Extended Abstract (208K)10.1
Real-time processing and characterization of atmospheric particulates
John Hallett, DRI, Reno, NV; and J. G. Hudson, D. H. Lowenthal, and R. Purcell
Knowledge of the properties of individual atmospheric particles is important for understanding their origin, evolution, and fate in clouds and precipitation. A class of instruments is evolving that enables specific properties to be measured in near real time. Such approaches are advantageous because particle mixing state is stable and chemical reactions are minimized. Some instruments for achieving this are compared and their advantages and limitations are discussed. Processing may be achieved by particle loss through volatilization and oxidation of organic and inorganic (e.g., water, sulfuric acid, ammonium sulfate, sodium chloride) compounds as a processing furnace increases sample temperature followed by optical or other detection. It may be achieved by controlled increases of supersaturation and measurement of hygroscopic particle growth, as in a water vapor diffusion chamber. It may be achieved by melting and/or evaporation or by controlled heating following capture and visual observation (forward and side) of a cloudscope. Alternatively, growth by controlled cooling and or freezing (to produce a supersaturation) may be examined.
Examples of such analyses will be shown from field observations from the viewpoint of determining measurement strategies to yield information on hygroscopicity, nucleus presence, and solubility (mineral particles may be detected and solute supersaturation determined). Furnace processing also suggests the production of nanometer-sized particles under non-steady-state conditions. This has implications for the techniques used to characterize such particles. Results suggest the universal presence of hygroscopic particles between the tail of the CCN spectrum and the optical resolution of the cloudscope (< 0.2 to >1um dry diameter) that could be important in the initiation of precipitation. Such particles are highly variable in concentration as is their occurrence in drizzle and cloud elements collected under maritime, continental, and anthropogenically-influenced environments.
Session 10, Aerosol Physics and Chemistry II
Friday, 7 June 2002, 10:30 AM-12:00 PM
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