Validation of acetonitrile (CH<sub>3</sub>CN) measurements in the stratosphere and lower mesosphere from the SMILES instrument on the International Space Station
<p>Acetonitrile (<span class="inline-formula">CH<sub>3</sub>CN</span>) 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-Em...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-04-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/13/2119/2020/amt-13-2119-2020.pdf |
| Summary: | <p>Acetonitrile (<span class="inline-formula">CH<sub>3</sub>CN</span>) 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 <span class="inline-formula">CH<sub>3</sub>CN</span> profiles.
The error in a <span class="inline-formula">CH<sub>3</sub>CN</span> 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 <span class="inline-formula">∼5.8</span> ppt (7.8 %) and 25 ppt (60 %), respectively, for a single observation at 15.7 hPa in the tropics, where the <span class="inline-formula">CH<sub>3</sub>CN</span> 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 <span class="inline-formula">CH<sub>3</sub>CN</span> spectroscopic parameters.
We compared the SMILES <span class="inline-formula">CH<sub>3</sub>CN</span> profiles with those of the microwave limb sounder (MLS) on the Aura satellite (version 4.2).
The SMILES <span class="inline-formula">CH<sub>3</sub>CN</span> values were consistent with those from MLS within the standard deviation (<span class="inline-formula">1<i>σ</i></span>) of the MLS observations.
The difference between the SMILES and MLS <span class="inline-formula">CH<sub>3</sub>CN</span> 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 <span class="inline-formula">CH<sub>3</sub>CN</span> profiles observed by different spectrometers, and hence, we do not recommend merging SMILES <span class="inline-formula">CH<sub>3</sub>CN</span> profiles derived from different spectrometers.
We found that the SMILES <span class="inline-formula">CH<sub>3</sub>CN</span> volume mixing ratio (VMR) in the upper stratosphere has a seasonal maximum in February.</p> |
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| ISSN: | 1867-1381 1867-8548 |