Secondary organic aerosol yields from cloud‐processing of isoprene oxidation products

While there is a growing understanding from laboratory studies of aqueous phase chemical processes that lead to secondary organic aerosol (SOA) formation in cloud droplets ( SOA drop ), the contribution of aqueous phase chemistry to atmospheric SOA burden is yet unknown. Using a parcel model including a multiphase chemical mechanism, we show that SOA drop carbon yields ( Y c ) from isoprene (1) depend strongly on the initial volatile organic carbon (VOC)/NO x ratio resulting in 42% > Y c > 0.4% over the atmospherically‐relevant range of 0.25 < VOC/NO x < 100; (2) increase with increasing cloud‐contact time; (3) are less affected by cloud liquid water content, pH, and droplet number. (4) The uncertainty associated with gas/particle‐partitioning of semivolatile organics introduces a relative error of −50% ≤ Δ Y c < +100 %. The reported yields can be applied to air quality and climate models as is done with SOA formed on/in concentrated aerosol particles ( SOA aer ).