| 1. |
- Ström, Johan, et al.
(författare)
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Snow albedo and its sensitivity to changes in deposited light-absorbing particles estimated from ambient temperature and snow depth observations at a high-altitude site in the Himalaya
- 2022
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Ingår i: Elementa. - : University of California Press. - 2325-1026. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Snow darkening by deposited light-absorbing particles (LAP) accelerates snowmelt and shifts the snow melt-out date (MOD). Here, we present a simple approach to estimate the snow albedo variability due to LAP deposition and test this method with data for 2 seasons (February–May 2016 and December 2016–June 2017) at a high-altitude valley site in the Central Himalayas, India. We derive a parameterization for the snow albedo that only depends on the daily observations of average ambient temperature and change in snow depth, as well as an assumed average concentration of LAP in snow precipitation. Linear regression between observed and parameterized albedo for the base case assuming an equivalent elemental carbon concentration [ECeq] of 100 ng g–1 in snow precipitation yields a slope of 0.75 and a Pearson correlation coefficient r2 of 0.76. However, comparing the integrated amount of shortwave radiation absorbed during the winter season using observed albedo versus base case albedo resulted in rather small differences of 11% and 4% at the end of Seasons 1 and 2, respectively. The enhanced energy absorbed due to LAP at the end of the 2 seasons for the base case scenario (assuming an [ECeq] of 100 ng g–1 in snow precipitation) was 40% and 36% compared to pristine snow. A numerical evaluation with different assumed [ECeq] in snow precipitation suggests that the relative sensitivity of snow albedo to changes in [ECeq] remains rather constant for the 2 seasons. Doubling [ECeq] augments the absorption by less than 20%, highlighting that the impact on a MOD is small even for a doubling of average LAP in snow precipitation.
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| 2. |
- Ström, Johan, 1963-, et al.
(författare)
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Snow cover duration in northern Finland and the influence of key variables through a conceptual framework based on observed variations in snow depth
- 2023
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Ingår i: Science of the Total Environment. - 0048-9697 .- 1879-1026. ; 903
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Tidskriftsartikel (refereegranskat)abstract
- Seasonal snow cover duration is the net result from many processes acting on snow fallen on the Earth's surface. Several of these processes feed back into the atmosphere-cryosphere system causing non-linear interactions. The timing of snow retreat is of essential importance, but the duration of snow cover has large spatiotemporal variabilities. However, from a large data set of observed snow depth changes in northern Finland, systematic similar evolutions are identified that allow for a considerable simplification and reduction of the complexity in snow depth changes. Here, a novel conceptual framework is designed based on dividing the season into two main periods (dark and bright period, based on solar irradiance), for which snow depth decrease is parameterized based on three variables, average temperature, incoming shortwave radiation, and light-absorbing particles (LAP) in the snow. The processes are simplified into two linear relations, and a new formulation for concentration enhancement of LAP, which is dependent on snow depth decrease, is given. The results show that the seasonal snow cover duration is shifted by about one day for every 10 mm snow water equivalent of precipitation. This effect is comparable in scale to that of doubling of the amount of LAP concentration in snow. We also found that the combined shift in snow cover duration from interannual variability in ambient temperature and shortwave radiation (warm and bright vs. cold and dark season) is large enough to explain the variability of a couple of weeks for a given precipitation amount in Northern Finland.
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| 3. |
- Svensson, Jonas, et al.
(författare)
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Soot-doped natural snow and its albedo - Results from field experiments
- 2016
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Ingår i: Boreal Environment Research. - 1239-6095. ; 21, s. 481-503
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Tidskriftsartikel (refereegranskat)abstract
- Soot has a pronounced effect on the cryosphere and experiments are still needed to reduce the associated uncertainties. This work presents a series of experiments to address this issue, with soot being deposited onto a natural snow surface after which the albedo changes were monitored. The albedo reduction was the most pronounced for the snow with higher soot content, and it was observed immediately following soot deposition. Compared with a previous laboratory study the effects of soot on the snow were not as prominent in outdoor conditions. During snowmelt, about 50% of the originally deposited soot particles were observed to remain at the snow surface. More detailed experiments are however needed to better explain soot’s effect on snow and to better quantify this effect. Our albedo versus soot parameterization agreed relatively well with previously published relationships.
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| 4. |
- Svensson, Jonas, et al.
(författare)
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Soot-on-snow experiment : artificial deposition of light-absorbing particles onto snow surfaces in 2018
- 2024
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Ingår i: Frontiers in Earth Science. - 2296-6463. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- The absorption of shortwave irradiance in snow depends on the physical properties of snow (e.g., snow grain size and shape, liquid water content, etc.) and light-absorbing particles (LAP). Originating from natural and anthropogenic sources, LAP has been reported to accelerate snowmelt significantly in different regions globally. Yet, our process-level understanding of LAP after deposition onto snow remains rather limited. Here we investigate the impacts of artificial deposition of different LAP onto snow surfaces in an outdoor environment of northern Finland. Following LAP dry deposition into a custom-made tent standing on top of the snowpack, the albedo was followed along with the properties of snow in snow pit measurements throughout the spring season. The results showed that the albedo decay at the end of the season for the different spots were linked to the initial amount and type of LAP that were deposited onto the snowpack. Measured snow temperature profiles from LAP doped snow versus natural reference snow illustrated that the LAP affected snow had higher temperatures in the subsurface snow layers. Collected snow samples analyzed for size distribution of soot particles revealed no apparent agglomeration of soot particles during thaw-freezing events taking place during the experiment. Despite the relatively large perturbation of the experimentally deposited LAP, their impact on the season length was only up to 3 days. Additional experiments are, nevertheless, needed to better constrain the effects of LAP on snow albedo, melt rate, and other associated processes.
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| 5. |
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| 6. |
- Zdanowicz, Christian, 1966-, et al.
(författare)
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Strategies and Best Practices for Monitoring Seasonal Snow Cover Composition
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Seasonal snow covers up to 45 million km^2 every winter. As such, it represents a major interface between the Earth's surface and atmosphere. It also offers a convenient sampling medium to monitor water isotopes in solid precipitation and the net deposition of a wide variety of atmospheric species, including nutrients, organic compounds (OCs), trace metals, dust, black carbon (BC), and many others. Impurities such as dust and BC are light-absorbing and as such can modify the radiative properties of snow, while other atmospheric species such as OCs or certain metals can adversely affect the aquatic environment and drinking water quality in meltwater-fed basins. Systematic monitoring of seasonal snowpack composition may therefore offer a way of supplementing direct observations of air and precipitation chemistry. It may also lend itself well to certain "citizen science" activities, provided a set of standardized protocols can be adopted, and an adequate platform for data collection and sharing be established. In recent years, some recommendations to this effect were made by the snow science community through the IASC Cryosphere Working Group, the WMO Global Cryosphere Watch and EU Harmosnow initiative. The purpose of this presentation is to stimulate a continued discussion of the merits, challenges and caveats of establishing a network of coordinated snowpack composition observations. Examples of existing or recently-developed monitoring protocols for snowpacks in Arctic and montane regions will be presented and discussed.
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