Modulation of the snow cover changes in the French Alps and the Pyrenees by the deposition of light absorbing particles over the last 40 years 

2021 ◽  
Author(s):  
Marion Réveillet ◽  
Marie Dumont ◽  
Simon Gascoin ◽  
Matthieu Lafaysse ◽  
Pierre Nabat ◽  
...  
Keyword(s):  
Snow Cover ◽  
Regional Scale ◽  
Saharan Dust ◽  
Climate Projections ◽  
Dust Deposition ◽  
Economic Implications ◽  
French Alps ◽  
Dust Events ◽  
Long Term Impact ◽  
The Impact

<p>By darkening the snow surface, mineral dust and black carbon (BC) deposition accelerate snowmelt and triggers numerous feedbacks. Assessments of their long-term impact at the regional scale are still largely missing despite the environmental and socio-economic implications of snow cover changes. Using detailed snowpack simulations, we show that dust and BC deposition advance snowmelt by 17 days on average in the French Alps and the Pyrenees over the 1979-2018 period, with major implications for water availability and ground temperature. The effect of BC compared to dust is generally prevailing except in the Southern Pyrenees more exposed to Saharan dust events. We also quantify a contribution of BC and dust deposition up to 30% to the variance of the snow melt-out date. Lastly, we demonstrate that the decrease in BC deposition since the 80's alleviated the impact of current warming on snow cover decline. Therefore, this study highlights the importance of accounting for the inter-annual fluctuations in light absorbing particles deposition to improve the accuracy of snow cover reanalyses and climate projections.</p>

scholarly journals Black carbon and dust alter the response of mountain snow cover under climate change

2021 ◽  
Author(s):  
Marion REVEILLET ◽  
Marie Dumont ◽  
Simon Gascoin ◽  
Matthieu Lafaysse ◽  
Pierre Nabat ◽  
...  
Keyword(s):  
Snow Cover ◽  
Black Carbon ◽  
Regional Scale ◽  
Climate Projections ◽  
Economic Implications ◽  
Future Evolution ◽  
Social Ecological Systems ◽  
Long Term Impact ◽  
Surface Mineral ◽  
The Impact

Abstract By darkening the snow surface, mineral dust and black carbon (BC) deposition enhances snowmelt and triggers numerous feedbacks. Assessments of their long-term impact at the regional scale are still largely missing despite the environmental and socio-economic implications of snow cover changes. Here we show, using numerical simulations, that dust and BC deposition has advanced snowmelt by 17 days on average in the French Alps and the Pyrenees over the 1979–2018 period, with major implications for water availability. We demonstrate that the decrease in BC deposition since the 1980s moderates the impact of current warming on snow cover decline. Hence, accounting for changes in light-absorbing particles deposition is required to improve the accuracy of snow cover reanalyses and climate projections, that are crucial for better understanding the past and future evolution of mountain social-ecological systems.

scholarly journals Sensitivity of the French Alps snow cover to the variation of climatic variables

1994 ◽  
Vol 12 (5) ◽  
pp. 469-477 ◽  
Author(s):  
E. Martin ◽  
E. Brun ◽  
Y. Durand
Keyword(s):  
Snow Cover ◽  
Internal State ◽  
Regional Scale ◽  
Climatic Conditions ◽  
Meteorological Conditions ◽  
French Alps ◽  
Snow Model ◽  
Analysis System ◽  
The Impact ◽  
Data Period

Abstract. In order to study the sensitivity of snow cover to changes in meteorological variables at a regional scale, a numerical snow model and an analysis system of the meteorological conditions adapted to relief were used. This approach has been successfully tested by comparing simulated and measured snow depth at 37 sites in the French Alps during a ten year data period. Then, the sensitivity of the snow cover to a variation in climatic conditions was tested by two different methods, which led to very similar results. To assess the impact of a particular "doubled CO2" scenario, coherent perturbations were introduced in the input data of the snow model. It was found that although the impact would be very pronounced, it would also be extremely differentiated, dependent on the internal state of the snow cover. The most sensitive areas are the elevations below 2400 m, especially in the southern part of the French Alps.

Can Saharan dust deposition impact snow stability in the French Alps?

2021 ◽  
Author(s):  
Oscar Dick ◽  
Léo Viallon-Galinier ◽  
Pascal Hagenmuller ◽  
Mathieu Fructus ◽  
Matthieu Lafaysse ◽  
...  
Keyword(s):  
Mechanical Stability ◽  
Mineral Dust ◽  
Winter Season ◽  
Temporal Distribution ◽  
Saharan Dust ◽  
Dust Deposition ◽  
French Alps ◽  
Multiphysics Simulations ◽  
Snow Stratigraphy ◽  
The Impact

<div><span>Mineral dust and black carbon are potent drivers of the snow cover evolution. After their deposition on the snow surface, they can impact snow albedo and thus the snowpack evolution including the timing of snow-melt. While BC deposition is rather constant along the winter season, mineral dust deposition is more sporadic in the French Alps, subject to large dust outbreak events coming from Sahara. The dust deposition drastically changes the snow color, its absorption of solar energy and, as a consequence, modifies the internal temperature of the snow layers and their metamorphism. While mountain practitioners often report higher avalanche activities after dust deposition events, there is, up to now, no clear evidence neither from observations nor modelling that dust deposition enhances avalanche activity. Here, we investigate, using ensemble detailed snowpack simulations, the impact of dust outbreak on snow metamorphism, snow stratigraphy and mechanical stability by comparing simulations with and without dust deposition under several meteorological conditions. The results show that the dust deposition can impact the spatial and temporal distribution of the unstable slopes. The effect of the deposition largely depends on the timing of dust deposition with respect to subsequent snowfalls. It also depends on the elevation, the aspect and the time since deposition event. By using multiphysics simulations, we were able to assess the robustness of our conclusions with respect to snowpack modelling errors.</span></div>

scholarly journals Saharan dust events in the European Alps: role on snowmelt and geochemical characterization

2018 ◽  
Author(s):  
Biagio Di Mauro ◽  
Roberto Garzonio ◽  
Micol Rossini ◽  
Gianluca Filippa ◽  
Paolo Pogliotti ◽  
...  
Keyword(s):  
Digital Images ◽  
Mineral Dust ◽  
Saharan Dust ◽  
European Alps ◽  
Snow Melt ◽  
Dust Deposition ◽  
Geochemical Characterization ◽  
Melting Dynamics ◽  
Dust Events ◽  
The Impact

Abstract. The input of mineral dust from arid regions impacts snow optical properties. The induced albedo reduction generally alters the melting dynamics of the snowpack, resulting in earlier snowmelt. In this paper, we evaluate the impact of dust depositions on the melting dynamics of snowpack in a high-altitude site (2160 m) in the European Alps (Torgnon, Aosta Valley, Italy) during three hydrological years (2013–2016). These years were characterized by several Saharan dust events that deposited significant amounts of mineral dust in the European Alps. We quantify the shortening of snow season due to dust deposition, by comparing observed snow depths and those simulated with the Crocus model accounting or not for the impact of impurities. The model was ran and tested using meteorological data from an Automated Weather Station. We propose the use of repeated digital images for tracking dust deposition and resurfacing in the snowpack. The good agreement between model prediction and digital images allowed us to propose the use of an RGB index (i.e. snow darkening index, SDI) for monitoring dust on snow using images from a digital camera. We also present a geochemical characterization of dust reaching the Alpine chain during spring in 2014. Elements found in dust were classified as a function of their origin and compared with Saharan sources. A strong enrichment in Fe was observed in snow containing Saharan dust. In our case study, impurities deposited in snow anticipated the disappearance of snow up to 38 days for the 2015/2016 season that was characterized by a strong dust deposition event, out of a total 7 months of typical snow persistence. During the other seasons considered here (2013/2014, and 2014/2015), the advancement in snow melt-out day was 18 and 11 days respectively. We conclude that the effect of the Saharan dust is to anticipate the snow melt-out dates, that is known to have a series of feedback effects: earlier snowmelt can propagate into altered hydrological cycle in the Alps, higher sensitivity to late summer drought, impact on vegetation phenology and carbon uptakes from the atmosphere.

scholarly journals Saharan dust events in the European Alps: role in snowmelt and geochemical characterization

2019 ◽  
Vol 13 (4) ◽  
pp. 1147-1165 ◽  
Author(s):  
Biagio Di Mauro ◽  
Roberto Garzonio ◽  
Micol Rossini ◽  
Gianluca Filippa ◽  
Paolo Pogliotti ◽  
...  
Keyword(s):  
Digital Images ◽  
Mineral Dust ◽  
Saharan Dust ◽  
Future Research ◽  
European Alps ◽  
Dust Deposition ◽  
Geochemical Characterization ◽  
Melting Dynamics ◽  
Dust Events ◽  
The Impact

Abstract. The input of mineral dust from arid regions impacts snow optical properties. The induced albedo reduction generally alters the melting dynamics of the snowpack, resulting in earlier snowmelt. In this paper, we evaluate the impact of dust depositions on the melting dynamics of snowpack at a high-elevation site (2160 m) in the European Alps (Torgnon, Aosta Valley, Italy) during three hydrological years (2013–2016). These years were characterized by several Saharan dust events that deposited significant amounts of mineral dust in the European Alps. We quantify the shortening of the snow season due to dust deposition by comparing observed snow depths and those simulated with the Crocus model accounting, or not, for the impact of impurities. The model was run and tested using meteorological data from an automated weather station. We propose the use of repeated digital images for tracking dust deposition and resurfacing in the snowpack. The good agreement between model prediction and digital images allowed us to propose the use of an RGB index (i.e. snow darkening index – SDI) for monitoring dust on snow using images from a digital camera. We also present a geochemical characterization of dust reaching the Alpine chain during spring in 2014. Elements found in dust were classified as a function of their origin and compared with Saharan sources. A strong enrichment in Fe was observed in snow containing Saharan dust. In our case study, the comparison between modelling results and observations showed that impurities deposited in snow anticipated the disappearance of snow up to 38 d a out of a total 7 months of typical snow duration. This happened for the season 2015–2016 that was characterized by a strong dust deposition event. During the other seasons considered here (2013–2014 and 2014–2015), the snow melt-out date was 18 and 11 d earlier, respectively. We conclude that the effect of the Saharan dust is expected to reduce snow cover duration through the snow-albedo feedback. This process is known to have a series of further hydrological and phenological feedback effects that should be characterized in future research.

scholarly journals The Impact of Intense Winter Saharan Dust Events on PM and Optical Properties at Urban Sites in the Southeast of the Iberian Peninsula

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1469
Author(s):  
Alba López-Caravaca ◽  
Ramón Castañer ◽  
Alvaro Clemente ◽  
Eduardo Yubero ◽  
Nuria Galindo ◽  
...  
Keyword(s):  
Optical Properties ◽  
Iberian Peninsula ◽  
Fine Particles ◽  
Saharan Dust ◽  
Percentile Method ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Dust Events ◽  
The Impact ◽  
Ångstrom Exponent

The influence of three Saharan dust events (SDE) on particulate matter (PM) concentrations and aerosol optical properties (AOP) during February 2021 was studied. The physical characteristics of the African aerosol were different for each episode. Therefore, the impacts of the three events on PM and AOP were analyzed separately. The monitoring sites were placed in Elche, in the southeast of the Iberian Peninsula. The sites can be classified as urban background locations. The procedure used to obtain the contribution of SDE to PM10 mass concentrations was the 40th percentile method. Nearly half of the days during the study period were under the influence of Saharan air masses. The average contribution of mineral dust (MD) to the PM10 mean concentration was ~50%, which was the highest contribution during the month of February in the last 14 years. The results show that those events characterized by a high input of fine particles (PM1 and PM2.5) caused larger increases in the absorption (σap) and scattering (σsp) coefficients than SDE in which coarse particles predominated. Nevertheless, as expected, SAE (Scattering Angström Exponent) values were lowest during these episodes. AAE (Absorption Angström Exponent) values during SDE were slightly higher than those observed in the absence of African dust, suggesting some contribution from MD to the absorption process.

Role of Saharan dust and black carbon deposition on snow cover in the French mountain ranges over the last 39 years.

2020 ◽  
Author(s):  
Marion Réveillet ◽  
Marie Dumont ◽  
Simon Gascoin ◽  
Pierre Nabat ◽  
Matthieu Lafaysse ◽  
...  
Keyword(s):  
Snow Cover ◽  
Black Carbon ◽  
Carbon Deposition ◽  
Mineral Dust ◽  
Explicit Representation ◽  
Dust Deposition ◽  
Mountain Ranges ◽  
Annual Variability ◽  
Snow Cover Duration ◽  
The Impact

<p>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).</p><p>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).</p><p>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.</p><p>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.</p>

40-years of Saharan dust events in the Carpathian Basin: background, frequency, intensity, changing patterns

2020 ◽  
Author(s):  
György Varga ◽  
Nadia Gammoudi ◽  
János Kovács
Keyword(s):  
Air Temperature ◽  
Surface Air Temperature ◽  
Flow Patterns ◽  
Carpathian Basin ◽  
Saharan Dust ◽  
Dust Deposition ◽  
Temperature Anomalies ◽  
Modis Aod ◽  
Dust Events ◽  
Air Temperature Anomalies

<p>Saharan dust events were investigated in the Carpathian Basin (Central Europe) for the period between 1979 and 2018 by using various satellite (TOMS and OMI Aerosol Index; MODIS AOD) and numerical forecast (Barcelona Supercomputing Centre’s DREAM, NMMB/BSC-Dust-model and SKIRON) products and modelled deposition of NASA’s Modern-Era Retrospective analysis for Research and Applications, Version 2. The identified 218 episodes were classified into three characteristic clusters based on synoptic background. 700 hPa geopotential height, wind vectors and meridional flow patterns, as well as backward trajectories of the episodes determined the classification.</p><p>Interannual variability of dust activity was remarkable, while seasonal frequencies of the episodes revealed clear spatiotemporal patterns with spring (40.2%) and summer (31.6%) maxima of the events. Mean values of dust deposition showed springtime maxima (44.1%) and dominance of wet deposition (77-93%), while amount of deposited dust material in the other seasons were quite similar, indicating the governing role of local weather conditions (e.g., precipitation patterns). Average warm advection of the episodes was 3.5°C (with spring minima, due to the more rain), but the decadal surface air temperature anomalies showed a general increasing trend.</p><p>Recently, a few more intense wintertime dust deposition events indicated changes in the deterministic atmospheric flow system. Seasonal and decadal zonal mean surface air temperature anomalies of dusty days showed clearly the increased warming of high latitudes during the last few winter episodes. The enhanced meridionality of (dust transporting) winds was also observable in the number of days with 15< m/s meridional wind component (at 700 hPa). Warmer Arctic region and more meandering air flow patterns could be responsible for these unusual dust episodes in the recent years.</p><p>Support of the National Research, Development and Innovation Office NKFIH KH130337 and NKFIH K120213 are gratefully acknowledged.</p>

scholarly journals Variability of mineral dust deposition in the western Mediterranean basin and south-east of France

2016 ◽  
Vol 16 (14) ◽  
pp. 8749-8766 ◽  
Author(s):  
Julie Vincent ◽  
Benoit Laurent ◽  
Rémi Losno ◽  
Elisabeth Bon Nguyen ◽  
Pierre Roullet ◽  
...  
Keyword(s):  
Mediterranean Basin ◽  
Mineral Dust ◽  
Sampling Site ◽  
Regional Scale ◽  
Western Mediterranean ◽  
Saharan Dust ◽  
Deposition Flux ◽  
Dust Deposition ◽  
Western Mediterranean Basin ◽  
Provenance Areas

Abstract. Previous studies have provided some insight into the Saharan dust deposition at a few specific locations from observations over long time periods or intensive field campaigns. However, no assessment of the dust deposition temporal variability in connection with its regional spatial distribution has been achieved so far from network observations over more than 1 year. To investigate dust deposition dynamics at the regional scale, five automatic deposition collectors named CARAGA (Collecteur Automatique de Retombées Atmosphériques insolubles à Grande Autonomie in French) have been deployed in the western Mediterranean region during 1 to 3 years depending on the station. The sites include, from south to north, Lampedusa, Majorca, Corsica, Frioul and Le Casset (southern French Alps). Deposition measurements are performed on a common weekly period at the five sites. The mean dust deposition fluxes are higher close to the northern African coasts and decrease following a south–north gradient, with values from 7.4 g m−2 year−1 in Lampedusa (35°31′ N, 12°37′ E) to 1 g m−2 year−1 in Le Casset (44°59′ N, 6°28′ E). The maximum deposition flux recorded is of 3.2 g m−2 wk−1 in Majorca with only two other events showing more than 1 g m−2 wk−1 in Lampedusa, and a maximum of 0.5 g m−2 wk−1 in Corsica. The maximum value of 2.1 g m−2 year−1 observed in Corsica in 2013 is much lower than existing records in the area over the 3 previous decades (11–14 g m−2 year−1). From the 537 available samples, 98 major Saharan dust deposition events have been identified in the records between 2011 and 2013. Complementary observations provided by both satellite and air mass trajectories are used to identify the dust provenance areas and the transport pathways from the Sahara to the stations for the studied period. Despite the large size of African dust plumes detected by satellites, more than 80 % of the major dust deposition events are recorded at only one station, suggesting that the dust provenance, transport and deposition processes (i.e. wet vs. dry) of dust are different and specific for the different deposition sites in the Mediterranean studied area. The results tend to indicate that wet deposition is the main form of deposition for mineral dust in the western Mediterranean basin, but the contribution of dry deposition (in the sense that no precipitation was detected at the surface) is far from being negligible, and contributes 10 to 46 % to the major dust deposition events, depending on the sampling site.

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