Technical Note: Recipe for monitoring of total ozone with a precision of around 1 DU applying mid-infrared solar absorption spectra

Abstract

Abstract. Mid-infrared solar absorption spectra recorded by a state-of-the-art ground-based FTIR system have the potential to provide precise total O 3 amounts. The currently bestperforming retrieval approaches use a combination of small and broad spectral O 3 windows between 780 and 1015 cm −1 . We show that for these approaches the uncertainties of the temperature profile are by far the major error sources. We demonstrate that a joint optimal estimation of temperature and O 3 profiles widely eliminates this error. The improvements are documented by an extensive theoretical error estimation. Our results suggest that mid-infrared FTIR measurements can provide total O 3 amounts with a precision of around 1 DU, placing this method among the most precise ground-based O 3 monitoring techniques. We recapitulate the requirements on the instrumental hardware and on the retrieval that are needed to achieve this high precision.

The MUSICA MetOp/IASI H<sub>2</sub>O and δD products: characterisation and long-term comparison to NDACC/FTIR data

“…2 of Schneider et al, 2012) as well as four spectral auxiliary microwindows containing CO 2 lines (in order to optimally estimate the temperature from the measured spectra; Schneider and Hase, 2008). We use HITRAN 2008 (High-Resolution Transmission Molecular Absorption Database) spectroscopic parameters (Rothman et al, 2009(Rothman et al, , with 2009, while for the water vapour isotopologues we use parameters that have been adjusted for the speeddependent Voigt line shape (Schneider et al, 2011b O, O 3 , N 2 O, CH 4 , HCl, and C 2 H 6 .…”

Comparison of ground-based Brewer and FTIR total column O<sub>3</sub> monitoring techniques

“…For operational O 3 measurements the FTIR spectra are measured with a resolution of 0.005 cm −1 , which corresponds to a resolution power λ/ λ at 1000 cm −1 of 2×10 5 . The spectral windows applied for the O 3 retrieval are similar to those of (Schneider and Hase, 2008). They consist of a total of 3600 spectral bins and contain many individual O 3 rotational-vibrational lines (at 991.25-993.80 allow the retrieval of a temperature profile which is expected to widely improve the precision of the retrieved total O 3 amount (Schneider and Hase, 2008).…”

“…The spectral windows applied for the O 3 retrieval are similar to those of (Schneider and Hase, 2008). They consist of a total of 3600 spectral bins and contain many individual O 3 rotational-vibrational lines (at 991.25-993.80 allow the retrieval of a temperature profile which is expected to widely improve the precision of the retrieved total O 3 amount (Schneider and Hase, 2008). It is important to mention that all these individual rotational-vibrational lines are resolved: in the middle infrared the shape of absorption lines is dominated by pressure broadening with a typical HWHM of 0.04 cm −1 at surface level, which is nearly one order of magnitude larger than the operational resolution of the FTIR spectrometer.…”

“…Their precision and accuracy are theoretically estimated in Schneider and Hase (2008) and Redondas and Cede (2006), respectively. Ground-based measurements are an important component of the global atmospheric monitoring system, since they are decisive for the validation of satellite data.…”

“…The measurements are performed at the Izaña Observatory, Canary Island of Tenerife, Spain. Currently the Izaña FTIR system provides the most precise FTIR O 3 data world-wide, which is due to both advanced instrumental equipment and an optimised O 3 retrieval strategy (Schneider and Hase, 2008). Concerning the Brewer, Izaña is the Regional Brewer Calibration Centre for Europe (http://www.rbcc-e.org/) of WMO/GAW (World Meteorological Organisation/Global Atmospheric Watch),…”