AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Use of Long-Term, Co-Located, Vertical and Ground-based Particle Number Concentration Data to Examine Nucleation Intensity Patterns in a Rural Continental Environment
ROBERT BULLARD, Charles Stanier, John Ogren, Patrick Sheridan, University of Iowa
Abstract Number: 470 Working Group: Remote and Regional Atmospheric Aerosols
Abstract Long-term records of aerosol number, nucleation event frequency, and vertical profiles of number concentration are valuable to the atmospheric modeling community but are rare. The extensive data record from multiagency monitoring assets at Bondville, IL can contribute important information on long term and vertically resolved patterns in these parameters. Highly time-resolved particle number concentration data have been measured for nearly twenty years by the NOAA ESRL Global Monitoring Division. Furthermore, vertically-resolved aerosol counts and other aerosol parameters are available from more than 300 flights of the NOAA Airborne Aerosol Observatory (AAO).
As documented in Asmi et al. 2013, the monthly average particle count has a statistically significant decrease from 1994 – 2012, and this is likely linked to decreases in SO$_2 mixing ratios. Relationships between a number of particle-number metrics (diurnal patterns, frequency and size of peaks in number concentration over time, and monthly and daily average concentrations) are analyzed with respect to available mixing ratios of precursor gases (SO$_2 and NH$_3) and indicators of particle mass and surface area. Considering monthly diurnal average patterns, the highest peaks in number concentration occur during the late spring months (April, May, June) with slightly lower peaks during the fall months (September, October). The diurnal pattern of aerosol number has a midday peak and the timing of the peak is seasonal (earlier in warmer months, later in colder months). Furthermore, the average diurnal peak height has a decreasing trend from 1994-2012 in all months except for April, May, and June. Average vertical profiles show a nearly monotonic decrease with altitude in all months, with peak magnitudes also occurring in the spring and fall. Historical data will be compared to preliminary size distribution data taken during a 2013 field campaign in Bondville, IL.