"mole concentration of hydroperoxyl radical in air" . . " Mole concentration means number of moles per unit volume, also called \"molarity\", and is used in the construction mole_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 the hydroperoxyl radical is HO2. In chemistry, a 'radical' is a highly reactive, and therefore shortlived, species." . . "Climate and Forecast (CF)" . .