Origin of atmospheric aerosols at the Pierre Auger Observatory using studies of air mass trajectories in South America.

THE PIERRE AUGER COLLABORATION.; S. J. SCIUTTO

ATMOSPHERIC RESEARCH

ELSEVIER SCIENCE INC

Lugar: Amsterdam; Año: 2014 vol. 149 p. 120 - 135

0169-8095

The Pierre Auger Observatory ismaking significant contributions towards understanding the natureand origin of ultra-high energy cosmic rays. One of its main challenges is the monitoring of theatmosphere, both in terms of its state variables and its optical properties. The aim of this work is toanalyse aerosol optical depth τa(z) valuesmeasured from2004 to 2012 at the observatory,which islocated in a remote and relatively unstudied area of Pampa Amarilla, Argentina. The aerosol opticaldepth is in average quite low ? annual mean τa(3.5 km) ∼ 0.04 ? and shows a seasonal trend with awinter minimum ? τa(3.5 km) ∼ 0.03 ?, and a summer maximum ? τa(3.5 km) ∼ 0.06 ?, and anunexpected increase from August to September ? τa(3.5 km) ∼ 0.055. We computed backwardtrajectories for the years 2005 to 2012 to interpret the air mass origin. Winter nights with lowaerosol concentrations show air masses originating from the Pacific Ocean. Average concentrationsare affected by continental sources (wind-blown dust and urban pollution), whilst the peakobserved in September and October could be linked to biomass burning in the northern part ofArgentina or air pollution coming from surrounding urban areas.