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Formenti, P, Andreae MO, Lange L, Roberts G, Cafmeyer J, Rajta I, Maenhaut W, Holben BN, Artaxo P, Lelieveld J.  2001.  Saharan dust in Brazil and Suriname during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) - Cooperative LBA Regional Experiment (CLAIRE) in March 1998. Journal of Geophysical Research-Atmospheres. 106:14919-14934.   10.1029/2000jd900827   AbstractWebsite

Advection of Saharan dust was observed via chemical and optical measurements during March 1998 in Brazil and Suriname during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA)-Cooperative LBA Airborne Regional Experiment (CLAIRE)-98 experiment. In Brazil the dust outbreak produced an increase of a factor of 3 in the daily mean mass concentration (up to 26 +/- 7 mug m(-3)) of particles smaller than 10 mum equivalent aerodynamic diameter (EAD), and in the daily mean aerosol particle scattering coefficient sigma (N) (up to 26 +/- 8 Mm(-1) STP, ambient humidity). Background levels of aerosol scattering (ambient) were sigma (s) similar to 10 Mm(-1). The effect of dust advection was evident for all major crustal elements (Al, Si, Ca, Ti, Mn, and Fe), as well as the sea-salt elements (Na, Cl, and S), as the dust layer was transported at low altitude (below 800 hPa). Coarse P and organic carbon (OC) concentrations were not influenced by the occurrence of dust, and were mainly emitted by the rain forest. The dry scattering mass efficiency of dust (particles smaller than 10 mum EAD) was estimated to be between 0.65 (+/- 0.06) and 0.89 (+/- 0.08) m(2) g(-1). Airborne profiles of aerosol scattering showed two distinct types of vertical structure in the dust layer over Suriname, either vertically uniform (15, 26 March), or plume-like (25 March). Dust layers extended generally up to 700 hPa, while scattering layers occasionally encountered at higher altitudes resulted from smoke emitted by biomass burning in Venezuela and Colombia, Observations in South America were supported by measurements in Israel and Tenerife (Canary Islands), where the dust outbreaks were also detected.

Furutani, H, Dall'osto M, Roberts GC, Prather KA.  2008.  Assessment of the relative importance of atmospheric aging on CCN activity derived from field observations. Atmospheric Environment. 42:3130-3142.   10.1016/j.atmosenv.2007.09.024   AbstractWebsite

The effect of atmospheric aging on the cloud condensation nuclei (CCN) activity of atmospheric aerosols was studied by comparing different air masses with different degrees of aging along the southern coast of California over the Pacific Ocean during a research cruise on the R/V Roger Revelle from 2-19 November 2004. Activation diameters (D(act)) were calculated using the measured CCN concentrations, condensation nuclei (CN) concentrations, and particle size distributions. Measurements of single particle size and chemistry, as well as black carbon (BC) concentrations with an aethalometer, were made to provide further insight into aerosol chemistry. A gradient of aerosol concentrations was encountered: along the coast of California, the highest BC and CN concentrations (1000-6000 ng m(-3) and 2000-15,000 cm(-3)) were measured which decreased as the ship moved away from shore to much lower values (<100 ng m(-3), similar to 300 cm(-3)). In all regions, external mixtures of organic carbon, elemental carbon, sea salt, and dust aerosols frequently associated with nitrate and sulfate were observed. A correlation plot between the CCN/CN ratio and D(act) exhibits a clear linear correlation, showing a distinct relationship between the extent of anthropogenic aging and CCN activity with the most highly aged air masses showing the highest CCN activity and smallest D(act). These results show changes in aerosol chemistry due to atmospheric aging that play an important role in determining the CCN activity of atmospheric aerosols. The present study demonstrates that variations in aerosol chemistry must be taken into account in models to adequately account for the physicochemical properties of atmospheric aerosols and their CCN activity. (C) 2007 Published by Elsevier Ltd.