Atmospheric Chemistry and Physics (Jun 2012)
Global stratospheric hydrogen peroxide distribution from MIPAS-Envisat full resolution spectra compared to KASIMA model results
Abstract
MIPAS-ENVISAT full resolution spectra were analyzed to obtain a global distribution of hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) in the stratosphere. H<sub>2</sub>O<sub>2</sub> acts as reservoir gas for the HO<sub>x</sub> family (= H+OH+HO<sub>2</sub>) and thus, observations of H<sub>2</sub>O<sub>2</sub> provide a better understanding of the HO<sub>x</sub> chemistry in the atmosphere. A retrieval approach based on constrained least squares fitting was developed and applied to small dedicated spectral analysis windows with maximum H<sub>2</sub>O<sub>2</sub> information and minimum contribution of interfering gases. Due to a low signal to noise ratio in the measured spectra single profiles cannot be used for scientific interpretation and about 100 profiles have to be averaged temporally or spatially. Our retrievals of H<sub>2</sub>O<sub>2</sub> from MIPAS measurements provide meaningful results between approximately 20 and 60 km. A possible impact by the high uncertainty of the reaction rate constant for HO<sub>2</sub> + HO<sub>2</sub>→H<sub>2</sub>O<sub>2</sub> + O<sub>2</sub> in our 3D-CTM KASIMA is discussed. We find best agreement between model and observations for applying rate constants according to Christensen et al. (2002) however, a mismatch in vertical profile shape remains. The observations were compared to the model results of KASIMA focusing on low to mid latitudes. Good agreement in spatial distribution and in temporal evolution was found. Highest vmr of H<sub>2</sub>O<sub>2</sub> in the stratosphere were observed and modeled in low latitudes shortly after equinox at about 30 km. The modelled diurnal cycle with lowest vmr shortly after sunrise and highest vmr in the afternoon is confirmed by the MIPAS observations.
