Comment on ‘ ‘ Instantaneous secondary organic aerosol yields and their comparison with overall aerosol yields for aromatic and biogenic hydrocarbons ’ ’ by Weimin Jiang

In the introduction to the Technical Note, ‘‘Instantaneous secondary organic aerosol yields and their comparison with overall aerosol yields for aromatic and biogenic hydrocarbons’’, Jiang (2003) states that ‘‘[t]o model the formation of secondary organic aerosol, SOA, a concept called aerosol yield (or SOA yield), loosely defined as the SOA mass formed per unit mass of reactive organic gas (ROG) reacted, has been widely used.’’ He goes on to suggest an expanded concept called instantaneous aerosol yield (IAY), applied to the case of pre-existing organic aerosol. While this IAY method may at first seem reasonable, there is a major assumption in its derivation that limits its use for atmospheric models. Additionally, aerosol yield approaches in general are inappropriate for describing the reversible partitioning process that occurs in the atmosphere. An aerosol-yield-based approach estimates the extent or increment of SOA formation based on the equation