Quantifying Atmospheric Parameter Ranges for Ambient Secondary Organic Aerosol Formation

Understanding of the fundamental chemical and physical processes that lead to the formation and evolution of secondary organic aerosol (SOA) in the atmosphere has been rapidly advancing over the past decades. Many of these advancements have been achieved through laboratory studies, particularly SOA studies conducted in environmental chambers. Results from such studies are used to develop simplified representations of SOA formation in regional- and global-scale air quality models. Although it is known that there are limitations in the extent to which laboratory experiments can represent the ambient atmosphere, there have been no systematic surveys of what defines atmospheric relevance in the context of SOA formation. In this work, GEOS-Chem version 12.3 was used to quantitatively describe atmospherically relevant ranges of chemical and meteorological parameters critical for predictions of the mass, composition, and physical properties of SOA. For some parameters, atmospherically relevant ranges are generally well represented in laboratory studies. However for other parameters, significant gaps exist between atmospherically relevant ranges and typical laboratory conditions. For example, cold winter (less than 0 degrees C) and humid (greater than 70% RH) conditions are relatively common on the Earth's surface but are poorly represented in published chamber data. Furthermore, the overlap in relative humidity and organic aerosol mass between chamber studies and ambient conditions is almost nonexistent. For parameters with significant gaps, extended laboratory studies and/or mechanistic models are needed to bridge these gaps.