Reactive nitrogen compounds and their contribution to new particle formation and growth

Atmospheric new particle formation (NPF) followed by growth of the particles to ~50-100 nm accounts for ~50% of the particles that can activate cloud droplets. As such, constraining how aerosols affect cloud lifecycle, properties, and processes and, more generally, the earth’s radiative balance requires knowledge of NPF and growth processes. However, our understanding of NPF and growth remains incomplete because these processes are governed by a complex interplay between the chemistry and physical state of the atmosphere. Additionally, ambient measurements of molecules, such as amines, that have been proposed to be important for NPF are sparse, thus limiting our ability to evaluate the global importance of different nucleation mechanisms. In this talk, I will discuss our work on NPF and growth at the Department of Energy Atmospheric Radiation Measurement Southern Great Plains (SGP) research station, one of the longest-running atmospheric measurement sites in North America. At this agricultural site, we investigate NPF and growth using a combination of long-term measurements of aerosol size distributions and intensive operating periods in which we measure NPF and growth precursors and chemically characterize the growing clusters using mass spectrometry. Our measurements provide insight into the contribution of various oxidized and reduced reactive nitrogen compounds to these processes and highlight the importance of ambient measurements in providing the scientific information required to improve our understanding of aerosol-cloud interactions.