Toward an Improved Understanding of Particle Dry Deposition Velocity

The investigators in this project will conduct experimental and theoretical work in order to improve our understanding of the rate of the dry deposition of particles, one of the processes by which particles settle and deposit onto surfaces. The speed at which particles undergo dry deposition, which is fundamental to our understanding of particles and our atmosphere, still has large uncertainties due to the complexity of making observations at the small spatial scales in which this process occurs. The project team will take measurements in controlled laboratory settings as well as in the field and use the knowledge gained to update model representations of the particle dry deposition process. This research is expected to lead to improvements in air quality and climate models. The project team will also develop a 5-week meteorology and air quality instrumentation seminar, which will count towards college credits, geared towards junior and senior undergraduate students. There are two primary scientific objectives in this work: (1) chamber measurements for exploring the impact of size, chemistry, and other parameters on dry deposition velocity; and (2) ambient measurements of refractory black carbon fluxes using both eddy covariance methods and filter deposition techniques. This project will provide the research community with updated parameters for the representation of dry deposition velocity, which could be used by a wide variety of models. The project team is motivated by the persistent large uncertainty (approximately two orders of magnitude) for dry deposition velocity. In order to reduce this uncertainty, the project team will: (1) carry out chamber measurements to assess the effects of aerosol size, phase, and shape on dry deposition velocity; (2) optimize techniques for measuring black carbon from filter extracts; (3) conduct ambient measurements of refractory black carbon turbulent fluxes and filter deposition; and (4) improve the current analytical formulation used in models for aerosol dry deposition. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.