Retrieval of nitrogen dioxide stratospheric profiles from ground-based zenith-sky UV-visible observations: validation of the technique through correlative comparisons

摘要

A retrieval algorithm based on the Optimal Estimation Method (OEM) has beendeveloped in order to provide vertical distributions of NO₂ in thestratosphere from ground-based (GB) zenith-sky UV-visible observations. Ithas been applied to observational data sets from the NDSC (Network forDetection of Stratospheric Change) stations of Harestua (60° N, 10° E)and Andøya (69° N, 16° E) in Norway. The information contentand retrieval errors have been analyzed following a formalism used forcharacterizing ozone profiles retrieved from solar infrared absorptionspectra. In order to validate the technique, the retrieved NO₂ verticalprofiles and columns have been compared to correlative balloon and satelliteobservations. Such extensive validation of the profile and column retrievalswas not reported in previously published work on the profiling from GBUV-visible measurements. A good agreement - generally better than 25% - has beenfound with the SAOZ (Système d'Analyse par ObservationsZénithales) and DOAS (Differential Optical Absorption Spectroscopy)balloons. A similar agreement has been reached with correlativesatellite data from the HALogen Occultation Experiment (HALOE) and Polar Ozoneand Aerosol Measurement (POAM) III instruments above 25km of altitude.Below 25km, a systematic underestimation - by up to 40% in some cases - of bothHALOE and POAM III profiles by our GB profile retrievals has been observed,pointing out more likely a limitation of both satellite instruments at these altitudes.We have concluded that our study strengthens our confidence in the reliability of theretrieval of vertical distribution information from GB UV-visible observations andoffers new perspectives in the use of GB UV-visible network data for validation purposes.