The response of ClO radical concentrations to variations in NO2 radical concentrations in the lower stratosphere

The response of ClO concentrations to changes in NO2 concentrations has been inferred from simultaneous observations of [ClO], [NO], [NO2] and [O3] in the mid‐latitude lower stratosphere. This analysis demonstrates that [ClO] is inversely correlated with [NO2], consistent with formation and photolysis of [ClONO2]. A factor of ten range in the concentration of NO2 was sampled (0.1 to 1×109 mol/cm³), with a comparable range in the ratio of [ClO] to total available inorganic chlorine (1% ≤ [ClO]/[Cly] ≤ 5%). This analysis leads to an estimate of [ClONO2]/[Cly] = 0.12 (×/÷2), in the mid‐latitude, lower‐stratospheric air masses sampled.