Measurements of hydrogen cyanide (HCN) and acetylene (C<sub>2</sub>H<sub>2</sub>) from the Infrared Atmospheric Sounding Interferometer (IASI)

Abstract

Abstract. Hydrogen cyanide (HCN) and acetylene (C2H2) are ubiquitous atmospheric trace gases with medium lifetime, which are frequently used as indicators of combustion sources and as tracers for atmospheric transport and chemistry. Because of their weak infrared absorption, overlapped by the CO2 Q branch near 720 cm−1, nadir sounders have up to now failed to measure these gases routinely. Taking into account CO2 line mixing, we provide for the first time extensive measurements of HCN and C2H2 total columns at Reunion Island (21° S, 55° E) and Jungfraujoch (46° N, 8° E) in 2009–2010 using observations from the Infrared Atmospheric Sounding Interferometer (IASI). A first order comparison with local ground-based Fourier transform infraRed (FTIR) measurements has been carried out allowing tests of seasonal consistency which is reasonably captured, except for HCN at Jungfraujoch. The IASI data shows a greater tendency to high C2H2 values. We also examine a nonspecific biomass burning plume over austral Africa and show that the emission ratios with respect to CO agree with previously reported values.

Towards IASI-New Generation (IASI-NG): impact of improved spectral resolution and radiometric noise on the retrieval of thermodynamic, chemistry and climate variables

“…It is only slightly perturbed by other weak absorption features of H 2 O and CO 2 . Previous experience has demonstrated that the TIR measurements provide information on the ozone vertical profile from the ground up to an altitude of about 40 km, with a maximum sensitivity located in the mid-troposphere (Worden et al, 2007;Boynard et al, 2009;Dufour et al, 2012). The density of the spectra makes it difficult to discriminate individual lines and hence information in the boundary layer can hardly be obtained.…”

Acetylene (C<sub>2</sub>H<sub>2</sub>) and hydrogen cyanide (HCN) from IASI satellite observations: global distributions, validation, and comparison with model

“…in a specific biomass burning plume (Clarisse et al, 2011a), as well as in an anthropogenic pollution plume uplifted in the free troposphere (Clarisse et al, 2011b). More recently, Duflot et al (2013) have shown that HCN and C 2 H 2 columns can be routinely retrieved from IASI spectra, even in the absence of exceptional columns or uplift mechanisms, when CO 2 line mixing is accounted for in the inversion scheme. These previous works were based on an optimal estimation method (OEM) developed and formalized by Rodgers (2000).…”

“…This gives the stability thresholds above which HCN column amount can be measured with a 10 % confidence in the independence of the retrieval method to the atmospheric parameters. Consequently, as the stability thresholds of the method for HCN in temperate and polar atmospheres are too high (1.2 and 1.6 × 10 16 molec cm −2 , respectively) to allow for the detection of HCN background abundances as compared to usual background column of typically 0.35 × 10 16 molec cm −2 (Vigouroux et al, 2012;Duflot et al, 2013), IASI HCN measurements have to be rejected in these two types of atmosphere, and considered in the tropical belt for values above 0.28 × 10 16 molec cm −2 . In order to broaden the exploitable latitude range, we performed the same study for subtropical latitudes (considering a mix of tropical and temperate atmospheres), and we found a 25 % confidence in the independence of the retrieval method to the atmospheric parameters (data not shown).…”

“…However, once cloudy spectra have been discarded, the measured column amount may also depend on (1) the proper suppression of the spectral background, (2) the conditions of thermal contrast (TC) with the surface, and (3) the accuracy of the FM to simulate the spectra used to build up the LUTs. The latter was discussed already by Duflot et al (2013). In order to test the impact of the two first factors (spectral background suppression and TC) on the retrieved column amount, HCN and C 2 H 2 profiles have been constructed with varying TC and concentrations of the interfering and target species.…”

“…Typical abundances of C 2 H 2 (HCN) range from 1 to 2 (2 to 5) × 10 15 molec cm −2 for background levels, and from 8 to 20 (30 to 40) × 10 15 molec cm −2 for biomass burning plume levels (Rinsland et al, 1999(Rinsland et al, , 2001Zander et al, 1991;Zhao et al, 2002;Clarisse et al, 2011a;Vigouroux et al, 2012;Duflot et al, 2013). Table 1 summarizes the main sources and sinks for HCN and C 2 H 2 .…”