Climate and Forecast (CF)

mass concentration of methyl peroxy radical in air

Mass concentration means mass per unit volume and is used in the construction mass_concentration_of_X_in_Y, where X is a material constituent of Y. A chemical species denoted by X may be described by a single term such as 'nitrogen' or a phrase such as 'nox_expressed_as_nitrogen'. The chemical formula for methyl_peroxy_radical is CH3O2. In chemistry, a 'radical' is a highly reactive, and therefore shortlived, species.