Increasing frequency and changing nature of Saharan dust storm events in the Carpathian Basin (2019–2023) – the new normal?
Abstract
The number and intensity of Saharan dust storm events identified in Europe has been increasing over the last decade. This can be explained by the role of ongoing climate change. An extension of previous studies covering a 40-year period is presented in this paper, with new data on the frequency, synoptic meteorological background, source areas, grain size, grain shape and general mineralogy of deposited dust for the period 2019–2023 in the Carpathian Basin. A total of 55 dust storm episodes have been identified in the region over the five-year period, which is significantly higher than the long-term average. The classification based on synoptic meteorological background clearly showed that the frequency of circulation types with a more pronounced meridional component increased and dust material reached further north more frequently than before. In several cases, large amounts of dust were deposited, from which samples were collected and subjected to detailed granulometric analysis. The varied grain size data showed that coarse silt (20–62.5 μm) and sand (62.5 < μm) fractions were also present in large quantities in the transported dust material.
References
Adebiyi, A.A. and Kok, J.F. 2020. Climate models miss most of the coarse dust in the atmosphere. Science Advances 6. https://doi.org/10.1126/sciadv.aaz9507
Adebiyi, A.A., Kok, J.F., Murray, B.J., Ryder, C.L., Stuut, J.-B.W., Kahn, R.A., Knippertz, P., Formenti, P., Mahowald, N.M., Pérez García-Pando, C., Klose, M., Ansmann, A., Samset, B.H., Ito, A., Balkanski, Y., di Biagio, C., Romanias, M.N., Huang, Y. and Meng, J. 2023. A review of coarse mineral dust in the Earth system. Aeolian Research 60. 100849. https://doi.org/10.1016/j.aeolia.2022.100849
Alpert, P., Kishcha, P., Shtivelman, A., Krichak, S.O. and Joseph, J.H. 2004. Vertical distribution of Saharan dust based on 2.5-year model predictions. Atmospheric Research 70. 109-130. https://doi.org/10.1016/j.atmosres.2003.11.001
Ansmann, A., Mamouri, R.-E., Bühl, J., Seifert, P., Engelmann, R., Hofer, J., Nisantzi, A., Atkinson, J.D., Kanji, Z.A., Sierau, B., Vrekoussis, M. and Sciare, J. 2019. Ice-nucleating particle versus ice crystal number concentrationin altocumulus and cirrus layers embedded in Saharan dust: A closure study. Atmospheric Chemistry and Physics 19. 15087-15115. https://doi.org/10.5194/acp-19-15087-2019
Arimoto, R. 2001. Eolian dust and climate: Relationships to sources, tropospheric chemistry, transport and deposition. Earth-Science Reviews 54. 29-42. https://doi.org/10.1016/S0012-8252(01)00040-X
Atalay, I. 1997. Red Mediterranean soils in some karstic regions of Taurus mountains, Turkey. Catena 28. 247-260. https://doi.org/10.1016/S0341-8162(96)00041-0
Barkan, J., Alpert, P., Kutiel, H. and Kishcha, P. 2005. Synoptics of dust transportation days from Africa toward Italy and central Europe. Journal of Geophysical Research 110. D07208. https://doi.org/10.1029/2004JD005222
Benedetti, A., Baldasano, J.M., Basart, S., Benincasa, F., Boucher, O., Brooks, M.E., Chen, J.-P., Colarco, P.R., Gong, S., Huneeus, N., Jones, L., Lu, S., Menut, L., Morcrette, J.-J., Mulcahy, J., Nickovic, S., Pérez García-Pando, C., Reid, J.S., Sekiyama, T.T., Tanaka, T.Y., Terradellas, E., Westphal, D.L., Zhang, X.-Y. and Zhou, C.-H. 2014. Operational dust prediction. In Mineral Dust: A Key Player in the Earth System. Eds.: Knippertz, P. and Stuut, J.-B.W., Dordrecht, Springer Netherlands, 223-265. https://doi.org/10.1007/978-94-017-8978-3_10
Bücher, A. and Lucas, G. 1984. Sédimentation éolienne intercontinentale, poussières sahariennes et géologie. Bulletin des Centres de Recherches Exploration 8. 151-165.
Čanić, K.Š., Vidič, S. and Klaić, Z.B. 2009. Precipitation chemistry in Croatia during the period 1981-2006. Journal of Environmental Monitoring 11. 839-851. https://doi.org/10.1039/b816432k
Coudé-Gaussen, G., Désiré, E. and Regrain, R. 1988. Particularité de poussières sahariennes distales tombées sur la Picardie et l'Ile-de-France le 7 Mai 1988. Hommes et Terres du Nord 4. 246-251. https://doi.org/10.3406/htn.1988.2190
Coudé-Gaussen, G. 1991. Les Poussières Sahariennes: Cycle Sédimentaire et Place dans les Environments et Paléoenvironments Désertiques. Montrouge, John Libby Eurotext.
Cuevas-Agulló, E., Barriopedro, D., García, R.D., Alonso-Pérez, S., González-Alemán, J.J., Werner, E., Suárez, D., Bustos, J.J., García-Castrillo, G., Garcíia, O., Barreto, Á. and Basart, S. 2023. Sharp increase of Saharan dust intrusions over the Western Mediterranean and Euro-Atlantic region in winters 2020-2022 and associated atmospheric circulation. EGUsphere 2023. 1749. 1-39. https://doi.org/10.5194/egusphere-2023-1749-supplement
Dumont, M., Gascoin, S., Réveillet, M., Voisin, D., Tuzet, F., Arnaud, L., Bonnefoy, M., Bacardit Peñarroya, M., Carmagnola, C., Deguine, A., Diacre, A., Dürr, L., Evrard, O., Fontaine, F., Frankl, A., Fructus, M., Gandois, L., Gouttevin, I., Gherab, A., Hagenmuller, P., Hansson, S., Herbin, H., Josse, B., Jourdain, B., Lefevre, I., Le Roux, G., Libois, Q., Liger, L., Morin, S., Petitprez, D., Robledano, A., Schneebeli, M., Salze, P., Six, D., Thibert, E., Trachsel, J., Vernay, M., Viallon- Galinier, L. and Voiron, C. 2023. Spatial variability of Saharan dust deposition revealed through a citizen science campaign. Earth System Science Data 15. 3075-3094. https://doi.org/10.5194/essd-15-3075-2023
Easterling, D.R., Meehl, G.A., Parmesan, C., Changnon, S.A., Karl, T.R. and Mearns, L.O. 2000. Climate extremes: Observations, modeling, and impacts. Science 289. 2068-2074. https://doi.org/10.1126/science.289.5487.2068
Francis, D., Eayrs, C., Chaboureau, J., Mote, T. and Holland, D.M. 2018. Polar jet associated circulation triggered a Saharan cyclone and derived the poleward transport of the African dust generated by the cyclone. Journal of Geophysical Research: Atmospheres 123. 11899-11917. https://doi.org/10.1029/2018JD029095
Francis, D., Fonseca, R., Nelli, N., Bozkurt, D., Cuesta, J. and Bosc, E. 2023. On the Middle East's severe dust storms in spring 2022: Triggers and impacts. Atmospheric Environment 296. 119539. https://doi.org/10.1016/j.atmosenv.2022.119539
Francis, J.A. and Vavrus, S.J. 2012. Evidence linking Arctic amplification to extreme weather in midlatitudes. Geophysical Research Letters 39. 6. 1029. https://doi.org/10.1029/2012GL051000
Garofalide, S., Postolachi, C., Cocean, A., Cocean, G., Motrescu, I., Cocean, I., Munteanu, B.S., Prelipceanu, M., Gurlui, S. and Leontie, L. 2022. Saharan dust storm aerosol characterization of the event (9 to 13 May 2020) over European AERONET sites. Atmosphere 13. (3): 493. https://doi.org/10.3390/atmos13030493
Gelaro, R., McCarty, W., Suárez, M.J., Todling, R., Molod, A., Takacs, L., Randles, C.A., Darmenov, A., Bosilovich, M.G., Reichle, R., Wargan, K., Coy, L., Cullather, R., Draper, C., Akella, S., Buchard, V., Conaty, A., da Silva, A.M., Gu, W., Kim, G.K., Koster, R., Lucchesi, R., Merkova, D., Nielsen, J.E., Partyka, G., Pawson, S., Putman, W., Rienecker, M., Schubert, S.D., Sienkiewicz, M. and Zhao, B. 2017. The modern-era retrospective analysis for research and applications, version 2 (MERRA-2). Journal of Climate 30. 5419-5454. https://doi.org/10.1175/JCLI-D-16-0758.1
Ginoux, P., Chin, M., Tegen, I., Prospero, J.M., Holben, B., Dubovik, O. and Lin, S.-J. 2001. Sources and distributions of dust aerosols simulated with the GOCART model. Journal of Geophysical Research: Atmospheres 106. 20255-20273. https://doi.org/10.1029/2000JD000053
Ginoux, P. 2017. Warming or cooling dust? Nature Geoscience 10. 246-248. https://doi.org/10.1038/ngeo2923
Goudie, A.S. and Middleton, N.J. 2001. Saharan dust storms: Nature and consequences. Earth-Science Reviews 56. 179-204. https://doi.org/10.1016/S0012-8252(01)00067-8
Harrison, S.P., Kohfeld, K.E., Roelandt, C. and Claquin, T. 2001. The role of dust in climate changes today, at the last glacial maximum and in the future. Earth-Science Reviews 54. 43-80. https://doi.org/10.1016/S0012-8252(01)00041-1
Hoose, C., Lohmann, U., Erdin, R. and Tegen, I. 2008. The global influence of dust mineralogical composition on heterogeneous ice nucleation in mixed-phase clouds. Environmental Research Letters 3. 025003. https://doi.org/10.1088/1748-9326/3/2/025003
Hrabcak, P. 2022. Saharský prach nad slovenskom v rokoch 2015-2020 (Saharan dust over Slovakia in the years 2015-2020). Meteorologický Časopis 25. 3-17.
IPCC 2022. AR5 Climate Change 2013: The Physical Science Basis. IPCC, WWW Document. Available at https://www.ipcc.ch/report/ar5/wg1/
Jackson, M.L., Clayton, R.N., Violante, A. and Violante, P. 1982. Eolian influence on terra rossa soils of Italy traced by quartz oxygen isotopic ratio. Developments in Sedmentology 28. 293-301.
Jahn, R., Zarei, M. and Stahr, K. 1991. Genetic implications of quartz in ''Terra Rossa'' soils in Portugal. In Proceedings of 7th Euroclay Conference. Eds.: Störr, M., Hennig, K.-H. and Adolphi, P., Dresden, Ernst-Moritz-Arndt-Universität, 541-546.
Kalnay, E., Kanamitsu, M., Kistler, R., Collins, W., Deaven, D., Gandin, L., Iredell, M., Saha, S., White, G., Woollen, J., Zhu, Y., Chelliah, M., Ebisuzaki, W., Higgins, W., Janowiak, J., Mo, K.C., Ropelewski, C., Wang, J., Leetmaa, A., Reynolds, R., Jenne, R. and Joseph, D. 1996. The NCEP/NCAR 40-year reanalysis project. Bulletin of the American Meteorological Society 77. 437-471. https://doi.org/10.1175/1520-0477(1996)077<0437:TNYRP>2.0.CO;2
Klose, M., Jorba, O., Gonçalves Ageitos, M., Escribano, J., Dawson, M.L., Obiso, V., di Tomaso, E., Basart, S., Montané Pinto, G., Macchia, F., Ginoux, P., Guerschman, J., Prigent, C., Huang, Y., Kok, J.F., Miller, R.L. and Pérez García-Pando, C. 2021. Mineral dust cycle in the Multiscale Online Nonhydrostatic AtmospheRe CHemistry model (MONARCH) Version 2.0. Geoscientific Model Development 14. 6403-6444. https://doi.org/10.5194/gmd-14-6403-2021
Kohfeld, K.E. and Tegen, I. 2007. 4.13 - Record of mineral aerosols and their role in the earth system. In Treatise on Geochemistry. Eds.: Holland, H.D. and Turekian, K.K.B.T. Oxford, Pergamon, 1-26. https://doi.org/10.1016/B978-008043751-4/00236-4
Kok, J.F., Ridley, D.A., Zhou, Q., Miller, R.L., Zhao, C., Heald, C.L., Ward, D.S., Albani, S. and Haustein, K. 2017. Smaller desert dust cooling effect estimated from analysis of dust size and abundance. Nature Geoscience 10. 274-278. https://doi.org/10.1038/ngeo2912
Kok, J.F., Storelvmo, T., Karydis, V.A., Adebiyi, A.A., Mahowald, N.M., Evan, A.T., He, C. and Leung, D.M., 2023. Mineral dust aerosol impacts on global climate and climate change. Nature Reviews Earth & Environment 4. 71-86. https://doi.org/10.1038/s43017-022-00379-5
MacLeod, D.A. 1980. The origin of the red Mediterranean soils in Epirus, Greece. Journal of Soil Science 31. 125-136. https://doi.org/10.1111/j.1365-2389.1980.tb02070.x
Maher, B.A., Prospero, J.M., Mackie, D., Gaiero, D., Hesse, P.P. and Balkanski, Y. 2010. Global connections between aeolian dust, climate and ocean biogeochemistry at the present day and at the last glacial maximum. Earth-Science Reviews 99. 61-97. https://doi.org/10.1016/j.earscirev.2009.12.001
Mahowald, N.M., Kohfeld, K., Hansson, M., Balkanski, Y., Harrison, S.P., Prentice, I.C., Schulz, M. and Rodhe, H. 1999. Dust sources and deposition during the last glacial maximum and current climate: A comparison of model results with paleodata from ice cores and marine sediments. Journal of Geophysical Research: Atmospheres 104. 15895-15916. https://doi.org/10.1029/1999JD900084
Mahowald, N.M., Muhs, D.R., Levis, S., Rasch, P.J., Yoshioka, M., Zender, C.S. and Luo, C. 2006. Change in atmospheric mineral aerosols in response to climate: Last glacial period, preindustrial, modern, and doubled carbon dioxide climates. Journal of Geophysical Research: Atmospheres 111. D10. https://doi.org/10.1029/2005JD006653
Mattsson, J.O. and Nihlén, T. 1996. The transport of Saharan dust to southern Europe: A scenario. Journal of Arid Environments 32. 111-119. https://doi.org/10.1006/jare.1996.0011
Meinander, O., Dagsson-Waldhauserova, P., Amosov, P., Aseyeva, E., Atkins, C., Baklanov, A., Baldo, C., Barr, S.L., Barzycka, B., Benning, L.G., Cvetkovic, B., Enchilik, P., Frolov, D., Gassó, S., Kandler, K., Kasimov, N., Kavan, J., King, J., Koroleva, T., Krupskaya, V., Kulmala, M., Kusiak, M., Lappalainen, H.K., Laska, M., Lasne, J., Lewandowski, M., Luks, B., McQuaid, J.B., Moroni, B., Murray, B., Möhler, O., Nawrot, A., Nickovic, S., O'Neill, N.T., Pejanovic, G., Popovicheva, O., Ranjbar, K., Romanias, M., Samonova, O., Sanchez-Marroquin, A., Schepanski, K., Semenkov, I., Sharapova, A., Shevnina, E., Shi, Z., Sofiev, M., Thevenet, F., Thorsteinsson, T., Timofeev, M., Umo, N.S., Uppstu, A., Urupina, D., Varga, G., Werner, T., Arnalds, O. and Vukovic Vimic, A. 2022. Newly identified climatically and environmentally significant high-latitude dust sources. Atmospheric Chemistry and Physics 22. 11889-11930. https://doi.org/10.5194/acp-22-11889-2022
Meinander, O., Kouznetsov, R., Uppstu, A., Sofiev, M., Kaakinen, A., Salminen, J., Rontu, L., Welti, A., Francis, D., Piedehierro, A.A., Heikkilä, P., Heikkinen, E. and Laaksonen, A. 2023. African dust transport and deposition modelling verified through a citizen science campaign in Finland. Scientific Reports 13. 21379. https://doi.org/10.1038/s41598-023-46321-7
Monteiro, A., Basart, S., Kazadzis, S., Votsis, A., Gkikas, A., Vandenbussche, S., Tobias, A., Gama, C., García-Pando, C.P., Terradellas, E., Notas, G., Middleton, N., Kushta, J., Amiridis, V., Lagouvardos, K., Kosmopoulos, P., Kotroni, V., Kanakidou, M., Mihalopoulos, N., Kalivitis, N., Dagsson-Waldhauserová, P., El-Askary, H., Sievers, K., Giannaros, T., Mona, L., Hirtl, M., Skomorowski, P., Virtanen, T.H., Christoudias, T., di Mauro, B., Trippetta, S., Kutuzov, S., Meinander, O. and Nickovic, S. 2022. Multi-sectoral impact assessment of an extreme African dust episode in the Eastern Mediterranean in March 2018. Science of The Total Environment 843. 156861. https://doi.org/10.1016/j.scitotenv.2022.156861
Muhs, D.R., Budahn, J., Avila, A., Skipp, G., Freeman, J. and Patterson, D.A. 2010. The role of African dust in the formation of Quaternary soils on Mallorca, Spain and implications for the genesis of Red Mediterranean soils. Quaternary Science Reviews 29. 2518-2543. https://doi.org/10.1016/j.quascirev.2010.04.013
Nickovic, S., Cvetkovic, B., Madonna, F., Rosoldi, M., Pejanovic, G., Petkovic, S. and Nikolic, J. 2016. Cloud ice caused by atmospheric mineral dust. Part 1: Parameterization of ice nuclei concentration in the NMME-DREAM model. Atmospheric Chemistry and Physics 16. 11367-11378. https://doi.org/10.5194/acp-16-11367-2016
Ozer, P., Erpicum, M., Cortemiglia, G.C. and Lucchetti, G. 1998. A dustfall event in November 1996 in Genoa, Italy. Weather 53. 140-145. https://doi.org/10.1002/j.1477-8696.1998.tb03982.x
Pérez, C., Haustein, K., Janjic, Z., Jorba, O., Huneeus, N., Baldasano, J.M., Black, T., Basart, S., Nickovic, S., Miller, R.L., Perlwitz, J.P., Schulz, M. and Thomson, M. 2011. Atmospheric dust modeling from meso to global scales with the online NMMB/BSC-Dust model. Part 1: Model description, annual simulations and evaluation. Atmospheric Chemistry and Physics 11. 13001-13027. https://doi.org/10.5194/acp-11-13001-2011
Pósfai, M. and Buseck, P.R. 2010. Nature and climate effects of individual tropospheric aerosol particles. Annual Review of Earth and Planetary Sciences 38. 17-43. https://doi.org/10.1146/annurev.earth.031208.100032
Ridgwell, A.J. 2002. Dust in the Earth system: The biogeochemical linking of land, air and sea. Philosophical Transactions of the Royal Society A 360. 2905-2924. https://doi.org/10.1098/rsta.2002.1096
Rieger, D., Steiner, A., Bachmann, V., Gasch, P., Förstner, J., Deetz, K., Vogel, B. and Vogel, H. 2017. Impact of the 4 April 2014 Saharan dust outbreak on the photovoltaic power generation in Germany. Atmospheric Chemistry and Physics 17.13391-13415. https://doi.org/10.5194/acp-17-13391-2017
Rodá, F., Bellot, J., Avila, A., Escarré, A., Piñol, J. and Terradas, J. 1993. Saharan dust and the atmospheric inputs of elements and alkalinity to mediterranean ecosystems. Water, Air, & Soil Pollution 66. 277-288. https://doi.org/10.1007/BF00479851
Rogora, M., Mosello, R. and Marchetto, A. 2004. Long-term trends in the chemistry of atmospheric deposition in Northwestern Italy: the role of increasing Saharan dust deposition. Tellus B: Chemical and Physical Meteorology 56. 426-434. https://doi.org/10.1111/j.1600-0889.2004.00114.x
Rostási, Á., Topa, B.A., Gresina, F., Weiszburg, T.G., Gelencsér, A. and Varga, G. 2022. Saharan dust deposition in Central Europe in 2016. A representative year of the increased north African dust removal over the last decade. Frontiers in Earth Science 10. 1-18. https://doi.org/10.3389/feart.2022.869902
Ryder, C.L., Marenco, F., Brooke, J.K., Estelles, V., Cotton, R., Formenti, P., McQuaid, J.B., Price, H.C., Liu, D., Ausset, P., Rosenberg, P.D., Taylor, J.W., Choularton, T., Bower, K., Coe, H., Gallagher, M., Crosier, J., Lloyd, G., Highwood, E.J. and Murray, B.J. 2018. Coarse-mode mineral dust size distributions, composition and optical properties from AER-D aircraft measurements over the tropical eastern Atlantic. Atmospheric Chemistry and Physics 18. 17225-17257. https://doi.org/10.5194/acp-18-17225-2018
Sala, J.Q., Cantos, J.O. and Chiva, E.M. 1996. Red dust rain within the Spanish Mediterranean area. Climatic Change 32. 215-228. https://doi.org/10.1007/BF00143711
Salvador, P., Pey, J., Pérez, N., Querol, X. and Artíñano, B. 2022. Increasing atmospheric dust transport towards the western Mediterranean over 1948-2020. Climate and Atmospheric Science 5. (1): 34. https://doi.org/10.1038/s41612-022-00256-4
Shepherd, T.G. 2014. Atmospheric circulation as a source of uncertainty in climate change projections. Nature Geoscience 7. 703-708. https://doi.org/10.1038/ngeo2253
Stein, A.F., Draxler, R.R., Rolph, G.D., Stunder, B.J.B., Cohen, M.D. and Ngan, F. 2015. Noaa's hysplit atmospheric transport and dispersion modeling system. Bulletin of the American Meteorological Society 96. (12): 2059-2077. https://doi.org/10.1175/BAMS-D-14-00110.1
Tegen, I. and Lacis, A.A. 1996. Modeling of particle size distribution and its influence on the radiative properties of mineral dust aerosol. Journal of Geophysical Research: Atmospheres 101. 19237-19244. https://doi.org/10.1029/95JD03610
Tomadin, L. and Lenaz, R. 1989. Eolian dust over the Mediterranean and their contribution to the present sedimentation. In Paleoclimatology and Paleometeorology: Modern and Past Patterns of Global Atmospheric Transport. Eds.: Leinen, M. and Sarnthein, M., Dordrecht, Springer Netherlands 267-282. https://doi.org/10.1007/978-94-009-0995-3_11
Van der Does, M. Knippertz, P., Zschenderlein, P., Giles Harrison, R. and Stuut, J.-B.W. 2018. The mysterious long-range transport of giant mineral dust particles. Science Advances 4. eaau2768. https://doi.org/10.1126/sciadv.aau2768
Varga, Gy., Kovács, J. and Újvári, G. 2013. Analysis of Saharan dust intrusions into the Carpathian Basin (Central Europe) over the period of 1979-2011. Global and Planetary Change 100. 333-342. https://doi.org/10.1016/j.gloplacha.2012.11.007
Varga, Gy. 2020. Changing nature of Saharan dust deposition in the Carpathian Basin (Central Europe): 40 years of identified North African dust events (1979-2018). Environment International 139. (June): 105712. https://doi.org/10.1016/j.envint.2020.105712
Varga, Gy., Dagsson-Walhauserová, P., Gresina, F. and Helgadottir, A. 2021. Saharan dust and giant quartz particle transport towards Iceland. Scientific Reports 11. 11891. https://doi.org/10.1038/s41598-021-91481-z
Varga, Gy., Meinander, O., Rostási, Á., Dagsson-Waldhauserova, P., Csávics, A. and Gresina, F. 2023. Saharan, Aral-Caspian and Middle East dust travels to Finland (1980-2022). Environment International 180. 108243. https://doi.org/10.1016/j.envint.2023.108243
Wagenbach, D. and Geis, K. 1989. The mineral dust record in a high alpine glacier (Colle Gnifett, Swiss Alps). In Paleoclimatology and Paleometeorology: Modern and Past Patterns of Global Atmospheric Transport. Eds.: Leinen, M. and Sarnthein, M., Dordrecht, Springer Netherlands, 543-564. https://doi.org/10.1007/978-94-009-0995-3_23
Weger, M., Heinold, B., Engler, C., Schumann, U., Seifert, A., Fössig, R., Voigt, C., Baars, H., Blahak, U., Borrmann, S., Hoose, C., Kaufmann, S., Krämer, M., Seifert, P., Senf, F., Schneider, J. and Tegen, I. 2018. The impact of mineral dust on cloud formation during the Saharan dust event in April 2014 over Europe. Atmospheric Chemistry and Physics 18. 17545-17572. https://doi.org/10.5194/acp-18-17545-2018
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