Numerical simulations of windblown dust over complex terrain: The Fiambalá Basin episode in June 2015

FOLCH,A.; OSORES, M.S.; ANDRIOLI,M.; COLLINI,E.A.; BUSTOS, E.; ALEXANDER, P.; COLLINI,E.A.; BUSTOS, E.; ALEXANDER, P.; MINGARI,L.; BAEZ,W.; RECKZIEGEL,F.; VIRAMONET,J.G.; MINGARI,L.; BAEZ,W.; RECKZIEGEL,F.; VIRAMONET,J.G.; FOLCH,A.; OSORES, M.S.; ANDRIOLI,M.

Puerto Varas

Congreso; Cities on Volcanoes 9; 2016

On 13th June 2015, the London Volcanic Ash Advisory Centre(VAAC) warned to Buenos Aires VAAC, within the frame of inter-VAACcollaboration, about a volcanic eruption from the ?Nevados Ojos del Salado?volcano (6,879 m), located on the Chilean-Argentinian border. A volcanic ashcloud was detected by the SEVIRI instrument on board the Meteosat SecondGeneration (MSG) satellites from 14:00 UTC on June 13th. Further studiesconcluded that the phenomenon was caused by remobilization of ancientpyroclastic deposits (4.5 Ka Cerro Blanco fallout) from the Bolsón de Fiambalá(Fiambalá Basin) in northwestern Argentina.Short-range numerical simulations of windblown dust from the FiambaláBasin were performed using the WRF-ARW / FALL3D modeling system downscalingmeteorological fields down to 2-km resolution in order to resolve the complexorography of the area. Results indicate that favorable conditions for dustuplift occurred at the north of the Fiambalá Basin, where orographic effectscaused strong surface winds. Dust particles were in general confined tonear-ground layers around the emission areas, thereby contributing to highnear-surface concentration values. However, in the central and southern regionsof the Fiambalá Basin, dust aerosols were injected up to 5-6 km high due toascending airflows driven by horizontal convergence. Long-range transportnumerical simulations were also performed to model dust cloud spreading overnorthern Argentina. Results of simulated vertical particle column mass werecompared with the MSG-SEVIRI retrieval product. We tested two numericalschemes. With the default configuration of the FALL3D model, difficulties tosimulate transport through orographic barriers were observed. An alternativeconfiguration, using a numerical scheme to more accurately compute thehorizontal advection in abrupt terrains, substantially improved the modelperformance.