[1] Ozone depletion in the colder than average 2004/2005 Arctic polar vortex is mapped and quantified using ozone profiles from two limb sounding satellite instruments, the Earth Observing System Microwave Limb Sounder (Aura/MLS) and the Odin Sub-Millimetre Radiometer (Odin/SMR). Profiles of chemically inert nitrous oxide (N 2 O) are used to trace vertical transport during the winter. Two methods are used for estimating the vortex average ozone losses north of 67°equivalent latitude. In a first step, the time evolution of ozone mixing ratios is described on N 2 O isopleths. Maximum ozone depletion is found on the 100 ppbv and 150 ppbv N 2 O isopleths (located in the 430-460 K potential temperature range in mid-March 2005) where vortex average ozone depletion totalled 1.0-1.1 ppmv for Aura/MLS and 0.7-0.9 ppmv for Odin/SMR. Second, ozone profiles from Aura/MLS and Odin/SMR are assimilated into the DIAMOND isentropic transport model. Ozone depletion is estimated by comparing assimilated fields to ozone fields passively transported from 1 January. On the 450 K potential temperature level, the Aura/MLS ozone fields indicate 0.9-1.3 ppmv vortex-averaged ozone depletion while the Odin/SMR fields indicate 0.6-0.9 ppmv depletion. The uncertainty depends mainly on the rates of cross-isentropic transport used in the study. The ozone depletion estimates in this study are lower than previously published estimates. The discrepancies to some studies can be attributed to the more adequate treatment of an ozone poor region that is found in the central polar vortex in the early winter.

Ozone depletion in the 2006/2007 Arctic winter is studied by assimilating ozone from the Odin/SMR satellite instrument into a 2‐D isentropic transport model. Cross‐isentropic transport is implemented by letting the vortex descend at a rate estimated from the inert tracer N2O. Ozone depletion is estimated by comparing ozone fields, passively transported in the model from 1 January 2007, to model fields continuously updated by assimilation of incoming satellite data. Significant ozone destruction is inferred in February and March 2007. By 15 March, an average ozone destruction in the range 0.5–1.0 ppmv is estimated north of 65° equivalent latitude at 475 K potential temperature, whilst 0.3–0.8 ppmv and 0.4–0.8 ppmv ozone destruction is estimated at 525 K and 575 K. By comparing the 2007 ozone depletion to losses inferred in 2003 and 2005 we conclude that the 2007 Arctic ozone destruction is the most severe found in the Odin/SMR data set.

The Sub-Millimetre Radiometer (SMR) on board Odin measures various important atmospheric species, including stratospheric ozone. In this study, we compare the three versions (v1.2, v2.0, and v2.1) of level 2 Odin/SMR global stratospheric ozone data to coincident level 2 MIPAS V4.61 and balloon sonde stratospheric ozone data during 2003. The most current product from Odin/SMR (at time of writing), the v2.1, showed the smallest systematic differences when compared to coincident MIPAS and sonde data. Between 17 and 55 km, v2.1 values agreed with MIPAS within 10% (a maximum of 0.42 ppmv), while comparisons to sonde measurements showed an agreement of typically 5-10% between 22 and 35 km (less than 0.5 ppmv below 33 km). Tropical latitudes below 35 km presented the largest absolute systematic differences between v2.1 and sonde coincidences, where Odin/SMR was systematically lower by ∼0.9 ppmv (more than 10% difference) at approximately 30 km. Comparisons concerning the previous two Odin/SMR versions showed much larger systematic differences, especially at the higher and lower stratospheric altitudes. The main conclusion here is that we suggest that v2.1 of Odin/SMR ozone data should be used for scientific studies. PACSNos.: 92.60.hd, 95.75.Rs, 95.85.Fm Résumé : Le radiomètre sous-millimétrique (SMR) à bord du satellite Odin mesure différents composants de l'atmosphère, incluant l'ozone stratosphérique. Ici, nous comparons les trois versions (v1.2, v2.0 et v2.1) des données globales d'ozone stratosphérique du niveau 2 Odin/SMR avec des mesures en coïncidence du niveau 2 de MIPAS V4.61 et avec des données prises par ballon sonde stratosphérique en 2003. Les résultats les plus courants de Odin/SMR (au moment d'écrire), la version 2.1, ont montré la plus petite différence systématique avec les mesures MIPAS et de ballon-sonde. Entre 17 et 55 km, v2.1 agrée avec MIPAS avec une précision meilleure que 10% (maximum de 0.42 ppmv), alors que la comparaison avec la sonde montre un accord à l'intérieur de 5-10% entre 22 et 35 km (moins de 0,55 ppmv sous 33 km). Les données sous les tropiques de Odin/SMR sous 35 km ont montré le plus grand écart avec la sonde, étant systématiquement plus bas par ∼0,9 ppmv (plus de 10% de différence) à environ 30 km. Les données des versions 1.2

Abstract. The objective of this study is to demonstrate how polar ozone depletion can be mapped and quantified by assimilating ozone data from satellites into the wind driven transport model DIAMOND, (Dynamical Isentropic Assimilation Model for OdiN Data). By assimilating a large set of satellite data into a transport model, ozone fields can be built up that are less noisy than the individual satellite ozone profiles. The transported fields can subsequently be compared to later sets of incoming satellite data so that the rates and geographical distribution of ozone depletion can be determined. By tracing the amounts of solar irradiation received by different air parcels in a transport model it is furthermore possible to study the photolytic reactions that destroy ozone.

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