Abstract
Abstract. Acetonitrile (CH3CN) is a volatile organic compound (VOC) and a potential tracer of biomass burning. We evaluated the capability of using observations derived from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the International Space Station (ISS) to measure CH3CN profiles. The error in a CH3CN vertical profile from the Level-2 research (L2r) product version 3.0.0 was estimated by theoretical error analysis and also compared with other instrumental measurements. We estimated the systematic and random errors to be ∼5.8 ppt (7.8 %) and 25 ppt (60 %), respectively, for a single observation at 15.7 hPa in the tropics, where the CH3CN measurements are enhanced. The major source of systematic error was the pressure-broadening coefficient, and its contribution to the total systematic error was approximately 60 % in the middle stratosphere (15.7–4.8 hPa). The random error decreased to less than 40 % after averaging 10 profiles in the pressure range of 28.8–1.6 hPa. The total error due to uncertainties in other molecular spectroscopic parameters (2.8 ppt) was comparable to that of CH3CN spectroscopic parameters. We compared the SMILES CH3CN profiles with those of the microwave limb sounder (MLS) on the Aura satellite (version 4.2). The SMILES CH3CN values were consistent with those from MLS within the standard deviation (1σ) of the MLS observations. The difference between the SMILES and MLS CH3CN profiles increased with altitude and was within 20–35 ppt (20 %–260 %) at 15.7–1.6 hPa. We observed discrepancies of 5–10 ppt (10 %–30 %) between the SMILES CH3CN profiles observed by different spectrometers, and hence, we do not recommend merging SMILES CH3CN profiles derived from different spectrometers. We found that the SMILES CH3CN volume mixing ratio (VMR) in the upper stratosphere has a seasonal maximum in February.
Highlights
Air pollution caused by biomass burning (BB) has become a serious problem with population growth (Marlon et al, 2008)
We found that the Submillimeter-Wave Limb-Emission Sounder (SMILES) CH3CN volume mixing ratio (VMR) in the upper stratosphere has a seasonal maximum in February
We investigated the diurnal variation in SMILES CH3CN observations at several altitudes (32, 40, and 48 km) for AOS1 and AOS2 individual observational periods and confirmed that there is no diurnal variation in stratospheric CH3CN observations
Summary
Air pollution caused by biomass burning (BB) has become a serious problem with population growth (Marlon et al, 2008). The study of atmospheric gas species associated with BB is significant because early estimates of pyrogenic emissions suggested that some atmospheric pollutants from BB could be comparable to those from fossil fuel burning (Crutzen and Andreae, 1990; Seiler and Crutzen, 1980). These emissions could, significantly affect the global atmosphere and its temperatures (Andreae, 1983). We performed a validation analysis comparing these results with the Aura MLS observation data
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