Ground-based stratospheric O<sub>3</sub> and HNO<sub>3</sub> measurements at Thule, Greenland: an intercomparison with Aura MLS observations

Abstract

Abstract. In response to the need for improving our understanding of the evolution and the interannual variability of the winter Arctic stratosphere, in January 2009 a GroundBased Millimeter-wave Spectrometer (GBMS) was installed at the Network for the Detection of Atmospheric Composition Change (NDACC) site in Thule (76.5 • N, 68.8 • W), Greenland. In this work, stratospheric GBMS O 3 and HNO 3 vertical profiles obtained from Thule during the winters 2010 (HNO 3 only), 2011 and 2012 are characterized and intercompared with co-located measurements of the Aura Microwave Limb Sounder (MLS) experiment. Using a recently developed algorithm based on Optimal Estimation, we find that the GBMS O 3 retrievals show good sensitivity (> 80 %) to atmospheric variations between ∼ 17 and ∼ 50 km, where their 1σ uncertainty is estimated to be the larger of ∼ 11 % or 0.2 ppmv. Similarly, HNO 3 profiles can be considered for scientific use between ∼ 17 and ∼ 45 km altitude, with a 1σ uncertainty that amounts to the larger of 15 % or 0.2 ppbv. Comparisons with Aura MLS version 3.3 observations show that, on average, GBMS O 3 mixing ratios are biased negatively with respect to MLS throughout the stratosphere, with differences ranging between ∼ 0.3 ppmv (8 %) and 0.9 ppmv (18 %) in the 17-50 km vertical range. GBMS HNO 3 values display instead a positive bias with respect to MLS up to 26 km, reaching a maximum of ∼ 1 ppbv (10 %) near the mixing ratio profile peak. O 3 and HNO 3 values from the two datasets prove to be well correlated at all altitudes, although their correlations worsen at the lower end of the altitude ranges considered. Column contents of GBMS and MLS O 3 (from 20 km upwards) and HNO 3 (from 17 km upwards) correlate very well and indicate that GBMS measurements can provide valuable estimates of column interannual and seasonal variations for these compounds.

Global OZone Chemistry And Related trace gas Data records for the Stratosphere (GOZCARDS): methodology and sample results with a focus on HCl, H<sub>2</sub>O, and O<sub>3</sub>

“…A number of discussions relating to signs of ozone recovery have been presented before (Newchurch et al, 2003;Wohltmann et al, 2007;Yang et al, 2008;Jones et al, 2009;Hassler et al, 2011;Salby et al, 2011Salby et al, , 2012Ziemke and Chandra, 2012;Gebhardt et al, 2014;Kuttipurath et al, 2013;Kirgis et al, 2013;Nair et al, 2013Nair et al, , 2015Shepherd et al, 2014;Frith et al, 2014). While there are some indications of small increases in O 3 in the past 10-15 years, further confirmation of an increase in global O 3 and its correlation with column increases is needed in order to more clearly distinguish between long-term forcings, notably from the 11-year solar cycle, slow changes in halogen source gases, temperature changes, and shorter-term variability.…”

First characterization and validation of FORLI-HNO<sub>3</sub> vertical profiles retrieved from IASI/Metop

“…In the stratosphere, the main source of NO x is nitrous oxide (N 2 O) which is emitted at the surface by a variety of sources, including agricultural activities (Chipperfield, 2009;McElroy et al, 1976) and is then transported to the stratosphere, where it photodissociates or reacts with O ( 1 D) to form two NO molecules (Fischer et al, 1997;Muller, 2011;Portmann et al, 2012). The formed NO x catalyse stratospheric ozone destruction through several cycles (Mohanakumar, 2008;Solomon, 1999).…”

“…HNO 3 has been measured by a variety of instruments since its first observation from infrared solar absorption spectra in 1968 (Murcray et al, 1968). Ground-based instruments (Fiorucci et al, 2013;Rinsland et al, 1991;Wood et al, 2004) as well as sounding instruments on board balloons or aircrafts (Jucks et al, 1999;Neuman et al, 2001) or embarked on satellites (Austin et al, 1986;Orsolini et al, 2009;Wespes et al, 2007) or aboard the space shuttle (Rinsland et al, 1996) have all contributed to the characterization of the HNO 3 distributions throughout the lower atmosphere. One of the most complete data sets has been acquired by the Microwave Limb Sounder (MLS) first on the Upper Atmosphere Research Satellite (UARS) from 1991 to 1998, then on the AURA satellite from 2004.…”

Observations of stratospheric and mesospheric O3 with a millimeter-wave radiometer at Rikubetsu, Japan

“…A millimeter-wave radiometer (MWR) enables the continuous measurement of the atmospheric constituents distributed from the middle stratosphere to the lower mesosphere, irrespective of day or night with a high temporal resolution of ~1 h, because it records an emission spectrum caused by the rotational transition of the atmospheric constituents. Such ground-based MWR measurements have been carried out at more than a dozen sites in the past decades (e.g., Daae et al 2014;Fiorucci et al 2013;Palm et al 2010;Parrish et al 2014;Schneider et al 2003;Studer et al 2012).…”