In Situ Characterization of Cloud Condensation Nuclei, Interstitial, and Background Particles Using the Single Particle Mass Spectrometer, SPLAT II

摘要

The aerosol indirect effect remains the most uncertainnaspect of climate change modeling, calling for characterizationnof individual particles sizes and compositions withnhigh spatial and temporal resolution. We present the firstndeployment of our single particle mass spectrometern(SPLAT II) operated in dual data acquisition mode tonsimultaneously measure particle number concentrations,ndensity, asphericity, and individual particle size andnquantitative composition, with temporal resolution betternthan 60 s, thus yielding all the required properties tondefinitively characterize the aerosol-cloud interaction innthis exemplary case. We find that particles are composednof oxygenated organics, many mixed with sulfates, biomassnburning particles, some with sulfates, and processednsea-salt. Cloud residuals are found to contain morensulfates than background particles, explaining their highernefficiency to serve as cloud condensation nuclei (CCN).nAdditionally, CCN sulfate content increased with time duento in-cloud droplet processing. A comparison between thensize distributions of background, CCN, and interstitialnparticles shows that while nearly all CCN particles arenlarger than 100 nm, over 80% of interstitial particles arensmaller than 100 nm. We conclude that for this cloud,nparticle size is the controlling factor on aerosol activationninto cloud-droplets, with higher sulfate content playing ansecondary role.