Simultaneous, in situ measurements of OH, HO2, O3, and H2O: A test of modeled stratospheric HOxchemistry

Simultaneous, in situ measurements of OH, HO2, H2O, and O3from 37–23 km are reported. The partitioning between OH and HO2and the total HOxconcentration are compared with expected steady‐state values. The ratio of HO2to OH varies from less than 2 at 36 km to more than 3 at 25 km; in the lower stratosphere this ratio is nearly a factor of two less than predicted. The data are used to calculate HOxproduction and loss rates. The measured HOxmixing ratio is consistent with production dominated by the reaction of O(1D) with H2O, and loss controlled by NOybelow 28 km and HOxabove 30 km. The steady‐state concentration of H2O2is inferred from the measured HO2concentration and calculated photolysis rate. The maximum H2O2mixing ratio (at 33 km) is predicted to be less than 0.2 ppb.