Measurement report: Aerosol vertical profiles over the westernNorth Atlantic Ocean during the North Atlantic Aerosols and MarineEcosystems Study (NAAMES)

The NASA North Atlantic Aerosols and Marine Ecosystems Study (NAAMES) shipand aircraft field campaign deployed to the western subarctic Atlanticbetween the years 2015 and 2018. One of the primary goals of NAAMES is toimprove the understanding of aerosol-cloud interaction (ACI) over theAtlantic Ocean under different seasonal regimes. ACIs currently represent thelargest source of uncertainty in global climate models. During three NAAMESfield campaigns (NAAMES-1 in November 2015, NAAMES-2 in May 2016, andNAAMES-3 in September 2017), multiple 10 h science flights were conductedusing the NASA C-130 aircraft to measure marine boundary layer aerosol andcloud properties. The standard flight pattern includes vertical spiralswhere the C-130 transitioned from high altitude to low altitude (and viceversa), collecting in situ measurements of aerosols, trace gases, clouds, andmeteorological parameters as a function of altitude. We examine the datacollected from 37 spirals during the three NAAMES field campaigns, and wepresent a comprehensive characterization of the vertical profiles of aerosolproperties under different synoptic conditions and aerosol regimes. Thevertical distribution of submicron aerosol particles exhibited strongseasonal variation, as well as elevated intra-seasonal variability dependingon emission sources and aerosol processes in the atmospheric column.Pristine marine conditions and new particle formation were prevalent in thewintertime (NAAMES-1) due to low biogenic emissions from the surface oceanand reduced continental influence. Higher concentrations of submicronaerosol particles were observed in the spring (NAAMES-2) due to strongphytoplankton activity and the arrival of long-range-transported continentalplumes in the free troposphere with subsequent entrainment into the marineboundary layer. Biomass burning from boreal wildfires was the main source ofaerosol particles in the region during the late summer (NAAMES-3) in boththe marine boundary layer and free troposphere.