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Article

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This item is available under a Creative Commons License for non-commercial use only

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1.4 CHEMICAL SCIENCES

Publication Details

Atmos.Chem.Phys.,19,10591–10618,2019

Abstract

The Forests gAses aeRosols Clouds Exploratory (FARCE) campaign was conducted in March–April 2015 on the tropical island of La Réunion. For the first time, several scientific teams from different disciplines collaborated to provide reference measurements and characterization of LaRéunionvegetation,volatileorganiccompounds(VOCs), biogenic VOCs (BVOCs), (bio)aerosols and composition of clouds, with a strong focus on the Maïdo mountain slope area. The main observations obtained during this 2-month intensivefieldcampaignaresummarized.Theyincludecharacterizations of forest structure, concentrations of VOCs and precursors emitted by forests, aerosol loading and optical properties in the planetary boundary layer (PBL), formation of new particles by nucleation of gas-phase precursors, icenucleatingparticlesconcentrations,andbiologicalloadingin bothcloud-freeandcloudyconditions.SimulationsandmeasurementsconfirmthattheMaïdoObservatorylieswithinthe PBL from late morning to late evening and that, when in the PBL, the main primary sources impacting the Maïdo Observatory are of marine origin via the Indian Ocean and of biogenic origin through the dense forest cover. They also show that(i)themarinesourceprevailslessandlesswhilereaching the observatory; (ii) when in the PBL, depending on the localizationofahorizontalwindshear,theMaïdoObservatory canbeaffectedbyairmassescomingdirectlyfromtheocean and passing over the Maïdo mountain slope, or coming from inland; (iii) bio-aerosols can be observed in both cloud-free and cloudy conditions at the Maïdo Observatory; (iv) BVOC emissions by the forest covering the Maïdo mountain slope can be transported upslope within clouds and are a potential cause of secondary organic aerosol formation in the aqueous phase at the Maïdo Observatory; and (v) the simulation of dynamicsparameters,emittedBVOCsandcloudlifecyclein the Meso-NH model are realistic, and more advanced MesoNH simulations should use an increased horizontal resolution (100m) to better take into account the orography and improve the simulation of the wind shear front zone within which lies the Maïdo

DOI

https://doi.org/10.5194/acp-19-10591-2019

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