Abstract
Abstract. A new module, ORACLE 2-D, simulating organic aerosol formation and evolution in the atmosphere has been developed and evaluated. The module calculates the concentrations of surrogate organic species in two-dimensional space defined by volatility and oxygen-to-carbon ratio. It is implemented into the EMAC global chemistry–climate model, and a comprehensive evaluation of its performance is conducted using an aerosol mass spectrometer (AMS) factor analysis dataset derived from almost all major field campaigns that took place globally during the period 2001–2010. ORACLE 2-D uses a simple photochemical aging scheme that efficiently simulates the net effects of fragmentation and functionalization of the organic compounds. The module predicts not only the mass concentration of organic aerosol (OA) components, but also their oxidation state (in terms of O : C), which allows for their classification into primary OA (POA, chemically unprocessed), fresh secondary OA (SOA, low oxygen content), and aged SOA (highly oxygenated). The explicit simulation of chemical OA conversion from freshly emitted compounds to a highly oxygenated state during photochemical aging enables the tracking of hygroscopicity changes in OA that result from these reactions. ORACLE 2-D can thus compute the ability of OA particles to act as cloud condensation nuclei and serves as a tool to quantify the climatic impact of OA.
Highlights
Atmospheric aerosols adversely affect human health and play a significant role in climate change on regional and global scales
All organic vapors are subject to photochemical reactions with OH in the gas phase, forming organic products with lower volatility that can recondense to the particulate phase as secondary organic aerosol (SOA)
We employ ORACLE 2-D based on the sensitivity analysis results of Tsimpidi et al (2017) and using the 2-D volatility basis set (VBS) at a resolution suitable for medium-term simulations with global chemistry–climate models. This chemical resolution includes 150 organic aerosol surrogate compounds compared to 34 Organic aerosol (OA) compounds in ORACLE, which results in a 16 % increase in the overall European Centre Hamburg (ECHAM)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) computational burden
Summary
Atmospheric aerosols adversely affect human health and play a significant role in climate change on regional and global scales. Tsimpidi et al.: ORACLE 2-D (v2.0): an efficient module to compute volatility and oxygen content approach, semi-volatile primary emissions, chemical aging, and SOA formation were unified within a common framework that is ideally suited for regional and global chemical modeling. This increase in OA oxygen content is important for its impact on climate through changes in cloud condensation nuclei (CCN) and ice nuclei (IN) activity. Donahue et al (2011) extended the original one-dimensional VBS framework to two dimensions (2-D VBS), tracking the saturation concentration and the oxygen content of OA during atmospheric transport This approach further improved the description of the atmospheric evolution of OA and its precursor gases that become increasingly more oxidized, less volatile, and more hygroscopic during their atmospheric aging.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
