ORACLE (v1.0): module to simulate the organic aerosol composition and evolution in the atmosphere

Abstract

Abstract.A computationally efficient module to describe organic aerosol (OA) partitioning and chemical aging has been developed and implemented into the EMAC atmospheric chemistry-climate model. The model simulates the formation of secondary organic aerosol (SOA) from semivolatile (SVOCs), intermediate-volatility (IVOCs), and volatile organic compounds (VOCs). It distinguishes SVOCs from biomass burning and all other combustion sources using two surrogate species for each source category with an effective saturation concentration at 298 K of C * = 0.1 and 10 µg m −3 . Two additional surrogate species with C * = 10 3 and 10 5 µg m −3 are used for the IVOCs emitted by the above source categories. Gas-phase photochemical reactions that change the volatility of the organics are taken into account. The oxidation products (SOA-sv, SOA-iv, and SOA-v) of each group of precursors (SVOCs, IVOCs, and VOCs) are simulated separately to keep track of their origin. ORACLE efficiently describes the OA composition and evolution in the atmosphere and can be used to (i) estimate the relative contributions of SOA and primary organic aerosol (POA) to total OA, (ii) determine how SOA concentrations are affected by biogenic and anthropogenic emissions, and (iii) evaluate the effects of photochemical aging and long-range transport on the OA budget. We estimate that the global average nearsurface OA concentration is 1.5 µg m −3 and consists of 7 % POA from fuel combustion, 11 % POA from biomass burning, 2 % SOA-sv from fuel combustion, 3 % SOA-sv from biomass burning, 15 % SOA-iv from fuel combustion, 28 % SOA-iv from biomass burning, 19 % biogenic SOA-v, and 15 % anthropogenic SOA-v. The modeled tropospheric burden of OA components is 0.23 Tg POA, 0.16 Tg SOA-sv, 1.41 Tg SOA-iv, and 1.2 Tg SOA-v.

ORACLE 2-D (v2.0): an efficient module to compute the volatility and oxygen content of organic aerosol with a global chemistry–climate model

“…1b), respectively . We distinguish anthropogenic and biogenic VOCs, and their firstgeneration oxidation products are distributed in four volatility bins (with C * at 298 K equal to 10 0 , 10 1 , 10 2 , and 10 3 µg m −3 ) by using the aerosol mass yields by Tsimpidi et al (2014). The O : C distributions of the first-generation VOC oxidation products are given by Murphy et al (2011) and vary with volatility ( Fig.…”

“…These organic compounds are allowed to partition between the gas and aerosol phases, resulting in the formation of OA. The change in aerosol mass of each size mode after the phase partitioning is determined by using a weighting factor as described in Tsimpidi et al (2014). Gas-phase photochemical reactions that modify the volatility of the organics are taken into account and the oxidation products of each group of precursors are simulated separately in the module to keep track of their origin.…”

“…The interface structure of MESSy links the base model with several atmospheric submodels that online simulate gas-phase chemistry (MECCA; Sander et al, 2011), inorganic aerosol microphysics and dynamics (GMXe; Pringle et al, 2010), organic aerosol formation and growth (ORACLE; Tsimpidi et al, 2014), emissions (ONLEM and OFFLEM; Kerkweg et al, 2006b), dry deposition and sedimentation (DRYDEP and SEDI; Kerkweg et al, 2006a), cloud scavenging (SCAV; Tost et al, 2006), cloud microphysics (CLOUD; Bacer et al, 2018), and aerosol optical properties (AEROPT; Lauer et al, 2007). EMAC has been extensively described and evaluated against ground-based and satellite observations (Pozzer et al, 2012;Tsimpidi et al, 2014Tsimpidi et al, , 2016Tsimpidi et al, , 2017Karydis et al, 2016Karydis et al, , 2017. In this study, the applied spectral resolution of the EMAC model is T63L31, corresponding to a horizontal grid resolution of 1.875 • × 1.875 • and 31 vertical layers extending to 18 km of altitude (10 hPa).…”

“…3370 A. P. : 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. Since 2006, many regional (Lane et al, 2008;Murphy and Pandis, 2009;Tsimpidi et al, , 2011Ahmadov et al, 2012;Athanasopoulou et al, 2013;Koo et al, 2014;Fountoukis et al, 2014;Ciarelli et al, 2017;Gao et al, 2017) and global (Pye and Seinfeld, 2010;Jathar et al, 2011;Jo et al, 2013;Tsimpidi et al, 2014;Hodzic et al, 2016) modeling studies have used the VBS to account for the semi-volatile nature and chemical aging of organic compounds, demonstrating improvements in reproducing the OA budget and its chemical resolution.…”

“…In this work, a computationally efficient module for the description of OA composition and evolution in the atmosphere (ORACLE; Tsimpidi et al, 2014) has been extended to allow for the first time in a global CCM the description of both the volatility and oxygen content of OA based on the 2-D VBS approach. Similar to ORACLE v1.0, the interface of the new version allows the user to have full control of the complexity of the OA scheme by adjusting the number of species and reactions (i.e., number of compounds, volatility bins, O : C bins) to optimize the computational cost according to the application and the desired chemical resolution.…”