The goal of this project is to measure particle deposition via eddy fluxes and particle hygroscopic growth during the two Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX) field campaigns. BEARPEX will be conducted at a ponderosa pine forested site in California to examine forest-atmosphere interactions; it includes an experimental examination of the chemical composition of secondary organic aerosol from forest emissions, the extent of hygroscopic growth of the aerosol, and the amount of aerosol that is deposited to the forest canopy. Aerosol size spectra consisting of optical measurements of particle concentration (0.3 - 2 micron dia.) using an instrument optimized for aerosol flux measurements (FAST), and 3-D wind speed data from a sonic anemometer will be collected from a tower above the canopy at 10 Hz. Turbulent fluxes will be determined from the aerosol concentrations and vertical winds using the eddy correlation (EC) technique. Two additional aerosol optical instruments will be operated at different relative humidities to determine the change in particle size distribution due to hygroscopic growth. This measured hygroscopic growth will be compared to growth predictions based on measured aerosol chemical composition from BEARPEX collaborators.
This project should lead to a better understanding of aerosol removal and its impacts on climate change, pollutant exposure, and ecosystem stresses. Broader impacts of the proposed research also include graduate and undergraduate education and incorporation of project results into class materials in atmospheric chemistry and aerosol microphysics.
