Atmospheric Sciences Division Seminar

Atmospheric aerosols can impact climate, air quality and visibility, and human health. Recent work suggest that newly formed particles exhibit enhanced hydroscopicity, may be more effective as Cloud Condensation Nuclei, and increase the indirect radiative effect beyond current estimates. It is thus critical to understand aerosol formation pathways, specifically, nucleation and growth.

Frequent new particle formation (NPF) has been observed regularly at Storm Peak Laboratory (SPL), a high elevation mountaintop observatory in Colorado. These events occurred during 52% of the 474 measurement days from 2001 to 2009, consistently during the mid-afternoon throughout the spring, summer and winter months. Average growth rates, condensation sinks, and formation rates for these NPF events will be presented. The strongest correlation factor with NPF is ultraviolet radiation. The events are not related to increased ozone concentration or pre-existing aerosol surface area, implying that nucleation can occur anywhere in the free troposphere.

During the Storm Peak Lab Cloud Property Validation Experiment (StormVEx), winter 2010-11, the second ARM mobile facility (AMF2) was deployed to Steamboat Springs, Colorado. An extensive suite of instruments was deployed for measurement of aerosol and cloud properties at and near SPL. 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 and Condensational Particle Counter were 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 will describe several case studies demonstrating new particle formation within clouds at SPL during StormVE