Validation of MIPAS-ENVISAT NO<sub>2</sub> operational data

Abstract

The comparison to ACE satellite observations exhibits only a small negative bias of MIPAS which appears not to be significant. The independent satellite instruments HALOE, SAGE II, and POAM III confirm in common for the spring-summer time period a negative bias of MIPAS in the Arctic and a positive bias in the Antarctic middle and upper stratosphere exceeding frequently the combined systematic error limits. In contrast to the ESA operational processor, the IMK/IAA retrieval code allows accurate inference of NO 2 volume mixing ratios under consideration of all important non-LTE proCorrespondence to: G. Wetzel (gerald.wetzel@imk.fzk.de) cesses. Large differences between both retrieval results appear especially at higher altitudes, above about 50 to 55 km. These differences might be explained at least partly by non-LTE under polar winter conditions but not at mid-latitudes. Below this altitude region mean differences between both processors remain within 5% (during night) and up to 10% (during day) under undisturbed (September 2002) conditions and up to 40% under perturbed polar night conditions (February and March 2004). The intercomparison of ground-based NDACC observations shows no significant bias between the FTIR measurements in Kiruna (68 • N) and MIPAS in summer 2003 but larger deviations in autumn and winter. The mean deviation over the whole comparison period remains within 10%. A mean negative bias of 15% for MIPAS daytime and 8% for nighttime observations has been determined for UV-vis comparisons over Harestua (60 • N). Results of a pole-to-pole comparison of ground-based DOAS/UV-visible sunrise and MIPAS mid-morning column data has shown that the mean agreement in 2003 falls within the accuracy limit of the comparison method. Altogether, it can be indicated that MIPAS NO 2 profiles yield valuable information on the vertical distribution of NO 2 in the lower and middle stratosphere (below about 45 km) during day and night with an overall accuracy of about 10-20% and a precision of typically 5-15% such that the data are useful for scientific studies. In cases where extremely high NO 2 occurs in the mesosphere (polar winter) retrieval results in the lower and middle stratosphere are less accurate than under undisturbed atmospheric conditions.

Diurnal variations of reactive chlorine and nitrogen oxides observed by MIPAS-B inside the January 2010 Arctic vortex

“…During day, NO 2 reacts rapidly to reform NO either by reaction with atomic oxygen (upper stratosphere) or photolysis: Wetzel et al, 2007;Kerzenmacher et al, 2008;Wolff et al, 2008). In this paper we focus on Arctic stratospheric mixing ratios of chlorine and nitrogen species which change quickly their concentration around the terminator between night and day.…”

Technical Note: Intercomparison of ILAS-II version 2 and 1.4 trace species with MIPAS-B measurements

“…A flight of the balloon version of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B) instrument was carried out from Kiruna (Sweden,68 • N) on 20/21 March 2003 as part of a validation campaign for the chemistry instruments MIPAS, GOMOS, and SCIAMACHY aboard the environmental satellite ENVISAT (see, e.g., Wetzel et al, 2007). Owing to the long duration of this flight, a good match with observations of the Improved Limb Atmospheric Spectrometer (ILAS)-II sensor aboard the ADEOS-II satellite could be managed.…”

Validation of ACE-FTS version 3.5 NO<sub><i>y</i></sub> species profiles using correlative satellite measurements

“…Similar approaches have been used before in other studies, e.g. Bracher et al (2005), , Wetzel et al (2007), Brohede et al (2007a), and Wolff et al (2008).…”

“…It was found that the two NO x data sets typically agreed within 20 % between 25 and 50 km. Wetzel et al (2007) found that, in the mid-stratospheric MIPAS ESA version 4.6 NO 2 , diurnally scaled using data from a 1-D photochemical model agreed best with balloon-borne measurements, with biases typically better than 10 %. In similar comparisons with correlative satellite-based solar occultation measurements, the MIPAS ESA profiles typically agreed within 10-30 %.…”