New particle formation observed in-cloud during STORMVEX

Description

Atmospheric aerosols can impact climate through direct and indirect radiative forcing, degrade air quality and visibility, and have detrimental effects on human health (e.g. Charlson et al. 1992, Akimoto 2003). Recent evidence suggests that newly formed particles exhibit enhanced hydroscopicity, may be more effective as cloud condensation nuclei (CCN), and may increase the indirect radiative effect beyond our current estimates (O’Halloran et al. 2009). Thus, understanding aerosol nucleation and growth is critical for assessing their role in climate change and atmospheric chemistry. Aerosol nucleation is defined as a rapid growth or “burst” of nanometer-sized particles. Nucleation mechanisms describe the initial formation of new atmospheric particles with diameters smaller than 3 nm. This is followed by rapid particle growth into the accumulation size mode (Kulmala et al. 2004a). During the Storm Peak Lab Cloud Property Validation Experiment (STORMVEX), winter 2010–2011, the second ARM Mobile Facility (AMF2) was deployed to Steamboat Springs, Colorado. The overall goal of this campaign was to measure cloud properties with remote sensing instruments such as cloud radars while aerosol and cloud microphysical measurements are made on the mountain crest at the Storm Peak Laboratory (SPL) and aloft from the University of Wyoming King Air research aircraft. An extensive suite of instruments was deployed for measurement of aerosol and cloud properties across the Steamboat Springs Ski Resort. At SPL, a TSI Nano-Scanning Mobility Particle Sizer (SMPS), a standard SMPS, and three Droplet Measurement Technology Cloud Probes (FSSP, CIP, and PIP) measured aerosol and cloud particle size distributions from 3 nm to 6.2 mm. An SMPS was also deployed at the AMF2 Aerosol Observing System (AOS) below SPL. Additionally, measurements of the cloud droplet size distribution were made from the King Air above SPL during the NSF-funded Colorado Airborne Multi-Phase Cloud Study (CAMPS) study. This presentation describes several case studies demonstrating new particle formation within clouds at SPL during STORMVEX, often with the King Air aircraft overhead. The growth evolution of newly formed 3 nm particles was observed at SPL. Concurrent cloud microphysical data collected at SPL and aboard the King Air will be presented. Aerosol growth episodes observed below cloud base at the AOS site will be discussed.