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

MINGARI L; ESTELA COLLINI; ARNAU FOLCH; BAEZ WALTER; EMILCE BUSTOS; OSORES SOLEDAD; FLORENCIA RECKZIEGEL; ALEXANDER P; JOSÉ VIRAMONTE

ATMOSPHERIC CHEMISTRY AND PHYSICS

COPERNICUS PUBLICATIONS

Lugar: Gottingen; Año: 2017

1680-7316

Abstract. On 13 June 2015, the London Volcanic Ash Advi-sory Centre (VAAC) warned the Buenos Aires VAAC abouta possible volcanic eruption from the Nevados Ojos delSalado volcano (6879m), located in the Andes mountainrange on the border between Chile and Argentina. A vol-canic ash cloud was detected by the SEVIRI instrument onboard theMeteosat Second Generation (MSG) satellites from14:00UTC on 13 June.In this paper, we provide the first comprehensive descrip-tion of this event through observations and numerical sim-ulations. Our results support the hypothesis that the phe-nomenon was caused by wind remobilization of ancient py-roclastic deposits (ca. 4.5 ka Cerro Blanco eruption) from theBolsón de Fiambalá (Fiambalá Basin) in northwestern Ar-gentina.We have investigated the spatiotemporal distributionof aerosols and the emission process over complex terrain togain insight into the key role played by the orography and thecondition that triggered the long-range transport episode.Numerical simulations of windblown dust were performedusing the ARW(Advanced ResearchWRF) core of theWRF(Weather Research and Forecasting) model (WRF-ARW)and FALL3D modeling system with meteorological fieldsdownscaled to a spatial resolution of 2 km in order to re-solve the complex orography of the area. Results indicatethat favorable conditions to generate dust uplifting occurredin northern Fiambalá Basin, where orographic effects caused strong surface winds. According to short-range numericalsimulations, dust particles were confined to near-ground lay-ers around the emission areas. In contrast, dust aerosols wereinjected up to 5?6 km high in central and southern regionsof the Fiambalá Basin, where intense ascending airflows aredriven by horizontal convergence.Long-range transport numerical simulations were also per-formed to model the dust cloud spreading over northern Ar-gentina. Results of simulated vertical particle column masswere compared with the MSG-SEVIRI retrieval product. Wetested two numerical schemes: with the default configura-tion of the FALL3D model, we found difficulties to simulatetransport through orographic barriers, whereas an alternativeconfiguration, using a numerical scheme to more accuratelycompute the horizontal advection in abrupt terrains, substan-tially improved the model performance.