Abstract
Abstract. We present global distributions of C2H2 and hydrogen cyanide (HCN) total columns derived from the Infrared Atmospheric Sounding Interferometer (IASI) for the years 2008–2010. These distributions are obtained with a fast method allowing to retrieve C2H2 abundance globally with a 5 % precision and HCN abundance in the tropical (subtropical) belt with a 10 % (25 %) precision. IASI data are compared for validation purposes with ground-based Fourier transform infrared (FTIR) spectrometer measurements at four selected stations. We show that there is an overall agreement between the ground-based and space measurements with correlation coefficients for daily mean measurements ranging from 0.28 to 0.81, depending on the site. Global C2H2 and subtropical HCN abundances retrieved from IASI spectra show the expected seasonality linked to variations in the anthropogenic emissions and seasonal biomass burning activity, as well as exceptional events, and are in good agreement with previous spaceborne studies. Total columns simulated by the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) are compared to the ground-based FTIR measurements at the four selected stations. The model is able to capture the seasonality in the two species in most of the cases, with correlation coefficients for daily mean measurements ranging from 0.50 to 0.86, depending on the site. IASI measurements are also compared to the distributions from MOZART-4. Seasonal cycles observed from satellite data are reasonably well reproduced by the model with correlation coefficients ranging from −0.31 to 0.93 for C2H2 daily means, and from 0.09 to 0.86 for HCN daily means, depending on the considered region. However, the anthropogenic (biomass burning) emissions used in the model seem to be overestimated (underestimated), and a negative global mean bias of 1 % (16 %) of the model relative to the satellite observations was found for C2H2 (HCN).
Highlights
Hydrogen cyanide (HCN) and acetylene 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
We compare HCN and C2H2 total columns retrieved from Infrared Atmospheric Sounding Interferometer (IASI) spectra and from ground-based Fourier transform infrared (FTIR) spectra for the years 2008–2010 for four selected groundbased FTIR observation sites: Wollongong (34◦ S; 151◦ E; 30 m above mean sea level, a.m.s.l.), Reunion Island (21◦ S; 55◦ E; 50 m a.m.s.l.), Izaña (28◦N; 16◦W; 2367 m a.m.s.l.) and Jungfraujoch (46◦ N; 8◦ E; 3580 m a.m.s.l.) (Fig. 6)
C2H2 total columns can be retrieved globally with 5 % precision, while HCN abundances can be retrieved for abundances greater than 0.28 × 1016 molec cm−2 with 10 % precision in the ±20◦ latitudinal band and with 25 % precision in the [±35◦ : ±20◦] latitudinal band
Summary
Hydrogen cyanide (HCN) and acetylene (or ethyne; 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. Satellite sounders have provided considerable new information in the past years, with measurements from the Atmospheric Chemistry Experiment (ACE-FTIR) (Lupu et al, 2009; González Abad et al, 2011), the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) (Parker et al, 2011; Wiegele et al, 2012; Glatthor et al, 2015) and the microwave limb sounder (MLS) (Pumphrey et al, 2011) These measurements were all made in limb geometry and mostly in the upper troposphere or higher; the spatial sampling from these instruments is limited, making it less well-suited when studying dynamical events on short timescales. The IASI spectra used in this study are calibrated radiance spectra provided by EUMETCast near-real-time service
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