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

MINGARI LEONARDO; ESTELA COLLINI; ARNAU FOLCH; BAEZ WALTER; EMILCE BUSTOS; OSORES SOLEDAD; FLORENCIA RECKZIEGEL; ALEXANDER P; ANDRIOLI M; J. G. VIRAMONTE

Puerto varas

Congreso; Cities on Volcanoes 9; 2016

IAVCEI

On 13th June 2015, the London Volcanic Ash Advisory Centre (VAAC) warned to BuenosAires VAAC, within the frame of inter-VAAC collaboration, about a volcanic eruption fromthe "Nevados Ojos del Salado" volcano (6,879 m), located on the Chilean-Argentinianborder. A volcanic ash cloud was detected by the SEVIRI instrument on board the MeteosatSecond Generation (MSG) satellites from 14:00 UTC on June 13th. Further studiesconcluded that the phenomenon was caused by remobilization of ancient pyroclastic deposits(4.5 Ka Cerro Blanco fallout) from the Bolsón de Fiambalá (Fiambalá Basin) in northwesternArgentina. Short-range numerical simulations of windblown dust from the Fiambalá Basinwere performed using the WRF-ARW / FALL3D modeling system downscalingmeteorological fields down to 2-km resolution in order to resolve the complex orography ofthe area. Results indicate that favorable conditions for dust uplift occurred at the north of theFiambalá Basin, where orographic effects caused strong surface winds. Dust particles were ingeneral confined to near-ground layers around the emission areas, thereby contributing tohigh near-surface concentration values. However, in the central and southern regions of theFiambalá Basin, dust aerosols were injected up to 5-6 km high due to ascending airflowsdriven by horizontal convergence. Long-range transport numerical simulations were alsoperformed to model dust cloud spreading over northern Argentina. Results of simulatedvertical particle column mass were compared with the MSG-SEVIRI retrieval product. Wetested two numerical schemes. With the default configuration of the FALL3D model,difficulties to simulate transport through orographic barriers were observed. An alternativeconfiguration, using a numerical scheme to more accurately compute the horizontal advectionin abrupt terrains, substantially improved the model performance