A long term study of polar ozone loss derived from data assimilation of Odin/SMR observations

Abstract

Abstract. Odin, a Swedish-led satellite project in collaboration with Canada, France and Finland, was launched on 20 February 2001 and continues to produce profiles of chemical species relevant to understanding the middle and upper atmosphere. Longterm observations of stratospheric ozone are useful for trend analysis of chemical ozone loss. This study concerns ozone loss over both poles utilizing 12 years of ozone data from Odin/Sub-Millimetre Radiometer (SMR). We have applied the data assimilation technique described by Rösevall et al. (2007) with a number of improvements to study the inter-annual Two SMR ozone products retrieved from the emission lines centred at 501 GHz and 544 GHz were used. An internal comparison of the two analyses using 501 GHz and 544 GHz ozone has been carried out by inspecting the vortex mean ozone in March and October during 2002and 2003-2012 in the Northern and Southern Hemisphere, respectively. Ozone de-10 rived from data assimilation using the two data sets match within 10% at the levels studied, while below 550 K in the Southern Hemispheremore than 50% of the difference is found. Here, 544 GHz ozone is 0.5 parts per million volume ( ppmv) lower than 501 GHz ozone because of better sensitivity in 544 GHz ozone in the lower stratosphere. Comparisons with other studies have been mainly performed against Sonkaew et al. (2013) since Sonkaew et al. (2013) is one of the few studies having consistent estimations of ozone depletion using a SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIA- IntroductionOzone depletion and climate change are indirectly linked. Several studies have predicted that the stratospheric cooling induced 5 by the increasing atmospheric carbon dioxide will enhance ozone depletion (Austin et al., 1992; Shindell et al., 1998). In practice, the Arctic lower stratosphere has been getting colder over the past decades (WMO, 2011). The linear dependence, demonstrated by (Rex et al., 2006), between the ozone depletion and the volume of air having temperature below the threshold for polar stratospheric cloud (PSC) formation implies that the stratospheric O 3 depletion in Northern Hemisphere may become worse if the cooling trend continues. It is therefore important to have continuous observations and trend analyses of the ozone 10 depletion.Ozone loss has been quantified by using a variety of techniques based on different assumptions and instruments (e.g. Eichmann et al., 2002;Grooß and Müller, 2003; Rex et al., 2006; Singleton et al., 2007; Tilmes et al., 2004; Tsvetkova et al., 2007). However, most of the studies were done for individual winters in the last decade. For instance, in the Arctic winter 2010/2011 several groups reported the unprecedented dramatic ozone depletion over the Arctic polar region approaching that 15 of the Antarctic ozone hole (e.g. Arnone et al., 2012; Manney et al., 2011; Sinnhuber et al., 2011). This winter was obviously different from other Arctic winters from 2000 since the polar vortex was strong and isolated the vo...

Two mechanisms of stratospheric ozone loss in the Northern Hemisphere, studied using data assimilation of Odin/SMR atmospheric observations

“…In this study, ozone measurements characterised by a response lower than 0.8 are excluded. A detailed comparison study between ozone products retrieved from the measurement of the 544.6 GHz and the 501.8 GHz emission lines is presented in Sagi and Murtagh (2016).…”

“…Previous DA-based studies of ozone loss were case studies of the cold winters of 2004/05 (Rösevall et al, 2008;Jackson and Orsolini, 2008;El Amraoui et al, 2008) or 2006/07 (Rösevall et al, 2007a;Søvde et al, 2011). In Sagi and Murtagh (2016), our estimated ozone loss has been compared to Rösevall et al (2008), Jackson and Orsolini (2008), and El Amraoui et al (2008) as well as to the O 3 loss derived from a passive tracer method based on SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartogra-phY) measurements (Sonkaew et al, 2013). We showed that our estimation is consistent within approximately 0.2 ppmv with the results from those studies.…”

“…In Sagi and Murtagh (2016), the year-to-year variability in O 3 loss between 2001 and 2013 is characterised for the first time over such a long period using a data assimilation approach, for both hemispheres. Our paper is focused on the study of the two main pathways driving the ozone chemical destruction in the stratosphere, as described above.…”

“…Observations from the Odin/Sub-Millimetre Radiometer (SMR) instrument have been assimilated into the DIAMOND model (Dynamic Isentropic Assimilation Model for OdiN Data), in order to estimate the chemical ozone (O 3 ) loss in the stratosphere. This data assimilation technique is described in Sagi and Murtagh (2016), in which it was used to study the inter-annual variability in ozone depletion during the entire Odin operational time and in both hemispheres. Our study focuses on the Arctic region, where two O 3 destruction mechanisms play an important role, involving halogen and nitrogen chemical families (i.e.…”

Coupled Stratospheric Chemistry–Meteorology Data Assimilation. Part I: Physical Background and Coupled Modeling Aspects

“…Between day 65 and 85 of the SPARC-IPY campaign, the FTIR sampled the air mass inside the polar vortex, as seen in the perturbed profile across all the gases. The 2006/2007 polar winter was characterized by a strong, cold polar vortex with significant amounts of ozone depletion [114,115]. This is well captured in the model, with ozone (panel (a)) tracking the FTIR columns extremely closely, both inside and outside the vortex.…”