Global stratospheric hydrogen peroxide distribution from MIPAS-Envisat full resolution spectra compared to KASIMA model results

摘要

MIPAS-ENVISAT full resolution spectra were analyzed to obtain a globaldistribution of hydrogen peroxide (H₂O₂) in the stratosphere.H₂O₂ acts as reservoir gas for the HO_x family (= H+OH+HO₂)and thus, observations of H₂O₂ provide a better understanding of theHO_x chemistry in the atmosphere. A retrieval approach based onconstrained least squares fitting was developed and applied to smalldedicated spectral analysis windows with maximum H₂O₂ information andminimum contribution of interfering gases. Due to a low signal to noise ratioin the measured spectra single profiles cannot be used for scientificinterpretation and about 100 profiles have to be averaged temporally orspatially. Our retrievals of H₂O₂ from MIPAS measurements providemeaningful results between approximately 20 and 60 km. A possible impact bythe high uncertainty of the reaction rate constant forHO₂ + HO₂→H₂O₂ + O₂ in our 3D-CTM KASIMA isdiscussed. We find best agreement between model and observations for applyingrate constants according to Christensen et al. (2002) however, a mismatch invertical profile shape remains. The observations were compared to the modelresults of KASIMA focusing on low to mid latitudes. Good agreement in spatialdistribution and in temporal evolution was found. Highest vmr of H₂O₂in the stratosphere were observed and modeled in low latitudes shortly afterequinox at about 30 km. The modelled diurnal cycle with lowest vmr shortlyafter sunrise and highest vmr in the afternoon is confirmed by the MIPASobservations.