UMD AOSC Seminar
The Amazonian Aerosol Characterization Experiment (AMAZE-08)
Professor Scot T. Martin
Gordon McKay Professor of Environmental Chemistry
Department of Atmospheric Sciences
The main objectives of AMAZE-08 were to understand the sources and regulators of organic particle mass in a pristine continental environment and the connections between particle chemistry and particle optical and hygroscopic properties. The AMAZE-08 tower measurements were conducted in Central Amazonia between February 7 and March 14, 2008 during the rainy reason. The winds were predominantly from the ENE across 1600 km of untouched forest from the Atlantic Ocean. The overall composition of submicron Amazonian aerosol particles for background conditions is 80 to 90% organic material, with the balance in sulfate. This talk will present several new stories, especially related to nucleation and growth, that have emerged during the analysis of the AMAZE-08 data set. For example, (1) particles collected and imaged by scanning electron microscopy suggest an extremely active production of secondary organic aerosol and that the resulting organic mass dominates the submicron particle fraction. (2) The variability in the CCN activity of submicron particles can be explained by diameter and by use of an effective hygroscopicity of mixing based on an organic parameter and a sulfate parameter; the organic parameter has the same value as obtained for SOA particles in laboratory experiments. (3) A major source of ice nuclei in the wet season of the Amazon is transcontinental transport of Saharan dust; a local source of biological particles also contributes to the IN population, likely dominating at warmer temperatures where ice initiation occurs more frequently. Further examples of other emerging findings will also be presented.
October 15, 2009, Thurday