Influence of air mass source region on nanoparticle events and hygroscopicity in central Virginia, U.S. During autumn, 2006, variation in the frequency of aerosol nucleation events, as inferred from nanoparticle growth events, and associated hygroscopicity were investigated as a function of air mass transport history at a mixed deciduous forest in central Virginia, U.S. Above-canopy size distributions of aerosols between 0.012 and 0.700 mm diameter, size-resolved particle hygroscopicity at eight dry diameters between 0.012 and 0.400 mm, and cloud condensation nuclei (CCN) activity were characterized. Air mass back trajectories were clustered to identify source regions. Growth events were most frequent in fastmoving air masses (mean ¼ 9ms1) that originated over the north central U.S. Under these flow regimes, mean values for preexisting sub-mm aerosol number concentrations (4700 cm3), corresponding surface area (142 mm2 cm3), air temperature (6.2 C), and relative humidity (RH, 49.4%) were relatively low compared to other regimes. Under stagnant flow conditions (mean ¼ 3ms1), mean number concentrations were higher (>6000 cm3) and size fractions
Posted on: Sun, 25 Jan 2015 10:08:43 +0000
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