Drift-corrected trends and periodic variations in MIPAS IMK/IAA ozone measurements

Abstract

Abstract. Drifts, trends and periodic variations were calculated from monthly zonally averaged ozone profiles. The ozone profiles were derived from level-1b data of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) by means of the scientific level-2 processor run by the Karlsruhe Institute of Technology (KIT), Institute for Meteorology and Climate Research (IMK). All trend and drift analyses were performed using a multilinear parametric trend model which includes a linear term, several harmonics with period lengths from 3 to 24 months and the quasi-biennial oscillation (QBO). Drifts at 2-sigma significance level were mainly negative for ozone relative to Aura MLS and Odin OSIRIS and negative or near zero for most of the comparisons to lidar measurements. Lidar stations used here include those at Hohenpeissenberg

On the improved stability of the version 7 MIPAS ozone record

“…Hatching indicates domains with less than 2σ significance. As pointed out by Eckert et al (2014), the old version exhibited mostly negative drifts, going down to -0.33 ppmv/decade and becoming more negative with altitudes up to ∼ 40 km. This clear pattern of significant negative drifts was extending over all 5 latitudes at altitudes over 30 km, and going down to 20 km at mid-latitudes.…”

“…This characterization was used throughout the mission (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012) to correct for non-linearity in detectors' responses. This deficient radiometric calibration caused a drift of the instrument (Kleinert et al, 2007;Kiefer et al, 2013;Eckert et al, 2014), making MIPAS data not suitable for trend studies without preliminary drift removal. Wagner and Birk (2005) proposed a new method to characterize the detector non-linearity from in-flight measurements 10 in raw data mode.…”

“…For consistency, both the old and the new versions were compared to the same version of reference instruments, the version 3.5/3.6 of ACE-FTS and the version 3.3 of MLS. The version 3.3 of MLS data was used instead of the version 4.2 in order to keep consistency with the analysis of Eckert et al (2014). To and D1/D2.…”

“…The drifts appear as artificial trends of a 5 signal due to imperfect instrument stability. To assess the long-term stability of the MIPAS ozone dataset, we compared it to a network of data including ozonesondes and ground-based lidars using the method from (Hubert et al, 2016), and with Aura MLS (Froidevaux et al, 2008), using the method described by Eckert et al (2014).…”

“…The differences between the MIPAS and MLS measurements were taken at every valid 10 altitude grid point of each profile pair; then monthly zonal means of these differences were calculated in 10-degrees latitude bins. The multi-linear regression model, described in Eckert et al (2014);von Clarmann et al (2010), was then applied to the timeseries. The resulting drifts are shown in the right panel of Figure 7 as a function of altitude and latitude band.…”