOT.

The algorithm has been improved with respect to cloud masking (based on clear snow spectral shape) using the ASCIA cloud identification algorithm (Jafariserajehlou et al., 2019). The modified AOT retrieval algorithm is applied to observations from Advanced Along-Track Scanning Radiometer (AATSR) on European Space Agency’s (ESA) measurements. The retrieved dataset provides long-term AOT at a spatial resolution of 1 km² over snow/ice covered surface in the extended Arctic region (60^°- 90^°) during polar day. The results show that Arctic haze events appearing every late-winter and early spring are very well captured in AATSR derived AOTs. To validate the retrieved AOTs, results are compared with ground-based AERONET data. The comparisons revealed partially excellent agreement but also limits of the retrieval algorithm are discussed. In addition, some preliminary results of a trend analysis of the long-term record will be presented. It is foreseen to use the results in the trans-regional research project (AC)³ investigating Arctic amplification.

References

[1] Istomina, L.: Retrieval of aerosol optical thickness over snow and ice surfaces in the Arctic using Advanced Along Track Scanning Radiometer, PhD thesis, University of Bremen, Bremen, Germany, 2012.

[2] Jafariserajehlou, S. and Mei, L. and Vountas, M. and Rozanov, V. and Burrows, J. P. and Hollmann, R., A cloud identification algorithm over the Arctic for use with AATSR/SLSTR measurements, Atmos. Meas. Tech., 12, 1059-1076, doi:10.5194/amt-12-1059-2019, 2019.

How to cite: Jafariserajehlou, S., Vountas, M., Istomina, L., and P. Burrows, J.: Aerosol retrieval based on 10 years of passive remote sensing satellite measurements over the Arctic – validation and trend analysis, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15037, https://doi.org/10.5194/egusphere-egu2020-15037, 2020.

Light absorbing impurities (LAP) in snow, such as dust or black carbon, trigger potent snow-climate feedbacks. However, detailed measurements of the evolution of LAPs in seasonal snow are scarce, especially in the Alps. Here, we conducted detailed measurements of LAP in snow, snow physical and optical properties in the French Alps at a high altitude site. The dataset includes chemical measurements of mineral dust and black carbon (precisely elemental carbon and refractory black carbon), as well as spectral albedo measurements. The analysis of this dataset reveals strong discrepancies between elemental carbon and refractory black carbon measured concentrations, making it challenging to link the content of LAP to their radiative impacts. Using the dataset, the ensemble version of the Crocus snow model is evaluated and used to estimate the impacts of light-absorbing particles on snow cover evolution. Their impact on snowmelt turns out to be extremely sensitive to both meteorological conditions and uncertainties of the snow model, with a median shortening of 10 days for both snow seasons.

How to cite: Dumont, M., Tuzet, F., Picard, G., Lamare, M., Voisin, D., Nabat, P., Lafaysse, M., Larue, F., Revuelto, J., and Arnaud, L.: Measurements and modelling of the impacts of light absorbing impurities during two contrasted snow seasons at Col du Lautaret, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3633, https://doi.org/10.5194/egusphere-egu2020-3633, 2020.

In this paper, we have investigated the snow darkening effects by light-absorbing aerosols on the regional changes of the water cycle over the Eurasian continent using the NASA GEOS-5 Model with aerosol tracers and a state-of-the-art snow darkening module, the Goddard SnoW Impurity Module (GOSWIM) for the land surface. Two sets of ten-member ensemble experiments for 10-years were carried out forced by prescribed sea surface temperature (2002-2011) with different atmospheric initial conditions, with and without SDE, respectively. Results show that SDE can exert a significant regional influence in partitioning the contributions of evaporative and advective processes on the hydrological cycle, during spring and summer season. Over western Eurasia, SDE-induced rainfall increase during early spring can be largely explained by the increased evaporation from snowmelt. Rainfall, however, decreases in early summer due to the reduced evaporation as well as moisture divergence and atmospheric subsidence associated with the development of an anomalous mid- to upper tropospheric anticyclonic circulation. On the other hand, in the East Asian monsoon region, moisture advection from adjacent ocean is a main contributor to rainfall increase in the melting season. Warmer land-surface caused by earlier snowmelt and subsequent drying further increases moisture transport and convergence significantly enhancing rainfall over the region. This findings suggest that the SDE may play an important role in leading to hotter and drier summer over western Eurasia, through coupled land-atmosphere interaction, while enhancing East Asian summer monsoonal precipitation via enhanced land-ocean thermal contrast and moisture transport due to SDE-induced warmer Eurasian continent.

This work was supported by the Korea Meteorological Administration Research and Development Program under grant KMI2018-03410.

How to cite: Sang, J., Kim, M.-K., Lau, W. K. M., and Kim, K.-M.: Impacts of Snow Darkening by Light-absorbing aerosols on the Water Cycle over the Western Eurasia and East Asia , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6556, https://doi.org/10.5194/egusphere-egu2020-6556, 2020.

Light-absorbing organic carbon aerosol – colloquially known as brown carbon (BrC) – is emitted from combustion processes and has a brownish or yellowish visual appearance, caused by enhanced light absorption at shorter visible and ultraviolet wavelengths (0.3 µm ≤ λ ≤ 0.5 µm). Recently, optical properties of atmospheric BrC aerosols have become the topic of intense research, but little is known about how BrC deposition onto snow surfaces affects the spectral snow albedo, which can alter the resulting radiative forcing and in-snow photochemistry. Wildland fires in close proximity to the cryosphere, such as peatland fires that emit large quantities of BrC, are becoming more common at high latitudes, potentially affecting nearby snow and ice surfaces.

In this study, we describe the artificial deposition of BrC aerosol with known optical, chemical, and physical properties onto the snow surface and we monitor its spectral radiative impact and compare it directly to modeled values. First, using small-scale combustion of Alaskan peat, BrC aerosols were artificially deposited onto the snow surface. UV-vis absorbance and total organic carbon (TOC) concentration of snow samples were measured for samples with and without artificial BrC deposition. These measurements were used to estimate the imaginary part of the refractive index of deposited BrC aerosol with a volume mixing rule. Single particle optical properties were calculated using Mie theory, and these values were used to show that the measured spectral snow albedo of snow with deposited BrC was in general agreement with modeled spectral snow albedo using calculated BrC optical properties. The instantaneous radiative forcing per unit mass of BrC deposited to the ambient snowpack was found to be 1.23 (+0.14/-0.11) W m^-2 per ppm.

How to cite: Beres, N., Sengupta, D., Samburova, V., Khlystov, A., and Moosmüller, H.: Deposition of brown carbon onto snow: changes of snow optical and radiative properties, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17565, https://doi.org/10.5194/egusphere-egu2020-17565, 2020.

Absorbing aerosols such as black carbon (BC) affects the cryospheric equilibrium by altering the ablation rate of snow. The influence of the albedo change on the glacial mass balance due to excess and earlier snow melting, and thereby an earlier glacier runoff, is expected to impact the downstream hydrology. This impact is specifically of concern for the Hindu Kush Himalayan (HKH) region as the Himalayan glaciers are the source of major rivers in South Asia, namely Ganges, Indus, Yamuna, and the Brahmaputra. While the measured data may serve as location and time-specific information, the ability of coarse-gridded models to adequately simulate the snow depth and thereby the BC concentration in snow and atmospheric BC radiative forcing is limited. In order to spatially map the estimates of atmospheric BC concentration and BC concentration in snow as adequately as possible, including the corresponding snow albedo reduction (SAR) over the HKH region, an integrated approach merging the relevant information from observations with a relatively consistent atmospheric chemical transport model estimates is applied in the present study. These estimates were based on free-running aerosol simulations (freesimu) and constrained aerosol simulations (constrsimu) from an atmospheric general circulation model, combined with numerical simulations of glacial mass balance model. BC concentration estimated from freesimu performed better over higher altitude (HA) HKH stations than that over lower altitude (LA) stations. The estimates from constrsimu mirrored well the measurements when implemented for LA stations. Estimates of the spatial distribution of BC concentration in the snowpack (BC_C) over the HKH region led to identifying a hot-spot zone located around Manora peak. Among glaciers over this zone, BC_C (> 60 μg kg⁻¹) and BC-induced SAR (≈5%) were estimated explicitly being high during the pre-monsoon for Pindari, Poting, Chorabari, and Gangotri glaciers. The rate of increase of BC_C in recent years (1961-2010) was, however, estimated being the highest for the Zemmu glacier. Sensitivity analysis with glacial mass balance model indicated the increase in annual runoff (ARI) from debris-free glacier area due to BC-induced SAR corresponding to BCC estimated for the HKH glaciers was 4%-18%, with the highest being for the Milam and Pindari glaciers. The rate of increase in annual glacier runoff per unit BC-induced SAR was specifically high for Milam, Pindari, and Shunkalpa glacier. Further analysis is carried out for other significant aerosol species, both anthropogenic and natural by origin (e.g. Sulfate, Organic carbon (OC) and Dust). Comparison of relative impact of aerosol constituents on the melting of snow from the glaciers, as well as the combined effects are estimated. The estimated ARI taking into account the effect of all the aerosols found to be significantly higher than in the case of only BC. The source-specific contribution to atmospheric BC aerosols by emission sources led to identifying the potential emission source being primarily from the biofuel combustion in the Indo-Gangetic plain south to 30° N, and open burning in a more remote region north to 30° N.

How to cite: Santra, S., Verma, S., Fujita, K., Chakraborty, I., Boucher, O., Takemura, T., Burkhart, J. F., Matt, F., and Sharma, M.: Simulations of black carbon (BC) aerosol impact over Hindu-Kush Himalayan sites: validation, sources, and implications on glacier runoff, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18830, https://doi.org/10.5194/egusphere-egu2020-18830, 2020.

High Latitude Dust (HLD) contributes 5% to the global dust budget, but HLD measurements are sparse. Iceland has the largest area of volcaniclastic sandy desert on Earth where dust is originating from volcanic, but also glaciogenic sediments. Total Icelandic desert areas cover 44,000 km² which makes Iceland the largest Arctic as well as European desert. Icelandic volcanic dust can be transported distances > 1700 km towards the Arctic and deposited on snow, ice and sea ice. It is estimated that about 7% of Icelandic dust can reach the high Arctic (N>80°). It is known that about 50% of Icelandic dust storms occurred during winter or subzero temperatures in the southern part of Iceland. The vertical distributions of dust aerosol in high atmospheric profiles during these winter storms and long-range transport of dust during polar vortex condition were unknown.

Dust observations from Iceland provide dust aerosol distributions during the Arctic winter for the first time, profiling dust storms as well as clean air conditions. Five winter dust storms were captured during harsh conditions.  Mean number concentrations during the non-dust flights were < 5 particles cm^-3 for the particles 0.2-100 µm in diameter and > 40 particles cm^-3 during dust storms. A moderate dust storm with > 250 particles cm^-3 (2 km altitude) was captured on 10^th January 2016 as a result of sediments suspended from glacial outburst flood Skaftahlaup in 2015. Similar particle number concentrations were reported previously in the Saharan air layer. Detected particle sizes were up to 20 µm close to the surface, up to 10 µm at 900 m altitude, up to 5 µm at 5 km altitude, and submicron at altitudes > 6 km.

Dust sources in the Arctic are active during the winter and produce large amounts of particulate matter dispersed over long distances and high altitudes. HLD contributes to Arctic air pollution and has the potential to influence ice nucleation in mixed-phase clouds and Arctic amplification.

Reference:

Dagsson-Waldhauserova, P., Renard, J.-B., Olafsson, H., Vignelles, D., Berthet, G., Verdier, N., Duverger, V., 2019. Vertical distribution of aerosols in dust storms during the Arctic winter. Scientific Reports 6, 1-11.

How to cite: Dagsson Waldhauserova, P., Renard, J.-B., Olafsson, H., Vignelles, D., Berthet, G., Verdier, N., and Duverger, V.: Vertical distribution of aerosols in dust storms during the Arctic winter, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20488, https://doi.org/10.5194/egusphere-egu2020-20488, 2020.

Seemingly small amounts of black carbon (BC) in snow, of the order of 10–100 parts per billion by mass (ppb), have been shown to decrease its albedo by 1–5 %. Due to the albedo-feedback mechanism, surface darkening accelerates snow and ice melt and contributes to Arctic warming.

Here we present the most recent procedures we use for sampling, filtering and analysis of Arctic snow, ice and water samples, to determine their black carbon (BC), organic carbon (OC) and total carbon (TC) contents. For the purpose, we apply the OCEC analyzer of the Finnish Meteorological Institute’s aerosol laboratory, Helsinki, Finland (60°12 N). Particles are collected on a quarz-fiber filter and subjected to different temperature ramps following the protocols (NIOSH-870, EUSAAR2, or IMPROVE). Pyrolysis correction is by laser transmittance. Light transmittance through the filter is monitored during the collection phase to quantify BC. The OCEC thermal-optical method is the current European standard method for determination of atmospheric BC.  

Our Arctic samples include surface snow and snow profile samples collected north of the Arctic Circle at the Finnish Meteorological Institute Arctic Space Center in Sodankylä, Finland (67◦37 N, 26◦63 E), which is also a World Meteorological Institute’s Global Atmospheric Watch station (WMO GAW). In addition, samples from H2020 EU-Interact stations of Faroes FINI, Iceland Sudurnes and UK Cairngorms, and elsewhere from Iceland and Finland, including Helsinki Kumpula SMEAR-III station (60°12 N, 24°57 E, Station for Measuring Ecosystem-Atmosphere Relations, https://www.atm.helsinki.fi/SMEAR/index.php/smear-iii) and the most northern research catchment area of Pallas (68°N, about 130 km north from the Arctic Circle, https://blogs.egu.eu/divisions/hs/2019/06/19/featured-catchment-series-pallas/), have been sampled and analyzed. The BC concentrations have been detected to vary according to the origin of the air masses and as a result of the seasonal snow melt process.

Acknowledgements. We gratefully acknowledge support from the EU-Interact-BLACK-project Black Carbon in snow and water (H2020 Grant Agreement No. 730938); the Academy of Finland NABCEA-project of Novel Assessment of Black Carbon in the Eurasian Arctic (No. 296302), Ministry for Foreign Affairs of Finland IBA-project Black Carbon in the Arctic and significance compared to dust sources (No. PC0TQ4BT-25); the Academy of Finland Center of Excellence program The Centre of Excellence in Atmospheric Science - From Molecular and Biological processes to The Global Climate (No. 272041), and The Nordic Center of Excellence CRAICC Cryosphere–Atmosphere Interactions in a Changing Arctic Climate.

How to cite: Meinander, O., Heikkinen, E., and Aurela, M.: Sampling, filtering and analyzing procedures for thermal-optical OCEC analysis to determine black carbon, organic carbon and total carbon concentrations in Arctic snow, ice and water samples, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7541, https://doi.org/10.5194/egusphere-egu2020-7541, 2020.

Current efforts to examine and quantify so-called ‘biomarkers’ present in polar ice samples offer exciting potential as biological and biochemical proxies for past climate and ocean dynamics. Here we present a new rapid and easily replicable method to provide measurements of the microscopic particulate content of ice samples from polar environments. Using an Amnis® Imagestream® Imaging Flow Cytometer, melted snow and ice samples from Patriot Hills in the Ellsworth Mountains, Antarctica were analysed for their particulate (biological and non-biological) content. Selective use of a nucleic acid stain pre-treatment allows for a straightforward gating strategy that resolves both autofluorescent and non-autofluorescent biological material in sample replicates. In the Patriot Hills samples this method clearly identifies marine picoplankton, along with non-biological particulates such as tephra and minerogenic material. Crucially, the 60x Brightfield images provided by the Imagestream offer a significant additional capability above standard flow cytometry systems; each object identified by the machine can be visually differentiated (automatically or manually) from particulates with similar fluorescence properties. Back-trajectory analysis with the NOAA Hybrid Single-Particle Lagrangian Integrated Trajectory (HySPLIT) model indicates that these ice-bound marine organisms originate from the Weddell and Amundsen-Bellingshausen Seas. This technique, when paired with established chemical and biochemical methods, shows considerable potential in providing valuable information about the nature and origin of aerosols and biomarker signals trapped in past ice layers.

How to cite: Harris, M., Fogwill, C., Power, A., Turney, C., Love, J., Cage, A., and Law, A.: Visual and fluorescence characterisation of particulate aerosols in ice cores with imaging flow cytometry, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9607, https://doi.org/10.5194/egusphere-egu2020-9607, 2020.

Ice cores provide records of past aerosol composition and have been used to reconstruct the relative contribution of different emission sources changing in time. A precise age scale is essential to achieve this goal, for which annual layer counting of seasonal cycles in water stable isotope ratios (δ¹⁸O and δD) and major ion concentrations have been basically utilized. Introducing additional time markers are helpful for reducing the uncertainty of the depth-age scale, and the fallout of volcanic products has offered useful time markers when they are well-dated. Here, we report lead isotope ratios (²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb) and concentrations of thallium (Tl) and major ions in a shallow ice core from the Styx Glacier (73°51 S, 163°41 E) in the Victoria Land, Antarctica, analyzed for discriminating volcanic products of the 1815 AD Tambora eruption, Indonesia from local volcanic inputs. Mechanically decontaminated 19 inner core pieces between the depth interval 40.8 – 42.4 m were analyzed. The results show that the increases of volcanic SO₄^2- input are accompanied by either (1) input of more-radiogenic lead (higher ²⁰⁶Pb/²⁰⁷Pb) and Tl or (2) relatively ²⁰⁸Pb enriched lead. These results suggest that the Tambora volcanic input is overprinted by local volcanic aerosol input and that the isotope-based assessment of the Pb sources can help to discriminate between remote and local components of the volcanic input signals recorded in Victoria Land glaciers.

How to cite: Han, C., Kim, S., Han, Y., Moon, J., Hong, S.-B., Chang, C., and Hur, S. D.: A multiproxy approach to identify the Tambora volcanic fallout in 1810s from the Styx glacier in Victoria Land, Antarctica, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3262, https://doi.org/10.5194/egusphere-egu2020-3262, 2020.

Coastal and fast ice polynyas in the Arctic seas can have a noticeable effect on the Arctic climate, increasing the temperature of the cold air which coming from continental Siberia in winter to these seas and in the Arctic basin [1-2]. In this paper, were studied the effect of polynyas on surface air temperature and on the meridional heat and moisture transfers by the ERA-Interim reanalysis data. From reanalysis, meridional heat transfers were obtained through 70 ° N and 74 ° N, air temperature profiles, wind speed in the region of the Laptev (100 - 140 ° E.) and Beaufort (120 - 160 ° W.) Seas, and polynyas which located in the Laptev Sea (120 - 130 ° E) and Beaufort (160 - 140 ° W.). It was confirmed that winter transfers of cold air from the mainland do not have a cooling effect on the average winter air temperature north of 74 ° N due to the heating effect of polynyas.

How to cite: Prokhorova, U., Urazgildeeva, A., and Alexeev, G.: Effect from polynyas in the Laptev and the Beaufort seas to atmospheric transport of heat and moisture, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2997, https://doi.org/10.5194/egusphere-egu2020-2997, 2020.

Under most atmospheric conditions, the albedo and temperature of surface snow and ice are two of the main influences on the energy budget for glacier melting. Given that surface albedo and temperature are linked, knowing where and when negative albedo and positive surface temperature anomalies coincide is important for identifying locations and time periods in which anomalously high rates of surface melting are likely. We used measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on NASA's AQUA and TERRA satellites to map the albedo and surface temperature of snow and ice  on glaciers in the of Southern Rocky Mountain Trench ecoregion in the summer months (June-August) from 2000 to 2018. We use these data to identify specific regions and time periods in which low albedo and high surface temperature coincide since these conditions are likely to support anomalously high rates of surface melting. We also use these data to identify regions/periods in which albedo is particularly low while surface temperature is average or low, since such conditions suggest localized and/or short-term decoupling between the two parameters. We found anomalously low albedo and average/low temperature consistently at multiple glaciers during time periods when there were major forest fire events. We suggest the low albedo results from deposition of pyrogenic carbon from forest fires. We found that, on average, ~25% of the glaciers in the region experienced increasingly negative albedo anomalies and increasingly positive temperature anomalies in summer months from 2000 to 2018. However, we also found that for ~45% of the glaciers that are small, there was a poor correlation between the timing of albedo and temperature anomalies. Our results indicate that the correlation between albedo and temperature was weaker for the small glaciers, and identify specific glaciers that are likely the most vulnerable to climate warming.

How to cite: Naeimi, A. and Sharp, M.: Classification of glaciers during summer in Southern Rocky Mountain Trench using surface albedo and temperature anomalies, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3168, https://doi.org/10.5194/egusphere-egu2020-3168, 2020.

Using the latest daily MODIS satellite snow cover data, the present study reveals distinctly different sources of 10-30-day intraseasonal snow cover variations over the western and eastern Tibetan Plateau (TP) during September-December. The intraseasonal snow variation over the western TP is related to a mid-latitude wave train associated with the Arctic Oscillation and that over the eastern TP is related to a subtropical wave train triggered by the North Atlantic Oscillation. The Rossby wave train in both cases leads to anomalous water vapor convergence and ascending motion, which contributes to snow accumulation and positive snow cover anomalies. For the western TP snow events, the moisture comes from the Caspian Sea. During the eastern TP snow events, the moisture originates from the Bay of Bengal.

How to cite: Song, L.: Different Sources of 10-30-day Intraseasonal Variations of Autumn Snow over Western and Eastern Tibetan Plateau, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12158, https://doi.org/10.5194/egusphere-egu2020-12158, 2020.