The BIO-MAÏDO (Bio-physicochemistry of tropical clouds at Maïdo (La Réunion Island): processes and impacts on secondary organic aerosols formation) campaign

BIO-MAÏDO is a French collaborative program founded by the ANR (Agence Nationale de La Recherche). BIO-MAÏDO aims at better understanding the chemical and biological multiphasic mechanisms that control the Secondary Organic Aerosol (SOA) formation. The tropical environment of the Reunion Island represents an ideal site to study SOA formation: (1) numerous biogenic volatile organic compounds, precursors of SOA are emitted in huge amount and the high solar intensity flux and the temperature favors their chemical transformations; (2) due to the high occurrence of orographic clouds over this region, this site allows evaluating the influence of aqueous processes on SOA formation. The strategy adopted is based on an intensive field campaign over several sites with the objective to characterize sources of gases and aerosols and to evaluate multiphasic pathways controlling the formation and oxidation of SOA. This work is done in synergy with modeling investigations using a lagrangian particle dispersion model (FLEXPART), a 0D process cloud model (CLEPS) together with a 3D chemistry/transport model (Meso-NH).

The campaign took place from 13^th of March to 4^th of April 2019 at La Réunion Island. The main objectives were to document the cloud cycle on the slope of the Maïdo, the boundary layer development and the chemical evolution of atmospheric composition (primary and secondary aerosols as well as gaseous precursors) along the slope up to the receptor site, the Maïdo observatory. For this reason, the campaign took place on five sites distributed on the slope from the Maïdo to the observatory. A innovative instrumentation was deployed: three PTR-MS, a tethered balloon, an instrumented mast measuring biogenic volatile organic compounds fluxes, a mobile mast with a cloud impactor, etc. Preliminary results from the campaign will be presented.