(673d) Determination of Seasonal, Diurnal, and Height Resolved Average Number Concentration Peaks in a Pollution Impacted Rural Continental Location

The impact of aerosols on Earth’s radiation balance and the associated climate forcing effects of aerosols represent the largest uncertainties in the Intergovernmental Panel on Climate Change’s 2007 fourth Assessment Report. The main source of ultrafine aerosols in the atmosphere is the nucleation and growth of gas phase molecules into liquid or solid phase particles.  In opposition to data on nucleation, which is limited both temporally and spatially, number concentration data is regularly available temporally and spatially.  The current objective is to use five years (2006 – 2010) of ground-based, highly time resolved, particle number concentration data (NOAA ESRL Global Monitoring Division) in conjunction with vertical data from more than 300 flights (NOAA Airborne Aerosol Observatory) near Bondville, IL to better understand the seasonal, diurnal, and vertical variation in aerosol number concentration. Preliminary analysis shows the highest peaks in condensation nuclei greater than 10 nm during the spring months (May, April) with slightly lower peaks during the fall months (September, October).  The diurnal pattern of aerosol number has a midday peak occurring earliest in warmer months and later in colder months.  Particle number peaks coincide with monthly and diurnal patterns associated with low aerosol mass and surface area.  Average vertical profiles show a nearly monotonic decrease with altitude in all months, and with peak magnitudes occurring in the spring and fall, thus correlating with the ground-based measurements.  Individual vertical profiles show evidence of plumes with enhanced number concentration, and periods when the entire boundary layer is enhanced by high particle number concentration.  These results, while not directly indicating nucleation, will assist field researchers and modelers by providing the seasonal intensity patterns of particle number increases on the ground and aloft.