References

ACP

Atmospheric Chemistry and Physics

ACP

1680-7324

Copernicus GmbH

Göttingen, Germany

10.5194/acp-12-11199-2012

Density currents as a desert dust mobilization mechanism

Solomos

¹ Kallos

¹ Mavromatidis

¹ ² Kushta

University of Athens, School of Physics, University of Athens Campus, Bldg. Phys-5, 15784 Athens, Greece

Ministry of Education/Higher Education Division, Athens, Greece

27 11 2012

12 22 11199 11211

This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

This article is available from http://www.atmos-chem-phys.net/12/11199/2012/acp-12-11199-2012.html

The full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/11199/2012/acp-12-11199-2012.pdf

The formation and propagation of density currents are well studied processes in fluid dynamics with many applications in other science fields. In the atmosphere, density currents are usually meso-β/γ phenomena and are often associated with storm downdrafts. These storms are responsible for the formation of severe dust episodes (haboobs) over desert areas. In the present study, the formation of a convective cool pool and the associated dust mobilization are examined for a representative event over the western part of Sahara desert. The physical processes involved in the mobilization of dust are described with the use of the integrated atmospheric-air quality RAMS/ICLAMS model. Dust is effectively produced due to the development of near surface vortices and increased turbulent mixing along the frontal line. Increased dust emissions and recirculation of the elevated particles inside the head of the density current result in the formation of a moving "dust wall". Transport of the dust particles in higher layers – outside of the density current – occurs mainly in three ways: (1) Uplifting of preexisting dust over the frontal line with the aid of the strong updraft (2) Entrainment at the upper part of the density current head due to turbulent mixing (3) Vertical mixing after the dilution of the system. The role of the dust in the associated convective cloud system was found to be limited. Proper representation of convective processes and dust mobilization requires the use of high resolution (cloud resolving) model configuration and online parameterization of dust production. Haboob-type dust storms are effective dust sources and should be treated accordingly in dust modeling applications.

References 1

Barahona, D. and Nenes, A.: Parameterizing the competition between homogeneous and heterogeneous freezing in ice cloud formation – polydisperse ice nuclei, Atmos. Chem. Phys., 9, 5933–5948, http://dx.doi.org/10.5194/acp-9-5933-2009doi:10.5194/acp-9-5933-2009, 2009.

Bou Karam, D., Flamant, C., Knippertz, P., Reitebuch, O., Pelon, J., Chong, M., and Dabas, A: Dust emissions over the Sahel associated with the West African Monsoon inter-tropical discontinuity region: a representative case study, Q. J. Roy. Meteor. Soc., 134, 621–634, 2008.

Cakmur, R. V., Miller, R. L., and Torres, O.: Incorporating the effect of small-scale circulations upon dust emission in an atmospheric general circulation model, J. Geophys. Res., 109, D07201, http://dx.doi.org/10.1029/2003JD004067doi:10.1029/2003JD004067, 2004.

Carbone, R. E.: A severe frontal rainband. Part I: Stormwide hydrodynamic structure, J. Atmos. Sci., 39, 258–279, 1981.

Carbone, R. E.: A Severe Frontal Rainband. Part II: Tornado Parent Vortex Circulation, J. Atmos. Sci., 40, 2639–2654, 1983.

Chen, W. and Fryrear, D.: Sedimentary characteristics of a haboob dust storm, Atmos. Res., 61, 75–85, 2002.

Chimonas, G. and Kallos, G.: Flow Dynamics and Stability in a Severe Rainband, J. Atmos. Sci., 43, 1505–1516, 1985.

Cotton W. R., Pielke Sr., R. A., Walko, R. L., Liston, G. E., Tremback, C. J., Jiang, H., McAnelly, R. L., Harrington, J. Y., Nicholls, M. E., Carrio, G. G., and McFadden, J. P.: RAMS 2001: Current status and future directions, Meteor. Atmos. Phys., 82, 5–29, 2003.

Emmel, C., Knippertz, P., and Schulz, O.: Climatology of convective density currents in the southern foothills of the Atlas Mountains, J. Geophys. Res., 115, D11115, http://dx.doi.org/10.1029/2009JD012863doi:10.1029/2009JD012863, 2010.

Fécan, F., Marticorena, B., and Bergametti, G.: Parametrization of the increase of the aeolian erosion threshold wind friction velocity due to soil moisture for arid and semi-arid areas, Ann. Geophys., 17, 149–157, http://dx.doi.org/10.1007/s00585-999-0149-7doi:10.1007/s00585-999-0149-7, 1999.

Fountoukis, C. and Nenes, A.: Continued Development of a Cloud Droplet Formation Parameterization for Global Climate Models, J. Geophys. Res., 110, D11212, http://dx.doi.org/10.1029/2004JD005591doi:10.1029/2004JD005591, 2005.

Givati, A. and Rosenfeld, D.: Quantifying precipitation suppression due to air pollution, J. Appl. Meteor., 43, 1038–1056, 2004.

Hastenrath, S.: Climate Dynamics of the Tropics, Kluwer Academic Publishers, Dordrecht, Netherlands, 488 pp., 1991.

Heinold, B., Helmert, J., Hellmuth, O., Wolke, R., Ansmann, A., Marticorena, B., Laurent, B., and Tegen, I.: Regional Modeling of Saharan Dust Events using LM-MUSCAT: Model Description and Case Studies, J. Geophys. Res., 112, D11204, http://dx.doi.org/10.1029/2006JD007443doi:10.1029/2006JD007443, 2007.

Iacono, M. J., Mlawer, E. J.,~Clough, S. A. and~Morcrette, J. J.: Impact of an improved longwave radiation model, RRTM, on the energy budget and thermodynamic properties of the NCAR Community Climate Model, CCM3, J. Geophys. Res., 105, 14873–14890, 2000.

IPCC: Changes in atmospheric constituents and radiative forcing: Climate change: the physical science basis, Cambridge University Press, New York, USA, and Cambridge, UK, 2007.

Kain, J. S. and Fritsch, J. M.: Convective parameterization for mesoscale models: The Kain-Fritsch scheme. The representation of cumulus convection in numerical models, Meteor. Monogr., No. 24, Amer. Meteor. Soc., 165–170, 1993.

Kandler, K., Schütz, L., Deutscher, C., Ebert, M., Hofmann, H., Jackel, S., Jaenicke, R., Knippertz, P., Lieke, K., Massling, A., Petzold, A., Schladitz, A., Weinzierl, B., Wiedensohler, A., Zorn, S., and Weinbruch, S.: Size distribution, mass concentration, chemical and mineralogical composition, and derived optical parameters of the boundary layer aerosol at Tinfou, Morocco, during SAMUM 2006, Tellus, 61B, 32–50, http://dx.doi.org/10.1111/j.1600-0889.2008.00385.xdoi:10.1111/j.1600-0889.2008.00385.x, 2008.

Knippertz, P., Christoph, M., and Speth, P.: Long-term precipitation variability in Morocco and the link to the large-scale circulation in recent and future climates, Meteorol. Atmos. Phys., 83, 67–88, 2003.

Knippertz, P., Deutscher, C., Kandler, K., Muller, T., Schulz, O., and Schutz L.: Dust mobilization due to density currents in the Atlas region. Observations from the Saharan Mineral Dust Experiment 2006 field campaign, J. Geophys. Res., 112, D21109, http://dx.doi.org/10.1029/2007JD008774doi:10.1029/2007JD008774, 2007.

Knippertz, P., Trentmann, J., and Seifert, A.: High-resolution simulations of convective cool pools over the northwestern Sahara, J. Geophys. Res., 114, D08110, http://dx.doi.org/10.1029/2008JD011271doi:10.1029/2008JD011271, 2009.

Lawson, T.: Haboob structure at Khartoum, Weather, 26, 105–112, 1971.

Levin, Z., Ganor, E., and Gladstein, V.: The effects of desert particles coated with sulfate on rain formation in the eastern Mediterranean, J. Appl. Meteorol., 35, 1511–1523, 1996.

Marsham, J. H., Knippertz, P., Dixon, N. S., Parker, D. J., and Lister, G. M. S.: The importance of the representation of deep convection for modeled dust-generating winds over West Africa during summer, Geophys. Res. Lett., 38, L16803, http://dx.doi.org/10.1029/2011GL048368doi:10.1029/2011GL048368, 2011.

Marticorena, B. and Bergametti, G.: Modeling the atmospheric dust cycle: 1. Design of a soil derived dust emission scheme, J. Geophys. Res., 100, 16415–16430, 1995.

Marticorena, B., Bergametti, G., Aumont, B., Callot, Y., N'Doumé, C., and Legrand, M.: Modeling the atmospheric dust cycle, 2, Simulation of Saharan dust sources, J. Geophys. Res., 102, 4387–4404, 1997.

Marticorena, B., Chatenet, B., Rajot, J. L., Traoré, S., Coulibaly, M., Diallo, A., Koné, I., Maman, A., NDiaye, T., and Zakou, A.: Temporal variability of mineral dust concentrations over West Africa: analyses of a pluriannual monitoring from the AMMA Sahelian Dust Transect, Atmos. Chem. Phys., 10, 8899–8915, http://dx.doi.org/10.5194/acp-10-8899-2010doi:10.5194/acp-10-8899-2010, 2010.

Membery, D.: A gravity-wave haboob?, Weather, 40, 214–221, 1985.

Meyers, M. P., Walko, R. L.,~Harrington, J. Y.,~and~Cotton, W. R: New RAMS cloud microphysics parameterization. Part II: The two-moment scheme, Atmos. Res., 45, 3–39, 1997.

Miller, S. D., Kuciauskas, A. P., Liu, M., Ji, Q., Reid, J. S., Breed, D. W., Walker, A. L., and Mandoos, A. A.: Haboob dust storms of the southern Arabian Peninsula, J. Geophys. Res., 113, D01202, http://dx.doi.org/10.1029/2007JD008550doi:10.1029/2007JD008550,2008

Mlawer, E. J., Taubman, S. J.,~Brown, P. D.,~Iacono, M. J., and~Clough, S. A.: Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model for the longwave, J. Geophys. Res., 102, 16663–16682, 1997.

Myhre, G., Grini, A., Haywood, J. M., Stordal, F., Chatenet, B., Tanr, D., Sundet, J. K., and Isaksen, I. S. A.: Modelling the radiative impact of mineral dust aerosol during the Saharan Dust Experiment (SHADE) campaign, J. Geophys. Res., 108, 8579, http://dx.doi.org/10.1029/2002JD002566doi:10.1029/2002JD002566, 2003.

Pielke, R. A.,~Cotton, W R.,~Walko, R L., Tremback, C J., Lyons, W A.,~Grasso, L D.,~Nicholls, M E., Moran, M D.,~Wesley, D A.,~Lee, T J., and~Copeland, J H.: A comprehensive meteorological modeling system – RAMS, Meteorol. Atmos. Phys., 49, 69–91, 1992.

Ramanathan, V., Ramana, M. V., Roberts, G., Kim, G., Corrigan, D., Chung, C., and Winker, D.: Warming trends in Asia amplified by brown cloud solar absorption, Nature, 448, 575–578, 2007.

Reinfried, F., Tegen, I., Heinold, B., Hellmuth, O., Schepanski, K., Cubasch, U., Hübener, H., and Knippertz, P.: Simulations of convectively-driven density currents in the Atlas Region using a regional model: Impacts on dust emission and sensitivity to horizontal resolution and convection schemes, J. Geophys. Res.-Atmos., 114, D08127, http://dx.doi.org/10.1029/2008JD010844doi:10.1029/2008JD010844, 2009.

Schepanski, K., Tegen, I., Todd, M. C., Heinold, B., Bönisch, G., Laurent, B., and Macke, A.: Meteorological processes forcing Saharan dust emission inferred from MSG-SEVIRI observations of subdaily dust source activation and numerical models, J. Geophys. Res., 114, D10201, http://dx.doi.org/10.1029/2008JD010325doi:10.1029/2008JD010325, 2009.

Schmetz, J. P., Pili, P., Tjemkes, S., Just, D., Kerkmann, J., Rota, S., and Ratier, A.: An Introduction to Meteosat Second Generation (MSG), B. Am. Meteorol. Soc., 83, 977–992, 2002.

Seigel, R. B. and van den Heever, S. C.: Dust Lofting and Ingestion by Supercell Storms, J. Atmos. Sci., 69, 1453–1473, http://dx.doi.org/10.1175/JAS-D-11-0222.1doi:10.1175/JAS-D-11-0222.1, 2012.

Seinfeld, J. H. and Pandis, S. N.: Atmospheric Chemistry and Physics: From Air Pollution to Climate Change, J. Wiley, New York, 1998.

Seinfeld, J. H., Carmichael, G. R., Arimoto, R., Conant, W. C., Brechtel, F. J., Bates, T. S., Cahill, T. A., Clarke, A. D., Doherty, S. J., Flatau, P. J., Huebert, B. J., Kim, J., Markowicz, K. M., Quinn, P. K., Russell, L. M., Russell, P. B., Shimizu, A., Shinozuka, Y., Song, C. H., Tang, Y., Uno, I., Vogelmann, A. M., Weber, R. J., Woo, J.-H., and Zhang, X. Y.: ACE-ASIA regional climate and Atmospheric chemical effects of Asian dust and pollution, B. Am. Meteorol. Soc., 85, 367–380, 2004.

Simpson, J. E.: Effects of the lower boundary on the head of a gravity current, J. Fluid Mech., 53, 759–768, 1972.

Solomos, S., Kallos, G., Kushta, J., Astitha, M., Tremback, C., Nenes, A., and Levin, Z.: An integrated modeling study on the effects of mineral dust and sea salt particles on clouds and precipitation, Atmos. Chem. Phys., 11, 873–892, http://dx.doi.org/10.5194/acp-11-873-2011doi:10.5194/acp-11-873-2011, 2011.

Spyrou, C., Mitsakou, C., Kallos, G., Louka, P., and Vlastou, G.: An improved limited-area model for describing the dust cycle in the atmosphere, J. Geophys. Res., 115, D17211, http://dx.doi.org/10.1029/2009JD013682doi:10.1029/2009JD013682, 2010.

Steppeler, J., Doms, G., Schattler, U., Bitzer, H. W., Gassman, A., Damrath, U., and Gregoric, G.: Meso-gamma scale forecasts using the nonhydrostatic model LM., Meteorol. Atmos. Phys., 82, 75–96, 2003.

Sutton, L.: Haboobs, Q. J. Roy. Meteor. Soc., 51, 25–30, 1925.

Takemi, T.: Explicit simulations of convective-scale transport of mineral dust in severe convective weather, J. Meteorol. Soc. Jpn., 83A, 187–203, 2005.

Tegen, I., Werner, M., Harrison, S. P., and Kohfeld, K. E.: Relative importance of climate and land use in determining present and future global soil dust emission, Geophys. Res. Lett., 31, L05105, http://dx.doi.org/10.1029/2003GL019216doi:10.1029/2003GL019216, 2004.

Von Karman, T.: The engineer grapples with nonlinear problems, B. Am. Math. Soc., 46, 615–683, 1940.

Zender, C. S., Bian, H., and Newman, D.: Mineral Dust Entrainment and Deposition (DEAD) model: Description and 1990s dust climatology, J. Geophys. Res., 108, 4416, http://dx.doi.org/10.1029/2002JD002775doi:10.1029/2002JD002775, 2003.